INTRODUCTION
Today, there are many different meat products on
the market. Domestic fermented sausages belong to a
group of dry fermented sausages, which are produced in
a traditional way and have desirable sensory properties.
Their sensory characteristics depend on various factors
including the selection and quality of raw materials
and basic ingredients, the formulation of sausage
emulsion, the metabolic activity of epiphytic microflora,
the physicochemical changes during smoking and
drying, the enzymatic decomposition of proteins and
fats, the conditions and length of ripening, as well as
external factors (temperature, relative humidity, and air
circulation) [1].
The quality of fermented sausages, as well as the
changes that occur during fermentation, drying, and
ripening, depends not only on the basic components of
the sausage emulsions, but also on the additives that
affect the transition of the emulsion into the fermented
product. Spices, additives, flavoring agents, enzymes,
sugars, carbohydrates, fibers, and protein products are
commonly used in manufacturing meat products.
When using additives, we should preserve
the characteristic properties of meat products [1].
Introducing non-meat ingredients into meat products
improves their quality and reduces the cost of
production. The most commonly used ingredients are
dairy products, eggs, plants, and probiotics, which
contribute to increased nutritional value, consumer
acceptance, and benefits for human health [2, 3].
The first impression about the quality of fermented
sausage is based on the visual experience, or the size,
shape, color, and gloss of products, either coated or
packed. The outer surface of the sausage depends, above
all, on the type and quality of coating and the intensity
of smoking (type of wood) and drying. Also, the sensory
evaluation of sausages includes the cross-section
color. According to the generally accepted criteria for
sensory properties of fermented sausages, the filling on
the cross-section should have the appearance of a mosaic
composed of approximately equal pieces of meat (stable
and uniform red color) and fat tissue (whitish color). The
filling ingredients must be evenly arranged and firmly
interconnected, with no visible cavities or cracks in the
cross-section [4].

The formation of odor and flavor of fermented
sausages depends on the fermentation of carbohydrates,
lipolysis and lipid oxidation, on proteolytic processes,
as well as the type and quantity of used spices, salt, and
additives [5, 6].
Non-meat proteins, such as soybean and whey
proteins, are often used to improve the texture of meat
products. These ingredients play an important role in
changing the functional properties such as emulsifying,
water and fat binding capacity, and texture. They are
used as additives that can improve yield and potentially
reduce the cost of products [7].
The previous works have studied the use of non-meat
proteins in cooked and semi-dry sausages, but there are
few studies on their effect on fermented sausages.
The main goal of this research was to study the
effect of soy and whey protein isolates on the quality
of domestic sausages traditionally fermented under
industrial conditions. The proteins were added to
improve the quality of sausage, rather than as a
substitute for meat. Adding soy and whey protein to
domestic fermented sausages and modelling their
quantitative ratio during product development can
improve the quality of the new product and reduce the
manufacturing time.
STUDY OBJECTS AND METHODS
Domestic fermented sausages were produced in
a traditional way under industrial conditions. The
emulsion consisted of mature pork (59.3%) and beef
meat (7.6%) of first and second category, pork back
fat (28.7%), nitric salt for curing (2.5%), spices (0.3%
garlic in granules, 0.4% hot red pepper, 0.4% sweet
red pepper, 0.3% ground black pepper), and additives
(0.3% glucono-delta-lactone GDL/TARI S 77 and
0.3% MIOCOLOR VS (a homogeneous mixture of
antioxidants based on the salt of ascorbic acid, edible
organic acids, and dextrose)).
For this study, we made five samples of domestic
fermented sausages: the control (without isolates); with
0.5% of whey isolate (Impact Whey isolate, Myprotein,
Norwich, UK); with 1.5% of whey isolates; with 0.5% of
soy isolate (IZOPROT S, Ireks Aroma, Zagreb, Croatia),
and with 1.5% of soy isolate. Duplicate batches were
prepared. The weight of each batch was 40 kg.
After grinding and mixing in the cutter, the sausage
emulsion was poured into natural coatings (pork
intestine) with a diameter ~ 30 mm. The sausages
were first tempered (22°C), then smoked (beech wood)
for three days (18°C to 20°C), and finally left for
fermentation (ripening) at 16°C. The relative humidity
gradually decreased from 85% at the beginning to 65%
at the end of ripening. Following the ripening stage,
the final sausages were vacuum packed and stored in a
cooling chamber at 4°C until sampling. Seven randomly
selected sausages were taken after the ripening stage and
during storage periods (1, 2, 3, and 6 months).
