Аннотация и ключевые слова
Аннотация (русский):
Gelatin is a natural amphiphilic biopolymer that is widely used in food products, pharmaceuticals, and cosmetics. We studied the effect of spray and freeze drying on the solubility and amphiphilicity of gelatin samples. The control sample was a commercially produced edible gelatin. The experimental samples were spray- and freeze-dried gelatins obtained by enzymatic-acid hydrolysis of cattle bone. Amino acid sequences were determined by matrix-activated laser desorption/ionization. Solubility was assessed visually. Bloom strength of the gelatin gels was measured by a texture analyzer. The ProtScale online service was used to predict the amphiphilic topology of gelatin proteins. Molecular weight distribution of proteins was carried out by electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate. Spray drying reduced protein degradation and retained more α-chains, while freeze drying increased gelatin’s hydrophobicity and decreased its solubility. The predicted topology of protein hydrophobicity based on the amino acid sequences was in line with our results on solubility. The freeze-dried gelatin had a 18% larger amount of low-molecular weight peptides, compared to the control and the spray-dried samples. This was probably caused by the cleavage of peptides during the drying process. Thus, freeze drying can lead to maximum degradation of gelatin components, which may be associated with a longer heat treatment, compared to spray drying. Thus, spray drying is more suitable for gelatin, since this method improves the stability of its outer and inner structure, ensuring high hydrophilic properties.

Ключевые слова:
Drying, gelatin, protein, amino acid sequence, hydrophilicity, hydrophobicity, solubility
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Gelatin is a protein substance that contains all
essential amino acids except tryptophan. It is formed
by cross-links between various polypeptide chains
that developed after the destruction of the fibrous
structure of collagen pre-treated with acid, alkaline, or
enzymes. This protein-based hydrocolloid has a wide
range of applications in various industries due to its
unique structural stability, nutritional properties, and
other physicochemical characteristics [1]. Particularly,
hydrogels and modified gelatin-based composites
are widely used in the food industry, biomedicine,
pharmaceuticals, and cosmetology. Gelatin is also used
in the production of food packaging materials due to its
biocompatibility, biodegradability, non-immunogenicity,
and ability to stimulate cell adhesion and proliferation.
It can absorb 5–10 times as much water as its weight
and is the main ingredient in hard and soft capsules for
pharmaceuticals [2–6].

There is a high demand for gelatin in the modern
market of food products and components, as well as in
the pharmaceutical, medical, and cosmetic markets,
with an annual average of 326 000 tons produced
worldwide. According to Grand View Research, the
global gelatin market was worth $2.91 billion in 2020.
It is estimated to grow by 8% per year and reach about
$5 billion by 2025. Russia seeks to produce food gelatin
domestically and therefore needs effective technological
and biotechnological solutions [7–10]. Current research
focuses on optimizing gelatin production technologies
and searching for new sources of raw materials to
replace the traditional ones (pig skins, bovine skins, and
cattle bones).
Today, gelatin is still produced with the technologies
developed several decades ago. The process contains
the following stages: pre-treatment of raw materials,
extraction of gelatin, processing of gelatin broths,
gelatinization, and drying. The efficiency of collagento-
gelatin conversion depends on extraction conditions
(temperature, time, and pH), concentration, the quality
of raw materials, and their pre-treatment methods.
Using chemical solvents for gelatin extraction can
result in a higher gelatin yield along with more lowmolecular-
weight protein fragments that will affect the
gel’s strength and melting point. However, industrial
production parameters are not always optimal, leading
to a low gelatin yield. Therefore, we need to search for
alternative solutions to optimize the process.
Drying is an important process to obtain gelatin
with improved functional properties. These properties
basically depend on the type of raw materials, pretreatment
methods, drying and extraction conditions,
as well as the spatial structure of protein molecules and
their state. Drying causes physicochemical changes in
the structure and functions of proteins. For example,
heating, which is part of the drying process, can break
covalent and non-covalent bonds leading to changes in
the protein structure. If significant, these changes can
greatly affect gelatin’s functional properties such as
solubility, gelation, foaming, emulsification, as well as
fat and water absorption. The extent of these changes
is mainly determined by the drying methods and
conditions [11–15].
