1Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
JOURNAL VITAE
School of Pharmaceutical and
Food Sciences
ISSN 0121-4004 | ISSNe 2145-2660
University of Antioquia
Medellin, Colombia
Filliations
1Instituto de Tecnología de Alimentos
y Procesos Químicos ITAPROQ
CONICET. Universidad de Buenos
Aires, Facultad de Ciencias Exactas
y Naturales, Departamento de
Industrias. Int. Güiraldes 2620,
Ciudad Universitaria. (C1428BGA)
Buenos Aires, Argentina.
2 Grupo de Investigación en
Bioeconomía y Sostenibilidad
Agroalimentaria, Escuela de
Administración de Empresas
Agropecuarias, Facultad Seccional
Duitama, Universidad Pedagógica
y Tecnológica de Colombia,
Carrera 18 con Calle 22, Duitama
150461, Colombia
3Grupo de investigación INVEAGRO,
Compañía Magia Artesanal
S.A.S. Calle 23 A 58 40 T 5AP,
Huila, Colombia. * Tel. (+57)
-3132211310. E-mail: edwgd@
di.fcen.uba.ar, alex.lopez01@uptc.
edu.co
*Corresponding
Edward Gomez-Delgado
edwgd@di.fcen.uba.ar
Received: 25 August 2022
Accepted: 16 July 2023
Published: 11 August 2023
Analysis of drying kinetic of brewer´s spent
grains: effect of the temperature on the
physical properties and the content of
bioactive compounds
Análisis de la cinética de secado del bagazo residual de
malta: efecto de la temperatura sobre las propiedades
físicas y el contenido de compuestos bioactivos
E. Gomez-Delgado1,2,3* , C. Medina-Jaramillo2 , A. Lopez-Cordoba2
ABSTRACT
Background: Brewer´s spent grain (BSG) is a biomass by-product generated in large volumes
during industrial beer production. BSG has become a growing environmental problem, as
most breweries discard it inappropriately, negatively impacting the environment. Alternatives
for the exploitation of this by-product have consisted of elaborating food supplements for
farm animals, obtaining biofuels, developing adsorbents, and obtaining substances for the
food industry. However, the high moisture content in BSG (approximately 70%), poses a
significant challenge in exploring various reuse alternatives. Therefore, the implementation
of a pre-drying process becomes essential. Objective: This study aimed to analyze the BSG
drying kinetics at different temperatures and the effect of the drying temperature on the
physical properties and the content of bioactive compounds. Methods: BSG samples were
dried at different temperatures (50, 60, 70, 80, 90, and 105°C) and analyzed for their moisture
ratio, water activity, total polyphenol content (TPC), and DPPH (1,1-diphenyl-2-picrylhydrazil)
radical scavenging activity. Also, four kinetics models were fitted to the drying data. Results:
It was determined that the effective diffusivity was between 5.23x10 -10 (m2 /s) and 2.49x10 -09
(m2 /s), and the value of the activation energy was 28.05 kJ/mol. In addition, it was found that
the content of phenolic compounds (1.27±0.120 mg gallic acid equivalents /g) and the DPPH
radical scavenging activity (0.21±0.015 mg gallic acid equivalents /g) were not significantly
affected by the variation in the drying temperatures studied. Conclusions: From an operational
point of view, the most suitable temperature for the drying process of BSG was 105°C since
it would allow to reach shorter drying times, and the TPC was not affected markedly by the
range of temperature studied.
Keywords: Brewer´s spent grain, dry kinetics, diffusion, polyphenols, by-products valorization.
ORIGINAL ARTICLE
Published 11 August 2023
Doi: https://doi.org/10.17533/udea.vitae.v30n2a351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
JOURNAL VITAE
School of Pharmaceutical and
Food Sciences
ISSN 0121-4004 | ISSNe 2145-2660
University of Antioquia
Medellin, Colombia
Filliations
1Instituto de Tecnología de Alimentos
y Procesos Químicos ITAPROQ
CONICET. Universidad de Buenos
Aires, Facultad de Ciencias Exactas
y Naturales, Departamento de
Industrias. Int. Güiraldes 2620,
Ciudad Universitaria. (C1428BGA)
Buenos Aires, Argentina.
2 Grupo de Investigación en
Bioeconomía y Sostenibilidad
Agroalimentaria, Escuela de
Administración de Empresas
Agropecuarias, Facultad Seccional
Duitama, Universidad Pedagógica
y Tecnológica de Colombia,
Carrera 18 con Calle 22, Duitama
150461, Colombia
3Grupo de investigación INVEAGRO,
Compañía Magia Artesanal
S.A.S. Calle 23 A 58 40 T 5AP,
Huila, Colombia. * Tel. (+57)
-3132211310. E-mail: edwgd@
di.fcen.uba.ar, alex.lopez01@uptc.
edu.co
*Corresponding
Edward Gomez-Delgado
edwgd@di.fcen.uba.ar
Received: 25 August 2022
Accepted: 16 July 2023
Published: 11 August 2023
Analysis of drying kinetic of brewer´s spent
grains: effect of the temperature on the
physical properties and the content of
bioactive compounds
Análisis de la cinética de secado del bagazo residual de
malta: efecto de la temperatura sobre las propiedades
físicas y el contenido de compuestos bioactivos
E. Gomez-Delgado1,2,3* , C. Medina-Jaramillo2 , A. Lopez-Cordoba2
ABSTRACT
Background: Brewer´s spent grain (BSG) is a biomass by-product generated in large volumes
during industrial beer production. BSG has become a growing environmental problem, as
most breweries discard it inappropriately, negatively impacting the environment. Alternatives
for the exploitation of this by-product have consisted of elaborating food supplements for
farm animals, obtaining biofuels, developing adsorbents, and obtaining substances for the
food industry. However, the high moisture content in BSG (approximately 70%), poses a
significant challenge in exploring various reuse alternatives. Therefore, the implementation
of a pre-drying process becomes essential. Objective: This study aimed to analyze the BSG
drying kinetics at different temperatures and the effect of the drying temperature on the
physical properties and the content of bioactive compounds. Methods: BSG samples were
dried at different temperatures (50, 60, 70, 80, 90, and 105°C) and analyzed for their moisture
ratio, water activity, total polyphenol content (TPC), and DPPH (1,1-diphenyl-2-picrylhydrazil)
radical scavenging activity. Also, four kinetics models were fitted to the drying data. Results:
It was determined that the effective diffusivity was between 5.23x10 -10 (m2 /s) and 2.49x10 -09
(m2 /s), and the value of the activation energy was 28.05 kJ/mol. In addition, it was found that
the content of phenolic compounds (1.27±0.120 mg gallic acid equivalents /g) and the DPPH
radical scavenging activity (0.21±0.015 mg gallic acid equivalents /g) were not significantly
affected by the variation in the drying temperatures studied. Conclusions: From an operational
point of view, the most suitable temperature for the drying process of BSG was 105°C since
it would allow to reach shorter drying times, and the TPC was not affected markedly by the
range of temperature studied.
Keywords: Brewer´s spent grain, dry kinetics, diffusion, polyphenols, by-products valorization.
ORIGINAL ARTICLE
Published 11 August 2023
Doi: https://doi.org/10.17533/udea.vitae.v30n2a351025
2Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
INTRODUCTION
Within the alcohol industry, beer is the most
consumed drink globally (1,2). Over time, the brewing
process has undergone various transformations until
it reaches the industrial production process that
we generally know today (1,3,4). The process of
obtaining the beer consists of the malting stage
of the fermentable source (barley grain, rice grain,
among others), grinding and maceration, obtaining
the wort, refrigeration, and fermentation (5). A solid
and wet by-product is obtained during maceration,
known as Brewer´s spent grain (BSG). BSG represents
85% of all solid by-products generated by beer
production (4,6).
World beer production for 2018 reached ~1940x10 6
hectolitres (194x10 6 m 3 ) (6), of which ~582x10 6
hectolitres (~30% of world production) were
produced in the Americas (7). The countries with
the highest beer production for 2020 were China
(~341x106 hectolitres), the USA (~212x106 hectolitres),
and Brazil (~152x10 6 hectolitres) (8). In Colombia, it
is estimated that the annual production of beer is
approximately 22x10 6 hectolitres (8), considering
that for every 100 liters of beer obtained, 20 kg
of BSG are produced (6), the amount of bagasse
generated is a little over 440x10 3 Ton per year.
These large volumes of by-products are becoming
a growing environmental problem due to their
unwillingness to discard them (4,6,7,9–11).
In recent years there has been growing scientific and
political interest in the exploitation and valorization
of residual biomass (12), such as BSG. It is partly
due to the concept of circular bioeconomy has
gained in the global economy (13,14). The circular
bioeconomy consists of an environmentally and
socially sustainable economy through biological
resources production, use and reuse (15,16).
Therefore, finding different alternatives for using
residual biomass, such as BSG, is considered a
current challenge for scientific research.
Searching for technological alternatives for the use
of BSG has brought with it the development and
application of different technologies, for example,
a food supplement for farm animals based on BSG
due to its rich protein content (17). Other studies
have found that it can be used for energy production
(18), obtaining biodiesel (19), and bioethanol (20).
Other authors have investigated the use of BSG for
various purposes, such as obtaining coenzymes,
graphene for electrode production (21), activated
carbons (22), and obtaining food products for
human consumption (23), among others.
The BSG has a high moisture content (~70-73%)
(19,24,25); this makes it challenging to handle
and store. In addition, higher moisture favors the
presence of microorganisms that degrade biomass
making it difficult to reuse and practical application
for the options mentioned above. In line with reusing
the BSG, it must be made a pre-drying treatment
to improve its handling and storage conditions.
Various drying techniques have been employed,
including infrared, freeze dr ying, convective
hot air drying, and solar drying. Among these
RESUMEN
Antecedentes: El Bagazo residual de malta (BSG por sus siglas en inglés) es un subproducto biomásico generado en grandes
volúmenes durante la producción industrial de cerveza. El BSG se ha convertido en un creciente problema para el medio
ambiente, debido a que la mayoría de las cervecerías descartan inapropiadamente este residuo generando un impacto negativo
al ambiente. Las alternativas para el aprovechamiento de este subproducto han consistido especialmente en la elaboración de
suplementos alimenticios para animales de granja, obtención de biocombustibles, desarrollo de adsorbentes y obtención de
productos para la industria alimentaria. Sin embargo, el alto contenido de humedad (~70%) del BSG representa un reto para el
desarrollo de diferentes alternativas de reutilización, por lo que se hace necesario un proceso de secado previo. Objetivos: En
este estudio se analizó la cinética de secado del BSG a diferentes temperaturas y el efecto de la temperatura de secado sobre
sus propiedades físicas y contenido de compuestos bioactivos. Métodos: Las muestras de BSG fueron secadas a diferentes
temperaturas (50, 60, 70, 80, 90 y 105°C) y analizadas en términos de razón de humedad, actividad acuosa, contenido de
polifenoles totales (TPC) y actividad secuestradora del radical DPPH. Además, se ajustaron 4 modelos cinéticos a los datos de
secado. Resultados: Se determinó que la difusividad efectiva del BSG varió entre 5.23x10 -10 (m2 /s) y 2.49x10 -09 (m2 /s). El valor de
la energía de activación fue de 28.05 kJ/mol. Además, se encontró que el contenido de compuestos fenólicos (1.27±0.120 mg
equivalentes de ácido gálico/g) y la actividad secuestradora del radical DPPH (0.21±0.015 mg equivalentes de ácido gálico/g)
no se vieron significativamente afectados por el rango de temperaturas estudiadas. Conclusiones: Desde un punto de vista
operativo, se determinó que la temperatura de secado más adecuada para el BSG fue de 105°C, debido a que permitió alcanzar
tiempos de secado más cortos, y además, el TPC no se vio significativamente afectado en el rango de temperaturas estudiadas.
Keywords: Bagazo residual de malta, cinética de secado, diffusion, polifenoles, valorización de subproductos.
INTRODUCTION
Within the alcohol industry, beer is the most
consumed drink globally (1,2). Over time, the brewing
process has undergone various transformations until
it reaches the industrial production process that
we generally know today (1,3,4). The process of
obtaining the beer consists of the malting stage
of the fermentable source (barley grain, rice grain,
among others), grinding and maceration, obtaining
the wort, refrigeration, and fermentation (5). A solid
and wet by-product is obtained during maceration,
known as Brewer´s spent grain (BSG). BSG represents
85% of all solid by-products generated by beer
production (4,6).
World beer production for 2018 reached ~1940x10 6
hectolitres (194x10 6 m 3 ) (6), of which ~582x10 6
hectolitres (~30% of world production) were
produced in the Americas (7). The countries with
the highest beer production for 2020 were China
(~341x106 hectolitres), the USA (~212x106 hectolitres),
and Brazil (~152x10 6 hectolitres) (8). In Colombia, it
is estimated that the annual production of beer is
approximately 22x10 6 hectolitres (8), considering
that for every 100 liters of beer obtained, 20 kg
of BSG are produced (6), the amount of bagasse
generated is a little over 440x10 3 Ton per year.
These large volumes of by-products are becoming
a growing environmental problem due to their
unwillingness to discard them (4,6,7,9–11).
In recent years there has been growing scientific and
political interest in the exploitation and valorization
of residual biomass (12), such as BSG. It is partly
due to the concept of circular bioeconomy has
gained in the global economy (13,14). The circular
bioeconomy consists of an environmentally and
socially sustainable economy through biological
resources production, use and reuse (15,16).