CIE L*, a*, b* c olor v alues ( L* – lightness,
a* – redness, b* – yellowness) were determined with a
Konica Minolta CM 2600d camera (Osaka, Japan). The
measurements were carried out on a fresh cut of sausage
samples. Five measurements were taken on three crosssections
of two sausages from each treatment. The
mean of 30 measurements was recorded for each color
parameter.
The hardness/softness was determined by a universal
texture meter, a TA.XT plus Texture Analyzer (Stable
Micro Systems, Godalming, UK). The cutting force was
measured by a Warner-Bratzler contact pin (parameters:
25 kg force, 4 mm/s rate, 20 mm distance). The test
samples were prepared by using a mold with eight
rectangular shapes (1×1 cm, approximately 5 cm) in
which the measurements were performed. The mean of
20 measurements was recorded.
The water activity (aw) was determined by a
LabMaster-aw hygrometer (Novasina, Switzerland)
at a constant temperature of 25°C. The mean of
5 measurements was recorded.
pH was measured by a digital pH meter (HANNA
HI 99161, Cluj-Napoca, Romania) equipped with a
combined penetration tip, which had been calibrated
with buffer solutions at pH 4 and 7. The mean of
5 measurements was recorded.
Using quantitative descriptive analysis
(ISO 6564:1985I), we evaluated the sensory properties of
sausages (external appearance, cross-section appearance
and color, odor, flavor and taste, texture and overall
acceptability). Ten panelists (6 females, 4 males, average
age of 35) took part in the evaluation. Based on the
average value of ratings for individual characteristics,
we calculated the overall quality score of the sausages.
Standard methods were used to analyze the chemical
quality parameters: water content – ISO 1442:1997II;
total fat content – ISO 1443:1973III; total protein content
– ISO 937:1978IV; total ash content – ISO 936:1998V;
total phosphorus content – ISO 13730:1996VI; sodium
chloride content – ISO 1841-1:1996VII; and nitrite content
I ISO 6564:1985. Sensory analysis. Methodology. Flavour profile
methods. Geneve: International Organization for Standardization;
1985. 8 p.
II ISO 1442:1997. Meat and meat products. Determination of moisture
content (Reference method). Geneve: International Organization for
Standardization; 1997. 8 p.
III ISO 1443:1973. Meat and meat products. Determination of total
fat content. Geneve: International Organization for Standardization;
1973. 4 p.
IV ISO 937:1978. Meat and meat products. Determination of nitrogen
content (Reference method). Geneve: International Organization for
Standardization; 1978. 3 p.
V ISO 936:1998. Meat and meat products. Determination of total ash.
Geneve: International Organization for Standardization; 1998. 10 p.
VI ISO 13730:1996. Meat and meat products. Determination of total
phosphorus content. Spectrometric method. Geneve: International
Organization for Standardization; 1996. 12 p.
VII ISO 1841-1:1996. Meat and meat products. Determination of
chloride content. Part 1: Volhard method. Geneve: International
Organization for Standardization; 1996. 6 p.
