Study on viscosity and electrical conductivity of fruit juices

Viscosity and electrical conductivity (EC) of a food product are critical parameters affecting Ohmic heating (OH). Viscosity of apple, pineapple, orange and tomato juices have been measured in the temperature range 25-70 degrees C using an Ostwald viscometer and EC have been measured at 1 and 10 kHz frequency using LCR bridge. The EC was more at 10 kHz than at I kHz in all the juices indicating that heating rate increases with increasing frequency. A strong dependence of EC on viscosity and temperature of the juices was observed. Tomato juice behaved differently compared to other juices. Activation energy values for flow of fruit juices varied from 17.07 to 19.58 kJ/mole.