Therefore, finding different alternatives for using
residual biomass, such as BSG, is considered a
current challenge for scientific research.
Searching for technological alternatives for the use
of BSG has brought with it the development and
application of different technologies, for example,
a food supplement for farm animals based on BSG
due to its rich protein content (17). Other studies
have found that it can be used for energy production
(18), obtaining biodiesel (19), and bioethanol (20).
Other authors have investigated the use of BSG for
various purposes, such as obtaining coenzymes,
graphene for electrode production (21), activated
carbons (22), and obtaining food products for
human consumption (23), among others.
The BSG has a high moisture content (~70-73%)
(19,24,25); this makes it challenging to handle
and store. In addition, higher moisture favors the
presence of microorganisms that degrade biomass
making it difficult to reuse and practical application
for the options mentioned above. In line with reusing
the BSG, it must be made a pre-drying treatment
to improve its handling and storage conditions.
Various drying techniques have been employed,
including infrared, freeze dr ying, convective
hot air drying, and solar drying. Among these
RESUMEN
Antecedentes: El Bagazo residual de malta (BSG por sus siglas en inglés) es un subproducto biomásico generado en grandes
volúmenes durante la producción industrial de cerveza. El BSG se ha convertido en un creciente problema para el medio
ambiente, debido a que la mayoría de las cervecerías descartan inapropiadamente este residuo generando un impacto negativo
al ambiente. Las alternativas para el aprovechamiento de este subproducto han consistido especialmente en la elaboración de
suplementos alimenticios para animales de granja, obtención de biocombustibles, desarrollo de adsorbentes y obtención de
productos para la industria alimentaria. Sin embargo, el alto contenido de humedad (~70%) del BSG representa un reto para el
desarrollo de diferentes alternativas de reutilización, por lo que se hace necesario un proceso de secado previo. Objetivos: En
este estudio se analizó la cinética de secado del BSG a diferentes temperaturas y el efecto de la temperatura de secado sobre
sus propiedades físicas y contenido de compuestos bioactivos. Métodos: Las muestras de BSG fueron secadas a diferentes
temperaturas (50, 60, 70, 80, 90 y 105°C) y analizadas en términos de razón de humedad, actividad acuosa, contenido de
polifenoles totales (TPC) y actividad secuestradora del radical DPPH. Además, se ajustaron 4 modelos cinéticos a los datos de
secado. Resultados: Se determinó que la difusividad efectiva del BSG varió entre 5.23x10 -10 (m2 /s) y 2.49x10 -09 (m2 /s). El valor de
la energía de activación fue de 28.05 kJ/mol. Además, se encontró que el contenido de compuestos fenólicos (1.27±0.120 mg
equivalentes de ácido gálico/g) y la actividad secuestradora del radical DPPH (0.21±0.015 mg equivalentes de ácido gálico/g)
no se vieron significativamente afectados por el rango de temperaturas estudiadas. Conclusiones: Desde un punto de vista
operativo, se determinó que la temperatura de secado más adecuada para el BSG fue de 105°C, debido a que permitió alcanzar
tiempos de secado más cortos, y además, el TPC no se vio significativamente afectado en el rango de temperaturas estudiadas.
Keywords: Bagazo residual de malta, cinética de secado, diffusion, polifenoles, valorización de subproductos.
3Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
methods, convective drying is the widely utilized
approach in industrial settings for mass production
(26–30). During the development of a laboratory-
scale production process, it is crucial to consider
upscaling it for industrial applications. Therefore,
gaining a comprehensive understanding of drying
kinetics becomes paramount, with theoretical and
semi-theoretical models playing a pivotal role in
this regard.
Semi-theoretical models are typically derived by
simplifying the general series of Fick’s second
law or modifying existing simplified models (31).
Empirical and semi-theoretical models have the
advantage of requiring less computational time
and do not necessitate complex assumptions about
the geometry, mass diffusivity, and conductivity
of the specific food product (31). These models
have been widely used for modeling the drying
kinetics of agri-food products such as watermelon
seeds, turnips, and coffee beans (26,29,32,33). In
the literature, few kinetic studies of BSG drying are
directed to find the best drying temperature and
its influence on some characteristics such as water
activity, intrinsic moisture of BSG drying, and the
content of antioxidant compounds present in the
extract obtained.
This work aimed to study a temperature range for the
drying process of the BSG, favoring the operation
time. For this purpose, drying kinetics were studied,
and different kinetic models were applied to the
experimental data to predict drying behavior. Fick’s
second law of mass transfer was used to determine
effective diffusivity and activation energy. The
change in moisture ratio, water activity, and color
of the BSG after drying at different temperatures
was also evaluated. Finally, the influence of the
drying temperature on the content of phenolic
compounds and the antioxidant activity of the BSG
was evaluated.
2. MATERIALS AND METHODS
2.1. Materials
Brewer´s spent grain (BSG) was supplied by a
brewing company in the tatacoa desert (Huila,
Colombia). The bagasse was frozen for storage and
later use. Ethanol (70% v/v) and analytical grade
sodium carbonate (Na2 CO3 ) (LOBA Chemie, India)
were used. Folin-Ciocalteu reagent, gallic acid, and
the 1,1-diphenyl-2-picrylhydrazil (DPPH) free radical
were purchased from PanReac ApliChem (Spain).
2.2. Drying assays
The drying process of the BSG was carried out
on a convection oven (Memert UF 110, Memmert
Universal, Schwabach, Germany) equipped with a
temperature controller. The evaluated temperatures
(50°C, 60°C, 70°C, 80°C, 90°C, and 105°C) were
selected based on previous studies and practical
considerations, aiming to cover a wide range
of drying conditions commonly encountered in
industrial and laboratory settings (26,29,33). The
process consisted of weighing approximately 10
g of BSG in a Petri box, putting it into the oven,
and drying it at the defined temperature. The
variation in the sample weight was recorded at
intervals; this procedure was repeated until constant
weight, indicating that the equilibrium had been
reached. The weight recorded up to equilibrium
also allowed the sample to obtain moisture. Under
the established conditions, it was assumed that the
resistance to heat transfer within the particle and in
the outer gaseous phase was negligible (33). The
reported results corresponded to average values
obtained from tests performed in triplicate at each
temperature.
The moisture ratio was (MR) obtained by applying
the following equation (Eq 1) (34):
t e
i e
m m
MR m m
−
= − (1)
where mt is the moisture content at time t, present
in the BSG; mi is the initial moisture content of the
sample, and m e is the moisture at the equilibrium
over a long enough time to ensure constant weight.
Four commonly used mathematical models were
used to adjust the drying curve under isothermal
conditions (31): Newton, Page, Logarithmic,
and Midilli-Kucuk. The differences between the
experimental and theoretical values given by each
model were evaluated using the statistics of the
adjusted coefficient of determination (R 2
a ), the
standard deviation (SD), and the coefficient of
variance (CV).
( )2 21
1 * 1
1
a
N
R R
N p
−
= − − − −
(2)
( )2
1
1
N
exp modi MR MR
SD N
= −
= −
∑ (3)
exp
SD
CV MR
= (4)
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
methods, convective drying is the widely utilized
approach in industrial settings for mass production
(26–30). During the development of a laboratory-
scale production process, it is crucial to consider
upscaling it for industrial applications. Therefore,
gaining a comprehensive understanding of drying
kinetics becomes paramount, with theoretical and
semi-theoretical models playing a pivotal role in
this regard.
Semi-theoretical models are typically derived by
simplifying the general series of Fick’s second
law or modifying existing simplified models (31).
Empirical and semi-theoretical models have the
advantage of requiring less computational time
and do not necessitate complex assumptions about
the geometry, mass diffusivity, and conductivity
of the specific food product (31). These models
have been widely used for modeling the drying
kinetics of agri-food products such as watermelon
seeds, turnips, and coffee beans (26,29,32,33). In
the literature, few kinetic studies of BSG drying are
directed to find the best drying temperature and
its influence on some characteristics such as water
activity, intrinsic moisture of BSG drying, and the
content of antioxidant compounds present in the
extract obtained.
This work aimed to study a temperature range for the
drying process of the BSG, favoring the operation
time. For this purpose, drying kinetics were studied,
and different kinetic models were applied to the
experimental data to predict drying behavior. Fick’s
second law of mass transfer was used to determine
effective diffusivity and activation energy. The
change in moisture ratio, water activity, and color
of the BSG after drying at different temperatures
was also evaluated. Finally, the influence of the
drying temperature on the content of phenolic
compounds and the antioxidant activity of the BSG
was evaluated.
2. MATERIALS AND METHODS
2.1. Materials
Brewer´s spent grain (BSG) was supplied by a
brewing company in the tatacoa desert (Huila,
Colombia). The bagasse was frozen for storage and
later use. Ethanol (70% v/v) and analytical grade
sodium carbonate (Na2 CO3 ) (LOBA Chemie, India)
were used. Folin-Ciocalteu reagent, gallic acid, and
the 1,1-diphenyl-2-picrylhydrazil (DPPH) free radical
were purchased from PanReac ApliChem (Spain).
2.2. Drying assays
The drying process of the BSG was carried out
on a convection oven (Memert UF 110, Memmert
Universal, Schwabach, Germany) equipped with a
temperature controller. The evaluated temperatures
(50°C, 60°C, 70°C, 80°C, 90°C, and 105°C) were
selected based on previous studies and practical
considerations, aiming to cover a wide range
of drying conditions commonly encountered in
industrial and laboratory settings (26,29,33). The
process consisted of weighing approximately 10
g of BSG in a Petri box, putting it into the oven,
and drying it at the defined temperature. The
variation in the sample weight was recorded at
intervals; this procedure was repeated until constant
weight, indicating that the equilibrium had been
reached. The weight recorded up to equilibrium
also allowed the sample to obtain moisture. Under
the established conditions, it was assumed that the
resistance to heat transfer within the particle and in
the outer gaseous phase was negligible (33). The
reported results corresponded to average values
obtained from tests performed in triplicate at each
temperature.
The moisture ratio was (MR) obtained by applying
the following equation (Eq 1) (34):
t e
i e
m m
MR m m
−
= − (1)
where mt is the moisture content at time t, present
in the BSG; mi is the initial moisture content of the
sample, and m e is the moisture at the equilibrium
over a long enough time to ensure constant weight.
Four commonly used mathematical models were
used to adjust the drying curve under isothermal
conditions (31): Newton, Page, Logarithmic,
and Midilli-Kucuk. The differences between the
experimental and theoretical values given by each
model were evaluated using the statistics of the
adjusted coefficient of determination (R 2
a ), the
standard deviation (SD), and the coefficient of
variance (CV).
( )2 21
1 * 1
1
a
N
R R
N p
−
= − − − −
(2)
( )2
1
1
N
exp modi MR MR
SD N
= −
= −
∑ (3)
exp
SD
CV MR
= (4)
4Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
where N is the number of experimental data; p is the
number of model parameters; R2 is the coefficient of
determination; MRexp is the experimental moisture
data; MRmod is the theoretical moisture, and expMR
is the average of the experimental moisture data.
2.3. Determination of the effective diffusivity
The equation of the second law of Fick Eq (5) was
used for effective diffusivity ( effD ) determination.
This equation describes the diffusion of water
during the drying process, where the resistance to
mass transfer that limits the drying speed is given
by internal resistance, that is, the transfer of water
from inside the BSG to the surface (35,36).
( )eff
MR D MR
t
∂ = ∇ ∇ ∂ (5)
One of the analytical solutions of the second law
of Fick for flat geometries, long drying periods and
values of MR<0.6 is presented in Eq (6) (37).
2
2 2
8 exp effD
MR t
L
π
π
= −
(6)
where D eff is the effective diffusivity (m2 /s), L is the
characteristic length (m), and t is the drying time (s).
Characteristic length L was determined using Eq. (7),
considering the mass of the sample W, the density
ρ, and the cross-sectional area of the sample At.
t
W
L A
ρ
= (7)
It is known that effective diffusivity can commonly
be determined by graphing the experimental data
linearizing Eq. (6) as shown in Eq (8).
( ) 2
2 2
8
ln ln üD
ü L
π
π
= −
(8)
After plotting ln(MR) vs. t, the D eff value was
obtained from the slope of equation Ec (8). For
calculating the activation energy Eo an expression
of Arrhenius was used (19,34) Eq. (9), which relates
effective diffusivity, temperature, and activation
energy. Where D o is the pre-exponential factor; T
is the absolute temperature; and R is the general
constant of the gases.
oE
R T
eff oD D exp
−
= (9)
2.4 Moisture and water activity.
For intrinsic moisture determination, approximately
0.5g of dry and ground BSG was weighed in a
moisture balance ( Citizen MB-50 Moisture Analyser
Balance, Japón). The water activity was determined
in a water activity analyzer equipment (AquaLab
PRE, USA), the sample was entered, and the value
determined by the equipment was recorded. All
measurements were made in triplicate for each
BSG sample dried at the studied temperatures. The
recorded value corresponds to the average value of
the measurements.
2.5 Color
The color of the dry samples was measured using
a tristimulus Minolta colorimeter (Konica-Minolta
CR-10, Osaka, Japan) and reported in CIELab
parameters (L*, a* and b* values), where L* was used
to denote lightness, a* redness and greenness, and
b* yellowness and blueness (38). The equipment
was calibrated using a white plate as standard.
