Mild thermal processing of pineapple juice using ohmic heating technology

Abstract

Ohmic heating is one of the novel thermal technologies widely used for the inactivation of microorganisms and enzymes. The optimization of ohmic heating process parameters such as voltage, temperature and holding time to inactivate microorganisms and the effects on the physico-chemical qualities of pineapple juice were studied. The pineapple juice was processed by ohmic heating at different voltage gradients (10–15 V/cm), temperatures (5060°C) and holding times (1–5 min). A higher reduction of microorganisms was observed with increased voltage gradient, treatment temperature and time. The highest reduction in bacteria, yeast and mold population was obtained for treatment with voltage gradient of 15 V/cm, temperature of 60°C and holding time of 3 min. Ascorbic acid showed a significant reduction with the increase in temperature and treatment time. A voltage gradient of 14.74 V/cm, process temperature of 56.45°C and holding time of 2.98 min was found to be the optimum ohmic heating condition to achieve a predicted bacterial log reduction of 3.75 and yeast and mold log reduction of 2.85.