INTRODUCTIONIntroducing slaughter by-products into foodformulations and technology is a promising directionin the meat industry that ensures a rational use ofprotein raw materials. Modern meat scientists aredeveloping new products using heat-treated offal of farmanimals [1–4].Such products include liver sausage, paste, headcheese, and jellied meat. Meat pastes are especiallypopular. They have a spreading consistency and canbe packaged in a casing or container. According tothe standards, pastes are classified into “meat pastes”(category A) with at least 20% of muscle tissue and“meat-containing pastes” (category B) with 0 to 20%of muscle tissue. Pastes are affordable meat productsdue to a lower cost of liver, skirt, lungs, kidneys, andmeat trimmings compared to meat. Our meat markettraditionally offers pastes in a casing that are popularamong students, schoolchildren, tourists, and passengerson trains and planes. These products are made frominexpensive protein-containing ingredients with a highnutritional value and are packaged in small portions. According to literature, modern meat scientistsare interested in combining meat products (includingpastes) with plant ingredients to enrich the product withbiologically active substances of natural origin (microandmacroelements, vitamins, amino acids, antioxidants,etc.) and increase its functional, technological, and otherproperties.For example, Gurinovich et al. formulated a meatpaste by combining animal protein with that of pine nutoilcake. This way, the authors improved the functionalproperties of meat systems and enriched the end productwith a plant-origin ingredient [5].Bazhenova et al. mixed forcemeat with wheat flourcontaining selenium, an essential trace mineral. Theauthors described how they selected their method ofintroducing selenium-enriched flour into the forcemeat.They concluded that a 10–15% protein-fat emulsionwith selenized flour increased the functional andtechnological parameters of forcemeat and provided50–70% of our daily requirement of selenium [6].Giro and Chirkova proposed enriching paste withiron [7]. They aimed to develop functional meat-basedproducts for people predisposed to, or suffering from,iron-deficiency anemia. Their study showed that offalbasedpastes enriched with chickpea could be usedto prevent disturbed hematopoiesis caused by irondeficiency. These products contain highly bioavailablemicroelements that help the body to quickly mobilize itscompensatory reactions.Another study by Okuskhanova et al. looked intothe composition and properties of maral deer pastesfortified with beans and protein. The authors developedthree formulations with varying amounts of the proteinfortifier and beans: no protein fortifier or beans; 15%protein fortifier and 20% beans; and 25% proteinfortifier and 10% beans. The study showed that thethird formulation had a higher content of essential andnon-essential amino acids compared to the first twovariants [8].Pastes from hypoallergenic horse meat and lambwere formulated by Lyakh et al. with the addition ofdried dill and Polisorbovit-95, a biologically activedietary supplement. According to their results, thiscombination of ingredients improved the product’ssensory and physicochemical properties [9].As we can see, meat scientists have created variousformulations of pastes with plant ingredients rich inbiologically active substances.Further, modern scientific literature shows increasedinterest in studying antioxidant capacities of naturalplant ingredients in order to introduce them into foodproducts to improve their functional properties andinhibit fat oxidation processes [10–21]. Antioxidants canneutralize the destructive effects of free radicals on ahuman body. Our antioxidant system is one of the mainmechanisms for stabilizing our adaptive potential. Thisis especially important for people who live in adverseenvironmental conditions and have an unbalanced dietcontaining synthetic ingredients.For example, Lisitsyn et al. studied the antioxidantactivity of aromatic plant extracts (black pepper,rosemary, sage, and thyme) at the