BSG samples were placed on this white plate,
and the values of the parameter’s “L”, “a” and “b”
were recorded. The total color difference (ΔE) was
calculated using equation Eq (10).
( ) ( ) ( )
ü
ü
E L L a a b b∆ = − + − + − (10)
2.6 Determination of the content of bioactive
compounds
Samples (1 g) of BSG were placed in 15 mL test
tubes and mixed with 6 mL of 70 %v/v ethanol. Then,
the tubes were immersed in an ultrasound bath
(BRANSON model 1800, Germany) with a rectangular
chamber (longe:10 cm, hight:12 cm, depth: 12 cm)
equipped with an industrial transducer operating at
40 kHz. A flow system (in/out) controlled the water
temperature from a heating bath (Memmert WNB14,
Germany), maintaining a constant temperature of
60 °C for 10 minutes. The extracts obtained were
filtered (Double ring qualitative filter paper, grade:
EXP DRQLM) and centrifuged at 5300 m/s 2 (4000
rpm) for 10 min. The extracts were suspended in
water for all determinations at a dilution factor of 9.
This test was carried out in triplicate for each dried
BSG sample at the studied temperatures.
2.6.1 Estimation of total polyphenols content
The total polyphenols content (TPC) of BSG was
determined by the Folin-Ciocalteu method (39).
where N is the number of experimental data; p is the
number of model parameters; R2 is the coefficient of
determination; MRexp is the experimental moisture
data; MRmod is the theoretical moisture, and expMR
is the average of the experimental moisture data.
2.3. Determination of the effective diffusivity
The equation of the second law of Fick Eq (5) was
used for effective diffusivity ( effD ) determination.
This equation describes the diffusion of water
during the drying process, where the resistance to
mass transfer that limits the drying speed is given
by internal resistance, that is, the transfer of water
from inside the BSG to the surface (35,36).
( )eff
MR D MR
t
∂ = ∇ ∇ ∂ (5)
One of the analytical solutions of the second law
of Fick for flat geometries, long drying periods and
values of MR<0.6 is presented in Eq (6) (37).
2
2 2
8 exp effD
MR t
L
π
π
= −
(6)
where D eff is the effective diffusivity (m2 /s), L is the
characteristic length (m), and t is the drying time (s).
Characteristic length L was determined using Eq. (7),
considering the mass of the sample W, the density
ρ, and the cross-sectional area of the sample At.
t
W
L A
ρ
= (7)
It is known that effective diffusivity can commonly
be determined by graphing the experimental data
linearizing Eq. (6) as shown in Eq (8).
( ) 2
2 2
8
ln ln üD
ü L
π
π
= −
(8)
After plotting ln(MR) vs. t, the D eff value was
obtained from the slope of equation Ec (8). For
calculating the activation energy Eo an expression
of Arrhenius was used (19,34) Eq. (9), which relates
effective diffusivity, temperature, and activation
energy. Where D o is the pre-exponential factor; T
is the absolute temperature; and R is the general
constant of the gases.
oE
R T
eff oD D exp
−
= (9)
2.4 Moisture and water activity.
For intrinsic moisture determination, approximately
0.5g of dry and ground BSG was weighed in a
moisture balance ( Citizen MB-50 Moisture Analyser
Balance, Japón). The water activity was determined
in a water activity analyzer equipment (AquaLab
PRE, USA), the sample was entered, and the value
determined by the equipment was recorded. All
measurements were made in triplicate for each
BSG sample dried at the studied temperatures. The
recorded value corresponds to the average value of
the measurements.
2.5 Color
The color of the dry samples was measured using
a tristimulus Minolta colorimeter (Konica-Minolta
CR-10, Osaka, Japan) and reported in CIELab
parameters (L*, a* and b* values), where L* was used
to denote lightness, a* redness and greenness, and
b* yellowness and blueness (38). The equipment
was calibrated using a white plate as standard.
BSG samples were placed on this white plate,
and the values of the parameter’s “L”, “a” and “b”
were recorded. The total color difference (ΔE) was
calculated using equation Eq (10).
( ) ( ) ( )
ü
ü
E L L a a b b∆ = − + − + − (10)
2.6 Determination of the content of bioactive
compounds
Samples (1 g) of BSG were placed in 15 mL test
tubes and mixed with 6 mL of 70 %v/v ethanol. Then,
the tubes were immersed in an ultrasound bath
(BRANSON model 1800, Germany) with a rectangular
chamber (longe:10 cm, hight:12 cm, depth: 12 cm)
equipped with an industrial transducer operating at
40 kHz. A flow system (in/out) controlled the water
temperature from a heating bath (Memmert WNB14,
Germany), maintaining a constant temperature of
60 °C for 10 minutes. The extracts obtained were
filtered (Double ring qualitative filter paper, grade:
EXP DRQLM) and centrifuged at 5300 m/s 2 (4000
rpm) for 10 min. The extracts were suspended in
water for all determinations at a dilution factor of 9.
This test was carried out in triplicate for each dried
BSG sample at the studied temperatures.
2.6.1 Estimation of total polyphenols content
The total polyphenols content (TPC) of BSG was
determined by the Folin-Ciocalteu method (39).
5Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Briefly, 400 μL of each extract were mixed with
2 mL of 1:10 diluted Folin-Ciocalteu reagent. The
mixtures were stirred for 30 s using a vortex mixer
(Benchmark, USA), and then 160 μL of sodium
carbonate (7% w/v) were added. After 30 min, the
absorbance of the samples was measured at 760
nm using a spectrophotometer (X-ma 1200 Human
Corporation, Loughborough, UK). Gallic acid was
used as standard. The total polyphenols content
was expressed as gallic acid equivalents (GAE) per
gram of BSG.
2.6.2 Estimation of the DPPH•–scavenging activity
DPPH radical scavenging activity was tested as
described Brand-Williams et al. (1995) (40). A volume
of 100 μL of each obtained extract was mixed with
3,9 mL of an ethanolic solution of DPPH• (25 ppm). It
was then vortexed for 30 s and kept in the dark for 30
min. Finally, the absorbance was measured at 517 nm
using the spectrophotometer. Gallic acid was also
used as standard, and the results were expressed
as mg gallic acid per gram BSG (mg GAE/g BSG).
3. RESULTS AND DISCUSSIONS
3.1. Drying kinetics analysis
Figure 1 shows the drying curves of Brewer´s
spent grain (BSG) obtained at the different studied
temperatures (50°C, 60°C, 70°C, 80°C, 90°C, and
105°C). It was observed that when the temperature
increases, the curve’s slope becomes greater,
indicating that the humidity of the BSG reaches
equilibrium or reaches a specific moisture ratio in
shorter times. The equilibrium time is defined as the
moment when sample mass does not vary in time;
according to this, for the dried sample at 105°C,
the equilibrium time was reached at 60 min, while
at 50 °C, the equilibrium time took 260 min, four
times more than observed at 105 °C. Recent studies
on the drying kinetics of biomass corroborate the
influence of temperature on the drying process. For
instance, Ghanem et. al. found that increasing the
drying temperature from 50 to 70 °C reduced the
drying time by 30 % (41). Similarly, another study
reported that temperature is a critical factor for
the drying kinetics of sawdust, affecting the drying
process (42). Additionally, the literature suggests
that the drying kinetics of biomass are affected
by various parameters, including the type and
size of biomass, airflow rate, and moisture ratio.
For example, a study by (43) examined the drying
kinetics of palm kernel shells and determined that
airflow rate and particle size significantly affect
the drying process. From these curves presented
in Figure 1, it was also determined that the initial
humidity of BSG was 71.7 % (±0.012). This moisture
ratio aligns with others reported in the literature
(37,44).
Figure 1. Drying curves of Brewer´s spent grain (BSG) using the
different temperatures studied (experimental points).
The drying speed curves of BSG obtained at the
different studied temperatures are shown in Figure
2. It was observed that as the temperature increased,
the slope of the curve was higher, indicating an
increase in the drying speed. Besides, at the
beginning of the curve, the positive slope indicated
a short period where the drying speed increased.
This increase corresponded to the period when the
temperature inside the oven raised, promoting the
evaporation process of the water from the particles’
surface. It should be noted that this period became
shorter as the temperature studied increased. Similar
observation has been reported in previous studies
on the effect of temperature on the drying rate of
biomass (45). A progressive decay of the drying
rate was observed because the moisture on the
surface of the particles was completely evaporated,
while the remaining water within the BSG matrix
evaporated slower. This behavior indicated that the
internal resistance limits the drying speed to mass
transfer, that is the diffusion of moisture from inside
the BSG to its surface. Similar drying mechanism
have been observed in other studies (19, 31, 33,
37, 46). These findings were consistent whit other
studies on the drying kinetics of bamboo sawdust
reported, the drying rate augmented with increasing
temperature, and the drying process can be divided
into three stages: the initial increasing rate period,
the constant rate period, and the falling rate period,
which was consistent with the observations made
in this (47, 48).
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Briefly, 400 μL of each extract were mixed with
2 mL of 1:10 diluted Folin-Ciocalteu reagent. The
mixtures were stirred for 30 s using a vortex mixer
(Benchmark, USA), and then 160 μL of sodium
carbonate (7% w/v) were added. After 30 min, the
absorbance of the samples was measured at 760
nm using a spectrophotometer (X-ma 1200 Human
Corporation, Loughborough, UK). Gallic acid was
used as standard. The total polyphenols content
was expressed as gallic acid equivalents (GAE) per
gram of BSG.
2.6.2 Estimation of the DPPH•–scavenging activity
DPPH radical scavenging activity was tested as
described Brand-Williams et al. (1995) (40). A volume
of 100 μL of each obtained extract was mixed with
3,9 mL of an ethanolic solution of DPPH• (25 ppm). It
was then vortexed for 30 s and kept in the dark for 30
min. Finally, the absorbance was measured at 517 nm
using the spectrophotometer. Gallic acid was also
used as standard, and the results were expressed
as mg gallic acid per gram BSG (mg GAE/g BSG).
3. RESULTS AND DISCUSSIONS
3.1. Drying kinetics analysis
Figure 1 shows the drying curves of Brewer´s
spent grain (BSG) obtained at the different studied
temperatures (50°C, 60°C, 70°C, 80°C, 90°C, and
105°C). It was observed that when the temperature
increases, the curve’s slope becomes greater,
indicating that the humidity of the BSG reaches
equilibrium or reaches a specific moisture ratio in
shorter times. The equilibrium time is defined as the
moment when sample mass does not vary in time;
according to this, for the dried sample at 105°C,
the equilibrium time was reached at 60 min, while
at 50 °C, the equilibrium time took 260 min, four
times more than observed at 105 °C. Recent studies
on the drying kinetics of biomass corroborate the
influence of temperature on the drying process. For
instance, Ghanem et. al. found that increasing the
drying temperature from 50 to 70 °C reduced the
drying time by 30 % (41). Similarly, another study
reported that temperature is a critical factor for
the drying kinetics of sawdust, affecting the drying
process (42). Additionally, the literature suggests
that the drying kinetics of biomass are affected
by various parameters, including the type and
size of biomass, airflow rate, and moisture ratio.
For example, a study by (43) examined the drying
kinetics of palm kernel shells and determined that
airflow rate and particle size significantly affect
the drying process. From these curves presented
in Figure 1, it was also determined that the initial
humidity of BSG was 71.7 % (±0.012). This moisture
ratio aligns with others reported in the literature
(37,44).
Figure 1. Drying curves of Brewer´s spent grain (BSG) using the
different temperatures studied (experimental points).
The drying speed curves of BSG obtained at the
different studied temperatures are shown in Figure
2. It was observed that as the temperature increased,
the slope of the curve was higher, indicating an
increase in the drying speed. Besides, at the
beginning of the curve, the positive slope indicated
a short period where the drying speed increased.
This increase corresponded to the period when the
temperature inside the oven raised, promoting the
evaporation process of the water from the particles’
surface. It should be noted that this period became
shorter as the temperature studied increased. Similar
observation has been reported in previous studies
on the effect of temperature on the drying rate of
biomass (45). A progressive decay of the drying
rate was observed because the moisture on the
surface of the particles was completely evaporated,
while the remaining water within the BSG matrix
evaporated slower. This behavior indicated that the
internal resistance limits the drying speed to mass
transfer, that is the diffusion of moisture from inside
the BSG to its surface. Similar drying mechanism
have been observed in other studies (19, 31, 33,
37, 46). These findings were consistent whit other
studies on the drying kinetics of bamboo sawdust
reported, the drying rate augmented with increasing
temperature, and the drying process can be divided
into three stages: the initial increasing rate period,
the constant rate period, and the falling rate period,
which was consistent with the observations made
in this (47, 48).
6Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
Figures 1 and 2 show that the drying speed was not
constant in any of the conditions studied, probably
because the thickness of the moisture layer, the “thin
layer” on the surface, was not constant, preventing
a continuous supply of moisture during the drying
process. This behavior has also been observed in
other studies (31, 46, 48).
Figure 2. Drying speed curves of Brewer´s spent grain (BSG) at
the different temperatures studied.
