INTRODUCTIONToday, there are many different meat products onthe market. Domestic fermented sausages belong to agroup of dry fermented sausages, which are produced ina traditional way and have desirable sensory properties.Their sensory characteristics depend on various factorsincluding the selection and quality of raw materialsand basic ingredients, the formulation of sausageemulsion, the metabolic activity of epiphytic microflora,the physicochemical changes during smoking anddrying, the enzymatic decomposition of proteins andfats, the conditions and length of ripening, as well asexternal factors (temperature, relative humidity, and aircirculation) [1].The quality of fermented sausages, as well as thechanges that occur during fermentation, drying, andripening, depends not only on the basic components ofthe sausage emulsions, but also on the additives thataffect the transition of the emulsion into the fermentedproduct. Spices, additives, flavoring agents, enzymes,sugars, carbohydrates, fibers, and protein products arecommonly used in manufacturing meat products.When using additives, we should preservethe characteristic properties of meat products [1].Introducing non-meat ingredients into meat productsimproves their quality and reduces the cost ofproduction. The most commonly used ingredients aredairy products, eggs, plants, and probiotics, whichcontribute to increased nutritional value, consumeracceptance, and benefits for human health [2, 3].The first impression about the quality of fermentedsausage is based on the visual experience, or the size,shape, color, and gloss of products, either coated orpacked. The outer surface of the sausage depends, aboveall, on the type and quality of coating and the intensityof smoking (type of wood) and drying. Also, the sensoryevaluation of sausages includes the cross-sectioncolor. According to the generally accepted criteria forsensory properties of fermented sausages, the filling onthe cross-section should have the appearance of a mosaiccomposed of approximately equal pieces of meat (stableand uniform red color) and fat tissue (whitish color). Thefilling ingredients must be evenly arranged and firmlyinterconnected, with no visible cavities or cracks in thecross-section [4].The formation of odor and flavor of fermentedsausages depends on the fermentation of carbohydrates,lipolysis and lipid oxidation, on proteolytic processes,as well as the type and quantity of used spices, salt, andadditives [5, 6].Non-meat proteins, such as soybean and wheyproteins, are often used to improve the texture of meatproducts. These ingredients play an important role inchanging the functional properties such as emulsifying,water and fat binding capacity, and texture. They areused as additives that can improve yield and potentiallyreduce the cost of products [7].The previous works have studied the use of non-meatproteins in cooked and semi-dry sausages, but there arefew studies on their effect on fermented sausages.The main goal of this research was to study theeffect of soy and whey protein isolates on the qualityof domestic sausages traditionally fermented underindustrial conditions. The proteins were added toimprove the quality of sausage, rather than as asubstitute for meat. Adding soy and whey protein todomestic fermented sausages and modelling theirquantitative ratio during product development canimprove the quality of the new product and reduce themanufacturing time.STUDY OBJECTS AND METHODSDomestic fermented sausages were produced ina traditional way under industrial conditions. Theemulsion consisted of mature pork (59.3%) and beefmeat (7.6%) of first and second category, pork backfat (28.7%), nitric salt for curing (2.5%), spices (0.3%garlic in granules, 0.4% hot red pepper, 0.4% sweetred pepper, 0.3% ground black pepper), and additives(0.3% glucono-delta-lactone GDL/TARI S 77 and0.3% MIOCOLOR VS (a homogeneous mixture ofantioxidants based on the salt of ascorbic acid, edibleorganic acids, and dextrose)).For this study, we made five samples of domesticfermented sausages: the control (without isolates); with0.5% of whey isolate (Impact Whey isolate, Myprotein,Norwich, UK); with 1.5% of whey isolates; with 0.5% ofsoy isolate (IZOPROT S, Ireks Aroma, Zagreb, Croatia),and with 1.5% of soy isolate. Duplicate batches wereprepared. The weight of each batch was 40 kg.After grinding and mixing in the cutter, the sausageemulsion was poured into natural coatings (porkintestine) with a diameter ~ 30 mm. The sausageswere first tempered (22°C), then smoked (beech wood)for three days (18°C to 20°C), and finally left forfermentation (ripening) at 16°C. The relative humiditygradually 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 acooling chamber at 4°C until sampling. Seven randomlyselected sausages were taken after the ripening stage andduring 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 aKonica Minolta CM 2600d camera (Osaka, Japan). Themeasurements were carried out on a fresh cut of sausagesamples. Five measurements were taken on three crosssectionsof two sausages from each treatment. Themean of 30 measurements was recorded for each colorparameter.The hardness/softness was determined by a universaltexture meter, a TA.XT plus Texture Analyzer (StableMicro Systems, Godalming, UK). The cutting force wasmeasured by a Warner-Bratzler contact pin (parameters:25 kg force, 4 mm/s rate, 20 mm distance). The testsamples were prepared by using a mold with eightrectangular shapes (1×1 cm, approximately 5 cm) inwhich the measurements were performed. The mean of20 measurements was recorded.The water activity (aw) was determined by aLabMaster-aw hygrometer (Novasina, Switzerland)at a constant temperature of 25°C. The mean of5 measurements was recorded.pH was measured by a digital pH meter (HANNAHI 99161, Cluj-Napoca, Romania) equipped with acombined penetration tip, which had been calibratedwith buffer solutions at pH 4 and 7. The mean of5 measurements was recorded.Using quantitative descriptive analysis(ISO 6564:1985I), we evaluated the sensory properties ofsausages (external appearance, cross-section appearanceand color, odor, flavor and taste, texture and overallacceptability). Ten panelists (6 females, 4 males, averageage of 35) took part in the evaluation. Based on theaverage value of ratings for individual characteristics,we calculated the overall quality score of the sausages.Standard methods were used to analyze the chemicalquality 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; sodiumchloride content – ISO 1841-1:1996VII; and nitrite contentI ISO 6564:1985. Sensory analysis. Methodology. Flavour profilemethods. Geneve: International Organization for Standardization;1985. 8 p.II ISO 1442:1997. Meat and meat products. Determination of moisturecontent (Reference method). Geneve: International Organization forStandardization; 1997. 8 p.III ISO 1443:1973. Meat and meat products. Determination of totalfat content. Geneve: International Organization for Standardization;1973. 4 p.IV ISO 937:1978. Meat and meat products. Determination of nitrogencontent (Reference method). Geneve: International Organization forStandardization; 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 totalphosphorus content. Spectrometric method. Geneve: InternationalOrganization for Standardization; 1996. 12 p.VII ISO 1841-1:1996. Meat and meat products. Determination ofchloride content. Part 1: Volhard method. Geneve: InternationalOrganization for Standardization; 1996. 6 p.261Velemir A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 259–267Table 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 isolateMoisture, % 21.95 ± 1.44 21.20 ± 1.44 21.80 ± 1.44 21.97 ± 1.28 22.10 ± 1.80Ash, % 4.92 ± 0.35 5.01 ± 0.41 4.91 ± 0.28 4.99 ± 0.29 5.06 ± 0.36Fat, % 49.38 ± 3.44 49.55 ± 2.10 49.58 ± 2.67 50.14 ± 1.54 48.55 ± 1.63Proteins, % 20.17 ± 1.89 20.75 ± 1.44 20.12 ± 1.15 19.83 ± 1.52 20.92 ± 1.21Fat-proteins ratio 2.44 2.40 2.47 2.47 2.30Moisture-proteins ratio 1.19 1.10 1.17 1.18 1.13NaCl, % 4.50 ± 0.17 4.60 ± 0.36 4.57 ± 0.02 4.52 ± 0.27 4.56 ± 0.32Total phosphates, % 0.47 ± 0.06 0.47 ± 0.04 0.49 ± 0.07 0.49 ± 0.06 0.51 ± 0.06Nitrites, mg/kg 3.04 ± 1.80 3.42 ± 1.37 2.84 ± 1.03 3.78 ± 1.41 4.22 ± 1.94Table 2 Water activity and pH values of sausages with protein isolates (average value ± SD)Storage period,monthsControl 0.5% whey isolate 1.5% whey isolate 0.5% soy isolate 1.5% soy isolateaw 0 0.832a,A ± 0.0005 0.807b,A ± 0.0005 0.819c,A ± 0.0005 0.819c,A ± 0.0005 0.823d,A ± 0.00051 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 ± 0.00052 0.808a,C ± 0.0005 0.822b,B ± 0.0005 0.836c,C ± 0.0005 0.842d,B ± 0.0005 0.834e,B ± 0.00053 0.824a,D ± 0.0005 0.822b,B ± 0.0005 0.830c,D ± 0.0005 0.807d,C ± 0.0005 0.817e,C ± 0.00056 0.823a,D ± 0.0005 0.822a,B ± 0.0004 0.831b,D ± 0.0004 0.807c,C ± 0.0008 0.815d,C ± 0.0004pH 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 ± 0.0161 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 ± 0.0302 5.70a,D ± 0.005 5.64b,C ± 0.010 5.60 c,C ± 0.012 5.59c,B ± 0.010 5.68a,A ± 0.0073 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 ± 0.0306 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 ± 0.012a–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 carriedout in 5 repetitions. All analyses were performedimmediately after production (0) and during storage (1,2, 3, and 6 months).Statistical analysis. Our results were presented asmean values accompanied with standard deviations. Afactorial analysis of variance (ANOVA) was performedusing 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. Repeatedmeasures ANOVA was used to test the differencesduring storage periods.RESULTS AND DISCUSSIONThe chemical composition of all the samples ofdomestic fermented sausages is shown as mean valuesof parameters measured after 0, 1, 2, 3, and 6 months ofstorage (Table 1).The moisture content of the sausage samples duringthe period monitored ranged from 21.2% to 22.1%.However, numerous studies report higher moisturecontents for similar products [8–10]. Using coatingswith a narrow diameter (about 30 mm), longer ripeningVIII ISO 2918:1975. Meat and meat products. Determination of nitritecontent (Reference method). Geneve: International Organization forStandardization; 1975. 3 p.or a higher fat content could result in a lower moisturecontent [11]. The fat content of the final product variedbetween 48.55% and 50.14%, which depended primarilyon the recipe, with similar fat contents reported bynumerous other studies [8, 12]. According to our results,soy and whey proteins in concentrations of 0.5 and1.5% did not have significant effects on the total proteincontent (P > 0.05), which agreed with earlier studies[13, 14]. The difference between the contents of fat andprotein was large, due to a high content of fat in theformulation, while the moisture and protein values werealmost identical, compared to other data for traditionalproducts [5].The salt content ranged from 4.5 to 4.6%, andother authors obtained similar or higher values fortraditionally fermented sausages [15, 16]. The ashcontents ranged from 4.9 to 5.06%, while the use ofadditives, whey and soy protein isolates, did not have asignificant effect on the values studied [17, 18].The average values of total phosphorus duringstorage ranged from 0.47 to 0.51%, with no majordifferences between the samples. This result was quiteexpectable as the meat protein content, the main sourceof phosphorus, did not change significantly (P > 0.05).The values of residual nitrite content after productionand during storage ranged from 2.84 to 4.22 mg/kg.These data confirm the fact that the nitrites weredecomposed during ripening and fermentation, which262Velemir A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 259–267After production, there were no significant differencesbetween the sausages (P > 0.05), with hardness rangingfrom 1.00 to 1.43. Similar values were recorded in otherstudies as well [1, 26]. Some authors cite higher values[9, 16]. Lee found that the products with the addition ofa soybean protein isolate show slightly higher hardnessvalues compared to the control sample [27].After the first month of storage, there was anincrease in hardness, especially in the sample containing0.5% soy protein isolate compared to other samples(P < 0.05). The texture of fermented sausages is relatedto the fat and salt content, as well as pH [16].The hardness test showed a noticeable effect of theadditives. The samples with a whey protein isolatehad a lower cutting force than the control, while thesample with 0.5% soy protein isolate had significantlyhigher hardness values during the entire storage period(P < 0.05).Priyadarshi pointed out that added soy and wheyproteins increased the hardness of cooked pork sausage,while many authors stated the opposite for cookedsausages and burgers [17, 28, 29]. Akesowan foundthat an amount greater than 2% of soy protein isolateaffected the strength of cooked pork sausages [13].The lightness (L*) values of the sausage samples areshown in Table 4. As we can see, they were consistentafter production, ranging from 49.07 to 50.20. Manystudies featured similar values [31, 32]. Kim et al.reported higher L* values, while most authors foundsignificantly 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 wasgenerally a slight decrease. Some studies showed similarresults [21, 33]. The decrease in the L* values was