GORO ResearchCenter for Ecological Resources (Rostov-on-Don,Russia). The scientists commercialized a new technologyfor processing aromatic raw materials – supercriticalCO2 extraction. This technology produces extractswith a significantly different composition from thoseobtained in traditional ways. Supercritical extractscontain a variety of terpene compounds, as well aswaxes, pigments, high molecular weight saturatedand unsaturated fatty acids, alkaloids, vitamins, andphytosterols. These substances have high biological,antimicrobial, and antioxidant activities. Accordingto the results, the highest and the lowest contents ofantioxidants were found in sage and black pepperextracts (3.1% and 0.07%, respectively). It is generallyaccepted that natural extracts with an antioxidantcontent of at least 0.1% can be considered as a dietarysupplement with antioxidant properties. Therefore,the authors recommended using sage, rosemary, andthyme extracts as antioxidant ingredients for meatproducts [10].Another group of researchers, Zabalueva et al.,looked at antioxidant contents in water-alcohol infusionsof medicinal plants, depending on the method of theirpreparation. They found that the concentration of watersolubleantioxidants in infusions obtained by macerationdid not differ significantly from those prepared byultrasound and an ultra-high frequency electromagneticfield. The study showed the potential of using wateralcoholinfusions from rose hips and barberry fruitsas antioxidant supplements in the production of meatproducts [15].A wide range of plant materials (vegetables, fruits,berries, and herbs), including wild plants, are introducedinto meat products in the natural form or as extracts,infusions, and decoctions treated in various ways.Edible and medicinal plants are collected, processed,and utilized almost without waste. However, waste fromprocessing wild plants is not always used rationally,being an environmentally friendly, renewable rawmaterial that could be used as a source of biologicallyactive natural substances. These wild plants includelingonberries growing in Transbaikalia (east of LakeBaikal) that are rich in biologically active compoundswith medicinal properties. Lingonberry leaves containphenolic glycosides (arbutin and methylarbutin),vaccinine, lycopene, hydroquinone derivatives, acids(ursulic, tartaric, gallic, quinic, and ellagic), tannin,hyperoside, and other flavonoids. Lingonberries are richin sugars, ascorbic acid, carotene, and organic acids [22].The chemical composition of lingonberry leaves andfruits indicates a high antioxidant capacity of respectiveproducts. In fact, lingonberries are processed in large252Bazhenovа B.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 250–258quantities for juice production. However, their byproducts– such as husks, pulp or marc – could also beused as a source of biologically active substances. Someauthors propose enriching meat products (e.g. liverpaste) with fresh or dried lingonberry and cranberrypulp [18, 19].For example, Bitueva and Ayusheeva introduceddried cranberry or lingonberry pulp, pre-crushed andreconstituted, into ground meat products. The powderedpulp was added at the stage of forcemeat preparation,replacing 13–15% of bread. This method enriched themeat products with biologically active substances [18].In another study, Ivanova and Izosimova proposeda formulation of meat paste with 19% polyfunctionaladditives – lingonberry or cranberry marc. The marccontains citric and malic acids that shift the medium’spH away from the isoelectric point, enhancing thedissociation of the main and acid groups of protein, aswell as increasing bound moisture and the yield of theend product. A high content of low-ester pectins in theberry marc also contributed to the system’s stabilization.Biologically active substances and antioxidantsincreased the microbiological resistance of the meat andplant paste. The product also had an improved vitaminand mineral composition [19].In our previous work, we prepared a water-alcoholextract of lingonberry marc which was then dried [23].The