INTRODUCTION
Polysaccharides have remained in the centre of
scientific attention for several decades. Previously,
polysaccharides were used mainly as auxiliary
substances in the pharmaceutical industry and were
considered as biologically active substances. However,
they are currently used as functional food ingredients and
technological additives in many areas of food industry.
Polysaccharides are highly beneficial for
human 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 texture
of food products, e.g. hardness, brittleness, density,
thickening, viscosity, stickiness, gel-forming ability, etc.
Many food products owe their soft, fragile, swollen, or
jelly-like structure to polysaccharides. Their impressive
variety of functions can be explained by the structural
properties of individual polysaccharides used as food
additives. They act as a gelling, thickening, filling,
emulsifying, swelling, or foaming agent. They can
prevent crystallization and syneresis. They increase
Research Article DOI: http://doi.org/10.21603/2308-4057-2019-2-X-X
Open Access Available online at http:jfrm.ru
IR-spectroscopy of polysaccharide
flaxseed (Linum usitatissimum L.) products
Irina E. Minevich1,* , Lidiia L. Osipova1, Alla P. Nechiporenko2 , Mariya I. Melnikova2 ,
and Tatyana B. Tsyganova3
1 Institution Federal Research Centre for Bust Fibre Crops, Tver, Russia
2 Saint Petersburg National Research University of Information Technologies, Mechanics and Optics,
St. Petersburg, Russia
3 Moscow State University of Food Production, Moscow, Russia
* e-mail: irina_minevich@mail.ru
Received March 11, 2019; Accepted in revised form April 02, 2018; Published X X, 2019
Abstract: Flax seeds are an excellent source of polyunsaturated fatty acids and high-grade protein. They are also rich in non-starch
polysaccharides that are concentrated in their mucus cells. Flaxseed polysaccharides are soluble dietary fibres, which makes them an
indispensable 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 of
polysaccharide flaxseed products are largely determined by the ratio of polysaccharide fractions and protein content, which depend
on the production process. This research featured the effect of the method of obtaining flaxseed polysaccharide products on the
protein content. The study employed chemical analysis and attenuated total internal reflection infrared spectroscopy (ATR-IR). The
protein 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. During
water extraction of whole flax seeds, polypeptide-containing polysaccharide complexes were removed from the seed coats. The
number, composition, and binding force between the peptide fragments and the polysaccharide matrix depended on the technological
parameters of the process. The polysaccharide products were tested for total protein content. The results were consistent with the band
intensity 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 products
Please cite this article in press as: Minevich IE, Osipova LL, Nechiporenko AP, Melnikova MI, Tsyganova TB. IR-spectroscopy
of 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 International
License (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. 2
E-ISSN 2310-9599
ISSN 2308-4057
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Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х
both viscosity and the biological and nutritional value of
the product. No other food additive can perform such a
variety of functions.
Their structural, physicochemical, functional,
and technological properties, as well as their effect
on biological activity, are studied by such modern
methods as nuclear magnetic resonance (NMR), infrared
spectroscopy, ultraviolet imaging, etc. [3, 4].
Flax seeds are known not only as a source of
polyunsaturated fatty acids and high-grade protein,
but also as a source of non-starch polysaccharides
that are concentrated in their mucus cells. Non-starch
polysaccharides represent a group of low-digestible
carbohydrates, or dietary fibre [5]. The polysaccharides
of flaxseed mucus are highly soluble in water. They also
reduce the glycaemic index and cholesterol. In addition,
they possess a prebiotic effect [6, 7].
The polysaccharides of flaxseed mucus are a mixture
of two fractions – neutral (75%) and acidic (25%) [8–10].
The neutral fraction has a high molecular weight and
contains arabinoxylan, while the acidic fraction contains
ramnegalacturonan. Flaxseed polysaccharide complex
contains 4–20% of proteins, depending on the flax
genotype and extraction conditions [10]. Proteins are
bound with acidic fraction polymers by non-covalent
bonds, while no protein has been found in the neutral
fraction.
