Evaluation of ascorbic acid content in different varieties of frozen of cherry fruit

Abstract

Cherry is the most common pit crop in our country. It is zoned in all soil-climatic zones of Ukraine and is a valuable fast-growing fruit breed that gives the fruit essential for human nutrition. It has high flavor qualities, contains 0.70–3.00 % valuable organic acids, 6.5–21.5 % sugar, vitamins, including 13-19 mg/100 g. of vitamin C. The latter plays an important role in human nutrition, since it is essential for normal metabolism. Human body provision with vitamin C (ascorbic acid) is of special concern as 50–80 % of the population manifests its lack, which has a negative effect on human health. Ascorbic acid content in fruit depends on the variety, ripeness degree, soil and climatic conditions of cultivation, harvesting time as well as transportation and storage conditions. Cherry fruit contain within 10−50 mg/100 g of vitamin C. However, the shelf life of cherries is only a few days. Therefore, the annual provision of the population with these fruits is only possible under organization of fresh long-term and canned storage. Freezing is one of the most advanced methods of preservation as it promotes better preservation in the fruit nutritional value, including labile vitamin C, than any other method of processing. Studies have found out that the cherriy fruit lose a significant amount of ascorbic acid during the freezing and in the storage period. The aim of the research was to study the dependence of the characteristics variety and the method of freezing cherry fruit on the change of ascorbic acid content. The fruit of the following cherry varieties were selected for the research in 2016−2018: Zhadana, Chance, Elegant, Optimist, Podbielska, Alpha, Memory of Artemenko grown at the pomology experimental station named after L.P. Symiyenko of IH NAAS. Cherry fruits harvested in the consumer stage of ripeness were sorted, examined, washed, frozen in pre-prepared sugar syrups in plastic cups at a temperature of −22–24 °C, kept at a temperature of −18 °C for up to 6 months. The following variants of fruit freezing were studied: in bulk (control), in 25 % sugar syrup, in 20 % sugar syrup with 4 % ascorutin, in 45 % sugar syrup. Before and after freezing, ascorbic acid content was determined in the fruit for three to six months. Studies on the freezing of cherry fruit were conducted in accordance with the guidelines for conducting research on frozen fruits, berries and vegetables. The chemical composition of the frozen fruit was investigated taking into account the mass losses. According to the research results, the content of ascorbic acid in fresh cherry fruits ranged from 16.25 to 19.15 mg/100 g. The highest content was noted in the cherry varieties of Memory of Artemenko (19.15 mg/100 g), and the lowest – in Optimist (16.25 mg/100 g). In six months following the freezing, compared with fresh fruits, there was a decrease in ascorbic acid by 7–8.85 mg/100 g which made 38.2–51.4 % compared to the fresh fruit. The smallest losses were in the fruits, frozen in 45 % of sugar syrup (35.5–43.2 %) and in 20 % of sugar syrup with 4 % of ascorutin (36.08–44.3 %). Aascorbic acid content at the end of storage was 48.6–553 % in the control and for fruit cherries, frozen in sugar syrups, it was higher and made 53.2–64.5 %. The highest content of ascorbic acid was retained in cherries frozen in 45 % sugar syrup – 56.9–64.5 % and in cherry fruit frozen in 20 % sugar syrup with 4 % ascorutin added – 55.42–63 %. Consequently, there was a decrease in ascorbic acid content by 38.2–51.4 % in the fruits of cherry during the freezing. Somewhat lower was the loss of its content in fruit frozen in sugar syrups, in particular in 45 % of sugar syrup – 35.5–43.2 % and in 20 % of sugar syrup with 4 % of ascorutin – 36.8–44.3 %. In general, the content of ascorbic acid for fruit cherries, frozen in sugar syrups, remained at 53.2–64.5 %. The best preservation of its content in frozen cherry fruits was found in 45 % sugar syrup and 20 % sugar syrup with addition of 4 % ascorutin. Key words: cherry fruit, ascorbic acid, sugar syrup, freezing.