dry extract is a powder rich in biologically activenutrients that is easy to store and transport. Due to ahigh concentration of dry substances, the extract canbe introduced in small amounts into the formulationof meat products, providing them with functionalproperties and eliminating negative effects on theproduct’s sensory and physicochemical characteristics.Thus, it is extremely relevant to create productsbased on a combination of meat and plant materialsto enrich them with micro- and macroelements,vitamins, amino acids, and antioxidants. Many typesof plant materials contain a variety of compoundswith an antioxidant effect. Even low concentrationsof antioxidants in the human body can slow down orprevent oxidation processes which are known to causepremature aging and disease. Thus, we can inhibit fatoxidation by introducing antioxidants into food products.In view of the above, we aimed to develop a meatpaste formulation with an extract from lingonberry marc(originating in Transbaikalia), as well as evaluate thetotal content of antioxidants and effect on the color andstability of the paste in the casing during storage.STUDY OBJECTS AND METHODSThe objects of the study included a dry lingonberrymarc extract (DLME), forcemeat, and a ready-madepaste in the casing.A dry extract of lingonberry marc was obtained inaccordance with Patent No. 2626565. Lingonberries werepressed for juice and the remaining marc was placed ona baking sheet in a 5–8 mm layer and then dried in anoven with infrared radiation at 35–40°C for 40–50 minto 10–15% moisture. The dried marc was crushed to apowder state and subjected to extraction with a wateralcoholsolution using a microwave electromagnetic field(700 W, 2450 MHz).The water-alcohol extracts were filtered andconcentrated on a rotary evaporator under vacuum ina water bath at temperature below 45°C until a syrupconsistency was reached (40–50% dry matter). Thesyrup was then vacuum-dried at a temperature below50°C for 3.5–4.5 h to obtain a powder with a residualmoisture of < 5%. Such process parameters do not causeany qualitative changes in thermolabile substances.They preserve maximum biological activity of activesubstances and ensure high quality of the extract.The main ingredients in the formulation of pastesamples were cheek meat, beef liver, meat trimmings,soy isolate, and semolina. To evaluate the DLME effectson forcemeat characteristics, samples were made with0.1, 0.2, 0.3, and 0.4% DLME previously dissolved inwater in a ratio of 1:5. The paste was made in a casingaccording to the traditional technology.A DLME-free paste sample was used as a control.To evaluate the shelf life of the paste, we conductedtwo experiments. For the first experiment, we preparedcontrol and DLME samples and stored them for 14 days.For the second experiment, we used a 0.2% acidityregulator – sodium lactate (E325) and stored the samplesfor 18 days.To evaluate the samples’ antioxidant activity, weperformed amperometric measurement of the totalcontent of antioxidants in terms of quercetin. The testsamples were subjected to extraction with bidistilledwater to isolate water-soluble compounds with anantioxidant effect. The total content of antioxidants wasmeasured on a Tsvet Yauza-01-AA analyzer. Quercetinsolutions were used to construct calibration graphs [24].The extraction efficiency was determined by the amountof phenolic compounds isolated spectrophotometricallyusing the Folin-Ciocalteu reagent. The content ofbenzoic acid was measured by the HPLC method.The optical density of the colored aqueous extractsof the test and control samples was determined bythe photocolorimetric method on a KFK-3-01 ZOMZphotometer. This method is based on measuring thepolychromatic radiation of the visible part of thespectrum. The dependence between light absorptionand the radiation wavelength is expressed by a curve(spectrum) of light absorbed by this solution. In thegraph, wavelengths are plotted along the abscissa, whileoptical densities are plotted along the ordinate.The sensory evaluation of the paste samples wascarried out on a nine-point scale according to StateStandard 9959. The peroxide value was determined bya method based on the interaction between fat oxidationproducts (peroxides and hydroperoxides) and potassium253Bazhenovа B.