The BSG drying curve was also evaluated using
different masses; for this purpose, 105°C was used
as the drying temperature because the process was
performed faster. Figure S1 describes the drying
curves at 105°C using different masses of BSG; it
can be seen that the slope of the curve increased
as the mass of BSG to be dried decreased. Also,
the humidity to reach balance took 50, 60, and 80
min for 5g, 10g, and 15g, respectively. Therefore,
the drying process took longer when there was
more bagasse mass. This result corroborated that
the internal resistance to mass transfer by the
diffusion of moisture from the inside BSG particle
to its surface was the limiting drying speed, as
mentioned above, which is a common limiting factor
in the drying kinetics of biomass. However, it is
important to note that the drying kinetics of diverse
types of biomasses may be influenced by various
factors such as temperature, relative humidity, and
particle size (30, 47, 48). Therefore, a comprehensive
understanding of the drying behavior of each type of
biomass is necessary to optimize the drying process
for industrial applications.
3.2. Analysis of the effective diffusivity and of
the activation energy of the drying process.
Assuming that the sample throughout the drying
process presented a negligible shrinkage, uniform
distribution, and a constant content of initial
moisture throughout the BSG particle, one of
Fick’s second law solutions was used to determine
effective diffusivity. Figure S2 shows the graphs of
Ln (moisture ratio (MR)) vs. t (min), using equation Eq
(8) and using the slope of each line was determined
the effective diffusivity in each temperature studied.
Table 1 shows the values of effective diffusivity at
different temperatures. Since D eff was influenced
by temperature, pressure, and molecular weight,
the pressure, and molecular weight was assigned a
constant value for this drying study. The increasing
temperature and the effective diffusivity were greater
because the higher the temperature increased the
energy necessary for the water particles to begin the
diffusion through the internal structure of the BSG
(Table 1). D eff values in this analysis were in the order
of magnitude found for other biomasses studies
using BSG (33, 37). However, other recent studies
have reported different results. For example, a study
on the drying kinetics of corn stover reported that
the effective diffusivity decreased with increasing
temperature due to the formation of a crust layer
on the biomass surface, which hindered moisture
transfer (49, 50). These discrepancies highlight the
importance of studying the specific characteristics
of each type of biomass and the potential formation
of crust layers during the drying process, as well
as the need for further research to optimize drying
conditions and reduce energy consumption in
biomass drying processes.
Table 1. Effective diffusivity at different temperatures and constant pressure (101.325 kPa)
Temperature (°C) 50 60 70 80 90 105
Effective diffusivity (m2 /s) 5.23x10-10 8.22x10 -10 1.29x10-09 1.39x10 -09 1.91x10 -09 2.49x10 -09
Figures 1 and 2 show that the drying speed was not
constant in any of the conditions studied, probably
because the thickness of the moisture layer, the “thin
layer” on the surface, was not constant, preventing
a continuous supply of moisture during the drying
process. This behavior has also been observed in
other studies (31, 46, 48).
Figure 2. Drying speed curves of Brewer´s spent grain (BSG) at
the different temperatures studied.
The BSG drying curve was also evaluated using
different masses; for this purpose, 105°C was used
as the drying temperature because the process was
performed faster. Figure S1 describes the drying
curves at 105°C using different masses of BSG; it
can be seen that the slope of the curve increased
as the mass of BSG to be dried decreased. Also,
the humidity to reach balance took 50, 60, and 80
min for 5g, 10g, and 15g, respectively. Therefore,
the drying process took longer when there was
more bagasse mass. This result corroborated that
the internal resistance to mass transfer by the
diffusion of moisture from the inside BSG particle
to its surface was the limiting drying speed, as
mentioned above, which is a common limiting factor
in the drying kinetics of biomass. However, it is
important to note that the drying kinetics of diverse
types of biomasses may be influenced by various
factors such as temperature, relative humidity, and
particle size (30, 47, 48). Therefore, a comprehensive
understanding of the drying behavior of each type of
biomass is necessary to optimize the drying process
for industrial applications.
3.2. Analysis of the effective diffusivity and of
the activation energy of the drying process.
Assuming that the sample throughout the drying
process presented a negligible shrinkage, uniform
distribution, and a constant content of initial
moisture throughout the BSG particle, one of
Fick’s second law solutions was used to determine
effective diffusivity. Figure S2 shows the graphs of
Ln (moisture ratio (MR)) vs. t (min), using equation Eq
(8) and using the slope of each line was determined
the effective diffusivity in each temperature studied.
Table 1 shows the values of effective diffusivity at
different temperatures. Since D eff was influenced
by temperature, pressure, and molecular weight,
the pressure, and molecular weight was assigned a
constant value for this drying study. The increasing
temperature and the effective diffusivity were greater
because the higher the temperature increased the
energy necessary for the water particles to begin the
diffusion through the internal structure of the BSG
(Table 1). D eff values in this analysis were in the order
of magnitude found for other biomasses studies
using BSG (33, 37). However, other recent studies
have reported different results. For example, a study
on the drying kinetics of corn stover reported that
the effective diffusivity decreased with increasing
temperature due to the formation of a crust layer
on the biomass surface, which hindered moisture
transfer (49, 50). These discrepancies highlight the
importance of studying the specific characteristics
of each type of biomass and the potential formation
of crust layers during the drying process, as well
as the need for further research to optimize drying
conditions and reduce energy consumption in
biomass drying processes.
Table 1. Effective diffusivity at different temperatures and constant pressure (101.325 kPa)
Temperature (°C) 50 60 70 80 90 105
Effective diffusivity (m2 /s) 5.23x10-10 8.22x10 -10 1.29x10-09 1.39x10 -09 1.91x10 -09 2.49x10 -09
7Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
For the biomass drying process, such as BSG, the
activation energy can be defined as the energy
necessary for water particles to begin to diffuse
through the solid structure of the BSG to the surface,
and the drying process occurs (32, 51). For Activation
Energy determination Eo (kJ/mol), the Deff values
recorded at the different temperatures were used;
for this purpose, the Ln (Deff ) vs. 1/T was plotted
(Figure S3). The results showed Eo values of around
28.05 kJ/mol. The pre-exponential coefficient D o
with a value of 2.04x10 -5 m2 /s was also determined.
Activation energy has been widely used to analyze
the drying kinetics of various types of biomasses,
such as stevia leaves (52), tea (53), fructus aurantii
(dried fruit of Citrus aurantium L.) (54), pomegranate
arils (55), wood (56). These studies have reported
activation energy values ranging from 13.5 kJ/
mol for tea to 41.5 kJ/mol for wood, indicating
that different types of biomasses have different
activation energies due to variations in their internal
structure and composition. In contrast, the Eo value
obtained in this study for BSG was 28.05 kJ/mol,
which is relatively low compared to other biomass
studies. This difference in Eo values between BSG
and other biomass is due to the unique structure
and composition of BSG.
3.3. Analysis of the kinetic models
For kinetics analysis, four mathematical models
were used to fit the experimental data: the model
of Newton, Page, Logarithmic, and Midilli-Kucuk.
With these models, it was desired to obtain the most
suitable equation to estimate the moisture ratio (MR)
of bagasse drying at different temperatures. Kinetic
models are represented by the following Eq. (11-14):
Newton model : ( )MR exp Kt= − (11)
Page model : ( )n
MR exp Kt= − (12)
Logarithmic model : ( )MR a b exp Kt= + − (13)
Midilli-Kucuk model : ( )n
MR a exp Kt bt= − + (14)
where K is the kinetic constant of each model, n is
a power constant, a and b are parameters of the
corresponding equation.
Figures 3 and 4 show the different models adjusted
to the experimental data to facilitate the graphical
analysis. The figures were grouped between the
best-adjusted models (Figure 3) and those with more
significant deviation (Figure 4).
Figure 3 shows the kinetic models that best fit the
experimental data, the Page and Midilli-Kucuk models.
In part, this is because the Midilli-Kucuk model
contains a greater number of parameters with respect
to the Page model; it was found that an equation with
two parameters allows to adequately describe the
drying kinetics of the BSG, in addition to being used
to estimate the moisture ratio. Figure 4 shows the
two kinetic models that had greater deviation when
adjusting to the experimental data, Newton and the
Logarithmic; observing that despite not adjusting
as well as the Page and Midilli-Kucuk models, they
could be used cautiously to have an estimated value
of moisture during the drying process.
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
For the biomass drying process, such as BSG, the
activation energy can be defined as the energy
necessary for water particles to begin to diffuse
through the solid structure of the BSG to the surface,
and the drying process occurs (32, 51). For Activation
Energy determination Eo (kJ/mol), the Deff values
recorded at the different temperatures were used;
for this purpose, the Ln (Deff ) vs. 1/T was plotted
(Figure S3). The results showed Eo values of around
28.05 kJ/mol. The pre-exponential coefficient D o
with a value of 2.04x10 -5 m2 /s was also determined.
Activation energy has been widely used to analyze
the drying kinetics of various types of biomasses,
such as stevia leaves (52), tea (53), fructus aurantii
(dried fruit of Citrus aurantium L.) (54), pomegranate
arils (55), wood (56). These studies have reported
activation energy values ranging from 13.5 kJ/
mol for tea to 41.5 kJ/mol for wood, indicating
that different types of biomasses have different
activation energies due to variations in their internal
structure and composition. In contrast, the Eo value
obtained in this study for BSG was 28.05 kJ/mol,
which is relatively low compared to other biomass
studies. This difference in Eo values between BSG
and other biomass is due to the unique structure
and composition of BSG.
3.3. Analysis of the kinetic models
For kinetics analysis, four mathematical models
were used to fit the experimental data: the model
of Newton, Page, Logarithmic, and Midilli-Kucuk.
With these models, it was desired to obtain the most
suitable equation to estimate the moisture ratio (MR)
of bagasse drying at different temperatures. Kinetic
models are represented by the following Eq. (11-14):
Newton model : ( )MR exp Kt= − (11)
Page model : ( )n
MR exp Kt= − (12)
Logarithmic model : ( )MR a b exp Kt= + − (13)
Midilli-Kucuk model : ( )n
MR a exp Kt bt= − + (14)
where K is the kinetic constant of each model, n is
a power constant, a and b are parameters of the
corresponding equation.
Figures 3 and 4 show the different models adjusted
to the experimental data to facilitate the graphical
analysis. The figures were grouped between the
best-adjusted models (Figure 3) and those with more
significant deviation (Figure 4).
Figure 3 shows the kinetic models that best fit the
experimental data, the Page and Midilli-Kucuk models.
In part, this is because the Midilli-Kucuk model
contains a greater number of parameters with respect
to the Page model; it was found that an equation with
two parameters allows to adequately describe the
drying kinetics of the BSG, in addition to being used
to estimate the moisture ratio. Figure 4 shows the
two kinetic models that had greater deviation when
adjusting to the experimental data, Newton and the
Logarithmic; observing that despite not adjusting
as well as the Page and Midilli-Kucuk models, they
could be used cautiously to have an estimated value
of moisture during the drying process.
8Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
Figure 3. Page and Midilli-Kucuk kinetic models adjusted to experimental drying curve data at different temperatures (50 °C, 60 °C,
70 °C, 80 °C, 90 °C, and 105 °C).
Figure 3. Page and Midilli-Kucuk kinetic models adjusted to experimental drying curve data at different temperatures (50 °C, 60 °C,
70 °C, 80 °C, 90 °C, and 105 °C).
9Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Figure 4. Newton and logarithmic kinetic models adjusted to experimental drying curve data at different temperatures (50 °C, 60
°C, 70 °C, 80 °C, 90 °C, and 105 °C).
Table 2 presents the parameters of the different
kinetic models adjusted to the experimental data.
All parameter values from the kinetic models used
are in the order of those found in the literature (29,
33, 51). The Page model was the one that best fit
the experimental data; this can be deduced because
this model obtained the values of R2 higher, lower
SD, lower CV, and better graphic fit (Figure 3, Table
2). This model contains relevant information to
drying kinetics from the two parameters that fit the
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Figure 4. Newton and logarithmic kinetic models adjusted to experimental drying curve data at different temperatures (50 °C, 60
°C, 70 °C, 80 °C, 90 °C, and 105 °C).
Table 2 presents the parameters of the different
kinetic models adjusted to the experimental data.
All parameter values from the kinetic models used
are in the order of those found in the literature (29,
33, 51). The Page model was the one that best fit
the experimental data; this can be deduced because
this model obtained the values of R2 higher, lower
SD, lower CV, and better graphic fit (Figure 3, Table
2). This model contains relevant information to
drying kinetics from the two parameters that fit the
10Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
Page equation. The kinetic constant K and n grew
slightly as the drying temperature increased. The
growth of K was in line with the above results; as
the temperature increased, the slope became larger.
From the above, we concluded that a kinetic model
with two parameters was sufficient to describe the
drying kinetics of BSG adequately. The Page model
allowed to have a robust model for predicting the
drying kinetics of the precursor without the need
to use a more complex equation using a greater
number of parameters.
