INTRODUCTIONPolysaccharides have remained in the centre ofscientific attention for several decades. Previously,polysaccharides were used mainly as auxiliarysubstances in the pharmaceutical industry and wereconsidered as biologically active substances. However,they are currently used as functional food ingredients andtechnological additives in many areas of food industry.Polysaccharides are highly beneficial forhuman organism. According to various researches,polysaccharides can produce pronounced antihypoxic,expectorant, anti-inflammatory, immunotropic, enterosorbing,hepatoprotective, hypolipidymic, antitumour,and general tonic effects [1, 2].Polysaccharides ensure the quality and textureof food products, e.g. hardness, brittleness, density,thickening, viscosity, stickiness, gel-forming ability, etc.Many food products owe their soft, fragile, swollen, orjelly-like structure to polysaccharides. Their impressivevariety of functions can be explained by the structuralproperties of individual polysaccharides used as foodadditives. They act as a gelling, thickening, filling,emulsifying, swelling, or foaming agent. They canprevent crystallization and syneresis. They increaseResearch Article DOI: http://doi.org/10.21603/2308-4057-2019-2-X-XOpen Access Available online at http:jfrm.ruIR-spectroscopy of polysaccharideflaxseed (Linum usitatissimum L.) productsIrina E. Minevich1,* , Lidiia L. Osipova1, Alla P. Nechiporenko2 , Mariya I. Melnikova2 ,and Tatyana B. Tsyganova31 Institution Federal Research Centre for Bust Fibre Crops, Tver, Russia2 Saint Petersburg National Research University of Information Technologies, Mechanics and Optics,St. Petersburg, Russia3 Moscow State University of Food Production, Moscow, Russia* e-mail: irina_minevich@mail.ruReceived March 11, 2019; Accepted in revised form April 02, 2018; Published X X, 2019Abstract: Flax seeds are an excellent source of polyunsaturated fatty acids and high-grade protein. They are also rich in non-starchpolysaccharides that are concentrated in their mucus cells. Flaxseed polysaccharides are soluble dietary fibres, which makes them anindispensable functional food ingredient. They can also serve as an additive, thus improving the structure of food, e.g. as a stabilizer,structure former, water and fat retention agent, etc. According to various researches, the functional and technological properties ofpolysaccharide flaxseed products are largely determined by the ratio of polysaccharide fractions and protein content, which dependon the production process. This research featured the effect of the method of obtaining flaxseed polysaccharide products on theprotein content. The study employed chemical analysis and attenuated total internal reflection infrared spectroscopy (ATR-IR). Theprotein polysaccharide products under analysis were obtained by water extraction from two varieties of whole flax seed (Russia),under various conditions of treatment, cleaning, and fractionation. The conditions included pH, temperature, and process time. Duringwater extraction of whole flax seeds, polypeptide-containing polysaccharide complexes were removed from the seed coats. Thenumber, composition, and binding force between the peptide fragments and the polysaccharide matrix depended on the technologicalparameters of the process. The polysaccharide products were tested for total protein content. The results were consistent with the bandintensity in the range of 1700–1500 cm–1, where protein carbonyl groups are usually manifested.Keywords: Flax seeds, polysaccharides, proteins, extraction, IR-spectra of polysaccharide productsPlease cite this article in press as: Minevich IE, Osipova LL, Nechiporenko AP, Melnikova MI, Tsyganova TB. IR-spectroscopyof polysaccharide flaxseed (Linum usitatissimum L.) products. Foods and Raw Materials. 2019;7(2):X–X. DOI: http://doi.org/10.21603/2308-4057-2019-2-X-X.Copyright © 2019, Minevich et al. