Ohmic heating characteristics and degradation kinetics of anthocyanin in mulberry juice

Abstract

Ohmic heating is considered as a novel technology for pasteurization. Ohmic heating rate is highly influenced by the electrical conductivity of the products. The heating rate and the stability of anthocyanin during ohmic heating need to be investigated in order to analyze the viability of ohmic heating for pasteurization of mulberry juice. Mulberry juice was heated using three different temperatures (80, 85 and 90°C) during 90 minutes. Electrical conductivity of mulberry juice increased from 0.014 Sm-1 at the initial of heating (32°C) to 0.033 Sm-1 at 90°C and the average heating rate was 0.568°C/s. The heating rate and electrical conductivity increased linearly with the increased in temperature. Degradation kinetic of anthocyanin followed the first order kinetic models with R2 > 0.9. The k-value of anthocyanin degradation increases along with the increasing of temperature ranging from 8-15 × 10-3/min. Anthocyanin shows relatively high temperature dependence with 135.83 kJ/mol energy activation value. Based on the heating rates obtained from this study, ohmic heating could be used as an alternative pasteurization method for mulberry juice.