Flaxseed polysaccharides are a source of soluble
dietary fibre, which is an indispensable functional
food ingredient. They are also a technological additive
that regulates the structure of food mass and can act
as a stabilizer, structure former, water and fat-holding
agent, etc. The functional properties that affect food
systems may result from the synergistic effect they
produce together with proteins [11]. According to Qian
et al., an acidic fraction with 8% of protein showed
higher emulsion properties as compared with the neutral
fraction [12]. Functional and technological properties of
flaxseed polysaccharide products are also determined by
the ratio of fractions, which depends on the conditions of
the technological process. According to Kaushik et al.,
the ratio of neutral and acidic fractions fell from 6.7
to 5.7 when the extraction temperature reached 90°C,
while water absorption capacity and emulsion activity
decreased [13].
Flaxseed polysaccharides have good prospects as a
multifunctional food ingredient. However, there are not
enough data on their component composition, functional
and technological properties, and production conditions.
Flax seeds of Russian varieties remain especially
understudied.
The research objective was to use IR-spectroscopy
to study the effect of the method of obtaining flaxseed
polysaccharide products on the protein content.
STUDY OBJECTS AND METHODS
The comparative study featured polysaccharide
products extracted from two Russian varieties of
whole flax seeds. The first variety was industrial and
corresponded with State Standard 10582-76*. The
second variety was of LM-98 brand. All the products
differed in extraction conditions: pH, temperature,
time, and extraction rate. The technological operations
included the following areas:
– neutral extraction at pH 6–7;
– acidic extraction at pH 4–5;
– fractionation of the polysaccharide complex obtained
in the neutral medium;
– combined sequential extraction.
Distilled water was used to extract polysaccharides
from flax seeds by constant stirring. The ratio of seed
mass and solvent volume (hydromodule) was 1:20. The
extract obtained was separated from the flax seeds using
a 4-layer gauze filter. After that, the target product was
obtained in two ways:
(1) The extract was dried in a thin layer of ≤ 0.5 cm
at 60–65°C and then crushed to obtain a dry extract of
polysaccharides;
(2) Polysaccharides were precipitated in a 3-fold
excess of ethanol. The residue was pressed, washed
with acetone, and dried in a drying cabinet at ≤ 50°C to
obtain a purified polysaccharide complex.
Thus, the main study objects were the dry extract of
polysaccharides (PS-extract) and a purified polysaccharide
complex (PS-complex). Protein content was determined
according to State Standard 13496.4-93**.
A Tensor 37 Fourier spectrometer (Bruker, Germany)
was used to define the IR-spectra of ATR-IR on the
surface of the dry samples. The device had an ATR
diamond element. The OPUS software package had
standard calibration capabilities in the frequency range
of 4000–500 cm–1 (32 scans) in absorption format.
RESULTS AND DISCUSSION
Spectra language. Natural polysaccharides, as a
rule, are not pure substances but multicomponent and
diverse complexes. They may include protein and lipid
components or their fragments. These fragments can
be identified by vibrational spectroscopy. To give a
clearer interpretation, Fig.1 illustrates the IR-spectra of
three main classes of biological substances: proteins,
lipids, and carbohydrates. They were obtained from dry
samples of polysaccharide obtained from flax seeds,
egg albumin, and linseed oil. In the spectrum of egg
albumin, proteins appeared as a pair of typical bands in
the range of 1680–1540 cm–1. They were caused by the
vibrations of the carbonyl C=O groups of Amide I and
Amide II [14, 15]. The spectrum of flaxseed oil is typical
of plant and animal lipids. It is clearly different from
the 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 animal
feed raw stuff. Methods of nitrogen and crude protein determination.
Moscow: Standartinform; 2011. 15 p.
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Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х
1743 cm–1 was caused by the vibrations of C=O groups of
fatty acids in triglycerides. The trident-shaped band with
a peak at 1160 cm–1 was due to the vibrations of C–O and
C–O–C bonds of carboxylic acids.