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 250–258iodide in a solution of acetic acid and chloroform,followed by the quantification of iodine released in asodium thiosulfate solution by the titrimetric method(State Standard R 51487-99I).The microbiological parameters of the paste sampleswere assessed according to State Standards R 50454-92IIand 9958-81III.The experiments were performed in triplicate.Statistical processing of the data was carried out inMicrosoft Excel.RESULTS AND DISCUSSIONFirst, we analyzed the chemical composition of thelingonberry marc extract originating in Transbaikalia(Table 1).As we can see, the main component of thelingonberry marc extract is a group of phenoliccompounds (6.63%), including water-soluble pigments,anthocyanins, and benzoic acid (1.34%). In a preliminarystudy [25], we used the disk diffusion method and foundthat the extract had antimicrobial activity, partly due tothe presence of benzoic acid with bactericidal properties.Thus, introducing the lingonberry marc extract intofood products, namely meat, can inhibit the growth ofmicroorganisms.Table 1 also shows a high total content ofantioxidants, including polyphenols, anthocyanins,vitamin C, and other compounds (382.6 mg/g).Anthocyanins (3.58%), accounting for half of allphenolic compounds, give lingonberries brightred or burgundy coloring. They include malvidinsand peonidins (polyphenolic compounds from theflavonoid group) which contain mono- and diglycosidesdecomposing into sugar and aglycon (anthocyanidins)upon hydrolysis.I State Standard R 51487-99. Vegetable oils and animal fats. Methodfor determination of peroxide value. Moscow: Standartinform;2008. 6 p.II State Standards R 50454-92. Meat and meat products. Detectionand enumeration of presumptive coliform bacteria and presumptiveEscherichia coli (Reference method). Moscow: Standartinform;2010. 7 p.III State Standards 9958-81. Sausage products and meat products.Methods of bacteriologikal analysis. Moscow: Izdatelʹstvo standartov;2001. 14 p.Anthocyanins are widely used in the food, medical,pharmacological, and cosmetic industries. A daily intakeof brightly colored berries (160–2000 mg) leads to theabsorption of anthocyanins (0.005–0.1%), which canhave an antioxidant effect. Solutions of anthocyaninsneutralize almost all radical forms of oxygen andnitrogen four times as efficiently as ascorbate orα-tocopherol. Even low concentrations of antioxidantsubstances can slow down or prevent oxidativeprocesses. For example, adding only 0.001–0.01% ofantioxidants to oil can slow down its oxidation for a longtime [26].When dissolved, the lingonberry marc extractretains its dark red color. When it is added to graynon-nitrite forcemeat, the latter acquires a purple hue.Anthocyanins are known to act as pigments and thecolor of plants depends on their concentration, as wellas the medium pH. They are red in acidic media, purplein neutral and blue in alkaline media. In this regard, westudied how the concentration of the dry lingonberryextract affected the forcemeat pH (Fig. 1).The forcemeat pH decreased with the introductionof the dry extract, while remaining closer to the neutralregion. The extract’s acidity was quite high (3.24, seeTable 1) due to the use of marc, whose biologically activesubstances are better extracted into the solution thanthose of the fruit juice. Therefore, the marc extract isrich in acids (about 2.5%) – citric, malic, benzoic, oxalic,acetic, glyoxylic, pyruvic, hydroxypyruvic, ketoglutaric,ascorbic, and others, with the highest content of benzoicacid (1.34%). This high concentration of acids providesthe extract with a low pH, so even very small amountsof the dry extract can significantly decrease theforcemeat pH.Before the extract was introduced into the forcemeat,it was pre-hydrated for uniform distribution. The DLMEconcentrations of 0.1, 0.2, 0.3, and 0.4% reduced theforcemeat