Table 2. Kinetics models parameters
Model
Temperature Parameters Statistics
(°C) a B n K (sn ) r 2 SD CV
Newton
50 - - - 0.0094 0.9897 0.038 0.085
60 - - - 0.0137 0.9791 0.050 0.110
70 - - - 0.0201 0.9724 0.055 0.112
80 - - - 0.0229 0.9710 0.060 0.142
90 - - - 0.0229 0.8964 0.108 0.344
105 - - - 0.0229 0.7347 0.065 0.222
Page
50 - - 1.2024 0.0038 0.9968 0.021 0.046
60 - - 1.3462 0.0033 0.9976 0.016 0.036
70 - - 1.3870 0.0046 0.9985 0.012 0.025
80 - - 1.4586 0.0042 0.9983 0.014 0.033
90 - - 1.5158 0.0049 0.9978 0.015 0.048
105 - - 1.5728 0.0063 0.9975 0.017 0.057
Logarítmico
50 1.00E-03 1.1000 - 0.0150 0.9281 0.095 0.213
60 3.00E-07 1.0687 - 0.0150 0.9838 0.042 0.092
70 6.00E-07 1.0721 - 0.0219 0.9792 0.045 0.091
80 3.00E-07 1.0863 - 0.0252 0.9774 0.048 0.114
90 6.00E-07 1.0863 - 0.0252 0.8906 0.102 0.326
105 5.00E-07 1.0863 - 0.0252 0.6951 0.056 0.190
Midilli-Kucuk
50 0.9583 0.00E+00 1.3223 0.0021 0.9976 0.016 0.036
60 1.0691 5.00E-07 1.0246 0.0137 0.9847 0.039 0.087
70 0.9863 6.00E-07 1.4262 0.0039 0.9985 0.011 0.023
80 0.9934 6.00E-06 1.5006 0.0037 0.9990 0.010 0.023
90 0.9786 4.00E-07 1.5753 0.0039 0.9978 0.014 0.044
105 0.9711 5.00E-07 1.6678 0.0044 0.9979 0.014 0.048
Figure S4 shows the kinetic models adjusted to
the drying curves at a temperature of 105 °C
using different masses of BSG. The parameters
of the kinetic models were reported in Table S1.
From Figure S4 and Table S1, the Page and Midilli-
Kucuk models presented the best adjustments to
the experimental data. In contrast, the Newton
and Logarithmic models presented the greatest
deviation. This behavior was similar to those
illustrated in Figures 3 and 4.
3.4. Analysis of moisture and water activity
The effect of drying temperature on moisture
content, water activity, and color of BSG after drying
was analyzed. In addition, it was explored whether
the BSG milling process affected the characteristics
mentioned above after the drying process. These
characteristics were compared in dry and whole BSG
with dry and ground BSG.
Figure 5 shows the behavior of the water activity
(aw ) and the moisture of BSG as a function of the
Page equation. The kinetic constant K and n grew
slightly as the drying temperature increased. The
growth of K was in line with the above results; as
the temperature increased, the slope became larger.
From the above, we concluded that a kinetic model
with two parameters was sufficient to describe the
drying kinetics of BSG adequately. The Page model
allowed to have a robust model for predicting the
drying kinetics of the precursor without the need
to use a more complex equation using a greater
number of parameters.
Table 2. Kinetics models parameters
Model
Temperature Parameters Statistics
(°C) a B n K (sn ) r 2 SD CV
Newton
50 - - - 0.0094 0.9897 0.038 0.085
60 - - - 0.0137 0.9791 0.050 0.110
70 - - - 0.0201 0.9724 0.055 0.112
80 - - - 0.0229 0.9710 0.060 0.142
90 - - - 0.0229 0.8964 0.108 0.344
105 - - - 0.0229 0.7347 0.065 0.222
Page
50 - - 1.2024 0.0038 0.9968 0.021 0.046
60 - - 1.3462 0.0033 0.9976 0.016 0.036
70 - - 1.3870 0.0046 0.9985 0.012 0.025
80 - - 1.4586 0.0042 0.9983 0.014 0.033
90 - - 1.5158 0.0049 0.9978 0.015 0.048
105 - - 1.5728 0.0063 0.9975 0.017 0.057
Logarítmico
50 1.00E-03 1.1000 - 0.0150 0.9281 0.095 0.213
60 3.00E-07 1.0687 - 0.0150 0.9838 0.042 0.092
70 6.00E-07 1.0721 - 0.0219 0.9792 0.045 0.091
80 3.00E-07 1.0863 - 0.0252 0.9774 0.048 0.114
90 6.00E-07 1.0863 - 0.0252 0.8906 0.102 0.326
105 5.00E-07 1.0863 - 0.0252 0.6951 0.056 0.190
Midilli-Kucuk
50 0.9583 0.00E+00 1.3223 0.0021 0.9976 0.016 0.036
60 1.0691 5.00E-07 1.0246 0.0137 0.9847 0.039 0.087
70 0.9863 6.00E-07 1.4262 0.0039 0.9985 0.011 0.023
80 0.9934 6.00E-06 1.5006 0.0037 0.9990 0.010 0.023
90 0.9786 4.00E-07 1.5753 0.0039 0.9978 0.014 0.044
105 0.9711 5.00E-07 1.6678 0.0044 0.9979 0.014 0.048
Figure S4 shows the kinetic models adjusted to
the drying curves at a temperature of 105 °C
using different masses of BSG. The parameters
of the kinetic models were reported in Table S1.
From Figure S4 and Table S1, the Page and Midilli-
Kucuk models presented the best adjustments to
the experimental data. In contrast, the Newton
and Logarithmic models presented the greatest
deviation. This behavior was similar to those
illustrated in Figures 3 and 4.
3.4. Analysis of moisture and water activity
The effect of drying temperature on moisture
content, water activity, and color of BSG after drying
was analyzed. In addition, it was explored whether
the BSG milling process affected the characteristics
mentioned above after the drying process. These
characteristics were compared in dry and whole BSG
with dry and ground BSG.
Figure 5 shows the behavior of the water activity
(aw ) and the moisture of BSG as a function of the
11Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
drying temperature. It was observed that the
moisture and the water activity of BSG did not vary
significantly, regardless of the temperature used
in the drying. Besides, the whole and ground BSG
samples showed moisture values of around 4.8%
(±1.614) and 4.0% (±0.366), respectively, while similar
aw values were obtained for both samples (aw ∼0.26-
0.28) (Figure 5a). This result is an advantage from an
application point of view since a material with low
water activity and low moisture could stay longer
in storage without affecting its shelf life, reducing
the deterioration risk of BSG.
Figure 5. Behavior of the water activity (a), and the moisture
content (b) of the BSG samples as a function of drying
temperature. These properties were measured for entire BSG
and ground BSG.
3.5. Color
Figure S5 shows images of the whole and ground
BSG samples, while the corresponding ΔE values are
shown in Table S2. It was observed that the different
temperatures studied did not cause significant
changes in the appearance of the samples nor in
their color attributes. This behavior was probably
due to the relatively low temperatures used, which
were insufficient to alter the pigments present
in both whole and ground BSG. Some studies
reported that high drying temperatures can lead
to a decrease in brightness and chroma of biomass
samples, indicating a color change (53, 54, 57, 58).
Therefore, it could be suggested that the effect
of drying temperature on color stability varies
depending on the specific type of biomass and the
drying conditions used.
3.6. Analysis of the total phenolic content and
DPPH radical scavenging activity
Figure 6 shows the behavior of the total polyphenol
content and the DPPH radical scavenging activity of
the BSG samples as a function of drying temperature.
The different drying temperature studied did not
significantly influence the TPC (Figure 6a) or the
DPPH radical scavenging activity (Figure 6b). The
average phenolic content and DPPH scavenging
activity were 1.27±0.120 mg GAE/g BSG and
0.21±0.015 mg GAE/g BSG, respectively. Yan
et al. reported that the drying temperature had
an impact on TPC and DPPH radical scavenging
activity in both hot-air-dried and sunlight-dried
orange black tea. Specifically, an increase in the
drying temperature of orange black tea led to a
decrease in TPC and antioxidant activity of the
extract, with a more pronounced effect when hot-
air was used as the drying method (53). Conversely,
a previous study on microwave drying of lemon
peel demonstrated an increased TPC when the
applied power was augmented. This behavior was
attributed to the generation of high vapor pressure
and temperature inside the plant tissue caused by
the intense heat produced by microwaves, leading
to the disruption of plant cell wall polymers. As
a result, bound or cell wall phenolics may be
released, potentially resulting in an increased
extraction of phenolic compounds (41).
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
drying temperature. It was observed that the
moisture and the water activity of BSG did not vary
significantly, regardless of the temperature used
in the drying. Besides, the whole and ground BSG
samples showed moisture values of around 4.8%
(±1.614) and 4.0% (±0.366), respectively, while similar
aw values were obtained for both samples (aw ∼0.26-
0.28) (Figure 5a). This result is an advantage from an
application point of view since a material with low
water activity and low moisture could stay longer
in storage without affecting its shelf life, reducing
the deterioration risk of BSG.
Figure 5. Behavior of the water activity (a), and the moisture
content (b) of the BSG samples as a function of drying
temperature. These properties were measured for entire BSG
and ground BSG.
3.5. Color
Figure S5 shows images of the whole and ground
BSG samples, while the corresponding ΔE values are
shown in Table S2. It was observed that the different
temperatures studied did not cause significant
changes in the appearance of the samples nor in
their color attributes. This behavior was probably
due to the relatively low temperatures used, which
were insufficient to alter the pigments present
in both whole and ground BSG. Some studies
reported that high drying temperatures can lead
to a decrease in brightness and chroma of biomass
samples, indicating a color change (53, 54, 57, 58).
Therefore, it could be suggested that the effect
of drying temperature on color stability varies
depending on the specific type of biomass and the
drying conditions used.
3.6. Analysis of the total phenolic content and
DPPH radical scavenging activity
Figure 6 shows the behavior of the total polyphenol
content and the DPPH radical scavenging activity of
the BSG samples as a function of drying temperature.
The different drying temperature studied did not
significantly influence the TPC (Figure 6a) or the
DPPH radical scavenging activity (Figure 6b). The
average phenolic content and DPPH scavenging
activity were 1.27±0.120 mg GAE/g BSG and
0.21±0.015 mg GAE/g BSG, respectively. Yan
et al. reported that the drying temperature had
an impact on TPC and DPPH radical scavenging
activity in both hot-air-dried and sunlight-dried
orange black tea. Specifically, an increase in the
drying temperature of orange black tea led to a
decrease in TPC and antioxidant activity of the
extract, with a more pronounced effect when hot-
air was used as the drying method (53). Conversely,
a previous study on microwave drying of lemon
peel demonstrated an increased TPC when the
applied power was augmented. This behavior was
attributed to the generation of high vapor pressure
and temperature inside the plant tissue caused by
the intense heat produced by microwaves, leading
to the disruption of plant cell wall polymers. As
a result, bound or cell wall phenolics may be
released, potentially resulting in an increased
extraction of phenolic compounds (41).
12Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
Figure 6. Behavior of the total polyphenols content (a), and the
DPPH radical scavenging activity (b) of the BSG samples as a
function of drying temperature.
CONCLUSIONS
Drying kinetics of Brewer´s spent grain at different
temperatures (50 °C, 60 °C, 70 °C, 80 °C, 90 °C, and
105 °C), and the effect of the drying temperature on
the physical properties and the content of bioactive
compounds were studied. It was observed that the
internal diffusion of moisture limited the drying speed;
the internal resistance is the governing mechanism
for moisture transfer. The effective diffusivity values
determined ranged from 5.23x10 -10 (m2 /s) to 2.49x10 -
09 (m2 /s), and the activation energy value was 28.05
kJ/mol. The Page and Midilli-Kucuk models showed
the best fit for the experimental data. In particular,
a kinetic model with two parameters, such as the
Page model, was sufficient to adequately describe
the drying kinetics of BSG without the need to use a
more complex equation using a greater number of
parameters. Regardless of the drying temperature,
the obtained BSG presented a low water activity and
low intrinsic humidity that favors, in principle, greater
storage and conservation times. It could be observed
that the total phenolic content of 1.27 (±0.120) mg
EAG/g BSG and DPPH radical scavenging activity
0.21 (±0.015) mg EAG/g BSG, present in the extract
obtained from BSG, was not affected by temperature
variation in the studied range. Therefore, phenolic
compounds have antioxidant properties and can
be used as animal food supplements. From an
operational point of view, it is possible to conclude
that the most suitable temperature for the drying
process of BSG was 105 °C since it allowed shorter
drying times. The latter would result in lower energy
and operating costs. Studies are recommended to
extract polyphenols utilizing Ultrasound-assisted
extraction (UAE) on a larger scale (pilot or industrial)
to determine the feasibility of reusing BSG as a source
of antioxidant substances by evaluating economic
aspects, energy, and operations.
Conflicts of Interest: The authors declare no
conflict of interest.
Acknowledgement: The authors acknowledge to
Universidad Pedagógica y Tecnológica de Colombia
(UPTC), Magia Artesanal S.A.S. company and its
research group INVEAGRO, Consejo Nacional de
Investigaciones Científicas y Técnicas (CONICET)
and Universidad de Buenos Aires for financial
support.
Author Contributions: Conceptualization was
devised by A.L.-C. and C.M.-J; methodology,
validation, and formal analyses, investigation,
resources, data curation, writing—original draft
preparation and writing—review and editing, data
visualization was performed by E.G.-D.; project
administration and funding acquisition were
performed by A.L.-C. All authors have read and
agreed to the published version of the manuscript.
REFERENCES
1. Gómez-Corona C, Escalona-Buendía H, García M, Chollet S,
Valentin D. Craft vs. industrial: Habits, attitudes and motivations
towards beer consumption in Mexico. Appetite. 2016;96:358–67.
DOI: https://doi.org/10.1016/j.appet.2015.10.002
2. Villacreces S, Blanco C, Caballero I. Developments and
characteristics of craft beer production processes. Food Biosci.