Drying methods used in the production of protein
ingredients (including gelatin) are convection drying,
infrared drying, spray drying, and freeze drying.
Convection is the most common method of food
drying. In convection drying, a stream of heated air is
directed at a wet sample. The air here is both a heating
agent and a dehydrator, since it carries away moisture
vapor from the dryer. As a result of this lengthy process
and elevated temperatures, the final product loses a
significant amount of micronutrients and bioactive
compounds. Although this method is simple to use,
convection dryers have low productivity which can lead
to uneven drying [16, 17].
Infrared heating with microwaves is a new method
of heat treatment (drying) that extends shelf life,
reduces drying time, and preserves food quality. The
microwaves transfer water to the surface where it
quickly evaporates under the influence of infrared
radiation, which reduces the drying time [18, 19].
Spray drying is widely used in the food industry
due to its simplicity and short drying time. This method
allows for a good quality powdered product. However,
spray drying causes particles to greatly shrink and
become denser [20, 21].
Freeze drying is a process of removing water from a
product by freezing it and then converting ice into steam.
This process consists of three main stages: freezing,
primary drying, and secondary drying. Freezing creates
a solid matrix suitable for drying. Primary drying
removes ice by sublimation, when the pressure in the
system is reduced but the temperature remains the same.
Secondary drying removes bound water reducing it to
residual moisture.
Several studies indicate that protein denaturation
during the formation of ice crystals can significantly
change the protein structure. Therefore, when
optimizing the freezing process, we should take into
account the ice surface area, since it can contribute to
protein denaturation caused by freezing [22–24].
In spray drying, evaporated material is sprayed
through the nozzles of a conical-cylindrical apparatus
(spray dryer) to obtain a product in the form of a
powder or granules. This method is used to dry
solutions or suspensions. Spray-dried products include
powdered milk, food and fodder yeast, and egg powder.
According to some studies, spray drying can effectively
eliminate many of the shortcomings of protein and
bioactive peptides, such as low bioavailability, high
hygroscopicity, physical and chemical instability, as
well as strong bitterness during and after storage [13].
It is also claimed that this method can improve gelatin’s
functional properties, compared to freeze or vacuum
drying [25]. Assumingly, various drying methods
affect the solubility and amphiphilicity of gelatin as a
high-protein product, thereby changing its functional
properties [26].
We studied the effect of spray and freeze drying on
the solubility and amphiphilicity (hydrophobicity and
hydrophilicity) of gelatin which we obtained in the
previous study by enzymatic acid hydrolysis [7].
The control sample was a commercially produced
edible gelatin. The experimental samples were sprayand
freeze-dried gelatins obtained by enzymatic-acid
hydrolysis of cattle bone. For this, 3 kg of defatted
beef bones was crushed to particles of 3.0 ± 0.5 mm in
a laboratory chain grinder. The bones were obtained
from a farm in Kuzbass (Russia). The crushed bones
were placed in a solution of hydrochloric acid (1M HCl)
which contained pepsin with an enzymatic activity
of 300 000 units. The hydrolysis was carried out at
27 ± 2°C for 60 to 240 min, with a pH of 1.5–2.0. MS-01
magnetic stirrers (ELMI) were used throughout the
Voroshilin R.A. et al. Foods and Raw Materials. 2022;10(2):252–261
experiment to stir the bone material at 100 rpm and
27 ± 2°C to ensure its uniform treatment with the
solution. The hydrolyzed material was centrifuged in
a high-speed Avanti J-26S centrifuge (Beckman) to
separate the mineral sediment from ossein. Then, the
resulting ossein was washed with demineralized water
and subjected to gelatin extraction. A detailed scheme
of hydrolysis and gelatin extraction is described in our
previous work [7].