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Table 1 Chemical composition of sausages with protein isolates (average value ± SD)
Parameter Control 0.5% whey isolate 1.5% whey isolate 0.5% soy isolate 1.5% soy isolate
Moisture, % 21.95 ± 1.44 21.20 ± 1.44 21.80 ± 1.44 21.97 ± 1.28 22.10 ± 1.80
Ash, % 4.92 ± 0.35 5.01 ± 0.41 4.91 ± 0.28 4.99 ± 0.29 5.06 ± 0.36
Fat, % 49.38 ± 3.44 49.55 ± 2.10 49.58 ± 2.67 50.14 ± 1.54 48.55 ± 1.63
Proteins, % 20.17 ± 1.89 20.75 ± 1.44 20.12 ± 1.15 19.83 ± 1.52 20.92 ± 1.21
Fat-proteins ratio 2.44 2.40 2.47 2.47 2.30
Moisture-proteins ratio 1.19 1.10 1.17 1.18 1.13
NaCl, % 4.50 ± 0.17 4.60 ± 0.36 4.57 ± 0.02 4.52 ± 0.27 4.56 ± 0.32
Total phosphates, % 0.47 ± 0.06 0.47 ± 0.04 0.49 ± 0.07 0.49 ± 0.06 0.51 ± 0.06
Nitrites, mg/kg 3.04 ± 1.80 3.42 ± 1.37 2.84 ± 1.03 3.78 ± 1.41 4.22 ± 1.94
Table 2 Water activity and pH values of sausages with protein isolates (average value ± SD)
Storage period,
months
Control 0.5% whey isolate 1.5% whey isolate 0.5% soy isolate 1.5% soy isolate
aw 0 0.832a,A ± 0.0005 0.807b,A ± 0.0005 0.819c,A ± 0.0005 0.819c,A ± 0.0005 0.823d,A ± 0.0005
1 0.816a,B ± 0.0005 0.820b,B ± 0.0005 0.826b,B ± 0.0005 0.818a,c,A ± 0.0005 0.821b,c,A ± 0.0005
2 0.808a,C ± 0.0005 0.822b,B ± 0.0005 0.836c,C ± 0.0005 0.842d,B ± 0.0005 0.834e,B ± 0.0005
3 0.824a,D ± 0.0005 0.822b,B ± 0.0005 0.830c,D ± 0.0005 0.807d,C ± 0.0005 0.817e,C ± 0.0005
6 0.823a,D ± 0.0005 0.822a,B ± 0.0004 0.831b,D ± 0.0004 0.807c,C ± 0.0008 0.815d,C ± 0.0004
pH 0 5.34a,A ± 0.063 5.54b,c,A ± 0.001 5.37a,A ± 0.020 5.51b,A ± 0.014 5.64c,A ± 0.016
1 5.57a,c,B,C ± 0.020 5.45b,B ± 0.050 5.53a,b,B ± 0.005 5.62c,B ± 0.020 5.63c,A ± 0.030
2 5.70a,D ± 0.005 5.64b,C ± 0.010 5.60 c,C ± 0.012 5.59c,B ± 0.010 5.68a,A ± 0.007
3 5.68a,C,D ± 0.037 5.70a,b,C ± 0.008 5.71a,b,D ± 0.025 5.68a,C ± 0.010 5.77b,B ± 0.030
6 5.48a,b,B ± 0.041 5.48a,b,A,B ± 0.010 5.50a.B ± 0.023 5.44b,D ± 0.012 5.55c,C ± 0.012
a–d values in the same column with different superscripts are significantly different (P < 0.05)
A–D values in the same row with different superscripts are significantly different (P < 0.05)
– ISO 2918:1975VIII. All measurements were carried
out in 5 repetitions. All analyses were performed
immediately after production (0) and during storage (1,
2, 3, and 6 months).
Statistical analysis. Our results were presented as
mean values accompanied with standard deviations. A
factorial analysis of variance (ANOVA) was performed
using the Statgraphic Plus 5.1 Professional Edition
(1994–2001, Statistical Graphics Corporation, USA).
The Multiple Range test was used to identify significant
(P < 0.05) differences between treatments. Repeated
measures ANOVA was used to test the differences
during storage periods.
RESULTS AND DISCUSSION
The chemical composition of all the samples of
domestic fermented sausages is shown as mean values
of parameters measured after 0, 1, 2, 3, and 6 months of
storage (Table 1).
The moisture content of the sausage samples during
the period monitored ranged from 21.2% to 22.1%.
However, numerous studies report higher moisture
contents for similar products [8–10]. Using coatings
with a narrow diameter (about 30 mm), longer ripening
VIII ISO 2918:1975. Meat and meat products. Determination of nitrite
content (Reference method). Geneve: International Organization for
Standardization; 1975. 3 p.
or a higher fat content could result in a lower moisture
content [11]. The fat content of the final product varied
between 48.55% and 50.14%, which depended primarily
on the recipe, with similar fat contents reported by
numerous other studies [8, 12]. According to our results,
soy and whey proteins in concentrations of 0.5 and
1.5% did not have significant effects on the total protein
content (P > 0.05), which agreed with earlier studies
[13, 14]. The difference between the contents of fat and
protein was large, due to a high content of fat in the
formulation, while the moisture and protein values were
almost identical, compared to other data for traditional
products [5].
The salt content ranged from 4.5 to 4.6%, and
other authors obtained similar or higher values for
traditionally fermented sausages [15, 16]. The ash
contents ranged from 4.9 to 5.06%, while the use of
additives, whey and soy protein isolates, did not have a
significant effect on the values studied [17, 18].