2022;45:101495. DOI: https://doi.org/10.1016/j.fbio.2021.101495
3. Melewar T, Skinner H. Territorial brand management: Beer,
authenticity, and sense of place. J Bus Res. 2020;116:680–9. DOI:
https://doi.org/10.1016/j.jbusres.2018.03.038
Figure 6. Behavior of the total polyphenols content (a), and the
DPPH radical scavenging activity (b) of the BSG samples as a
function of drying temperature.
CONCLUSIONS
Drying kinetics of Brewer´s spent grain at different
temperatures (50 °C, 60 °C, 70 °C, 80 °C, 90 °C, and
105 °C), and the effect of the drying temperature on
the physical properties and the content of bioactive
compounds were studied. It was observed that the
internal diffusion of moisture limited the drying speed;
the internal resistance is the governing mechanism
for moisture transfer. The effective diffusivity values
determined ranged from 5.23x10 -10 (m2 /s) to 2.49x10 -
09 (m2 /s), and the activation energy value was 28.05
kJ/mol. The Page and Midilli-Kucuk models showed
the best fit for the experimental data. In particular,
a kinetic model with two parameters, such as the
Page model, was sufficient to adequately describe
the drying kinetics of BSG without the need to use a
more complex equation using a greater number of
parameters. Regardless of the drying temperature,
the obtained BSG presented a low water activity and
low intrinsic humidity that favors, in principle, greater
storage and conservation times. It could be observed
that the total phenolic content of 1.27 (±0.120) mg
EAG/g BSG and DPPH radical scavenging activity
0.21 (±0.015) mg EAG/g BSG, present in the extract
obtained from BSG, was not affected by temperature
variation in the studied range. Therefore, phenolic
compounds have antioxidant properties and can
be used as animal food supplements. From an
operational point of view, it is possible to conclude
that the most suitable temperature for the drying
process of BSG was 105 °C since it allowed shorter
drying times. The latter would result in lower energy
and operating costs. Studies are recommended to
extract polyphenols utilizing Ultrasound-assisted
extraction (UAE) on a larger scale (pilot or industrial)
to determine the feasibility of reusing BSG as a source
of antioxidant substances by evaluating economic
aspects, energy, and operations.
Conflicts of Interest: The authors declare no
conflict of interest.
Acknowledgement: The authors acknowledge to
Universidad Pedagógica y Tecnológica de Colombia
(UPTC), Magia Artesanal S.A.S. company and its
research group INVEAGRO, Consejo Nacional de
Investigaciones Científicas y Técnicas (CONICET)
and Universidad de Buenos Aires for financial
support.
Author Contributions: Conceptualization was
devised by A.L.-C. and C.M.-J; methodology,
validation, and formal analyses, investigation,
resources, data curation, writing—original draft
preparation and writing—review and editing, data
visualization was performed by E.G.-D.; project
administration and funding acquisition were
performed by A.L.-C. All authors have read and
agreed to the published version of the manuscript.
REFERENCES
1. Gómez-Corona C, Escalona-Buendía H, García M, Chollet S,
Valentin D. Craft vs. industrial: Habits, attitudes and motivations
towards beer consumption in Mexico. Appetite. 2016;96:358–67.
DOI: https://doi.org/10.1016/j.appet.2015.10.002
2. Villacreces S, Blanco C, Caballero I. Developments and
characteristics of craft beer production processes. Food Biosci.
2022;45:101495. DOI: https://doi.org/10.1016/j.fbio.2021.101495
3. Melewar T, Skinner H. Territorial brand management: Beer,
authenticity, and sense of place. J Bus Res. 2020;116:680–9. DOI:
https://doi.org/10.1016/j.jbusres.2018.03.038
13Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
4. Anderson H, Santos I, Hildenbrand Z, Schug K. A review of the
analytical methods used for beer ingredient and finished product
analysis and quality control. Anal Chim Acta. 2019;1085:1–20.
DOI: https://doi.org/10.1016/j.aca.2019.07.061
5. Mussatto S, Dragone G, Roberto I. Brewers’ spent grain:
Generation, characteristics and potential applications. J
Cereal Sci. 2006;43(1):1–14. DOI: https://doi.org/10.1016/j.
jcs.2005.06.001
6. Sganzerla W, Ampese L, Mussatto S, Forster-Carneiro T. A
bibliometric analysis on potential uses of brewer’s spent grains
in a biorefinery for the circular economy transition of the beer
industry. Biofuels, Bioproducts and Biorefining. 2021;15(6):1965–
88. DOI: https://doi.org/10.1002/bbb.2290
7. Wagner E, Pería M, Ortiz G, Rojas N, Ghiringhelli P. Valorization
of brewer’s spent grain by different strategies of structural
destabilization and enzymatic saccharification. Ind Crops Prod.
2021;163. DOI: https://doi.org/10.1016/j.indcrop.2021.113329
8. Statista. Statista.com. Leading 10 countries in worldwide beer
production in 2020. 2020 [cited 2022 Feb 28]. Available from:
https://es.statista.com/estadisticas/1147467/lideres-produccion-
cerveza-mundial/
9. Contreras M, Lama-Muñoz A, Romero-García J, García-Vargas M,
Romero I, Castro E. Production of renewable products from brewery
spent grains. Waste Biorefinery. Elsevier Inc.; 2021. 305–347 p. DOI:
http://dx.doi.org/10.1016/B978-0-12-821879-2/00011-9
10. Chetrariu A, Dabija A. Brewer’s spent grains: Possibilities of
valorization, a review. Applied Sciences. 2020;10(16):1–17. DOI:
https://doi.org/10.3390/app10165619
11. Mussatto S, Fernandes M, Rocha G, Ór fão J, Teixeira J,
Roberto I. Production, characterization and application of
activated carbon from Brewer’s spent grain lignin. Bioresour
Technol. 2010;101(7):2450–7. DOI: http://dx.doi.org/10.1016/j.
biortech.2009.11.025
12. Antar M, Lyu D, Nazari M, Shah A, Zhou X, Smith D. Biomass
for a sustainable bioeconomy: An overview of world biomass
production and utilization. Renewable and Sustainable Energy
Reviews. 2021;139:110691. DOI: https://doi.org/10.1016/j.
rser.2020.110691
13. Patermann C, Aguilar A. A bioeconomy for the next decade.
EFB Bioeconomy Journal. 2021;1:100005. DOI: https://doi.
org/10.1016/j.bioeco.2021.100005
14. Brandão A, Gonçalves A, Santos J. Circular bioeconomy
strategies: From scientific research to commercially viable
products. J Clean Prod. 2021;295. DOI: https://doi.org/10.1016/j.
jclepro.2021.126407
15. Hadley E, Hartley S, McLeod C, Polson P. The Sustainable Path
to a Circular Bioeconomy. Trends Biotechnol. 2021;39(6):542–5.
DOI: https://doi.org/10.1016/j.tibtech.2020.10.015
16. Stegmann P, Londo M, Junginger M. The circular bioeconomy: Its
elements and role in European bioeconomy clusters. Resources,
Conservation and Recycling: X. 2020;6:100029. DOI: https://doi.
org/10.1016/j.rcrx.2019.100029
17. Kao T. Health Potential for Beer Brewing Byproducts. Current
Topics on Superfoods. 2018. DOI: https://doi.org/10.5772/
intechopen.76126
18. Maqhuzu A, Yoshikawa K, Takahashi F. Prospective utilization of
brewers’ spent grains (BSG) for energy and food in Africa and its
global warming potential. Sustain Prod Consum. 2020;26:146–59.
DOI: https://doi.org/10.1016/j.spc.2020.09.022
19. Mallen E, Najdanovic-Visak V. Brewers’ spent grains: Drying
kinetics and biodiesel production. Bioresour Technol Rep.
2018;1:16–23. DOI: https://linkinghub.elsevier.com/retrieve/pii/
S2589014X18300057
20. Rojas-Chamorro J, Cara C, Romero I, Ruiz E, Romero-García
J, Mussat to S. Ethanol Produc tion from Brewers’ Spent
Grain Pretreated by Dilute Phosphoric Acid. Energy and
Fuels. 2018;32(4):5226–33. DOI: https://doi.org/10.1021/acs.
energyfuels.8b00343
21. Cancelliere R, Carbone K, Pagano M, Cacciotti I, Micheli L. Biochar
from Brewers’ Spent Grain: A Green and Low-Cost Smart Material
to Modify Screen-Printed Electrodes. Biosensors. 2019;9(4):139.
DOI: https://www.mdpi.com/2079-6374/9/4/139
22. Gonçalves G, Nakamura P, Furtado D, Veit M. Utilization of
brewery residues to produces granular activated carbon and bio-
oil. J Clean Prod. 2017;168:908–16. DOI: https://doi.org/10.1016/j.
jclepro.2017.09.089
23. Thai S, Avena-Bustillos R, Alves P, Pan J, Osorio-Ruiz A, Miller
J. Influence of drying methods on health indicators of brewers
spent grain for potential upcycling into food products. Applied
Food Research. 2022;2(1):100052. DOI: https://doi.org/10.1016/j.
afres.2022.100052
24. Singh A, Mandal R, Shojaei M, Singh A, Kowalczewski P, Ligaj M.
Novel drying methods for sustainable upcycling of brewers’ spent
grains as a plant protein source. Sustainability. 2020;12(9):1–17.
DOI: https://doi.org/10.3390/su12093660
25. Mussatto S. Brewer’s spent grain: A valuable feedstock for
industrial applications. J Sci Food Agric. 2014;94(7):1264–75.
DOI: https://doi.org/10.1002/jsfa.6486
26. Kong D, Wang Y, Li M, Liu X, Huang M, Li X. Analysis of drying
kinetics, energy and microstructural properties of turnips using a
solar drying system. Solar Energy. 2021;230:721–31. DOI: https://
doi.org/10.1016/j.solener.2021.10.073
27. Hasibuan R, Sari W, Manurung R, Alexande V. Drying Kinetic
Models of Rice Applying Fluidized Bed Dryer. Mathematical
Modelling of Engineering Problems. 2023 28;10(1):334–9. DOI:
https://doi.org/10.18280/mmep.100138
28. Perazzini H, Perazzini M, Freire F, Freire F, Freire J. Modeling and
cost analysis of drying of citrus residues as biomass in rotary dryer
for bioenergy. Renew Energy. 2021;175:167–78. DOI: https://doi.
org/10.1016/j.renene.2021.04.144
29. Dhurve P, Kumar V, Kumar D, Malakar S. Drying kinetics, mass
transfer parameters, and specific energy consumption analysis of
watermelon seeds dried using the convective dryer. Mater Today
Proc. 2022. DOI: https://doi.org/10.1016/j.matpr.2022.02.008
30. Huang D, Yang P, Tang X, Luo L, Sunden B. Application of infrared
radiation in the drying of food products. Trends Food Sci Technol.
2021;110:765–77. DOI: https://doi.org/10.1016/j.tifs.2021.02.039
31. Ertekin C, Firat MZ. A comprehensive review of thin-layer drying
models used in agricultural products. Crit Rev Food Sci Nutr.
2017; 57(4):701–17. DOI: https://doi.org/10.1080/10408398.201
4.910493
32. Alean J, Maya JC, Chejne F. Mathematical model for the mass
transport in multiple porous scales. J Food Eng. 2018;233:28–39.
DOI: https://doi.org/10.1016/j.jfoodeng.2018.03.024
33. Chen D, Zheng Y, Zhu X. Determination of effective moisture
dif f usivit y and dr ying k inetic s for p oplar s awdus t by
thermogravimetric analysis under isothermal condition. Bioresour
Technol. 2012;107:451–5. DOI: http://dx.doi.org/10.1016/j.
biortech.2011.12.032
34. Vega-Gálvez A, Miranda M, Díaz LP, Lopez L, Rodriguez K, di Scala
K. Effective moisture diffusivity determination and mathematical
modelling of the drying curves of the olive-waste cake. Bioresour
Technol. 2010;101(19):7265–70. DOI: https://linkinghub.elsevier.
com/retrieve/pii/S0960852410007224
35. Crank J. The mathematics of diffusion. 2nd ed. Oxford university
press; 1979.
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
4. Anderson H, Santos I, Hildenbrand Z, Schug K. A review of the
analytical methods used for beer ingredient and finished product
analysis and quality control. Anal Chim Acta. 2019;1085:1–20.
DOI: https://doi.org/10.1016/j.aca.2019.07.061
5. Mussatto S, Dragone G, Roberto I. Brewers’ spent grain:
Generation, characteristics and potential applications. J
Cereal Sci. 2006;43(1):1–14. DOI: https://doi.org/10.1016/j.
jcs.2005.06.001
6. Sganzerla W, Ampese L, Mussatto S, Forster-Carneiro T. A
bibliometric analysis on potential uses of brewer’s spent grains
in a biorefinery for the circular economy transition of the beer
industry. Biofuels, Bioproducts and Biorefining. 2021;15(6):1965–
88. DOI: https://doi.org/10.1002/bbb.2290
7. Wagner E, Pería M, Ortiz G, Rojas N, Ghiringhelli P. Valorization
of brewer’s spent grain by different strategies of structural
destabilization and enzymatic saccharification. Ind Crops Prod.