pH by 1.49, 2.98, 3.7, and 4.47%, respectively.However, the absolute value of the forcemeat pHremained close to neutral, which did not affect thefunctional and technological properties of the forcemeatsystem.Adding the DLME in concentrations from 0.1 to0.4% affected the forcemeat color. To select the optimalTable 1 Qualitative indicators of dry lingonberry marc extractIndicator MeaningAppearance loose massTaste and smell sweet and sour, tangy, withlingonberry flavorColor burgundyAcidity, pH units 3.24 ± 0.08Moisture, % 4.52 ± 0.08Phenolic compounds, %including anthocyanins6.63 ± 0.043.58 ± 0.04Benzoic acid, % 1.34 ± 0.02Total antioxidants, mg/g 382.60 ± 8.70Figure 1 Amounts of dry lingonberry marc extractvs. forcemeat acidity66.26.46.66.80 0.1 0.2 0.3 0.4Forcemeat pHDry extract, %03060900 Total antioxidants, mg/100 g0.40.81.21.6Optical density D254Bazhenovа B.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 250–258concentration, we analyzed the color characteristicsof ready-made pastes in the casing after heat treatment(Table 2).As we can see, 0.1% and 0.2% DLME concentrationsdid not change the habitual sectional color of paste, graybrownor slightly darker. However, larger amounts ofthe extract (even 0.3%) gave the paste a purple hue. Thischange is associated with the presence of anthocyanins,water-soluble plant pigments, in the extract.Lingonberries may contain such anthocyanins ascyanidin-3-galactoside, peonidin-3-galactoside, cyanidin-3-arabinoside, peonidin-3-arabinoside, cyanidin-3-glucoside, and others. However, their qualitativecomposition depends on the growth conditions. Of greatimportance for the color of plant pigments is the pH ofvacuoles where pigments accumulate. The same pigmentin different media can exhibit varying colors: yellowgreenin an alkaline medium, purple in a neutral, and redin an acidic medium [27].In the DLME, just like in lingonberries, the mediumis strongly acidic (pH 3.24), so the color is bright red.When the extract is introduced into the forcemeat,whose medium is close to neutral, it acquires a purpletint from water-soluble anthocyanins. The color,however, depends on the concentration of pigments inthe forcemeat.For the quantitative and qualitative analysis of watersolublecompounds, we determined the optical density ofthe paste samples with different DLME concentrations,using the spectrophotometric method (Fig. 2).Optical density is known to be directly proportionalto the concentration of compounds in a solution. Thescale of the abscissa did not show a significant differencein the samples. However, a thorough analysis indicatedthat the highest peaks for the control sample (curve 1),0.1% DLME sample (curve 2), 0.2% DLME sample(curve 3), and 0.3% DLME sample (curve 4) were atwavelengths of 554 nm, 557 nm, 557 nm, and 559 nm,respectively (Fig. 2). As we know, the spectral rangefrom 500 to 560 nm corresponds to purple, while thatfrom 560 to 575 nm to purple. Our study showed thesame results: the sample with 0.3% DLME had a violethue (Table 2).Optical density along the ordinate axis characterizesthe color intensity. It means that the height of the peakscorresponds to the concentration of dissolved substances(polyphenols) in the samples. As we can see, the opticaldensity values for the control sample (curve 1), 0.1%DLME sample (curve 2), 0.2% DLME sample (curve3), and 0.3% DLME sample (curve 4) were 0.86, 0.92,0.93, and 0.93, respectively. The results show that largeramounts of the extract led to higher concentrations ofwater-soluble compounds, having reached a maximumon curve 4 (0.3% DLME sample).Thus, we found that increasing the DLMEconcentration to 0.3% provided the paste with a highcontent of antioxidants, but added a purple hue to itscolor due to the presence of anthocyanins, which mightspoil the product’s appearance.Antioxidants, including phenolic compounds,neutralize lipid peroxidation, all radical forms of oxygenand nitrogen. Therefore, we analyzed the samples for thetotal content of antioxidants (Fig. 3).Figure 3 shows a correlation between increasedamounts of lingonberry marc