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 InternationalLicense (http://creativecommons.org/licenses/by/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix,transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license.Foods and Raw Materials, 2019, vol. 7, no. 2E-ISSN 2310-9599ISSN 2308-405757Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Хboth viscosity and the biological and nutritional value ofthe product. No other food additive can perform such avariety of functions.Their structural, physicochemical, functional,and technological properties, as well as their effecton biological activity, are studied by such modernmethods as nuclear magnetic resonance (NMR), infraredspectroscopy, ultraviolet imaging, etc. [3, 4].Flax seeds are known not only as a source ofpolyunsaturated fatty acids and high-grade protein,but also as a source of non-starch polysaccharidesthat are concentrated in their mucus cells. Non-starchpolysaccharides represent a group of low-digestiblecarbohydrates, or dietary fibre [5]. The polysaccharidesof flaxseed mucus are highly soluble in water. They alsoreduce the glycaemic index and cholesterol. In addition,they possess a prebiotic effect [6, 7].The polysaccharides of flaxseed mucus are a mixtureof two fractions – neutral (75%) and acidic (25%) [8–10].The neutral fraction has a high molecular weight andcontains arabinoxylan, while the acidic fraction containsramnegalacturonan. Flaxseed polysaccharide complexcontains 4–20% of proteins, depending on the flaxgenotype and extraction conditions [10]. Proteins arebound with acidic fraction polymers by non-covalentbonds, while no protein has been found in the neutralfraction.Flaxseed polysaccharides are a source of solubledietary fibre, which is an indispensable functionalfood ingredient. They are also a technological additivethat regulates the structure of food mass and can actas a stabilizer, structure former, water and fat-holdingagent, etc. The functional properties that affect foodsystems may result from the synergistic effect theyproduce together with proteins [11]. According to Qianet al., an acidic fraction with 8% of protein showedhigher emulsion properties as compared with the neutralfraction [12]. Functional and technological properties offlaxseed polysaccharide products are also determined bythe ratio of fractions, which depends on the conditions ofthe technological process. According to Kaushik et al.,the ratio of neutral and acidic fractions fell from 6.7to 5.7 when the extraction temperature reached 90°C,while water absorption capacity and emulsion activitydecreased [13].Flaxseed polysaccharides have good prospects as amultifunctional food ingredient. However, there are notenough data on their component composition, functionaland technological properties, and production conditions.Flax seeds of Russian varieties remain especiallyunderstudied.The research objective was to use IR-spectroscopyto study the effect of the method of obtaining flaxseedpolysaccharide products on the protein content.STUDY OBJECTS AND METHODSThe comparative study featured polysaccharideproducts extracted from two Russian varieties ofwhole flax seeds. The first variety was industrial andcorresponded with State Standard 10582-76*. Thesecond variety was of LM-98 brand. All the productsdiffered in extraction conditions: pH, temperature,time, and extraction rate. The technological operationsincluded the following areas:– neutral extraction at pH 6–7;– acidic extraction at pH 4–5;– fractionation of the polysaccharide complex obtainedin the neutral medium;– combined sequential extraction.Distilled water was used to extract polysaccharidesfrom flax seeds by constant stirring. The ratio of seedmass and solvent volume (hydromodule) was 1:20. Theextract obtained was separated from the flax seeds usinga 4-layer gauze filter. After that, the target product wasobtained in two ways:(1) The extract was dried in a thin layer of ≤ 0.5 cmat 60–65°C and then crushed to obtain a dry extract ofpolysaccharides;(2) Polysaccharides were precipitated in a 3-foldexcess of ethanol. The residue was pressed, washedwith acetone, and dried in a drying cabinet at ≤ 50°C toobtain a purified polysaccharide complex.Thus, the main study objects were the dry extract ofpolysaccharides (PS-extract) and a purified polysaccharidecomplex (PS-complex). Protein content was determinedaccording to State Standard 13496.4-93**.A Tensor 37 Fourier spectrometer (Bruker, Germany)was used to define the IR-spectra of ATR-IR on thesurface of the dry samples. The device had an ATRdiamond element. The OPUS software package hadstandard calibration capabilities in the frequency rangeof 4000–500 cm–1 (32 scans) in absorption format.RESULTS AND DISCUSSIONSpectra language. Natural polysaccharides, as arule, are not pure substances but multicomponent anddiverse complexes. They may include protein and lipidcomponents or their fragments. These