The average values of total phosphorus during
storage ranged from 0.47 to 0.51%, with no major
differences between the samples. This result was quite
expectable as the meat protein content, the main source
of phosphorus, did not change significantly (P > 0.05).
The values of residual nitrite content after production
and during storage ranged from 2.84 to 4.22 mg/kg.
These data confirm the fact that the nitrites were
decomposed during ripening and fermentation, which
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After production, there were no significant differences
between the sausages (P > 0.05), with hardness ranging
from 1.00 to 1.43. Similar values were recorded in other
studies as well [1, 26]. Some authors cite higher values
[9, 16]. Lee found that the products with the addition of
a soybean protein isolate show slightly higher hardness
values compared to the control sample [27].
After the first month of storage, there was an
increase in hardness, especially in the sample containing
0.5% soy protein isolate compared to other samples
(P < 0.05). The texture of fermented sausages is related
to the fat and salt content, as well as pH [16].
The hardness test showed a noticeable effect of the
additives. The samples with a whey protein isolate
had a lower cutting force than the control, while the
sample with 0.5% soy protein isolate had significantly
higher hardness values during the entire storage period
(P < 0.05).
Priyadarshi pointed out that added soy and whey
proteins increased the hardness of cooked pork sausage,
while many authors stated the opposite for cooked
sausages and burgers [17, 28, 29]. Akesowan found
that an amount greater than 2% of soy protein isolate
affected the strength of cooked pork sausages [13].
The lightness (L*) values of the sausage samples are
shown in Table 4. As we can see, they were consistent
after production, ranging from 49.07 to 50.20. Many
studies featured similar values [31, 32]. Kim et al.
reported higher L* values, while most authors found
significantly lower values, ranging from 30 to 45 [5, 18,
23, 32].
During storage, the L* values changed significantly
(P < 0.05) from 40.72 to 50.92, although there was
generally a slight decrease. Some studies showed similar
results [21, 33]. The decrease in the L* values was related
Table 3 Hardness of sausages with protein isolates (average value ± SD)
Samples Storage period, months
0 1 2 3 6
Control 1.43a,A ± 1.30 2.12a,B ± 1.01 2.02a,B ± 0.67 1.98a,b,B ± 0.61 2.05a,B ± 0.62
0.5% whey isolate 1.12a,A ± 0.63 1.66a,B ± 1.14 1.60a,A,B ± 0.92 1.59a,A,B ± 0.78 1.62b,B ± 0.62
1.5% whey isolate 1.14a,A ± 0.62 1.62a,B ± 1.04 1.77a,B ± 0.85 1.81a,b,B ± 0.71 1.84a,b,B ± 0.59
0.5% soy isolate 1.00a,A ± 0.29 3.70b,B ± 1.64 3.41b,B ± 1.35 3.16c,B ± 1.08 3.04c,B ± 0.79
1.5% soy isolate 1.06a,A ± 0.41 2.06a,B ± 1.16 2.02a,B ± 0.77 2.11b,B ± 0.80 2.07a,B ± 0.59
a, b values in the same column with different superscripts are significantly different (P < 0.05)
A, B values in the same row with different superscripts are significantly different (P < 0.05)
Table 4 L* values of sausages with protein isolates during storage (average ± SD)
Samples Storage period, months
0 1 2 3 6
Control 49.61a,A ± 4.26 49.79a,A ± 5.91 42.52a,b,B ± 6.21 50.41a,A ± 5.47 46.52a,C ± 3.09
0.5% whey isolate 50.16a,A,C ± 7.22 50.92a,A ± 6.31 42.93a,b,B ± 6.09 44.29a,A,C ± 5.12 46.94a,C ± 4.89
1.5% whey isolate 49.41a,A ± 4.64 48.15a,b,A ± 4.73 44.57a,B ± 5.05 44.36b,B ± 5.17 45.15a,B ± 3.037
0.5% soy isolate 50.20a,A ± 4.65 45.89b,B ± 4.04 42.94a,b,C ± 3.145 43.09b,C ± 3.91 45.65a,B ± 3.77
1.5% soy isolate 49.07a,A ± 5.18 45.54b,B ± 4.22 40.72b,C ± 5.32 44.67b,B ± 4.32 45.83a,B ± 3.31
a, b values in the same column with different superscripts are significantly different (P < 0.05)
A–C values in the same row with different superscripts are significantly different (P < 0.05)
was reported by many authors [8, 19]. In the Slavonian
sausage of Kulen, the content of nitrite after ripening
was 2.93–14.3 mg/kg [20]. As we can see, there were
no significant differences (P > 0.05) in the chemical
composition between the samples.