extract and higher totalantioxidant capacity of the paste. According to theresults, the total antioxidants in the test samples with 0.1,0.2, 0.3%, and 0.4% DLME was higher than that of thecontrol by 1.3, 1.5, 1.8, and 2.05 mg/g, respectively. Theextract antioxidant complexes were rich in polyphenolsTable 2 Paste color with different concentrations of drylingonberry marc extractPaste samples Color in sectionControl (without DLME) Gray-brownTest (with DLME):0.1% Gray-brown0.2% Dark gray-brown0.3% Brown with a light purple hue0.4% Brown with a light violet hue1 – control, 2 – 0.1% DLME sample, 3 – 0.2% DLME sample, 4 – 0.3% DLME sampleFigure 2 Optical density of paste samples with different concentrations of dry lingonberry marc extract66.26.46.66.80 0.1 0.2 0.3 0.4Forcemeat pHDry extract, %03060900 0.1 0.2 0.3 0.4Total antioxidants, mg/100 gDry extract concentration, %00.40.81.21.6700 680 660 640 620 600 580 560 540 520 500Optical density DWavelength, nm1 2 3 401234Peroxide value, mmol O/kg01230 7 10 15 18Peroxide value, mmol O/kg1234255Bazhenovа B.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 250–258(6.63%; Table 1). They also contained organic acids,vitamins, lycopene, and other antioxidant compounds.Further, we performed a sensory evaluation of thepaste on a nine-point scale to establish how the extractaffected the product’s consumer appeal (Table 3).According to the results, small amounts of the drylingonberry marc extract did not significantly affect thetexture, smell, or taste of the end product. However, itsconcentrations above 0.2% had a negative effect on thepaste color in section. As we could see in Table 2, thesample with 0.3% DLME acquired a light purple hue andthat with 0.4% DLME, a light purple tint. The sensoryevaluation showed a concentration of 0.2% as optimalsince it did not spoil the characteristics of the endproduct while enriching it with antioxidant compounds(Fig. 3). Therefore, we used this concentration in furtherstudies. For a physicochemical analysis, we prepared acontrol and a test sample with 0.2% DLME (Table 4).The results showed that the dry lingonberry marcextract did not affect the quality of the paste, but itdoubled the total content of antioxidants. The content ofphenolic compounds in the extract is the most importantindicator of its biological value, which determines itsantioxidant activity.To assess the extract’s antioxidant capacity,we studied the process of fat oxidation. For this,we prepared a control and a test paste samples anddetermined the peroxide value which characterizes theaccumulation of primary lipid decomposition productsduring storage.Storage periods were selected in accordance withState Standard R 55334-2012IV (10 days for pastes inpolyamide casings and 15 days for pastes with acidityregulators). Our experiment consisted of two tests. Inthe first test, the control and the test samples (withoutDLME and with 0.2% DLME, respectively) weremade without acidity regulators and stored for 14 days(Fig. 4). In the second test, the control and the testsamples (without DLME and with 0.2% DLME,respectively) contained 0.2% sodium lactate as anacidity regulator and were stored for 18 days (Fig. 5).The reason for this experiment was that acidityregulators are necessarily used in production, especiallyin summer, to increase the shelf life of perishable meatproducts. Thus, the experiment could show the DLMErole in the inhibition of peroxidation of animal lipids.The samples were stored under identical conditions, inthe dark at 2 ± 2ºС.Figure 4 shows the effect of DLME on the process offat oxidation in the paste.In Fig. 4, we can see an irreversible process offat oxidation with the accumulation of primary fatdecomposition products. Animal fats contained in thepaste undergo auto-oxidation or peroxidation. Thepolyamide casing cannot completely prevent oxidation,since it is caused by a complex of factors: oxygen, light,positive temperature, unsaturated fatty acids, etc.According to regulatory documents, the peroxidevalue for a high-quality fat product, low-oxidized rawmaterials, and fat raw