Investigation of selected thermal and non-thermal preservative techniques to produce high quality and safe to drink sour cherry, red grape and pomegranate juices.

Abstract

Red-coloured fruit juices, due to their main bioactive components such as phenolic compounds and anthocyanins, have gained much attention. Present study was focused on the evaluation of pasteurization (at 90°C for 30s), mild heat treatment (at 60°C for 8min), sonication (at amplitude level of 42.7μm and 25°C for 8min) and thermosonication (at amplitude level of 42.7μm and 60°C for 8min) preservation techniques, on physico-chemical and safety attributes of red grape, pomegranate and sour cherry juices. The results indicated that all four treatment methods, had insignificant effects on brix, pH and titratable acidity of the treated fruit. Furthermore, while pasteurization had significant (p < 0.05) effects on the loss of vitamin C, total phenolic, total anthocyanin contents, and antioxidant activity of all juices, the sonication and mild heat treatment had minimum effects on the vitamin C and total anthocyanin contents of the juices. Among all four selected preservative methods, thermosonication significantly increased total phenolic content of three juices and reduced existed aerobic and coliform bacteria, moulds and yeasts population of the treated fruit juices as compared to that of the untreated, mild heat treated and sonicatioted samples.