The degree of reducing the aw value depends on the
composition of sausages, temperature, relative humidity,
and the ripening time. During drying and ripening,
the concentration of water in the product decreases,
followed by dehydration and reduction of aw [11].
The results of water activity can be seen in Table 2.
After production, the aw values of the analyzed samples
ranged from 0.807 to 0.832, which was confirmed by
Suvajdžić [16]. Mastanjević received higher values in the
study of Slavonian kulen [21]. Operta et al. reported that
the activity of water in traditional fermented sausages
ranged from 0.83 to 0.89 at the end of drying, which was
also the case for dry fermented chicken sausages with
the addition of corn oil and soybean isolates [22, 23].
During storage, there were noticeable significant
differences (P < 0 .05), with values of a w ranging from
0.807 to 0.842 (Table 2). Operta et al. reported similar
results indicating that the products with a soybean
protein isolate showed a slight decrease in aw values
during storage [22].
After the production, the pH values of the samples
were from 5.34 to 5.64 (Table 2). During storage, they
ranged from 5.44 to 5.77, with noticeable significant
differences (P < 0.05). Many authors cited similar
or lower values as a characteristic of fermented
sausages [24, 25].
Table 3 shows changes in the samples texture after
production and during a six-month storage period.
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to the loss of moisture and also to low fat and high water
contents [4, 25].
Škaljac reported that the loss of water from the
Petrovačka sausage during aging increased the
concentration of myoglobin [11]. On the other hand, the
dehydrated muscle tissue absorbed a higher amount of
light which resulted in a darker color of the product and
decreased L* values.
In the soy protein samples, the L* values remained
approximately the same or decreased , although some
authors had opposite results [13, 14, 23, 34]. Using
whey protein also led to lower L* values [18, 35].
Serdaroglu, however, claimed that milk additives slightly
increased L* values, with similar observations made by
Hughes et al. [17, 36]. Barbut reported no significant
changes caused by whey supplements [37].
The values of redness (a*) are shown in Table 5.
After production, these values ranged from 12.72 to
14.50. This color parameter was significantly different
between the samples and during storage (P < 0.05).
Many authors reported higher values and greater
deviations [4, 31]. A reduction of the a* value was due
to a higher amount of lactic acid, which denatured
myoglobin, nitrosylmyoglobin, and oxymyoglobin [4].
A lower protein content had the same effect, while a low
fat level and a high water content led to increased a*
values.
Serdaroglu and Abdolghafour found no effect of
dairy supplements on the a* value, although some
authors reported a decline in this value when using
additives, which was confirmed by our study [17,
18, 37]. The use of soy protein resulted in lower a*
values [13, 34].
The values of yellowness (b*) are shown in Table 6.
Immediately after production, they ranged from
12.35 to 14.79 in the 0.5% whey protein and 0.5% soy
protein samples, respectively. However, during further
storage, this parameter reached 12.49 and 18.00 for
the 0.5% whey protein and 0.5% soy protein samples,
respectively. Thus, the differences between the samples
and during storage were significant (P < 0.05). Similar
data were reported by other authors [4]. Lower values
were given by Skaljac et al. for sausages stored under
controlled conditions in an industrial chamber [4].
Higher values for vacuum-packed Petrovska sausage
were reported by Skaljac et al. [38]. The decrease in the
b* values was assumed to be caused by microorganisms
that use oxygen during fermentation, thus reducing
the amount of a muscle pigment that beneficially
affected the b* value [37]. Another study reported
higher fermentation temperature and the addition
of autochthonous starter culture as a cause of the
decrease [21].
Most authors agree that adding whey and soy protein
isolates decreases the b* values or that they do not
change significantly [34, 37]. Abdolghafour reported that
the decrease of the b* value was caused by soy protein,
which was confirmed by our results [18]. Hughes et al.
found that adding whey protein lead to an increase
in lightness (L*) and a decrease in redness (a*) and
yellowness (b*) [36].
