Concentration of beetroot juice colorant (betalains) by forward osmosis and its comparison with thermal processing

Abstract This study is aimed to concentrate the natural pigment of beetroot (Beta vulgaris, Variety: Ruby Queen) juice for possible application in foods. The beetroot juice was concentrated to 12-fold (from 5 to ~60°B) by thermal evaporation (TE) as well as by forward osmosis (FO). The juice concentrate obtained by both the processes were reconstituted to original juice TSS, and physical as well as physio-chemical properties were compared. In the reconstituted sample the ratio of betanin/isobetanin and color shade (CS) values of fresh, FO and TE were 8.5:1, 8.6:1, 7.4:1 and 0.52, 0.53, 0.62, respectively, which indicated higher stability of betalains in juice concentrated by FO than TE. The stability of beetroot juice was evaluated for both concentrates at different pH, temperature, and light conditions. The results showed betalains obtained by FO concentration was more stable than thermally processed concentrate. The juice concentrate obtained by both the processes was added to yogurt to study its stability in food system. The degradation of betalains followed first-order kinetics and the rate constants for FO and TE were found to be 0.0066 and 0.0205 day−1, respectively. It indicated that the degradation of betalains in FO concentrate was slower (~3 times) than TE concentrate.