Effect of Ohmic Heating on the Electrical Conductivity, Biochemical and Rheological Properties of Papaya Pulp

A laboratory scale static ohmic heating unit of 1L capacity was designed and fabricated for conducting the study. The electrical conductivity of the pulp was measured over a temperature range of 35-95C. Ohmic heating was conducted at three voltage gradients (6.66, 13.33 and 20V/cm) and holding times (1, 2 and 3min). Voltage gradient of 13.33V/cm with a holding time of 2min was optimized statistically for the pasteurization of papaya pulp based on the microbial analysis. The ohmic heated pulp was compared with fresh pulp with respect to the biochemical and rheological properties. Ohmic heated pulp retained 86.44% lycopene, 87.13% -carotene and 85.23% ascorbic acid. Rheologically, papaya pulp exhibited a non-Newtonian (n<1) and pseudoplastic behavior with yield stress following Herschel-Bulkley model (R-2 0.99). The frequency sweep curve established the resemblance of ohmic heated pulp to that of the fresh pulp without any structural breakdown upon processing. Practical ApplicationsPapaya fruit possesses high nutritional and medicinal properties which are recommended for infants and adults. But owing to its faster rate of deterioration, about 50% of the fruit harvest suffers heavy postharvest losses. A thermal processing technology is required in order to prevent the postharvest losses and make the pulp suitable for infant formulations. Novel thermal processing technology, such as ohmic heating, could preserve the pulp for a long period without compromising on the microbial stability and quality of the product. Hence, this research was planned to concentrate on understanding the suitability of ohmic heating for the pasteurization of papaya pulp. The research finding would contribute toward the growth of pulp processing and infant formulating industries.