fragments canbe identified by vibrational spectroscopy. To give aclearer interpretation, Fig.1 illustrates the IR-spectra ofthree main classes of biological substances: proteins,lipids, and carbohydrates. They were obtained from drysamples of polysaccharide obtained from flax seeds,egg albumin, and linseed oil. In the spectrum of eggalbumin, proteins appeared as a pair of typical bands inthe range of 1680–1540 cm–1. They were caused by thevibrations of the carbonyl C=O groups of Amide I andAmide II [14, 15]. The spectrum of flaxseed oil is typicalof plant and animal lipids. It is clearly different fromthe spectrum of other substances. The narrow band at* State Standard 10582-76. Oil flax-seed. Industrial raw material.Specifications. Moscow: Standartinform; 2010. 4 p.** State Standard 13496.4-93. Fodder, mixed fodder and animalfeed raw stuff. Methods of nitrogen and crude protein determination.Moscow: Standartinform; 2011. 15 p.58Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х1743 cm–1 was caused by the vibrations of C=O groups offatty acids in triglycerides. The trident-shaped band witha peak at 1160 cm–1 was due to the vibrations of C–O andC–O–C bonds of carboxylic acids.A broad structured band with a peak at 1030 cm–1 istypical of polysaccharides. It partially overlapped thelipid band (1160 cm–1). The spectra of all three samplescontained bands in the range of 3010–2800 cm–1, whichreflected the vibrations of CHn functional groups thatappeared in all classes of substances. Lipids withunsaturated fatty acids in their composition were markedwith stretching and bending bands of CH functionalgroup with a CH double bond (3008 cm–1 and 722 cm–1,respectively). Vibrations of OH groups often overlapin the range of 3400–3220cm–1. These are bound watermolecules and NHn groups, which quite clearly manifestthemselves in the albumin spectrum as bands ofdifferent intensity with peaks at 3250 and 3020 cm–1.The optical characteristics of variouspolysaccharides showed some remarkable results, ifcompared. Figure 2 demonstrates the spectra of drypreparations of plant and animal polysaccharides.According to the structure of all bands, animalpolysaccharides differed from plant polysaccharides.However, they had a common spectral absorption region,although there can be no absolute coincidence of bandson the wave-number scale.Hyaluronic acid is the main carbohydrate componentof the mucopolysaccharides in animal connectivetissue [16, 17]. In the area of protein structures (1,700–1,500 cm–1), its spectrum showed an intense band witha shoulder on the right branch. This was due to thehyaluronic acid dimer, which had carbonyls (C=O) inthe COOH group and the CONH group, a peptide bondanalogue. The mucopolysaccharide spectrum showedan intense structured carbohydrate band with a peak at1031 cm–1, which was typical of plant polysaccharides.Chitosan is obtained from chitin and is a precursorof a number of glycosaminoglycans. The chitindeacetylation reaction is incomplete [16, 17]. As a result,it contained up to 30% of residual acetyl groups boundto the amine CH3CONH. CONH-composition is typicalof hyaluronic acid. It was the presence of the CONHcompositionin the structure of chitosan that explaineda narrow intense band with a peak at 1640 cm–1 in itsspectrum.Starch and cellulose showed one and two weakbands in this region, respectively. They might resultfrom both the natural properties of the samples andthe technological features of the production process.Thus, the granules of insoluble starch are enclosed ina thin protein shell, which is partially damaged duringgrinding, washing, and drying. Its manifestation canbe seen in the starch spectrum. To obtain solublestarch, the protein shell of starch granules is destroyedby acid treatment. Currently, starch can be obtainedsynthetically. This starch is identical to the naturalproduct, except that it lacks the granular structuretypical of natural plant products. Cellulose production ismuch more complicated and includes a greater numberof chemical treatment stages.All linear polymers, i.e. hyaluronic acid, chitosan,and cellulose, have bands with adjacent peaks, accordingto the analysis of the structure of the carbohydrate bandin the polysaccharide spectra. Chitosan and celluloseare structural analogues [18]. The intensity of the bandswith double peaks in their spectra is significantly lowerthan that of mucopolysaccharide. Starch