Next, the gelatin broths were dried by the spray- and
freeze-drying methods. The spray-dried gelatin was
obtained in a B-290 Mini Spray Dryer (Buchi, Sweden)
at 95°С and а rate of 3.0–3.2 mL/min. The freeze-dried
gelatin was obtained in an INEY-6M freeze-drier. For
this, gelatin broth was poured onto pallets in 1-cm layers
and placed in the drying chambers. The chambers were
closed with lids and the refrigerator was turned on. The
unit entered the freezing mode within 15 min and when
the evaporator temperature reached minus –35°С, the
vacuum pump turned on to start the drying mode. The
freeze-dried gelatin was then ground in an NS-2000
automatic laboratory mill.
The amino acid sequence of gelatin proteins, which
is represented by a single letter code, was determined
by matrix-activated laser desorption/ionization on
a MALDI Biotyper (Bruker). Amino acid residues,
isoelectric point, aliphatic index, molar absorption
coefficient, as well as the surface area of the peptides,
were determined by the in silico bioinformatic methods
on the PepDraw online server. The gelatin samples’
solubility was evaluated visually. For this, 500 mg
of gelatin was mixed with 50 mL of distilled water
and stirred actively (200 rpm) with MS-01 magnetic
stirrers (ELMI). Dissolution was monitored at water
temperatures of 25 and 50°C.
The Bloom strength of gelatin gels was determined
on a ST-2 Strukturometr texture analyzer with a Bloom
indenter. For this, 7.5 g of gelatin was placed in a glass
of cold water (105 mL) and kept at 22°C max for 180
min. Next, the swollen gelatin was heated to 60°C
in a water bath and stirred for 15 min until complete
dissolution. The solution (6.67% concentration) was
poured into a calibrated beaker and kept at 10.0 ± 0.1°C
for 17 h. The prepared samples were then placed on the
analyzer’s table under the Bloom indenter for the study.
The arithmetic mean of two determinations was taken as
the final result.
The ProtScale online service was used to predict
the topology of the hydrophobicity and hydrophilicity
of gelatin proteins. In particular, this service allows
us to compute and represent (in the form of a twodimensional
graph) the profile produced by any amino
acid scale for a selected protein. The amino acid scale
is defined by a numerical value assigned to each type of
amino acid. ProtScale uses the Kyte and Doolittle scale
that assigns individual values to 20 amino acids, namely
Ala: 1.800, Arg: –4.500, Asn: –3.500, Asp: –3.500, Cys:
2.500, Gln: –3.500, Glu: –3.500, Gly: –0.400, His:
–3.200, Ile: 4.500, Leu: 3.800, Lys: –3.900, Met: 1.900,
Phe: 2.800, Pro: –1.600, Ser: –0.800, Thr: –0.700, Trp:
–0.900, Tyr: –1.300, and Val: 4.200, –3.500, –3.500,
The molecular weight distribution of proteins was
carried out by polyacrylamide gel electrophoresis in
the presence of an anionic detergent, sodium dodecyl
sulfate (SDS-Na). For this, the dried gelatin samples
were dissolved in deionized water at 60°C to create
a 0.2% solution. The solution was then mixed with a
loading buffer containing 5 μL of dithiothreitol (DTT)
and subjected to heat denaturation in boiling water
for 5 min. After that, 15-μL samples were loaded into
polyacrylamide gels containing 6% of separating gel and
5% of stacking gel to perform electrophoresis. Then, the
gels were stained with 0.1% Coomassie Blue R-250 in
25% isopropanol and 10% acetic acid for 2 h, followed
by decoloring with 5% alcohol and 10% acetic acid.
Next, 2-D gels were detected using the Gel Doc XR Plus
Bio-RAD system.
First, we spray- and freeze-dried the experimental
samples of gelatin obtained by enzymatic acid
hydrolysis. Next, we determined the amino acid
sequence of all the dried gelatins (Table 1).
