Hoang Pham, Weerachet Jittanit, and Tanaboon Sajjaanantakul

pp. 317 - 324

Abstract

Ready-to-eat fruits packed in sealed containers are highly perishable due to their intrinsic characteristics and lack of
full thermal process. Ohmic heating has the advantages of rapid liquid heating through electrical current. The aim of this
research was to investigate the effect of indirect ohmic heating on pH, total soluble solids, polyphenol oxidase activity, color
and texture of ready-to-eat pineapple packed in a polypropylene pouch with 1% calcium chloride and 0.3% ascorbic acid
packing solution. The pre-packed sample in a pouch was placed in the ohmic heating jar filled with 0.5% sodium chloride
ohmic heating solution which was then ohmic heated at different voltage gradients (20, 30, 40 V/cm), to different packing
solution temperatures (60, 70, 80°C) for 60s. Samples were kept at 4°C for quality measurement. It was found that browning
index of ready-to-eat pineapple treated with 20 V/cm at 80°C, 30 V/cm at 70°C and 80°C, 40 V/cm at 80°C did not change during
12 days cold storage (p>0.05). Polyphenol oxidase was inactivated when the temperature of the pineapple was 62°C or higher.
After 10 days at 4°C, the pineapple heated with 30V/cm at 70°C had much higher firmness than the un-heated sample kept at
the same storage condition. Indirect ohmic heating of pre-packed ready-to-eat pineapple in polypropylene pouch with 30
V/cm at 70°C packing solution temperature for 60s could be used as minimal heating methods to maintain the quality of
ready-to-eat fruits in 12 days at 4°C.