2021;163. DOI: https://doi.org/10.1016/j.indcrop.2021.113329
8. Statista. Statista.com. Leading 10 countries in worldwide beer
production in 2020. 2020 [cited 2022 Feb 28]. Available from:
https://es.statista.com/estadisticas/1147467/lideres-produccion-
cerveza-mundial/
9. Contreras M, Lama-Muñoz A, Romero-García J, García-Vargas M,
Romero I, Castro E. Production of renewable products from brewery
spent grains. Waste Biorefinery. Elsevier Inc.; 2021. 305–347 p. DOI:
http://dx.doi.org/10.1016/B978-0-12-821879-2/00011-9
10. Chetrariu A, Dabija A. Brewer’s spent grains: Possibilities of
valorization, a review. Applied Sciences. 2020;10(16):1–17. DOI:
https://doi.org/10.3390/app10165619
11. Mussatto S, Fernandes M, Rocha G, Ór fão J, Teixeira J,
Roberto I. Production, characterization and application of
activated carbon from Brewer’s spent grain lignin. Bioresour
Technol. 2010;101(7):2450–7. DOI: http://dx.doi.org/10.1016/j.
biortech.2009.11.025
12. Antar M, Lyu D, Nazari M, Shah A, Zhou X, Smith D. Biomass
for a sustainable bioeconomy: An overview of world biomass
production and utilization. Renewable and Sustainable Energy
Reviews. 2021;139:110691. DOI: https://doi.org/10.1016/j.
rser.2020.110691
13. Patermann C, Aguilar A. A bioeconomy for the next decade.
EFB Bioeconomy Journal. 2021;1:100005. DOI: https://doi.
org/10.1016/j.bioeco.2021.100005
14. Brandão A, Gonçalves A, Santos J. Circular bioeconomy
strategies: From scientific research to commercially viable
products. J Clean Prod. 2021;295. DOI: https://doi.org/10.1016/j.
jclepro.2021.126407
15. Hadley E, Hartley S, McLeod C, Polson P. The Sustainable Path
to a Circular Bioeconomy. Trends Biotechnol. 2021;39(6):542–5.
DOI: https://doi.org/10.1016/j.tibtech.2020.10.015
16. Stegmann P, Londo M, Junginger M. The circular bioeconomy: Its
elements and role in European bioeconomy clusters. Resources,
Conservation and Recycling: X. 2020;6:100029. DOI: https://doi.
org/10.1016/j.rcrx.2019.100029
17. Kao T. Health Potential for Beer Brewing Byproducts. Current
Topics on Superfoods. 2018. DOI: https://doi.org/10.5772/
intechopen.76126
18. Maqhuzu A, Yoshikawa K, Takahashi F. Prospective utilization of
brewers’ spent grains (BSG) for energy and food in Africa and its
global warming potential. Sustain Prod Consum. 2020;26:146–59.
DOI: https://doi.org/10.1016/j.spc.2020.09.022
19. Mallen E, Najdanovic-Visak V. Brewers’ spent grains: Drying
kinetics and biodiesel production. Bioresour Technol Rep.
2018;1:16–23. DOI: https://linkinghub.elsevier.com/retrieve/pii/
S2589014X18300057
20. Rojas-Chamorro J, Cara C, Romero I, Ruiz E, Romero-García
J, Mussat to S. Ethanol Produc tion from Brewers’ Spent
Grain Pretreated by Dilute Phosphoric Acid. Energy and
Fuels. 2018;32(4):5226–33. DOI: https://doi.org/10.1021/acs.
energyfuels.8b00343
21. Cancelliere R, Carbone K, Pagano M, Cacciotti I, Micheli L. Biochar
from Brewers’ Spent Grain: A Green and Low-Cost Smart Material
to Modify Screen-Printed Electrodes. Biosensors. 2019;9(4):139.
DOI: https://www.mdpi.com/2079-6374/9/4/139
22. Gonçalves G, Nakamura P, Furtado D, Veit M. Utilization of
brewery residues to produces granular activated carbon and bio-
oil. J Clean Prod. 2017;168:908–16. DOI: https://doi.org/10.1016/j.
jclepro.2017.09.089
23. Thai S, Avena-Bustillos R, Alves P, Pan J, Osorio-Ruiz A, Miller
J. Influence of drying methods on health indicators of brewers
spent grain for potential upcycling into food products. Applied
Food Research. 2022;2(1):100052. DOI: https://doi.org/10.1016/j.
afres.2022.100052
24. Singh A, Mandal R, Shojaei M, Singh A, Kowalczewski P, Ligaj M.
Novel drying methods for sustainable upcycling of brewers’ spent
grains as a plant protein source. Sustainability. 2020;12(9):1–17.
DOI: https://doi.org/10.3390/su12093660
25. Mussatto S. Brewer’s spent grain: A valuable feedstock for
industrial applications. J Sci Food Agric. 2014;94(7):1264–75.
DOI: https://doi.org/10.1002/jsfa.6486
26. Kong D, Wang Y, Li M, Liu X, Huang M, Li X. Analysis of drying
kinetics, energy and microstructural properties of turnips using a
solar drying system. Solar Energy. 2021;230:721–31. DOI: https://
doi.org/10.1016/j.solener.2021.10.073
27. Hasibuan R, Sari W, Manurung R, Alexande V. Drying Kinetic
Models of Rice Applying Fluidized Bed Dryer. Mathematical
Modelling of Engineering Problems. 2023 28;10(1):334–9. DOI:
https://doi.org/10.18280/mmep.100138
28. Perazzini H, Perazzini M, Freire F, Freire F, Freire J. Modeling and
cost analysis of drying of citrus residues as biomass in rotary dryer
for bioenergy. Renew Energy. 2021;175:167–78. DOI: https://doi.
org/10.1016/j.renene.2021.04.144
29. Dhurve P, Kumar V, Kumar D, Malakar S. Drying kinetics, mass
transfer parameters, and specific energy consumption analysis of
watermelon seeds dried using the convective dryer. Mater Today
Proc. 2022. DOI: https://doi.org/10.1016/j.matpr.2022.02.008
30. Huang D, Yang P, Tang X, Luo L, Sunden B. Application of infrared
radiation in the drying of food products. Trends Food Sci Technol.
2021;110:765–77. DOI: https://doi.org/10.1016/j.tifs.2021.02.039
31. Ertekin C, Firat MZ. A comprehensive review of thin-layer drying
models used in agricultural products. Crit Rev Food Sci Nutr.
2017; 57(4):701–17. DOI: https://doi.org/10.1080/10408398.201
4.910493
32. Alean J, Maya JC, Chejne F. Mathematical model for the mass
transport in multiple porous scales. J Food Eng. 2018;233:28–39.
DOI: https://doi.org/10.1016/j.jfoodeng.2018.03.024
33. Chen D, Zheng Y, Zhu X. Determination of effective moisture
dif f usivit y and dr ying k inetic s for p oplar s awdus t by
thermogravimetric analysis under isothermal condition. Bioresour
Technol. 2012;107:451–5. DOI: http://dx.doi.org/10.1016/j.
biortech.2011.12.032
34. Vega-Gálvez A, Miranda M, Díaz LP, Lopez L, Rodriguez K, di Scala
K. Effective moisture diffusivity determination and mathematical
modelling of the drying curves of the olive-waste cake. Bioresour
Technol. 2010;101(19):7265–70. DOI: https://linkinghub.elsevier.
com/retrieve/pii/S0960852410007224
35. Crank J. The mathematics of diffusion. 2nd ed. Oxford university
press; 1979.
14Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
36. Hall KR, Eagleton LC, Acrivos A, Vermeulen T. Pore- and solid-
diffusion kinetics in fixed-bed adsorption under constant-pattern
conditions. Industrial and Engineering Chemistry Fundamentals.
1966;5(2):212–23. DOI: https://doi.org/10.1021/i160018a011
37. Arranz JI, Miranda MT, Sepúlveda FJ, Montero I, Rojas CV.
Analysis of Drying of Brewers’ Spent Grain. Proc West Mark
Ed Assoc Conf. 2018;2(23):1467. DOI: https://doi.org/10.3390/
proceedings2231467
38. Shroti GK, Saini CS. Development of edible films from protein
of brewer’s spent grain: Effect of pH and protein concentration
on physical, mechanical and barrier properties of films. Applied
Food Research. 2022;2(1):100043. DOI: https://doi.org/10.1016/j.
afres.2022.100043
39. Medina-Jaramillo C, Quintero-Pimiento C, Díaz-Díaz D,
Goyanes S, López- Córdoba A. Improvement of andean
blueberries postharvest preservation using carvacrol/alginate-
edible coatings. Polymers. 2020;12(10):1–17. DOI: https://doi.
org/10.3390/polym12102352
40. Brand-Williams W, Cuvelier ME, Berset C. Use of a free radical
method to evaluate antioxidant activity. LWT - Food Science
and Technology. 1995;28(1):25–30. DOI: https://doi.org/10.1016/
S0023-6438(95)80008-5
41. Ghanem N, Mihoubi D, Bonazzi C, Kechaou N, Boudhrioua N.
Drying Characteristics of Lemon By-product (Citrus limon. v.
lunari): Effects of Drying Modes on Quality Attributes Kinetics’.
Waste Biomass Valorization. 2020;11(1):303–22. DOI: https://doi.
org/10.1007/s12649-018-0381-z
42. Bryś A, Kaleta A, Górnicki K, Głowacki S, Tulej W, Bryś J. Some
Aspects of the Modelling of Thin-Layer Drying of Sawdust.
Energies. 2021;14(3):726. DOI: ht tps://doi.org/10.3390/
en14030726
43. Hussain M, Zabiri H, Tufa LD, Yusup S, Ali I. A kinetic study and
thermal decomposition characteristics of palm kernel shell using
model-fitting and model-free methods. Biofuels. 2022;13(1):105–
16. DOI: https://doi.org/10.1080/17597269.2019.1642642
44. Arranz JI, Sepúlveda FJ, Montero I, Romero P, Miranda MT.
Feasibility analysis of brewers’ spent grain for energy use: Waste
and experimental pellets. Applied Sciences. 2021;11(6). DOI:
https://doi.org/10.3390/app11062740
45. Sozzi A, Zambon M, Mazza G, Salvatori D. Fluidized bed drying
of blackberry wastes: Drying kinetics, particle characterization
and nutritional value of the obtained granular solids. Powder
Technol. 2021;385:37– 49. DOI: https://doi.org/10.1016/j.
powtec.2021.02.058
46. Lopez A, Iguaz A, Esnoz A, Virseda P. Thin-layer dr ying
behaviour of vegetable wastes from wholesale market.
Drying Technology. 2000;18(4–5):995–1006. DOI: https://doi.
org/10.1080/07373930008917749
47. Maia GD, Horta ACL, Felizardo MP. From the conventional
to the intermittent biodrying of orange solid waste biomass.
Chemical Engineering and Processing - Process Intensification.
2023;188:109361. DOI: https://doi.org/10.1016/j.cep.2023.109361
48. EL-Mesery HS, El-khawaga SE. Drying process on biomass:
Evaluation of the drying performance and energy analysis
of different dryers. Case Studies in Thermal Engineering.
2022;33:101953. DOI: https://doi.org/10.1016/j.csite.2022.101953
49. Ahmad-Qasem MH, Barrajon-Catalan E, Micol V, Cárcel
JA, Garcia-Perez J. Influence of air temperature on drying
kinetics and antioxidant potential of olive pomace. J Food
Eng. 2013;119(3):516 –24. DOI: ht tps://doi.org/10.1016/j.
jfoodeng.2013.06.027
50. Şahin Fİ, Acaralı N. Effective moisture diffusivity and activation
energy during convective drying of bread containing clove
oil/orange oil. Journal of the Indian Chemical Societ y.
2 0 2 3;10 0 ( 3 ):10 0 952 . D O I : h t t p s : //d o i .o r g /10 .1016 / j .
jics.2023.100952
51. Yan Y, Qi B, Zhang W, Wang X, Mo Q. Investigations into the drying
kinetics of biomass in a fluidized bed dryer using electrostatic
sensing and digital imaging techniques. Fuel. 2022;308:122000.
DOI: https://doi.org/10.1016/j.fuel.2021.122000
52. Lemus-Mondaca R, Zura-Bravo L, Ah-Hen K, Di Scala K.
Effect of drying methods on drying kinetics, energy features,
thermophysical and microstructural proper ties of Stevia
rebaudiana leaves. J Sci Food Agric. 2021;101(15):6484–95. DOI:
https://doi.org/10.1002/jsfa.11320
53. Yan Z, Zhou Z, Jiao Y, Huang J, Yu Z, Zhang D, et al. Hot-Air
Drying Significantly Improves the Quality and Functional
Activity of Orange Black Tea Compared with Traditional Sunlight
Drying. Foods. 2023;12(9):1913. DOI: https://doi.org/10.3390/
foods12091913
54. Bai T, Wan Q, Liu X, Ke R, Xie Y, Zhang T. Drying kinetics and
attributes of fructus aurantii processed by hot air thin-layer drying
at different temperatures. Heliyon. 2023;9(5):e15554. DOI: https://
doi.org/10.1016/j.heliyon.2023.e15554
55. Kaveh M, Golpour I, Gonçalves JC, Ghafouri S, Guiné R.
Determination of drying kinetics, specific energy consumption,
shrinkage, and colour properties of pomegranate arils submitted
to microwave and convective drying. Open Agric. 2021;6(1):230–
42. DOI: https://doi.org/10.1515/opag-2020-0209
56. Wan Nadhari WNA, Hashim R, Danish M, Sulaiman O, Hiziroglu
S. A Model of Drying Kinetics of Acacia mangium Wood at
Different Temperatures. Drying Technology. 2014;32(3):361–70.