A broad structured band with a peak at 1030 cm–1 is
typical of polysaccharides. It partially overlapped the
lipid band (1160 cm–1). The spectra of all three samples
contained bands in the range of 3010–2800 cm–1, which
reflected the vibrations of CHn functional groups that
appeared in all classes of substances. Lipids with
unsaturated fatty acids in their composition were marked
with stretching and bending bands of CH functional
group with a CH double bond (3008 cm–1 and 722 cm–1,
respectively). Vibrations of OH groups often overlap
in the range of 3400–3220cm–1. These are bound water
molecules and NHn groups, which quite clearly manifest
themselves in the albumin spectrum as bands of
different intensity with peaks at 3250 and 3020 cm–1.
The optical characteristics of various
polysaccharides showed some remarkable results, if
compared. Figure 2 demonstrates the spectra of dry
preparations of plant and animal polysaccharides.
According to the structure of all bands, animal
polysaccharides differed from plant polysaccharides.
However, they had a common spectral absorption region,
although there can be no absolute coincidence of bands
on the wave-number scale.
Hyaluronic acid is the main carbohydrate component
of the mucopolysaccharides in animal connective
tissue [16, 17]. In the area of protein structures (1,700–
1,500 cm–1), its spectrum showed an intense band with
a shoulder on the right branch. This was due to the
hyaluronic acid dimer, which had carbonyls (C=O) in
the COOH group and the CONH group, a peptide bond
analogue. The mucopolysaccharide spectrum showed
an intense structured carbohydrate band with a peak at
1031 cm–1, which was typical of plant polysaccharides.
Chitosan is obtained from chitin and is a precursor
of a number of glycosaminoglycans. The chitin
deacetylation reaction is incomplete [16, 17]. As a result,
it contained up to 30% of residual acetyl groups bound
to the amine CH3CONH. CONH-composition is typical
of hyaluronic acid. It was the presence of the CONHcomposition
in the structure of chitosan that explained
a narrow intense band with a peak at 1640 cm–1 in its
spectrum.
Starch and cellulose showed one and two weak
bands in this region, respectively. They might result
from both the natural properties of the samples and
the technological features of the production process.
Thus, the granules of insoluble starch are enclosed in
a thin protein shell, which is partially damaged during
grinding, washing, and drying. Its manifestation can
be seen in the starch spectrum. To obtain soluble
starch, the protein shell of starch granules is destroyed
by acid treatment. Currently, starch can be obtained
synthetically. This starch is identical to the natural
product, except that it lacks the granular structure
typical of natural plant products. Cellulose production is
much more complicated and includes a greater number
of chemical treatment stages.
All linear polymers, i.e. hyaluronic acid, chitosan,
and cellulose, have bands with adjacent peaks, according
to the analysis of the structure of the carbohydrate band
in the polysaccharide spectra. Chitosan and cellulose
are structural analogues [18]. The intensity of the bands
with double peaks in their spectra is significantly lower
than that of mucopolysaccharide. Starch is a mixture
of branched and helicoid macromolecules of two
polysaccharides: amylopectin and amylase. Starch is
clearly separated from the group. The peak of its broad
band is bathochromically shifted by 40 cm–1 from the
peak of linear polysaccharides.
1. Products of primary and secondary flaxseed
extraction in neutral medium (pH 6–7). In Minevich
et al., we described the kinetics of primary extraction of
polysaccharides from industrial flax seeds in a neutral
medium at 60°C [19]. The time interval was 5–120 min,
and standard methods of chemical analysis were used
as control. However, we would like to point it out again
Figure 1 IR-spectra of different classes of substances: (1) dry
flaxseed polysaccharide (2.4% protein), (2) dry egg albumin,
(3) flaxseed oil
Figure 2 IR-spectra of dry samples of plant and animal
polysaccharides: (1) hyaluronic acid, (2) insoluble starch, (3)
fibrous cellulose, (4) chitosan
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that the extraction process proceeds in steps. According
to our own results, supported by various scientific data,
the process starts with low molecular weight fractions
entering the solution and ends with high molecular
weight fractions doing the same. All the fractions
contained various amounts of protein components.
