PREPARATION OF POMEGRANATE JUICE CONCENTRATE BY VARIOUS HEATING METHODS AND APPRAISAL OF ITS PHYSICOCHEMICAL CHARACTERISTICS

Clarified pomegranate juice of ‘Bhagwa’ was concentrated by various heating methods. The final juice concentration of 65°Brix was achieved in 37, 78 and 106 min by using atmospheric heating, microwave and rotary vacuum evaporation techniques, respectively. The juice concentrates prepared by various techniques were analyzed for physicochemical and sensorial parameters viz., concentrate recovery, specific gravity, pH, viscosity, percent moisture, colour change, TSS, acidity, sugars, phenols anthocyanins, antioxidant activity, colour, flavour, taste and overall acceptability. Hunter L*, a* and b* values were used to estimate the extent of colour loss. Decrease in pH and colour values of fresh pomegranate juice was observed with notable two- to three-fold increase in TSS, acidity, sugars, polyphenols, anthocyanins and antioxidant activity content on concentration irrespective of heating methods used. Maximum concentrate recovery on weight (24.35%) and volume (20.44%) basis was recorded in rotary vacuum heating process. It also recorded maximum moisture (24.46%), polyphenols (833.92 mg/100 g fruit), anthocyanins (321.97 mg/100 g fruit), antioxidant activity (76.41%) with maximum overall acceptability score (8.607). The maximum extent of colour loss on Hunter parameters was recorded in microwave heating method while minimum in rotary vacuum evaporation. Highest viscosity (120.20 mPa.s) was noted in juice concentrate prepared by microwave heating. No microbial count was recorded in concentrate samples prepared by all the three methods.