is a mixtureof branched and helicoid macromolecules of twopolysaccharides: amylopectin and amylase. Starch isclearly separated from the group. The peak of its broadband is bathochromically shifted by 40 cm–1 from thepeak of linear polysaccharides.1. Products of primary and secondary flaxseedextraction in neutral medium (pH 6–7). In Minevichet al., we described the kinetics of primary extraction ofpolysaccharides from industrial flax seeds in a neutralmedium at 60°C [19]. The time interval was 5–120 min,and standard methods of chemical analysis were usedas control. However, we would like to point it out againFigure 1 IR-spectra of different classes of substances: (1) dryflaxseed polysaccharide (2.4% protein), (2) dry egg albumin,(3) flaxseed oilFigure 2 IR-spectra of dry samples of plant and animalpolysaccharides: (1) hyaluronic acid, (2) insoluble starch, (3)fibrous cellulose, (4) chitosan59Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Хthat the extraction process proceeds in steps. Accordingto our own results, supported by various scientific data,the process starts with low molecular weight fractionsentering the solution and ends with high molecularweight fractions doing the same. All the fractionscontained various amounts of protein components.Figure 3 shows the kinetics of extraction processstudied by means of IR-spectroscopy. The intensity ofthe bands in the range of 1540–1680 cm–1 at differentextraction times correlated with the total proteincontent measured by chemical methods. The fractionsthat entered the solution in the first 10 min presumablycontained the maximum amount of protein substances(8.6%). The next peak in the total protein content (17%)could be explained by the fact that it was releasedFigure 3 IR-spectra of dry extracts of industrial flax seedsaccording to extraction time: (1) 5 min, (2) 10 min, (3) 15 min,(4) 20 min, (5) 25 mindirectly from the nucleus when the seed coat swelled andpartially slipped off.Protein constituents were present in all extractionproducts obtained from whole flax seeds, both in thePS-extracts and in the PS-complexes. It was indicated bya broad structured band of 1540–1680 cm–1. The spectraof the obtained extraction products were compared withthe egg albumin spectrum (Fig. 1, curve 2). However,the results suggested that water extraction releasedpolysaccharides with polypeptide fragments of differentcomposition and, possibly, size. This assumption wasconfirmed by the increase in the fragment of this region(Fig. 4a). All the samples had a single band with variouslystructured peaks in the range of 1595–1605 cm–1.Only the spectrum of sample 5 (25 min) showed twoclear undifferentiated bands in the form of a structuredshoulder (≈ 1670 cm–1 and 1520 cm–1) on the right andleft branches of the global peak. This, in turn, couldindicate a different binding force, both of the washed outpolysaccharide segments and the protein components.The longer the sample contacted with the solvent, thelower the binding force.In our previous research, we analysed thisfragment of the spectra for the PS-extracts andPS-complexes obtained from industrial andLM-98 flax seeds under identical conditions(60°C, 20 min), as in Figure 4b [19]. All samplesshowed structuring of the global band (1590 cm–1)with the same wave numbers in varying degrees.However, it was most pronounced in the productsderived from industrial flax seeds (1640 and 1540 cm–1).Moreover, in all the cases under consideration, thestructure of the global band was more clearly manifested(a) (b)(aFigure 4 (a) Fragment of the spectra from Figure 1; (b) (1) PS-complex of LM-98 flax seeds, (2) PS-complex of industrial flaxseeds, (3) extract of industrial flax seeds, (4) extract of LM-98 flax seeds1680 1650 1620 1590 1560 1530 15000,000,010,020,030,040,05Полисахариды 0,06ATR UnitsWavenumber, cm-1123451680 1640 1600 1560 15200,000,010,020,030,040,050,06Рисунок 1 - Полисахариды 0,07ATR UnitsWavenumber, cm-11234а) б)Рисунок 4 – а) Фрагмент спектров из рисунка 1; б) 1 – ПС-комплекс ЛМ-98,2 – ПС-комплекс промышленный, 3 – экстракт промышленный, 4 – экстракт ЛМ-980,080,100,120,14Рисунок 4Units1231680 1650 1620 1590 1560 1530 15000,000,010,020,030,040,05Полисахариды 0,06ATR UnitsWavenumber, cm-1123451680 1640 1600 1560 15200,000,010,020,030,040,050,06Рисунок 1 - Полисахариды 0,07ATR UnitsWavenumber, cm-11234а) б)Рисунок 4 – а) Фрагмент спектров из рисунка 1; б) 1 – ПС-комплекс