Figure 3 shows the kinetics of extraction process
studied by means of IR-spectroscopy. The intensity of
the bands in the range of 1540–1680 cm–1 at different
extraction times correlated with the total protein
content measured by chemical methods. The fractions
that entered the solution in the first 10 min presumably
contained 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 released
Figure 3 IR-spectra of dry extracts of industrial flax seeds
according to extraction time: (1) 5 min, (2) 10 min, (3) 15 min,
(4) 20 min, (5) 25 min
directly from the nucleus when the seed coat swelled and
partially slipped off.
Protein constituents were present in all extraction
products obtained from whole flax seeds, both in the
PS-extracts and in the PS-complexes. It was indicated by
a broad structured band of 1540–1680 cm–1. The spectra
of the obtained extraction products were compared with
the egg albumin spectrum (Fig. 1, curve 2). However,
the results suggested that water extraction released
polysaccharides with polypeptide fragments of different
composition and, possibly, size. This assumption was
confirmed by the increase in the fragment of this region
(Fig. 4a). All the samples had a single band with variously
structured peaks in the range of 1595–1605 cm–1.
Only the spectrum of sample 5 (25 min) showed two
clear undifferentiated bands in the form of a structured
shoulder (≈ 1670 cm–1 and 1520 cm–1) on the right and
left branches of the global peak. This, in turn, could
indicate a different binding force, both of the washed out
polysaccharide segments and the protein components.
The longer the sample contacted with the solvent, the
lower the binding force.
In our previous research, we analysed this
fragment of the spectra for the PS-extracts and
PS-complexes obtained from industrial and
LM-98 flax seeds under identical conditions
(60°C, 20 min), as in Figure 4b [19]. All samples
showed structuring of the global band (1590 cm–1)
with the same wave numbers in varying degrees.
However, it was most pronounced in the products
derived from industrial flax seeds (1640 and 1540 cm–1).
Moreover, in all the cases under consideration, the
structure 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 flax
seeds, (3) extract of industrial flax seeds, (4) extract of LM-98 flax seeds
1680 1650 1620 1590 1560 1530 1500
0,00
0,01
0,02
0,03
0,04
0,05
Полисахариды 0,06
ATR Units
Wavenumber, cm-1
1
2
3
4
5
1680 1640 1600 1560 1520
0,00
0,01
0,02
0,03
0,04
0,05
0,06
Рисунок 1 - Полисахариды 0,07
ATR Units
Wavenumber, cm-1
1
2
3
4
а) 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-98
0,08
0,10
0,12
0,14
Рисунок 4
Units
1
2
3
1680 1650 1620 1590 1560 1530 1500
0,00
0,01
0,02
0,03
0,04
0,05
Полисахариды 0,06
ATR Units
Wavenumber, cm-1
1
2
3
4
5
1680 1640 1600 1560 1520
0,00
0,01
0,02
0,03
0,04
0,05
0,06
Рисунок 1 - Полисахариды 0,07
ATR Units
Wavenumber, cm-1
1
2
3
4
а) 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-98
0,08
0,10
0,12
0,14
Рисунок 4
Units
1
2
3
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Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х
in the position and shape of the left, high-frequency
branch of the band.
In addition, differences in the structure of the bands
in these samples suggested a greater variety of chemical
bonds between the protein and polysaccharide in the
PS-extract obtained from industrial flax seeds. In its
spectrum, the right branch of the central peak revealed
a clear band in the range of 1540 cm–1. The band was
practically absent in the spectrum of PS-extract obtained
from LM-98 variety.