materials should not exceed0.5, 3.5, and 10 mmol of active oxygen per 1 kg of fat.As we can see in Fig. 4, the peroxide value in thecontrol and test samples immediately after preparationwas 0.71–0.75 mmol O/kg. After six days of storage,it increased 3.17 times in the control and 2.98 timesin the test sample, reaching 2.38 and 2.12 mmol O/kg,respectively. We found that on day 6, the peroxidationprocess in the test sample slowed down by 10.9%compared to the control. After 10 days (the shelf lifefor this type of product), the process of lipid oxidationcontinued to intensify and the peroxide value increasedto 3.1 mmol O/kg in the control sample (6.2 as high asIV State Standard R 55334-2012. Meat and meat containing pate.Specifications. Moscow: Standartinform; 2014. 34 p.Figure 3 Total content of antioxidants in paste samples withdifferent concentrations of dry lingonberry marc extract0.403060900 0.1 0.2 0.3 0.4Total antioxidants, mg/100 gDry extract concentration, %620 600 580 560 540 520 500Wavelength, nm2 3 401230 7 10 15 18Peroxide value, mmol O/kgStorage period, daysконтроль опытTable 3 Sensory characteristics of paste samples with drylingonberry marc extractCharacteristic Control Test samples with DLME0.1% 0.2% 0.3% 0.4%Appearance 8.5 ± 0.2 8.5 ± 0.1 8.5 ± 0.2 8.3 ± 0.1 8.2 ± 0.1Texture 8.4 ± 0.2 8.5 ± 0.2 8.4 ± 0.1 8.4 ± 0.2 8.3 ± 0.2Color andappearancein section8.6 ± 0.2 8.6 ± 0.1 8.6 ± 0.1 8.0 ± 0.1 7.4 ± 0.1Smell and taste 8.7 ± 0.2 8.7 ± 0.1 8.7 ± 0.2 8.3 ± 0.2 8.1 ± 0.2Table 4 Physicochemical characteristics of paste in casing(0.2% DLME)Characteristics Paste in casingTest ControlContent, %moisture 71.5 ± 0.1 71.8 ± 0.03protein 13.6 ± 0.1 13.3 ± 0.1fat 11.9 ± 0.05 12.1 ± 0.2minerals 1.4 ± 0.02 1.2 ± 0.1salt 1.6 ± 0.02 1.6 ± 0.02Total antioxidants, mg/100 g 67.84 31.23256Bazhenovа B.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 250–258the initial value) and to 2.7 mmol O/kg in the test sample(3.8 times as high as the initial value). On day 10, thedifference between the control and the test samplesreached 12.9%.Further analysis of the oxidation process showed thatafter 12 days, the peroxide values in the control and thetest samples were 3.55 and 3.1 mmol O/kg, respectively.After 14 days, the process accelerated and the valuesreached 4.1 and 3.7 mmol O/kg, respectively. Thedifference between the control and the test samples was12.7% on day 12 and 9.7% on day 14. Thus, the steadilylower peroxide value in the test sample, compared to thecontrol, indicated a decreased rate of lipid peroxidationreactions throughout the whole storage period. Thisresult can be explained by the presence of DLME rich inantioxidant compounds that can neutralize the effects offree radicals playing a significant role in chain reactionsof lipid oxidation.The first test showed that introducing DLME intothe paste made without acidity regulators helped toslow down fat oxidation and increase the shelf life bytwo days (total of 12 days without signs of oxidativedamage).In the second test, the control (without DLME) andtest (0.2% DLME) samples contained 0.2% sodiumlactate as an acidity regulator (Fig. 5).The growth of peroxide values indicated theaccumulation of fat oxidation products in the pastesamples with sodium lactate throughout storage.However, we found a certain inhibition of the oxidationprocess compared to the first test, in which the sampleswere made without an acidity regulator. For example,on day 10, the peroxide values of the DLME sampleswithout and with sodium lactate were 2.7 and 2.5 mmolO/kg, respectively. Thus, we can see a synergistic effectof sodium lactate and DLME antioxidant compoundsduring fat oxidation in the paste.Further, we compared the peroxide values in thecontrol and test samples with sodium lactate. We foundthat after 15 and 18 days of storage, the peroxide value ofthe test samples was 20% lower compared to the control,which was significantly higher than in the sampleswithout sodium lactate (12.9%).At this stage, we concluded that a combination oflingonberry extract with sodium lactate produced a morepronounced