ЛМ-98,2 – ПС-комплекс промышленный, 3 – экстракт промышленный, 4 – экстракт ЛМ-980,080,100,120,14Рисунок 4Units12360Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Хin the position and shape of the left, high-frequencybranch of the band.In addition, differences in the structure of the bandsin these samples suggested a greater variety of chemicalbonds between the protein and polysaccharide in thePS-extract obtained from industrial flax seeds. In itsspectrum, the right branch of the central peak revealeda clear band in the range of 1540 cm–1. The band waspractically absent in the spectrum of PS-extract obtainedfrom LM-98 variety.An analysis of the full spectra (Fig. 5) showed thefollowing results. Dry PS-extracts obtained in theprimary extraction cycle (curves 1 and 2) had similarspectra of polysaccharide bands. However, the spectrumof the PS-extract obtained from industrial flax seedswas higher throughout the entire wave range. It mayindicate a higher degree of extractability of both thepolysaccharide and protein components from the rawmaterial of this variety.Curves 1 and 3 characterized the spectra of primaryand secondary PS-extracts from industrial flax seeds.Their comparison showed that they had almost identicalstructure of the bands: the highest peak corresponded tothe position of the left shoulder, while the second, lessintense peak corresponded to the position of the rightshoulder. The central maximum in the spectrum of theprimary PS-extract corresponded to a small right-sidedshoulder in the spectrum of the secondary PS-extract.This suggested a redistribution of the contribution offractions of different forms of polypeptide structureswith a polysaccharide base. Thus, an increase inextraction cycles could trigger significant changes in thestructure of the entire protein-carbohydrate complex.PS-complexes of secondary extraction were obtainedto study the possibility of an additional extraction cyclethat could follow the separation of primary extractsand the re-treatment of the oil cake. Table 1 featuresthe conditions and results of both extraction cycles.However, unlike the secondary cycle, the primaryextraction had different technological parameters.Figure 6 shows a comparative study of the spectralparameters of polysaccharide products of secondaryextraction. The position of the peaks, as well asthe shape and pattern of the bands show that theseparameters are almost identical qualitatively. The maindifference was in the intensity of the bands, which wasmuch higher in the spectrum of sample A. This wasalso true for the bands of protein structures, whoseintensity ratio corresponds to the results of the chemicalanalysis. Table 1 proves that the extraction efficiency ofPS-complexes with a high content of the protein insample A was due to the state of the oil cake after theinitial treatment, i.e. temperature and time of theprimary extraction.However, both samples revealed three distinct peaksin the structure of the protein band. This experimentalfact may indicate the possibility of at least threeways polypeptide fragments can be bound with thepolysaccharide matrix, depending on the technologicalconditions of the process.Figure 5 IR-spectra of extractions from two varieties of flaxseeds: (1) primary PS-extract of industrial seeds, (2) primaryPS-extract of LM-98varieties, (3) secondary PS-extract ofindustrial flax seeds1680 1650 1620 1590 1560 1530 15000,000,010,020,030,040,05Полисахариды 0,06ATR UnitsWavenumber, cm-1123451680 1640 1600 1560 15200,000,010,020,030,040,050,06Рисунок 1 - Полисахариды 0,07ATR UnitsWavenumber, cm-11234а) б)Рисунок 4 – а) Фрагмент спектров из рисунка 1; б) 1 – ПС-комплекс ЛМ-98,2 – ПС-комплекс промышленный, 3 – экстракт промышленный, 4 – экстракт ЛМ-983500 3000 2500 2000 1500 10000,000,020,040,060,080,100,120,14Рисунок 4ATR UnitsWavenumber, cm-1123Figure 6 IR-spectra of PS-complexes of the secondaryextraction of industrial flax seeds in a neutral medium:(1) 17.0, (2) 10.2% of proteinTable 1 Two cycles: primary and secondary extractions from industrial flax seedsExperiment PrimaryextractionconditionsPrimary extraction products(PS-complexes)Secondary extractionconditionsSecondary extraction products(PS-complexes)Protein content, % Name Protein content, %I 90°C, 10 min 8.6 70°C, 60 min, precipitationin excess of ethanolSample A 17.0II 22°C, 60 min 6.3 Sample B 10.261Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х2. Flaxseed