An analysis of the full spectra (Fig. 5) showed the
following results. Dry PS-extracts obtained in the
primary extraction cycle (curves 1 and 2) had similar
spectra of polysaccharide bands. However, the spectrum
of the PS-extract obtained from industrial flax seeds
was higher throughout the entire wave range. It may
indicate a higher degree of extractability of both the
polysaccharide and protein components from the raw
material of this variety.
Curves 1 and 3 characterized the spectra of primary
and secondary PS-extracts from industrial flax seeds.
Their comparison showed that they had almost identical
structure of the bands: the highest peak corresponded to
the position of the left shoulder, while the second, less
intense peak corresponded to the position of the right
shoulder. The central maximum in the spectrum of the
primary PS-extract corresponded to a small right-sided
shoulder in the spectrum of the secondary PS-extract.
This suggested a redistribution of the contribution of
fractions of different forms of polypeptide structures
with a polysaccharide base. Thus, an increase in
extraction cycles could trigger significant changes in the
structure of the entire protein-carbohydrate complex.
PS-complexes of secondary extraction were obtained
to study the possibility of an additional extraction cycle
that could follow the separation of primary extracts
and the re-treatment of the oil cake. Table 1 features
the conditions and results of both extraction cycles.
However, unlike the secondary cycle, the primary
extraction had different technological parameters.
Figure 6 shows a comparative study of the spectral
parameters of polysaccharide products of secondary
extraction. The position of the peaks, as well as
the shape and pattern of the bands show that these
parameters are almost identical qualitatively. The main
difference was in the intensity of the bands, which was
much higher in the spectrum of sample A. This was
also true for the bands of protein structures, whose
intensity ratio corresponds to the results of the chemical
analysis. Table 1 proves that the extraction efficiency of
PS-complexes with a high content of the protein in
sample A was due to the state of the oil cake after the
initial treatment, i.e. temperature and time of the
primary extraction.
However, both samples revealed three distinct peaks
in the structure of the protein band. This experimental
fact may indicate the possibility of at least three
ways polypeptide fragments can be bound with the
polysaccharide matrix, depending on the technological
conditions of the process.
Figure 5 IR-spectra of extractions from two varieties of flax
seeds: (1) primary PS-extract of industrial seeds, (2) primary
PS-extract of LM-98varieties, (3) secondary PS-extract of
industrial flax seeds
1680 1650 1620 1590 1560 1530 1500
0,00
0,01
0,02
0,03
0,04
0,05
Полисахариды 0,06
ATR Units
Wavenumber, cm-1
1
2
3
4
5
1680 1640 1600 1560 1520
0,00
0,01
0,02
0,03
0,04
0,05
0,06
Рисунок 1 - Полисахариды 0,07
ATR Units
Wavenumber, cm-1
1
2
3
4
а) 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-98
3500 3000 2500 2000 1500 1000
0,00
0,02
0,04
0,06
0,08
0,10
0,12
0,14
Рисунок 4
ATR Units
Wavenumber, cm-1
1
2
3
Figure 6 IR-spectra of PS-complexes of the secondary
extraction of industrial flax seeds in a neutral medium:
(1) 17.0, (2) 10.2% of protein
Table 1 Two cycles: primary and secondary extractions from industrial flax seeds
Experiment Primary
extraction
conditions
Primary extraction products
(PS-complexes)
Secondary extraction
conditions
Secondary extraction products
(PS-complexes)
Protein content, % Name Protein content, %
I 90°C, 10 min 8.6 70°C, 60 min, precipitation
in excess of ethanol
Sample A 17.0
II 22°C, 60 min 6.3 Sample B 10.2
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2. Flaxseed extraction in an acidic medium
(pH 4–5). The extraction was carried out at 50°C for
30 min. When re-precipitated with an excess of ethanol,
two products were obtained: fibrous and amorphous. A
chemical analysis showed that they had the same content
of total protein: 2.60–2.63%. The IR-spectra of these
samples (Fig. 7) showed that the amorphous sample had
a much higher intensity of the bands. The difference is
associated with the features of the less dense, amorphous
structure, which results from the formation of lower
molecular weight segments due to partial hydrolysis and
the destruction of chemical bonds.