relatedTable 3 Hardness of sausages with protein isolates (average value ± SD)Samples Storage period, months0 1 2 3 6Control 1.43a,A ± 1.30 2.12a,B ± 1.01 2.02a,B ± 0.67 1.98a,b,B ± 0.61 2.05a,B ± 0.620.5% 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 ± 0.621.5% 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 ± 0.590.5% 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 ± 0.791.5% 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 ± 0.59a, 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, months0 1 2 3 6Control 49.61a,A ± 4.26 49.79a,A ± 5.91 42.52a,b,B ± 6.21 50.41a,A ± 5.47 46.52a,C ± 3.090.5% 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 ± 4.891.5% 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 ± 3.0370.5% 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 ± 3.771.5% 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 ± 3.31a, 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 Slavoniansausage of Kulen, the content of nitrite after ripeningwas 2.93–14.3 mg/kg [20]. As we can see, there wereno significant differences (P > 0.05) in the chemicalcomposition between the samples.The degree of reducing the aw value depends on thecomposition 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 samplesranged from 0.807 to 0.832, which was confirmed bySuvajdžić [16]. Mastanjević received higher values in thestudy of Slavonian kulen [21]. Operta et al. reported thatthe activity of water in traditional fermented sausagesranged from 0.83 to 0.89 at the end of drying, which wasalso the case for dry fermented chicken sausages withthe addition of corn oil and soybean isolates [22, 23].During storage, there were noticeable significantdifferences (P < 0 .05), with values of a w ranging from0.807 to 0.842 (Table 2). Operta et al. reported similarresults indicating that the products with a soybeanprotein isolate showed a slight decrease in aw valuesduring storage [22].After the production, the pH values of the sampleswere from 5.34 to 5.64 (Table 2). During storage, theyranged from 5.44 to 5.77, with noticeable significantdifferences (P < 0.05). Many authors cited similaror lower values as a characteristic of fermentedsausages [24, 25].Table 3 shows changes in the samples texture afterproduction and during a six-month storage period.263Velemir A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 259–267to the loss of moisture and also to low fat and high watercontents [4, 25].Škaljac reported that the loss of water from thePetrovačka sausage during aging increased theconcentration of myoglobin [11]. On the other hand, thedehydrated muscle tissue absorbed a higher amount oflight which resulted in a darker color of the product anddecreased L* values.In the soy protein samples, the L* values remainedapproximately the same or decreased , although someauthors had opposite results [13, 14, 23, 34]. Usingwhey protein also led to lower L* values [18, 35].Serdaroglu, however, claimed that milk additives slightlyincreased L* values, with similar observations made byHughes et al. [17, 36]. Barbut reported no significantchanges caused by whey supplements [37].The values of redness (a*) are shown in Table 5.After production, these values ranged from 12.72 to14.50. This color parameter was significantly differentbetween the samples and during storage (P < 0.05).Many authors reported higher values and greaterdeviations [4, 31]. A reduction of the a* value was dueto a higher amount of lactic acid, which denaturedmyoglobin, nitrosylmyoglobin, and oxymyoglobin [4].A lower protein content had the same effect, while a lowfat level and a high water content led to increased a*values.Serdaroglu and Abdolghafour found no effect ofdairy supplements on the a* value, although someauthors reported a decline in this value when usingadditives, 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 from12.35 to 14.79 in the 0.5% whey protein and 0.5% soyprotein samples, respectively. However, during furtherstorage, this parameter reached 12.49 and 18.00 forthe 0.5% whey protein and 0.5% soy protein samples,respectively. Thus, the differences between the samplesand during storage were significant (P < 0.05). Similardata were reported by other authors [4]. Lower valueswere given by Skaljac et al. for sausages stored undercontrolled conditions in an industrial chamber [4].Higher values for vacuum-packed Petrovska sausagewere reported by Skaljac et al. [38]. The decrease in theb* values was assumed to be