Physicochemical properties of grape juice pasteurized by ohmic heating technology

Abstract

Physicochemical properties are essential factors during processing and preservation of food. The changes in physicochemical properties of the product depend upon the processing technique. The effect of ohmic heating on the some physicochemical properties like pH, TSS, titratable acidity, ascorbic acid, total sugar and colour of grape juice were studied. Grape juice was pasteurized at different combinations of voltage gradient (10-40 V cm-1), temperature (55-85 °C) and holding time (1-5 min). Then the pasteurized juice samples were stored for 21 days at refrigerated condition. The changes in properties were less at low voltage gradient and less holding time. Ascorbic acid was observed to be degraded faster at higher voltage gradients. The pH, TSS and total sugar increased while the titratable acidity, ascorbic acid and colour decreased significantly as the voltage gradient, heating temperature and holding time were increased. Ohmic heating treatment aids in retaining the physicochemical properties for a long time. Based on overall quality of grape juice pasteurized by ohmic heating, the best treatment was 30 V cm-1:85 °C: 5 min.