EFFECT OF FREQUENCY ON VITAMIN C DEGRADATION IN POMELO JUICE USING OHMIC HEATING

Abstract

Ohmic heating is an electric heating technique used to pasteurize pomelo juice. The effect of frequency during Ohmic heating time on vitamin C degradation was investigated. The frequency values of 50, 60, 70, 100, 500, 1000, 10000, 20.000 Hz and the fixed electric field strength of 30 V/cm were used to examined vitamin C change. Decrease of the vitamin depends on the frequency, at 50 Hz or above 1 kHz, the vitamin C content reduced compared to that of the control sample. At the experimental frequencies of 60, 500Hz, the vitamin C content was not changed during the 60 s at 60 - 90^oC (p> 0,05). Pomelo juice declined approximately 2% of vitamin C due to the non-heat effect when the sample temperature increased from 20 to 90^oC. The results indicate that Ohmic heating is likely to effectively used to pasteurize pomelo juice.