The proteins of the control, spray-dried, and freezedried
samples are represented by peptide sequences of
85, 93, and 95 amino acids, respectively (Table 1).
These sequences allowed us to determine the amino
acid composition (% or g/100 g of total amino acids) of
the control and experimental samples. This is a critical
indicator of gelatin quality largely depending on raw
Table 1 Amino acid sequences of gelatin samples (one-letter coding)*
Control Experimental samples
Spray-dried gelatin Freeze-dried gelatin
*A – alanine; C – cysteine; D – aspartic acid; E – glutamic acid; F – phenylalanine; G – glycine; H – histidine; I – isoleucine; K – lysine;
L – leucine; M – methionine; N – asparagine; P – proline; Q – glutamine; R – arginine; S – serine; T – threonine; V – valine; W – tryptophan;
Y – tyrosine
Voroshilin R.A. et al. Foods and Raw Materials. 2022;10(2):252–261
materials. Glycine and proline are the most important
amino acids in gelatin. Collagen consists of three
identical or different polypeptide chains with a repeating
pattern (Gly-XY)n (X and Y stand for any amino acid)
and a high content of imino acids with a triple helical
structure due to hydrogen bonds [27–29].
The composition and content of amino acids,
especially imino acids, in gelatin have a significant
impact on its structure and functional properties. In
particular, the gel’s supercoil structure is stabilized
by both the hydrogen bonds forming between amino
acid residues and the pyrrolidine rings of imino acids.
A higher content of imino acids ensures a higher gel
modulus, gelling temperature, and melting point [30].
The amino acid composition (% or g/100 g of total
amino acids) of the control and experimental gelatin
samples are presented in Table 2.
We found that the samples varied mostly in the
content of alanine, accounting for 25.840% in the
control sample and only 1% in the experimental samples.
None of the samples contained phenylalanine, lysine,
or tryptophan. According to literature, the absence of
tryptophan is what makes gelatin different from other
hydrocolloids of animal origin. This amino acid is
mainly present in membrane proteins and has aromatic
residues in its structure.
Histidine, arginine, and threonine were not detected
in the control sample.
Using the PepDraw online server, we determined
the mass of amino acid residues defined as a sum of
monoisotopic masses of all amino acid residues in
the peptide. We also calculated the isoelectric point
represented by a pH value at which the total charge
of the peptide equals zero. This calculation shows
the partial charge of the peptide at various pH values,
starting from 0. Then, we determined the aliphatic index
of the protein defined as a relative volume of aliphatic
side chains (alanine, valine, isoleucine, and leucine). It
can be considered a positive factor in increasing thermal
stability of globular proteins.
The mass of amino acid residues in the control,
spray-dried, and freeze-dried samples amounted to
13173.86, 10830.72, and 11156.79, respectively.
The aliphatic index values in the control, spray-dried,
and freeze-dried samples were 95.96, 87.53, and 70.74,
The isoelectric points in the control, spray-dried,
and freeze-dried samples were 5.97, 4.89, and 5.96,
The molar absorption coefficients in the control,
spray-dried, and freeze-dried samples were 8960.00,
12800.00, and 3840.00 M–1∙cm–1, respectively.
The surface area values in the control, spray-dried,
and freeze-dried samples were 21223.00, 23040.00, and
18407.00, respectively.
We concluded that the control and the spray-dried
samples had more thermostable proteins, since their
aliphatic indexes (87 and 96, respectively) were higher
than those of the freeze-dried sample (70). The samples’
isoelectric points indicated a slightly acidic reaction,
therefore their protein molecules were neutral at a pH
value of 4.89 to 5.97.
