The effect of freezing on biochemical composition and commercial quality of black currant berries (Ribes nigrum L.) of Siberian variety

We investigated the biochemical composition and commercial quality of 12 Siberian varieties of black currants. The purpose of this research was to identify the optimal technological mode of freezing and storage of fruit and berries. The effect of two processing modes freezing was studied (at - 24°C and - 37°C with subsequent storage at - 16°C for 12 months) on the biochemical composition and the commercial quality of black currant berries from Siberia. After freezing blackcurrant berries at -37°C and stored at -16°C for 12 months reduction of mono- and oligosaccharides was slightly less pronounced compared to the conventional method at - 24°C (48 0%). According to the conventional freezing method and stored for 12 months the acid value was reduced by 4.8 %. Sugar-acid ratio after 12 months of storage ranged from 3.2 % in Poklon Borisovoi to 4.88 % in Lama. All studied varieties contained more than 1 % pectin, the highest concentration was found in Maryushka, it was equal to 2.89 %, and the lowest was 1.4 % in Lama. The reduction of vitamin C in the studied varieties of black currants was observed after 12 months of storage and was equal to 17.5 %. To the end of the storage the anthocyanins level decreased on average by 5.1 %. Goods assessment of the quality of frozen berries showed that only 5 pomological varieties (Garmoniya, Kalinovka, Poklon Borisovoi, Sumrak and Yadryonaya) belonged to the highest commercial grade after the application of traditional and shock freezing regimens, and the number of conglomerates of agglomerated berries was 2 times less than in the mode shock freezing. It was established that the optimum mode was the shock freezing at - 37°C with subsequent storage for 12 months at - 16°C. Changes in low nutritional value and the number of defects were much smaller than in the samples subjected to traditional freezing.