The spectra of the samples under consideration
revealed three clearly manifested peaks with similar
intensity ratio in the region of protein structures.
However, the central peak dominated in either case.
3. Fractionation of the PS-complex obtained by
water extraction (pH 6–7). Of the two polysaccharide
fractions present in the mucus of flax seeds, it is the
acid fraction that contains most of the total protein to
be released during extraction [12]. The PS-complex
was fractionated to study the protein-polysaccharide
interactions. Table 2 shows the processing steps.
Sample D was extracted from the PS-complex
(sample C) in an acidic medium (pH-5). After the
extraction, the residue of the PS-complex was dissolved
in water, and sample 5 was precipitated in an excess of
ethanol. A purified PS-complex (sample E) was, in fact,
obtained as a result of additional purification removal of
acid-soluble substances. Its protein content was 1.49%.
Figure 8 shows the IR spectra of the amorphous
sample of the dry extract obtained by acidic extraction,
PS-complex obtained by water extraction (sample C,
Table 2), and the first fractionation product obtained by
acidic extraction (sample D, Table 2). The obtained data
showed a decrease in the spectra of the samples as the
initial extract was purified. The decrease in the total
protein was relatively small: 2.60–2.36%. The pattern of
the bands and the position of the peaks changed greatly
in 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 acidic
medium. However, a comparison of their IR-spectra
showed a significant rise in the entire spectrum of
sample E. The intensity of the bands increased in the
region of the absorption of protein components, in spite
of the fact that their content in the sample decreased.
The same was true for all the samples of the PScomplexes
obtained from various flax seeds. In addition,
the spectrum of sample E showed a distinctive single
peak in the region of 1640 cm–1.
Thus, the conditions of polysaccharide extraction
from flax seeds and the subsequent processing of the
products affect not both the content of polypeptide
fragments and structural relationships with the
polysaccharide matrix.
4. Combined sequential extraction. Extraction
conditions have an effect on the protein content in
polysaccharide products and protein-polysaccharide
interrelations. To study the process, a sequential
extraction of polysaccharide products from industrial
flax seeds was conducted at different temperature and
pH values. Table 3 shows the scheme of the experiment.
Stage I involved an aqueous extraction at room
temperature for 60 min. Polysaccharide complex PSCFigure
7 IR-spectra of PS-complexes of industrial flax seeds
in an acidic medium: (1) fibrous, (2) amorphous
Table 2 Fractionation of the PS-complex and characteristics
of the products obtained
Processing stages
of the PS-complex (sample C)
Fractionation products
of the PS complex
Name Protein
content, %
I 1.1 Extraction in an acidic medium
pH-5, 22°C, 60 min
1.2 Precipitation with an excess
of ethanol
Sample D 2.36
II 2.1 Water extraction, 50°C, 60 min
2.2 Precipitation with an excess
of ethanol
Sample E 1.49
3500 3000 2500 2000 1500 1000
0,00
0,05
0,10
0,15
Ðèñóí î ê 6
ATR Units
Wavenumber, cm-1
1
2
3
Figure 8 IR-spectra of polysaccharide products: (1) dry
amorphous extract, (2) PS-complex, (3) sample D, Table 2
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Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х
1 was precipitated from the extract with an excess of
ethanol During stage II, the seed residue (primary oil
cake) was subjected to the second water extraction at
70°C for 60 min. Polysaccharide complex PSC-2 was
obtained from the secondary oil cake with an excess
of ethanol. The seeds that remained after the second
extraction, or secondary oil cake (stage II, Table 3), were
subjected to a third aqueous extraction at pH 4 and 40°C
for 1 h (stage III). Polysaccharide complex PSC-3 was
precipitated from the extract with an excess of ethanol.
Table 3 demonstrates the total protein content in the
resulting products.