caused by microorganismsthat use oxygen during fermentation, thus reducingthe amount of a muscle pigment that beneficiallyaffected the b* value [37]. Another study reportedhigher fermentation temperature and the additionof autochthonous starter culture as a cause of thedecrease [21].Most authors agree that adding whey and soy proteinisolates decreases the b* values or that they do notchange significantly [34, 37]. Abdolghafour reported thatthe 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 increasein lightness (L*) and a decrease in redness (a*) andyellowness (b*) [36].The external appearance of the sausages at the endof production, as well as during the storage period,was satisfactory without any statistically significantdifferences between the samples (P > 0.05). The coatwas not separated from the emulsion, deformed orTable 5 a* values of sausages with protein isolates during storage (average ± SD)Samples Storage period, months0 1 2 3 6Control 14.50a,A ± 2.25 12.37a,B ± 2.88 16.56a,c,C ± 2.45 12.32a,B ± 2.77 14.85a,A ± 2.710.5% 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 ± 2.151.5% 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 ± 1.910.5% 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 ± 2.051.5% 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 ± 1.58a–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, months0 1 2 3 6Control 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 ± 4.530.5% 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 ± 4.091.5% 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 ± 4.290.5% 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 ± 3.541.5% 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 ± 4.23a–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)264Velemir A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 259–267damaged; it was slightly wrinkled and highly graded forall the samples. Similar results were obtained by Vasilevet al. for a functional sausage with fatty tissue [39].After production, the cross-section of the sampleshad a mosaic appearance, with slightly larger particles offat tissue, which is characteristic of this product. Insidethe sausage were no visible cracks, and the componentswere well connected. The appearance of the sectionwas rated very highly in all the test samples duringstorage. The lowest values were recorded, as expected,after 6 months of storage, from 4.36 to 4.86. Mostpanelists pointed out the presence of a high contentof fatty tissue at the intersection of the sausage, whichwas confirmed by an extremely high fat content in thesamples. Bratulić et al. made the same conclusion,having examined sausages from the Istrian region [12].The sensory evaluation of the cross-section color, aswell as odor, flavor, and taste in the analyzed sausagesamples during a six-month storage period are presentedin Fig. 1. The cross-section color after production wasadequate, with minimal deviations. The meat pieceswere red and the particles of fat tissue were whitish. Thegrades ranged from 4.65 to 4.77, and later, between the1st and the 3rd months, they varied from 4.38 to 5.00. Atthe end of the test period, after six months of storage, theratings were lower, ranging from 3.84 to 4.48, but theywere still acceptable. The color was noticeably lighter inthe samples with soy protein, although the other sampleswere characterized as slightly brighter than expected(pieces of meat). After six months, a greater change incolor was noticeable, especially at the edges, which wasmore expressed in the whey samples.Abdolghafour and Zaki cited higher grades for thesamples with added whey, which declined during storage[18, 35]. According to Akesowana, adding soybeans hada positive effect on the color, while Krasnowska et al.did not indicate a significant difference between thesamples with soy and whey compared to the controlsample [13, 34].The most obvious changes in sensory characteristicswere in odor, taste, and flavor during the storageperiod. We found that the use of additives hardlyaffected the characteristic pleasant smell of fermentedproducts after ripening and the mild smell of smoke.The grades after production ranged from 3.77 to4.92. Adding soy proteins during this period reducedthe intensity of aroma and flavor, contributingto a bland taste. Many authors reported similarobservations: adding up to 3% of soy protein maskedthe intensity of other flavors, reduced juicinessand salinity [40]. Serdaroglu concluded that