Сельское хозяйство/4. Технология хранения и переработки сельскохозяйственной продукции

Cherno N.K., Osolina S.A., Nikitina A.V.

Odessa National Academy of Food Technologies, Odessa, Ukraine

BIOPOLYMER COMPLEXES FROM

PLEUROTUS OSTREATUS AS ANTIOXIDANTS

Mushrooms are a source of many biologically active compounds. Ethanol-soluble substances show antibacterial and antioxidant properties; the water-soluble fraction of mushrooms has immunomodulatory, antitumor, antibacterial and anti-oxidant properties [1]. Alkaline-insoluble remainder of mushrooms is an effective enterosorbent of xenobiotics, it shows cholesterol-lowering activity [2]. We can also predict the antioxidant properties of these samples, because they are biopolymer complexes. These complexes consist of glucan, chitin and melanin [3]. The latter substance is one of the most effective native antioxidant [4]. If we confirm the antioxidant properties of biopolymeric complexes, the area of their application will expand.

Cultivated mushrooms are a prospective source of biopolymer complexes, because their growing under controlled conditions provides the safety of the raw-material. Pleurotus ostreatus has the highest content of insoluble fraction among these mushrooms [5].

The aim of this work was to obtain biopolymer complexes from Pleurotus ostreatus and to evaluate their antioxidant properties.

Biopolymer complexes were prepared by sequential processing of mushrooms with hot water, acid and alkaline solutions. The concentration of the alkaline agent was 3 % and 7 %, the time of treatment was 90 and 270 min.

The chemical composition of the isolated biopolymer complexes is given in Table 1. It is found that carbohydrates are the main component of the samples. They compose of easily and hardly hydrolysable polysaccharides. Increasing the concentration of sodium hydroxide and the contact time with the raw materials reduces carbohydrate content in the samples. The level of easily hydrolysable polysaccharides in the complexes is less than the one of hardly hydrolysable polysaccharides. However, the sample obtained by treating the raw material with 7 % alkaline solution during 270 minutes has a higher content of this polysaccharide fraction. It can be explained that the part of carbohydrate complex is modified by alkaline agent. Then it transits to the category of easily hydrolysable polysaccharides. The hardly hydrolysable polysaccharide content in the samples with the increase concentration of alkaline and treatment time reduces in 1.7 times respectively.

Table 1

The chemical composition of biopolymer complexes, % (of dry matter)

Rate	3 % NaOH		7 % NaOH
	90	270	90	270
The total amount of polysaccharides	88,8	86,7	83,9	79,1
including easily hydrolysable polysaccharides	33,0	28,2	28,6	46,2
including chitin	7,5	8,1	10,0	12,7
Melanin	2,5	3,4	7,9	10,3

Only glucose is identified by the chromatography method in the hydrolysates of easily hydrolysable polysaccharide. The hydrolysates of hardly hydrolysable polysaccharides in addition to the glucose contain monosaccharide glucosamine also. It is the product of the hydrolytic destruction of chitin. Thus, the biopolymer complexes contain polysaccharides – glucan and chitin. The level of latter compound increases in 1.7 times when the concentration of sodium hydroxide solution and the duration of the alkaline treatment rises.

The polymer of phenolic nature – melanin is a accompanying component to the carbohydrate. Its level increases in 4.1 times with the rise both alkaline reagent concentration and treatment time. Protein in the samples is in the minor amounts.

The samples may be classified as the dietary fibres based on the analysis of their chemical composition. This was confirmed by their resistance to the action of digestive enzymes in vitro.

The antioxidant activity of the samples is evaluated according to their ability to inhibit the formation of oxidation products during the influence oxygen on the oil at high temperature [6].

As it is shown in Fig. 1, the antioxidant activity of the biopolymer complexes depends on such factors as the concentration of the alkali, treatment time of the raw materials, the sample content in reacting mixture.

Fig. 1 The antioxidant activity of the biopolymer complexes:

1 – biopolymer complex isolated in the processing of raw materials with 3 % NaOH solution during 90 min;

2 – biopolymer complex isolated in the processing of raw materials with 3 % NaOH solution during 270 min;

3 – biopolymer complex isolated in the processing of raw materials with 7 % NaOH solution during 90 min;

4 – biopolymer complex isolated in the processing of raw materials with 7 % NaOH sodium hydroxide solution during 270 min.

The samples inhibit peroxide oxidation of oil much better while alkaline solution concentration rises. For example, under the same conditions (the treatment time and concentration of the complexes) the antioxidant activity of the preparations 3 and 4 is 1.1 – 25.8 times higher than preparation 1 and 2.

The antioxidant activity of the biopolymer complexes increases in 2.3 – 24.6 times, if the raw-material is treated by 3 % solution of sodium hydroxide. The intensity in change of this index decreases when mushrooms are processed with more concentrated reagent solution.

These characteristics depend on changing the ratio of components in the complexes. There is a direct correlation between the antioxidant activity and melanin content in the samples. Probability, amino polysaccharide content might influence on the value of this index.

It was shown that the antioxidant activity of the biopolymer complexes increases if the sample content in reacting mixture rises. However, when the amount of complexes 3 and 4 increases from 40 to 50 mg in reacting mixture the value of this index does not change significantly. The antioxidant activity of these preparations and 10 mg ascorbic acid that is widely used in the food industry as an antioxidant is the same.

Despite the efficacy of antioxidants obtained by the industrial synthesis their addition to the food product can cause a number of undesirable effects for consumers. Mushroom biopolymer complex is a safe substitution to such compounds. It can be a means for inhibiting the lipid peroxidation. It will prevent decreasing biological value of food products due to keeping essential fatty acids.

Thus, the biopolymer complexes obtained from Pleurotus ostreatus are the effective antioxidants. The foodstuff containing these preparations will have more prolonged storage life.

References:

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2. Cherno, N.K. Comparative analysis of biopolymer complexes from mushrooms (Agaricus bisporus) / Cherno N.K., Osolina S.A., Gural L.S., Nikitina A.V. // Сборник научных трудов SWorld. Материалы междун. науч.-практ. конф. «Современные направления теоретических и прикладных исследований ’ 2013». – Вып 1. Т. 37. – Одесса: Куприенко, 2013. – Цит.: 113-0925. – С. 54-59.

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