For this series of samples, IR-spectra showed a
logical relationship with the amount of total protein, if
to analyze one band of 1750–1500 cm–1, which is the
structured band of stretching vibrations of C=O groups
of protein components. However, this band demonstrated
significant qualitative differences between the products.
Samples PSC-2 and PSC-3 had two clear peaks of
different intensity and a well-structured shoulder of the
same intensity on the right branch of the first peak. The
PSC-1 spectrum showed one narrow peak of a relatively
low intensity. Its position corresponded with the
shoulders at the most intense peaks of PSC-2 and PSC-3.
The general contour of the polysaccharide bands of
1030 cm–1 remained the same. However, their intensity
in the spectra of PSC-2 and PSC-3 changed their relative
position, if compared to the sequence of the curves in the
protein band. PSC-2 had a more intense band. For these
samples, this sequence in the arrangement of the spectral
curves remained in the bands of 3500–2750 cm–1and
1500–1250 cm–1. These bands characterized the stretching
and bending vibrations of the CHn, NHn, and OH groups.
All the bands in the PSC-1 sample showed the lowest
intensity. However, the vibration bands of these functional
groups shifted to a higher frequency region, which
indicated a stronger bond. It could also indicate a stronger
or more compact structure of the sample.
CONCLUSION
The study featured polysaccharide products obtained
with different technological extraction parameters from
two Russian varieties of whole flax seeds. The results
make it possible to draw the following conclusions:
(1) The content of the protein component
(polypeptides) in the polysaccharide extracts and their
complexes was affected by the pH of the medium,
temperature, time and sequence of the technological
stages. An increase in the extraction temperature
and a decrease in the pH of the medium contributed
to a significant increase in the protein content of the
polysaccharide product – by 5–10 times.
(2) The same technological parameters
predetermined the proportion, the force, and the
mechanism of chemical bond with the polysaccharide
matrix for at least three types of polypeptide structures.
This was clearly manifested in the variation of the
intensity, shape, structure pattern, and the position of
4000 3500 3000 2500 2000 1500 1000 500
0,0
0,1
0,2
0,3
0,4
0,5
0,6
Ðèñóí î ê 7
ATR Units
Wavenumber, cm-1
1
2
3
Figure 9 IR-spectra of the PS-complexes: (1) PS-complex
of industrial flax seeds, (2) PS-complex of LM-98 seeds,
(3) purified PS-complex obtained from sample E, Table 2
Table 3 Conditions and results of the combined sequential
extraction
Stage Conditions Extracted
polysaccharide
complex, PSC
Protein
content, %
I 20°C, 60 min, pH 7,
precipitation with
an excess of ethanol
PSC-1 2.4
II 70°C, 60 min, pH 7,
precipitation with
an excess of ethanol
PSC-2 10.2
III 40°C, 60 min, pH 4
precipitation with
an excess of ethanol
PSC-3 25.4
Figure 10 IR-spectra of the PS-complex samples that resulted
from sequential extraction of flax seeds: (1) PSC-1 (2.4% of
protein), (2) PSC-2 (10.2% of protein), (3) (PSC-3 (25.4% of
protein)
63
Minevich I.E. et al. Foods and Raw Materials, 2019, vol. 7, no. 2, pp. Х–Х
the peaks in the band in the range of 1700–1500 cm–1.
This range reflected protein components within
polysaccharide complexes.
Thus, the choice of technological parameters
determines the component composition of
polysaccharide products during their extraction from
flax seeds. The protein component affects the functional
and technological properties of the products. As a
result, one can obtain polysaccharide products with
programmed functional properties for various food
technologies.
Flaxseed polysaccharides are a dietary fibre,
which makes them a physiologically necessary dietary
component. Thus, flaxseed polysaccharides are both
a technological additive and a biologically valuable
functional ingredient. In this regard, their production
may expand the range of domestic functional food
ingredients.
CONFLICT OF INTEREST
The authors declare that there is no conflict of
interest related to this article.
FUNDING
The research was conducted according to the
research plan of the Federal Research Center for Bust-
Fibre Crops.

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