antioxidant effect. At the end of the storageperiod (18 days), the peroxide values of the control andtest samples were 3.5 and 2.7 mmol of active oxygen per1 kg of fat. This means that the paste’s shelf life could beextended by three days.Thus, our experiment showed that although DLMEcontributed to the inhibition of lipid oxidation, itssynergism with sodium lactate could significantly slowdown these reactions.The shelf life of paste containing a large amountof water (71–72%) is affected by not only oxidativeFigure 4 Effect of dry lingonberry marc extracton the peroxide value of paste without acidity regulatorsduring storage0700 680 660 640 620 600 580 560 540 520 500Wavelength, nm1 2 3 4012340 6 8 10 12 14Peroxide value, mmol O/kgStorage period, daysконтроль опыт01230 7 10 15 18Peroxide value, mmol O/kgStorage period, dayscontrol test контроль опытFigure 5 Effect of dry lingonberry marc extract on theperoxide value of paste with sodium lactate during storage0.3 0.4extract, %0300 0.1 0.2 0.3 0.4Total antioxidants, Dry extract concentration, %640 620 600 580 560 540 520 500Wavelength, nm2 3 412 14daysопыт01230 7 10 15 18Peroxide value, mmol O/kgStorage period, daysкcоoнnтtrрoоl л ь о tпesыtтTable 5 Microbiological indicators of control and test samples during storageIndicator Storage of paste without sodium lactate, daysDLME test samples Control0 6 10 12 0 6 10 12QMAFAnM, CFU/g 1.4×102 4.1×102 6.2×102 7.3×102 1.4×102 5.8×102 7.5×102 8.5×102Coliforms in 1 g not detectedIndicator Storage of paste with sodium lactate, daysDLME test samples Control0 7 15 18 0 7 15 18QMAFAnM, CFU/g 1.4×102 4.5×102 8.4×102 1.6×103 1.4×102 6.1×102 1.0×103 2.1×103Coliforms in 1 g not detected257Bazhenovа B.A. et al. Foods and Raw Materials, 2020, vol. 8, no. 2, pp. 250–258processes, but also by the growth of microorganisms.According to Table 1, the dry lingonberry extract is richin benzoic acid (1.34%) that has strong antimicrobial,antiseptic, and bactericidal effects inhibiting decayand fermentation processes. As a result, lingonberrieslast quite a long time without canning. Also, previousstudies have proven the antimicrobial activity of DLMEadded to bakery products [25].In our study, we investigated a possibility ofinhibiting microorganisms in the DLME paste sampleswith and without sodium lactate (Table 5).As we can see, all the samples showed a growth ofmicroorganisms. However, it was less intensive in theDLME test samples with and without sodium lactate,compared to the controls. Thus, the presence of benzoicacid with strong bactericidal action slowed down thegrowth of microorganisms and had a positive effect onthe test samples’ shelf life.As for pathogens, no E. coli bacteria were detectedin any of the test samples, which might be due to thepreliminary heat treatment of the raw materials and theuse of a polyamide casing that excludes the product’scontact with air, containers or equipment.CONCLUSIONThus, our study showed that 0.2% of dry lingonberrymarc extract was the optimal amount to be introducedinto paste forcemeat. This amount increased thenutritional and biological value of the paste andmaintained high consumer appeal. We found that theextract provided the product with a high content ofpolyphenols with antioxidant properties, includinganthocyanins. Rich in antioxidant compounds, theextract inhibited fat oxidation in the paste and, incombination with sodium lactate, produced a synergisticeffect on lipid peroxidation processes. In addition, thedry lingonberry marc extract slowed down the growthof microorganisms due to a high content of benzoicacid with antimicrobial and bactericidal properties. Theintegrated effect of the extract’s components extendedthe shelf life of the paste in a casing by two or threedays.CONTRIBUTIONAuthors are equally related to the writing of themanuscript and are equally responsible for plagiarism.CONFLICT OF INTERESTThe authors declare that they have no conflict ofinterest.FUNDINGThis study was part of State AssignmentNo. 19.5486.2017/BCh commissioned by the Ministryof Science and Highev Education of the RussianFederation.