The external appearance of the sausages at the end
of production, as well as during the storage period,
was satisfactory without any statistically significant
differences between the samples (P > 0.05). The coat
was not separated from the emulsion, deformed or
Table 5 a* values of sausages with protein isolates during storage (average ± SD)
Samples Storage period, months
0 1 2 3 6
Control 14.50a,A ± 2.25 12.37a,B ± 2.88 16.56a,c,C ± 2.45 12.32a,B ± 2.77 14.85a,A ± 2.71
0.5% whey isolate 12.72b,A,B ± 2.82 12.14a,B ± 2.87 14.53b,C ± 2.51 12.06a,B ± 1.81 14.01a,B,C ± 2.15
1.5% whey isolate 14.15a,b,A ± 2.29 12.12a,B ± 2.31 15.45a,b,C ± 2.95 12.86a,b,B ± 2.02 12.20b,B ± 1.91
0.5% soy isolate 14.30a,A ± 2.81 14.67b,A ± 2.18 17.60c,B ± 3.00 14.58c,A ± 2.26 16.48c,B ± 2.05
1.5% soy isolate 14.24a,A ± 2.22 13.46a,b,A ± 2.31 17.93c,B ± 2.83 14.15b,c,A ± 2.58 14.53a,A ± 1.58
a–c values in the same column with different superscripts are significantly different (P < 0.05)
A–C values in the same row with different superscripts are significantly different (P < 0.05)
Table 6 b* values of sausages with protein isolates during storage (average ± SD)
Samples Storage period, months
0 1 2 3 6
Control 13.93a,b,A,B ± 3.13 14.20a,b,A,B ± 3.47 15.75a,A ± 4.32 13.34a,b,B ± 3.83 15.86a,c,A ± 4.53
0.5% whey isolate 12.35a,A ± 2.78 12.55a,A ± 3.70 12.53b,A ± 3.44 12.49a,A ± 2.45 15.55a,B ± 4.09
1.5% whey isolate 14.39a,b,A,B ± 3.86 12.94a,A ± 3.11 16.25a,B ± 4.83 13.58a,b,A ± 2.35 12.58b,A ± 4.29
0.5% soy isolate 14.79b,A ± 3.24 15.88b,A,B ± 3.65 17.85a,B ± 5.43 13.99a,b,A ± 4.12 18.00c,B ± 3.54
1.5% soy isolate 14.20a,b,A,C ± 3.30 13.93a,b,A ± 3.17 17.09a,B ± 3.06 14.83b,A,C ± 3.96 16.01a,c,B,C ± 4.23
a–c values in the same column with different superscripts are significantly different (P < 0.05)
A–C values in the same row with different superscripts are significantly different (P < 0.05)
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damaged; it was slightly wrinkled and highly graded for
all the samples. Similar results were obtained by Vasilev
et al. for a functional sausage with fatty tissue [39].
After production, the cross-section of the samples
had a mosaic appearance, with slightly larger particles of
fat tissue, which is characteristic of this product. Inside
the sausage were no visible cracks, and the components
were well connected. The appearance of the section
was rated very highly in all the test samples during
storage. The lowest values were recorded, as expected,
after 6 months of storage, from 4.36 to 4.86. Most
panelists pointed out the presence of a high content
of fatty tissue at the intersection of the sausage, which
was confirmed by an extremely high fat content in the
samples. Bratulić et al. made the same conclusion,
having examined sausages from the Istrian region [12].
The sensory evaluation of the cross-section color, as
well as odor, flavor, and taste in the analyzed sausage
samples during a six-month storage period are presented
in Fig. 1. The cross-section color after production was
adequate, with minimal deviations. The meat pieces
were red and the particles of fat tissue were whitish. The
grades ranged from 4.65 to 4.77, and later, between the
1st and the 3rd months, they varied from 4.38 to 5.00. At
the end of the test period, after six months of storage, the
ratings were lower, ranging from 3.84 to 4.48, but they
were still acceptable. The color was noticeably lighter in
the samples with soy protein, although the other samples
were characterized as slightly brighter than expected
(pieces of meat). After six months, a greater change in
color was noticeable, especially at the edges, which was
more expressed in the whey samples.
Abdolghafour and Zaki cited higher grades for the
samples with added whey, which declined during storage
[18, 35]. According to Akesowana, adding soybeans had
a positive effect on the color, while Krasnowska et al.
did not indicate a significant difference between the
samples with soy and whey compared to the control
sample [13, 34].
The most obvious changes in sensory characteristics
were in odor, taste, and flavor during the storage
period. We found that the use of additives hardly
affected the characteristic pleasant smell of fermented
products after ripening and the mild smell of smoke.