DOI: https://doi.org/10.1080/07373937.2013.829855
57. Nahar N, Hazra S, Raychaudhuri U, Adhikari S. Effect of different
drying methods on drying kinetics, modeling, energy-economic,
texture profile, color, and antioxidant of lotus rhizomes (Nelumbo
nucifera). J Food Process Preserv. 2022;46(10). DOI: https://doi.
org/10.1111/jfpp.16842
58. Huang D, Men K, Li D, Wen T, Gong Z, Sunden B. Application of
ultrasound technology in the drying of food products. Ultrason
Sonochem. 2020;63:104950. DOI: https://doi.org/10.1016/j.
ultsonch.2019.104950
36. Hall KR, Eagleton LC, Acrivos A, Vermeulen T. Pore- and solid-
diffusion kinetics in fixed-bed adsorption under constant-pattern
conditions. Industrial and Engineering Chemistry Fundamentals.
1966;5(2):212–23. DOI: https://doi.org/10.1021/i160018a011
37. Arranz JI, Miranda MT, Sepúlveda FJ, Montero I, Rojas CV.
Analysis of Drying of Brewers’ Spent Grain. Proc West Mark
Ed Assoc Conf. 2018;2(23):1467. DOI: https://doi.org/10.3390/
proceedings2231467
38. Shroti GK, Saini CS. Development of edible films from protein
of brewer’s spent grain: Effect of pH and protein concentration
on physical, mechanical and barrier properties of films. Applied
Food Research. 2022;2(1):100043. DOI: https://doi.org/10.1016/j.
afres.2022.100043
39. Medina-Jaramillo C, Quintero-Pimiento C, Díaz-Díaz D,
Goyanes S, López- Córdoba A. Improvement of andean
blueberries postharvest preservation using carvacrol/alginate-
edible coatings. Polymers. 2020;12(10):1–17. DOI: https://doi.
org/10.3390/polym12102352
40. Brand-Williams W, Cuvelier ME, Berset C. Use of a free radical
method to evaluate antioxidant activity. LWT - Food Science
and Technology. 1995;28(1):25–30. DOI: https://doi.org/10.1016/
S0023-6438(95)80008-5
41. Ghanem N, Mihoubi D, Bonazzi C, Kechaou N, Boudhrioua N.
Drying Characteristics of Lemon By-product (Citrus limon. v.
lunari): Effects of Drying Modes on Quality Attributes Kinetics’.
Waste Biomass Valorization. 2020;11(1):303–22. DOI: https://doi.
org/10.1007/s12649-018-0381-z
42. Bryś A, Kaleta A, Górnicki K, Głowacki S, Tulej W, Bryś J. Some
Aspects of the Modelling of Thin-Layer Drying of Sawdust.
Energies. 2021;14(3):726. DOI: ht tps://doi.org/10.3390/
en14030726
43. Hussain M, Zabiri H, Tufa LD, Yusup S, Ali I. A kinetic study and
thermal decomposition characteristics of palm kernel shell using
model-fitting and model-free methods. Biofuels. 2022;13(1):105–
16. DOI: https://doi.org/10.1080/17597269.2019.1642642
44. Arranz JI, Sepúlveda FJ, Montero I, Romero P, Miranda MT.
Feasibility analysis of brewers’ spent grain for energy use: Waste
and experimental pellets. Applied Sciences. 2021;11(6). DOI:
https://doi.org/10.3390/app11062740
45. Sozzi A, Zambon M, Mazza G, Salvatori D. Fluidized bed drying
of blackberry wastes: Drying kinetics, particle characterization
and nutritional value of the obtained granular solids. Powder
Technol. 2021;385:37– 49. DOI: https://doi.org/10.1016/j.
powtec.2021.02.058
46. Lopez A, Iguaz A, Esnoz A, Virseda P. Thin-layer dr ying
behaviour of vegetable wastes from wholesale market.
Drying Technology. 2000;18(4–5):995–1006. DOI: https://doi.
org/10.1080/07373930008917749
47. Maia GD, Horta ACL, Felizardo MP. From the conventional
to the intermittent biodrying of orange solid waste biomass.
Chemical Engineering and Processing - Process Intensification.
2023;188:109361. DOI: https://doi.org/10.1016/j.cep.2023.109361
48. EL-Mesery HS, El-khawaga SE. Drying process on biomass:
Evaluation of the drying performance and energy analysis
of different dryers. Case Studies in Thermal Engineering.
2022;33:101953. DOI: https://doi.org/10.1016/j.csite.2022.101953
49. Ahmad-Qasem MH, Barrajon-Catalan E, Micol V, Cárcel
JA, Garcia-Perez J. Influence of air temperature on drying
kinetics and antioxidant potential of olive pomace. J Food
Eng. 2013;119(3):516 –24. DOI: ht tps://doi.org/10.1016/j.
jfoodeng.2013.06.027
50. Şahin Fİ, Acaralı N. Effective moisture diffusivity and activation
energy during convective drying of bread containing clove
oil/orange oil. Journal of the Indian Chemical Societ y.
2 0 2 3;10 0 ( 3 ):10 0 952 . D O I : h t t p s : //d o i .o r g /10 .1016 / j .
jics.2023.100952
51. Yan Y, Qi B, Zhang W, Wang X, Mo Q. Investigations into the drying
kinetics of biomass in a fluidized bed dryer using electrostatic
sensing and digital imaging techniques. Fuel. 2022;308:122000.
DOI: https://doi.org/10.1016/j.fuel.2021.122000
52. Lemus-Mondaca R, Zura-Bravo L, Ah-Hen K, Di Scala K.
Effect of drying methods on drying kinetics, energy features,
thermophysical and microstructural proper ties of Stevia
rebaudiana leaves. J Sci Food Agric. 2021;101(15):6484–95. DOI:
https://doi.org/10.1002/jsfa.11320
53. Yan Z, Zhou Z, Jiao Y, Huang J, Yu Z, Zhang D, et al. Hot-Air
Drying Significantly Improves the Quality and Functional
Activity of Orange Black Tea Compared with Traditional Sunlight
Drying. Foods. 2023;12(9):1913. DOI: https://doi.org/10.3390/
foods12091913
54. Bai T, Wan Q, Liu X, Ke R, Xie Y, Zhang T. Drying kinetics and
attributes of fructus aurantii processed by hot air thin-layer drying
at different temperatures. Heliyon. 2023;9(5):e15554. DOI: https://
doi.org/10.1016/j.heliyon.2023.e15554
55. Kaveh M, Golpour I, Gonçalves JC, Ghafouri S, Guiné R.
Determination of drying kinetics, specific energy consumption,
shrinkage, and colour properties of pomegranate arils submitted
to microwave and convective drying. Open Agric. 2021;6(1):230–
42. DOI: https://doi.org/10.1515/opag-2020-0209
56. Wan Nadhari WNA, Hashim R, Danish M, Sulaiman O, Hiziroglu
S. A Model of Drying Kinetics of Acacia mangium Wood at
Different Temperatures. Drying Technology. 2014;32(3):361–70.
DOI: https://doi.org/10.1080/07373937.2013.829855
57. Nahar N, Hazra S, Raychaudhuri U, Adhikari S. Effect of different
drying methods on drying kinetics, modeling, energy-economic,
texture profile, color, and antioxidant of lotus rhizomes (Nelumbo
nucifera). J Food Process Preserv. 2022;46(10). DOI: https://doi.
org/10.1111/jfpp.16842
58. Huang D, Men K, Li D, Wen T, Gong Z, Sunden B. Application of
ultrasound technology in the drying of food products. Ultrason
Sonochem. 2020;63:104950. DOI: https://doi.org/10.1016/j.
ultsonch.2019.104950
15Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Figure S1. Drying curves at 105°C using different mass of Brewer´s spent grain.
Figure S2. Ln MR vs time, for determination Deff at different temperatures 50, 60 y 70 °C a) and 80, 90, 105°C b).
Appendix A. Supplementary data
Analysis of drying kinetic of brewer´s spent grains: effect of
the temperature on the physical properties and the content
of bioactive compounds
Análisis de la cinética de secado del bagazo residual de malta: efecto de la
temperatura sobre las propiedades físicas y el contenido de compuestos bioactivo
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Figure S1. Drying curves at 105°C using different mass of Brewer´s spent grain.
Figure S2. Ln MR vs time, for determination Deff at different temperatures 50, 60 y 70 °C a) and 80, 90, 105°C b).
Appendix A. Supplementary data
Analysis of drying kinetic of brewer´s spent grains: effect of
the temperature on the physical properties and the content
of bioactive compounds
Análisis de la cinética de secado del bagazo residual de malta: efecto de la
temperatura sobre las propiedades físicas y el contenido de compuestos bioactivo
16Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 02 | Article 351025E. Gomez-Delgado, C. Medina Jaramillo, A. Lopez-Cordoba
Figure S3. Plot Ln (Deff ) vs 1/(T+273.15)
Figure S4. Kinetic models to describe the drying process using different masses of BSG to dry: 5g (a), 10 (b) and 15g (c). Drying
temperature: 105 °C.
Figure S3. Plot Ln (Deff ) vs 1/(T+273.15)
Figure S4. Kinetic models to describe the drying process using different masses of BSG to dry: 5g (a), 10 (b) and 15g (c). Drying
temperature: 105 °C.
17Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 02 | Article 351025
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Table S1. Parameters of the different drying kinetic models using different BSG mass at constant temperature of 105°C.
Modelo
Sample mass Parameters Statistics
(g) a b n K (s n
) r2 SD CV
Newton
5 - - - 0.0600 0.9748 0.053 0.233
10 - - - 0.0420 0.9647 0.065 0.222
15 - - - 0.0279 0.9585 0.073 0.189
Page
5 - - 1.4564 0.0153 0.9956 0.021 0.094
10 - - 1.5728 0.0063 0.9975 0.017 0.057
15 - - 1.5805 0.0034 0.9968 0.020 0.051
Logarítmico
5 5.00E-06 1.0693 - 0.0639 0.9767 0.048 0.211
10 5.00E-08 1.0968 - 0.0458 0.9700 0.056 0.190
15 8.00E-08 1.1000 - 0.0308 0.9670 0.062 0.159
Midilli-Kucuk
5 0.9548 9.21E-06 1.6085 0.0092 0.9966 0.018 0.078
10 0.9711 5.00E-07 1.6678 0.0044 0.9979 0.014 0.048
15 0.9795 6.00E-08 1.6464 0.0026 0.9969 0.018 0.047
Figure S5. Brewer´s spent grain (BSG), BSG dry and entire (left) and BSG dry and ground (right).
Table S2. Drying kinetic models parameters, at a constant temperature of 105°C.
Temperature (°C)
Whole BSG Ground BSG
L a+ b- ΔE L a+ b- ΔE
50 31.8 8.7 26.5 58.10 53.9 4.8 17.5 34.30
60 32.1 6.5 24.1 56.36 50.2 5.2 16.8 37.04
70 33.9 10.5 24.2 55.54 51.8 2.5 19.7 36.95
80 32.5 9.8 24.7 56.84 52.6 4.7 17.2 35.17
90 34.1 9.1 22.9 54.48 53.1 3.9 18.5 35.37
105 33.5 10.2 23.9 55.68 54.2 5.2 18.1 34.48
Analysis of drying kinetic of brewer´s spent grains: effect of the temperature on the physical properties and the content of bioactive compounds
Table S1. Parameters of the different drying kinetic models using different BSG mass at constant temperature of 105°C.
Modelo
Sample mass Parameters Statistics
(g) a b n K (s n
) r2 SD CV
Newton
5 - - - 0.0600 0.9748 0.053 0.233
10 - - - 0.0420 0.9647 0.065 0.222
15 - - - 0.0279 0.9585 0.073 0.189
Page
5 - - 1.4564 0.0153 0.9956 0.021 0.094
10 - - 1.5728 0.0063 0.9975 0.017 0.057
15 - - 1.5805 0.0034 0.9968 0.020 0.051
Logarítmico
5 5.00E-06 1.0693 - 0.0639 0.9767 0.048 0.211
10 5.00E-08 1.0968 - 0.0458 0.9700 0.056 0.190
15 8.00E-08 1.1000 - 0.0308 0.9670 0.062 0.159
Midilli-Kucuk
5 0.9548 9.21E-06 1.6085 0.0092 0.9966 0.018 0.078
10 0.9711 5.00E-07 1.6678 0.0044 0.9979 0.014 0.048
15 0.9795 6.00E-08 1.6464 0.0026 0.9969 0.018 0.047
Figure S5. Brewer´s spent grain (BSG), BSG dry and entire (left) and BSG dry and ground (right).
Table S2. Drying kinetic models parameters, at a constant temperature of 105°C.
Temperature (°C)
Whole BSG Ground BSG
L a+ b- ΔE L a+ b- ΔE
50 31.8 8.7 26.5 58.10 53.9 4.8 17.5 34.30
60 32.1 6.5 24.1 56.36 50.2 5.2 16.8 37.04
70 33.9 10.5 24.2 55.54 51.8 2.5 19.7 36.95
80 32.5 9.8 24.7 56.84 52.6 4.7 17.2 35.17
90 34.1 9.1 22.9 54.48 53.1 3.9 18.5 35.37
105 33.5 10.2 23.9 55.68 54.2 5.2 18.1 34.48