The content of flavonoids in various varieties of pears of Kazakhstan selection

Relevance. Fruits and vegetables are an excellent source of substances with antioxidant and healthy properties. Such substances include polyphenols, carotenoids and triterpenoids. Phenolic compounds have strong antioxidant, anti-inflammatory, antiviral and anti-carcinogenic properties. Pear is the main fruit crop of regions with mild climate and have growing cultivation scales. Pear flavonoids contribute to the coloring of fruits, protect them against pathogens and are healthy ingredients of fruits. The purpose of the research is to analyze the content of flavonoids in pears of Kazakhstan selection.

Methods. The methods used in the study are as follows: determining solids content (the found value is expressed in units of the mass fraction of sucrose in an aqueous solution of sucrose, which under given conditions has the same refractive index as the analyzed solution, in %) titratable acidity (determination of the mass concentration of titratable acids in terms of malic, tartaric or citric acids (μg/mL) was carried out using potentiometric titration with sodium hydroxide solution to pH = 8.1), total sugars (the permanganate method is based on the ability of sugar carbonyl groups to reduce copper (II) oxide to copper (I) oxide in an alkaline medium), sugar-acid index, ascorbic acid (vitamin C) content, total phenolic compounds content, total flavonoids content.

Results. The comparison analyses shows Syilyk and Zhazdyk varieties have the highest values of studied traits,. Specifically, physico-chemical indicators: solids content, total sugars and titratable acidity. Also the best indicators are shown in biological active compounds: sugar-acid index, ascorbic acid (vitamin C) content, total phenolic content and total flavonoids content. The polyphenols content in all pear varieties have high values in the range 107–124 μg/mL. Extracts of Syilyk and Zhazdyk pears have highest values of biologically active substances, and might be recommended for the development of technology in order to obtain concentrates and to enrich the compositions of the food products. 

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