The grades after production ranged from 3.77 to
4.92. Adding soy proteins during this period reduced
the intensity of aroma and flavor, contributing
to a bland taste. Many authors reported similar
observations: adding up to 3% of soy protein masked
the intensity of other flavors, reduced juiciness
and salinity [40]. Serdaroglu concluded that whey
caused the absence of meat flavor [17]. We found
changes in sensory properties during storage. The
samples with 1.5% of additives had less expressed
characteristics, a mismatch of aroma and taste. The
whey samples had a sour odor. Krasnowska et al.
cited slightly lower grades for flavor and juiciness, and
better grades for taste in the samples with soy and whey
proteins [13, 30, 34].
The texture of the sausages after production was
satisfactory, with minor deviations (Fig. 2). Observing
a sausage cut, we found that the mass was compact and
that the additives had a noticeable effect on chewiness.
The ratings after production were from 4.00 to 4.92.
During storage, there were changes in texture, with the
grades ranging from 3.92 to 4.57. The whey samples
became softer and less connected, while the soy samples
were harder than expected. After six months, the grades
were lower, ranging from 3.45 to 4.23. The products
crumbled during the cutting and also demonstrated some
toughness. The samples with a higher amount of added
protein attained lower grades, while the 0.5% soy protein
sample had the best texture. Many authors reported a
positive effect of added soy and whey on the texture, and
therefore on the grades, compared to the control sample
[13, 18, 34].
The overall sensory quality of all the samples was
quite high during the entire test period, with no major
Figure 1 Sensory evaluation of cross-section color, odor, flavor, and taste of sausages with protein isolates
3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Colour-section
Control 0.5% whey isolate
1.5% whey isolate 0.5% soy isolate
1.5% soy isolate
3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
2
2B 3A 3B
3 2
K 2A 2B 3A 3B
0
1
2
2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Colour-section
Control 0.5% whey isolate
1.5% whey isolate 0.5% soy isolate
1.5% soy isolate
3 2
K 2A 2B 3A 3B
3 K 2A 3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
3 6
Сolor, odor, flavor
K 2A 3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3 2
K 2A 2B 3A 3B
3 K 2A 3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
3 6
Сolor, odor, flavor
K 2A 3 2
K 2A 2B 3A 3B
3 2
K 2A 2B 3A 3B
3
3.5
4
4.5
5
0
1
3 2
6
Cross-section color
K 2A 2B 3A 3B
2.5
3
3.5
4
4.5
5
0
1
3 2
6
Сolor, odor, flavor
K 2A 2B 3A 3B
265
Velemir A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 259–267
deviations from the maximum quality (P > 0.05). After
production, the grades ranged from 4.37 to 4.79. The
whey samples received high grades (4.71), almost as the
control (4.77), while the soy samples rated slightly lower
(4.37 and 4.44, respectively). During the storage period,
there were no major changes, with the mean scores
ranging from 4.35 to 4.82, and the samples with smaller
amounts of additives were rated slightly better. After
six months of storage, the marks were somewhat lower
(3.98 to 4.32). In this period, the soy samples were given
better grades, just as the samples with smaller amounts
of additives We found that all the samples showed good
ratings and acceptability during the entire test period.
Krasnowska et al. found that the products with whey
and soy proteins had better sensory parameters [34].
Many authors agree that whey and soy protein
supplements have a positive influence on sensory
characteristics [18, 30, 40].
CONCLUSION
The results of our study showed that protein
supplements possessed excellent functional properties
in fermented products, including the emulsifying and
binding properties. We found a significantly noticeable
reduction of water activity, which is very important in
Figure 2 Texture and overall sensory quality of sausages with protein isolates
the production of fermented sausages in terms of the
ripening rate. Slower moisture losses during storage
were observed in the samples with additives. Another
effect was that on hardness: a 0.5% soy protein isolate
resulted in a tougher product. We also found a minor
effect on the color: the samples with the additives
showed a slightly lower L* value, while those with
soy protein had higher yellowness (b*). The use of
the additives did not have a significant effect on the
chemical composition and sensory properties of the
product (P > 0.05) because of their low concentrations.
The main characteristics of meat products were
preserved despite the addition of non-meat proteins.
However, the effect of non-fat proteins on the quality
of fermented sausages needs further investigation to
determine the optimal concentration for obtaining high
quality products.
CONTRIBUTION
Authors are equally related to the writing of the
manuscript and are equally responsible for plagiarism.
CONFLICTS OF INTEREST
The authors declare that there is no conflict of
interests.

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