Solubility is an important property of gelatin in food
systems. In cold water, gelatin hydrates and swells, and
Table 2 Amino acid contents in the control and experimental gelatin samples
Amino acid Content of total amino acids, % or g/100 g
Control Spray-dried gelatin Freeze-dried gelatin
A – alanine 25.840 1.050 1.080
C – cysteine ND 6.320 ND
D – aspartic acid 1.120 11.580 1.080
E – glutamic acid 3.370 6.320 16.130
F – phenylalanine ND ND ND
G – glycine 8.990 9.470 2.150
H – histidine ND 6.320 6.450
I – isoleucine 8.990 7.370 8.600
K – lysine ND ND ND
L – leucine 8.990 7.370 8.600
M – methionine ND 3.160 6.450
N – asparagine 10.110 4.210 3.230
P – proline 15.730 10.530 21.510
Q – glutamine 2.250 5.260 4.300
R – arginine ND 2.110 7.530
S – serine 3.370 4.210 6.450
T – threonine 3.37 ND ND
V – valine ND 4.21 3.23
W – tryptophan ND ND ND
Y – tyrosine 7.87 10.53 3.23
ND – not detected
Voroshilin R.A. et al. Foods and Raw Materials. 2022;10(2):252–261
at temperatures above 40°C, it forms a colloidal solution
(sol). The solubility index depends on the method
of gelatin production. New methods are currently
being developed to obtain water-soluble gelatin at
temperatures below 40°C. Such gelatin usually has an
amorphous powdery form.
Next, we visually assessed the degree of solubility
of the gelatin samples at water temperatures of 25 and
50°C (Fig. 1).
As we can see, the control and the spray-dried
samples showed higher protein solubility at 25 and 50°C
than the freeze-dried sample. According to Fig. 1c and
f, gelatin particles did not dissolve after 1 min of mixing
at different temperatures, settling on the bottom and on
the surface. After 3 min of mixing at 25 or 50°C, the
freeze-dried sample still did not dissolve completely,
its particles settling on the water surface (Fig. 1f). This
could be due to the sample’s mechanical grinding in a
laboratory mill at the final stage of freeze-drying, which
resulted in larger particles than those in the spray-dried
gelatin and affected its solubility. We can also assume
that spray drying exposes protein molecules to less
thermal stress than freeze drying, which causes the
highest degree of thermal and dehydration stress.
Next, we evaluated the Bloom strength of the gelatin
gels (Fig. 2).
The Bloom value is an important parameter of
gelatin’s physical and mechanical properties used in
food production. It is also used as a criterion in gelatin
The gel strength index depends on the protein
content and the molecular weight of peptides formed
in gelatin. In our study, this index was quite high in
the control and spray-dried samples, amounting to
229.0 ± 0.5 and 224.0 ± 0.5 Bloom, respectively. The
freeze-dried sample’s index (186.0 ± 0.5 Bloom) was by
17 and 19% lower than for the control and spray-dried
samples. Assumingly, the proteins of the freeze-dried
gelatin had a lower molecular weight, which worsened
its structural and mechanical properties. We can also
assume that this sample might have more low-molecular
weight (below 20 kDa) peptides.
Next, we determined the degree of protein
hydrophilicity and hydrophobicity based on the amino
acid sequences. Using the ProtScale online service (the
Kyte and Doolittle scale), we predicted the topology of
protein hydrophobicity and hydrophilicity for the control
and experimental gelatin samples (Fig. 3).
On the Kyte and Doolittle scale, the peaks above
0 refer to hydrophobicity and those below 0 refer to
hydrophilicity. As we can see in Fig. 3a, the control
sample had higher hydrophilic properties since its peaks
along the X axis ranged from 3 to 21, with a peptide
sequence of PAAGGPAY GGPILILAPA I. Most of its
peaks were for alanine, proline, isoleucine, and glycine.
These amino acids had hydrophobic properties and 1 to
4 uncharged side radicals at pH = 6–7. In general, these
peaks characterized a sequence of amino acids with
hydrophobic properties.
Figure 1 Dissolution of gelatin samples at 25 and 50°C for 1–3 min
a b c
Freeze-dried sample, t = 25°С
1 мин. 3 мин.
1 мин. 3 мин.
1 мин. 3 мин.
a. Контрольный образец, t=25°С b. Опытный образец 1, t=25°С c. Опытный образец 2, t=25°С
1 мин. 3 мин.