wheycaused the absence of meat flavor [17]. We foundchanges in sensory properties during storage. Thesamples with 1.5% of additives had less expressedcharacteristics, a mismatch of aroma and taste. Thewhey samples had a sour odor. Krasnowska et al.cited slightly lower grades for flavor and juiciness, andbetter grades for taste in the samples with soy and wheyproteins [13, 30, 34].The texture of the sausages after production wassatisfactory, with minor deviations (Fig. 2). Observinga sausage cut, we found that the mass was compact andthat 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 thegrades ranging from 3.92 to 4.57. The whey samplesbecame softer and less connected, while the soy sampleswere harder than expected. After six months, the gradeswere lower, ranging from 3.45 to 4.23. The productscrumbled during the cutting and also demonstrated sometoughness. The samples with a higher amount of addedprotein attained lower grades, while the 0.5% soy proteinsample had the best texture. Many authors reported apositive effect of added soy and whey on the texture, andtherefore on the grades, compared to the control sample[13, 18, 34].The overall sensory quality of all the samples wasquite high during the entire test period, with no majorFigure 1 Sensory evaluation of cross-section color, odor, flavor, and taste of sausages with protein isolates3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B33.544.55013 26Colour-sectionControl 0.5% whey isolate1.5% whey isolate 0.5% soy isolate1.5% soy isolate3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B22B 3A 3B3 2K 2A 2B 3A 3B0122B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B33.544.55013 26Colour-sectionControl 0.5% whey isolate1.5% whey isolate 0.5% soy isolate1.5% soy isolate3 2K 2A 2B 3A 3B3 K 2A 33.544.55013 26Cross-section colorK 2A 2B 3A 3B3 6Сolor, odor, flavorK 2A 3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.5503 26Сolor, odor, flavorK 2A 2B 3A 3 2K 2A 2B 3A 3B3 K 2A 33.544.55013 26Cross-section colorK 2A 2B 3A 3B3 6Сolor, odor, flavorK 2A 3 2K 2A 2B 3A 3B3 2K 2A 2B 3A 3B33.544.55013 26Cross-section colorK 2A 2B 3A 3B2.533.544.55013 26Сolor, odor, flavorK 2A 2B 3A 3B265Velemir A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 259–267deviations from the maximum quality (P > 0.05). Afterproduction, the grades ranged from 4.37 to 4.79. Thewhey samples received high grades (4.71), almost as thecontrol (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 scoresranging from 4.35 to 4.82, and the samples with smalleramounts of additives were rated slightly better. Aftersix months of storage, the marks were somewhat lower(3.98 to 4.32). In this period, the soy samples were givenbetter grades, just as the samples with smaller amountsof additives We found that all the samples showed goodratings and acceptability during the entire test period.Krasnowska et al. found that the products with wheyand soy proteins had better sensory parameters [34].Many authors agree that whey and soy proteinsupplements have a positive influence on sensorycharacteristics [18, 30, 40].CONCLUSIONThe results of our study showed that proteinsupplements possessed excellent functional propertiesin fermented products, including the emulsifying andbinding properties. We found a significantly noticeablereduction of water activity, which is very important inFigure 2 Texture and overall sensory quality of sausages with protein isolatesthe production of fermented sausages in terms of theripening rate. Slower moisture losses during storagewere observed in the samples with additives. Anothereffect was that on hardness: a 0.5% soy protein isolateresulted in a tougher product. We also found a minoreffect on the color: the samples with the additivesshowed a slightly lower L* value, while those withsoy protein had higher yellowness (b*). The use ofthe additives did not have a significant effect on thechemical composition and sensory properties of theproduct (P > 0.05) because of their low concentrations.The main characteristics of meat products werepreserved despite the addition of non-meat proteins.However, the effect of non-fat proteins on the qualityof fermented sausages needs further investigation todetermine the optimal concentration for obtaining highquality products.CONTRIBUTIONAuthors are equally related to the writing of themanuscript and are equally responsible for plagiarism.CONFLICTS OF INTERESTThe authors declare that there is no conflict ofinterests.