extraction in an acidic medium(pH 4–5). The extraction was carried out at 50°C for30 min. When re-precipitated with an excess of ethanol,two products were obtained: fibrous and amorphous. Achemical analysis showed that they had the same contentof total protein: 2.60–2.63%. The IR-spectra of thesesamples (Fig. 7) showed that the amorphous sample hada much higher intensity of the bands. The difference isassociated with the features of the less dense, amorphousstructure, which results from the formation of lowermolecular weight segments due to partial hydrolysis andthe destruction of chemical bonds.The spectra of the samples under considerationrevealed three clearly manifested peaks with similarintensity ratio in the region of protein structures.However, the central peak dominated in either case.3. Fractionation of the PS-complex obtained bywater extraction (pH 6–7). Of the two polysaccharidefractions present in the mucus of flax seeds, it is theacid fraction that contains most of the total protein tobe released during extraction [12]. The PS-complexwas fractionated to study the protein-polysaccharideinteractions. Table 2 shows the processing steps.Sample D was extracted from the PS-complex(sample C) in an acidic medium (pH-5). After theextraction, the residue of the PS-complex was dissolvedin water, and sample 5 was precipitated in an excess ofethanol. A purified PS-complex (sample E) was, in fact,obtained as a result of additional purification removal ofacid-soluble substances. Its protein content was 1.49%.Figure 8 shows the IR spectra of the amorphoussample of the dry extract obtained by acidic extraction,PS-complex obtained by water extraction (sample C,Table 2), and the first fractionation product obtained byacidic extraction (sample D, Table 2). The obtained datashowed a decrease in the spectra of the samples as theinitial extract was purified. The decrease in the totalprotein was relatively small: 2.60–2.36%. The pattern ofthe bands and the position of the peaks changed greatlyin the region of absorption of protein structures.Sample D (Fig. 8) was obtained in an acidic medium,while sample E (Fig. 9) was a PS-complex (1.49%protein) purified from compounds soluble in an acidicmedium. However, a comparison of their IR-spectrashowed a significant rise in the entire spectrum ofsample E. The intensity of the bands increased in theregion of the absorption of protein components, in spiteof the fact that their content in the sample decreased.The same was true for all the samples of the PScomplexesobtained from various flax seeds. In addition,the spectrum of sample E showed a distinctive singlepeak in the region of 1640 cm–1.Thus, the conditions of polysaccharide extractionfrom flax seeds and the subsequent processing of theproducts affect not both the content of polypeptidefragments and structural relationships with thepolysaccharide matrix.4. Combined sequential extraction. Extractionconditions have an effect on the protein content inpolysaccharide products and protein-polysaccharideinterrelations. To study the process, a sequentialextraction of polysaccharide products from industrialflax seeds was conducted at different temperature andpH values. Table 3 shows the scheme of the experiment.Stage I involved an aqueous extraction at roomtemperature for 60 min. Polysaccharide complex PSCFigure7 IR-spectra of PS-complexes of industrial flax seedsin an acidic medium: (1) fibrous, (2) amorphousTable 2 Fractionation of the PS-complex and characteristicsof the products obtainedProcessing stagesof the PS-complex (sample C)Fractionation productsof the PS complexName Proteincontent, %I 1.1 Extraction in an acidic mediumpH-5, 22°C, 60 min1.2 Precipitation with an excessof ethanolSample D 2.36II 2.1 Water extraction, 50°C, 60 min2.2 Precipitation with an excessof ethanolSample E 1.493500 3000 2500 2000 1500 10000,000,050,100,15Ðèñóí î ê 6ATR UnitsWavenumber, cm-1123Figure 8 IR-spectra of polysaccharide products: (1) dryamorphous extract, (2) PS-complex, (3) sample D, Table 262Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х1 was precipitated from the extract with an excess ofethanol During stage II, the seed residue (primary oilcake) was subjected to the second water extraction at70°C for 60 min. Polysaccharide complex PSC-2 wasobtained from the secondary oil cake with an excessof ethanol. The seeds that remained after the secondextraction, or