1 мин. 3 мин.
1 мин. 3 мин.
d. Контрольный образец, t=50°С e. Опытный образец 1, t=50°С f. Опытный образец 2, t=50°С
1 мин. 3 мин.
1 мин. 3 мин.
1 мин. 3 мин.
a. Контрольный образец, t=25°С b. Опытный образец 1, t=25°С c. Опытный образец 2, t=25°С
1 мин. 3 мин.
1 мин. 3 мин.
1 мин. мин.
d. Контрольный образец, t=50°С e. Опытный образец 1, t=50°С f. Опытный образец 2, t=50°С
Control, t = 25°С Spray-dried sample, t = 25°С
1 min 3 min 1 min 3 min 1 min 3 min
Control, t = 50°С Spray-dried sample, t = 50°С Freeze-dried sample, t = 50°С
1 min 3 min 1 min 3 min 1 min 3 min
d e f
Voroshilin R.A. et al. Foods and Raw Materials. 2022;10(2):252–261
The region from 22 to 53 had a sequence of
whereas the region from 56 to 85 was represented by
21 out of 85 amino acids had hydrophobic properties.
According to Fig. 3a (control), leucine had maximum
hydrophobicity of 2.585 units at point 17 and aspargin
had highest hydrophilicity of –2.678 at 89.
Figure 2 Bloom strength of gelatin gels
229 224
Control Spray-dried sample Freeze-dried sample
Gel strength, Bloom
The profile of the spray-dried sample is shown in
Fig. 3b. As we can see, the peptide region from 5 to 21
represented by AGGPAY GGPILILAPA I and the region
from 55 to 57 with a NIL sequence had hydrophobic
properties. Most of the peaks were located above
0 and were represented by alanine, isoleucine, and
proline. These amino acids had hydrophobic properties
and 1 to 3 uncharged side radicals. Leucine (18) had a
maximum hydrophobicity value of 2.500 units, while
10 20 30 40 50 60 70 80 90
Figure 3 Predicted topology of protein hydrophobicity and hydrophilicity in the control and experimental gelatins (a – control;
b – spray-dried sample; c – freeze-dried sample)
10 20 30 40 50 60 70 80
a b
20 40 60 80 100
Voroshilin R.A. et al. Foods and Raw Materials. 2022;10(2):252–261
glutamine (77) had a maximum hydrophilicity value of –
3.511. Thus, 20 out of 91 amino acids had hydrophobic
The profile of the freeze-dried sample is shown
in Fig. 3c. As can be seen, the peptide region from
5 to 26 was represented by a sequence of VILEIL
ESHILEMILH ILMILS, the region from 32 to 39 had
a sequence of EEPEEEMP, and the one from 57 to 61
was represented by PHPI. Glutamic acid, isoleucine,
and leucine had most peaks in the hydrophobicity area.
They also had from 4 to 7 uncharged side radicals at
pH = 6–7. Isoleucine (6) had maximum hydrophobicity
of 3.856 units, while glutamine (76) had maximum
hydrophilicity of –5.504 units. Thus, 36 out of 93
amino acids had hydrophobic properties. Our results
were consistent with literature on the amphiphilic
(hydrophobic and hydrophilic) properties of these amino
acids [31–38].
The hydrophobicity values based on the amino acid
sequences of the gelatin samples confirmed our data
on their solubility. In particular, they proved that the
method of drying affects the gelatin’s structural and
mechanical properties, as well as its physicochemical
parameters. Spray drying can improve the proteins’
functional properties compared to freeze drying.
Therefore, we can conclude that different drying
methods affect the solubility and amphiphilicity
properties of gelatin, thereby changing its functional
Finally, we analyzed the molecular weight
distribution of proteins by polyacrylamide gel electrophoresis
in the presence of an anionic detergent,
sodium dodecyl sulfate (Fig. 4, Table 3).
According to the results, the control sample’s protein
fractions were more evenly distributed by molecular
weight compared to the experimental samples. Its
fractions between 50 and 100 kDa accounted for
72.6% and those below 20 kDa amounted to 6.1138%
of the total content. The spray-dried sample showed a
somewhat different molecular weight distribution. Its
protein fractions between 40 to 100 kDa made up 73.8%,
while those below 20 kDa accounted for 5.026315%.
The freeze-dried sample had a completely different
distribution of protein fractions. Most peptides were
found at the level of 40 kDa (42.83855%). Yet, this
sample had 30.214499% of proteins with a molecular
weight below 20 kDa, which was by 20.23% more than
in the control and by 16.64% more than in the spraydried
gelatin. This increase in low-molecular weight
peptides by an average of 18% was most likely caused
by the cleavage of peptides during freeze drying.
Our results showed that the degree of degradation
of gelatin components can depend on the method
of drying gelatin broths. Freeze drying can lead to
maximum degradation, which may be associated with
long heat treatment (5 h). This time is much longer
compared to spray drying, although the process of
freeze drying takes place at a lower temperature (60°C).
Also, temperatures below 0°C cause gelation followed
by freezing, which can also lead to structural changes
in gelatin. In addition, a faster process of spray drying
can slow down the degradation of gelatin proteins.
These results were consistent with those for gelatin
solubility (Fig. 2). Therefore, spray drying is more
suitable for maintaining the structure of gelatin and its
functional properties.
We studied the effect of spray and freeze drying
of gelatin broths on the solubility and amphiphilicity
of gelatin. The results showed that spray drying can
reduce the breakdown of gelatin proteins and retain
more α-chains, while freeze drying increases the
hydrophobicity of gelatin and decreases its solubility.
The predicted topology of protein hydrophobicity, which
was based on the amino acid sequences of the gelatin
samples, confirmed the results on solubility. Particularly,
the freeze-dried gelatin had 36 amino acids with
hydrophobic properties out of 93, compared to 21 out
of 85 in the control and 20 out of 91 in the spray-dried
We found that the freeze-dried sample had by 18%
more low-molecular weight peptides (below 20 kDa)
compared to the control and the spray-dried samples.
This was most likely caused by the cleavage of peptides
during the drying process. Freeze drying can lead to
Figure 4 Electropherogram of the molecular weight
distribution of gelatin samples (1 – marker; 2 – control,
3 – spray-dried sample, 4 – freeze-dried sample)
200 кДа
150 кДа
100 кДа
85 кДа
60 кДа
50 кДа
40 кДа
30 кДа
25 кДа
20 кДа
1 2 3 4
Voroshilin R.A. et al. Foods and Raw Materials. 2022;10(2):252–261
maximum degradation of gelatin components due to
long heat treatment. Temperatures below 0°C cause
gelation followed by freezing, which can also cause
structural changes in gelatin. By contrast, a faster spray
drying process can, to a certain extent, slow down the
degradation of gelatin proteins.
Thus, spray drying is more suitable for gelatin
drying, since this method improves the stability of
gelatin’s outer and inner structure, which was confirmed
by high hydrophilicity values of the spray-dried sample.
Table 3 Molecular weight distribution of gelatin samples
Molecular weight, kDa Molecular weight distribution, %
Control Spray-dried sample Freeze-dried sample
200 1.316515 3.878759 6.386503
150 3.101737 5.118362 1.334564
100 19.4574 17.810301 1.301436
85 17.85029 13.035829 1.367691
60 14.53681 8.429303 42.83855
50 20.790700 21.727447 3.170772
40 10.111660 12.89394 3.459454
30 0.220568 6.732710 3.530442
25 2.909430 1.157420 3.452356
20 3.591122 4.189303 2.974374
Below 20 6.113800 5.026315 30.214499
Further research could search for optimal parameters
and modes of spray drying for gelatin broths.
The authors were equally involved in writing the
manuscript and are equally responsible for plagiarism.
The authors declare that there is no conflict of
interest regarding the publication of this article. 

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