secondary oil cake (stage II, Table 3), weresubjected to a third aqueous extraction at pH 4 and 40°Cfor 1 h (stage III). Polysaccharide complex PSC-3 wasprecipitated from the extract with an excess of ethanol.Table 3 demonstrates the total protein content in theresulting products.For this series of samples, IR-spectra showed alogical relationship with the amount of total protein, ifto analyze one band of 1750–1500 cm–1, which is thestructured band of stretching vibrations of C=O groupsof protein components. However, this band demonstratedsignificant qualitative differences between the products.Samples PSC-2 and PSC-3 had two clear peaks ofdifferent intensity and a well-structured shoulder of thesame intensity on the right branch of the first peak. ThePSC-1 spectrum showed one narrow peak of a relativelylow intensity. Its position corresponded with theshoulders at the most intense peaks of PSC-2 and PSC-3.The general contour of the polysaccharide bands of1030 cm–1 remained the same. However, their intensityin the spectra of PSC-2 and PSC-3 changed their relativeposition, if compared to the sequence of the curves in theprotein band. PSC-2 had a more intense band. For thesesamples, this sequence in the arrangement of the spectralcurves remained in the bands of 3500–2750 cm–1and1500–1250 cm–1. These bands characterized the stretchingand bending vibrations of the CHn, NHn, and OH groups.All the bands in the PSC-1 sample showed the lowestintensity. However, the vibration bands of these functionalgroups shifted to a higher frequency region, whichindicated a stronger bond. It could also indicate a strongeror more compact structure of the sample.CONCLUSIONThe study featured polysaccharide products obtainedwith different technological extraction parameters fromtwo Russian varieties of whole flax seeds. The resultsmake it possible to draw the following conclusions:(1) The content of the protein component(polypeptides) in the polysaccharide extracts and theircomplexes was affected by the pH of the medium,temperature, time and sequence of the technologicalstages. An increase in the extraction temperatureand a decrease in the pH of the medium contributedto a significant increase in the protein content of thepolysaccharide product – by 5–10 times.(2) The same technological parameterspredetermined the proportion, the force, and themechanism of chemical bond with the polysaccharidematrix for at least three types of polypeptide structures.This was clearly manifested in the variation of theintensity, shape, structure pattern, and the position of4000 3500 3000 2500 2000 1500 1000 5000,00,10,20,30,40,50,6Ðèñóí î ê 7ATR UnitsWavenumber, cm-1123Figure 9 IR-spectra of the PS-complexes: (1) PS-complexof industrial flax seeds, (2) PS-complex of LM-98 seeds,(3) purified PS-complex obtained from sample E, Table 2Table 3 Conditions and results of the combined sequentialextractionStage Conditions Extractedpolysaccharidecomplex, PSCProteincontent, %I 20°C, 60 min, pH 7,precipitation withan excess of ethanolPSC-1 2.4II 70°C, 60 min, pH 7,precipitation withan excess of ethanolPSC-2 10.2III 40°C, 60 min, pH 4precipitation withan excess of ethanolPSC-3 25.4Figure 10 IR-spectra of the PS-complex samples that resultedfrom sequential extraction of flax seeds: (1) PSC-1 (2.4% ofprotein), (2) PSC-2 (10.2% of protein), (3) (PSC-3 (25.4% ofprotein)63Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Хthe peaks in the band in the range of 1700–1500 cm–1.This range reflected protein components withinpolysaccharide complexes.Thus, the choice of technological parametersdetermines the component composition ofpolysaccharide products during their extraction fromflax seeds. The protein component affects the functionaland technological properties of the products. As aresult, one can obtain polysaccharide products withprogrammed functional properties for various foodtechnologies.Flaxseed polysaccharides are a dietary fibre,which makes them a physiologically necessary dietarycomponent. Thus, flaxseed polysaccharides are botha technological additive and a biologically valuablefunctional ingredient. In this regard, their productionmay expand the range of domestic functional foodingredients.CONFLICT OF INTERESTThe authors declare that there is no conflict ofinterest related to this article.FUNDINGThe research was conducted according to theresearch plan of the Federal Research Center for Bust-Fibre Crops.