Variation in Electrical Conductivity of Selected Fruit Juices During Continuous Ohmic Heating

Measurements and modeling of electrical conductivity (EC) of selected fruit juices were done during continuous ohmic heating. Ten-cm long acrylic heating cell with 3.8 cm internal diameter was utilized to measure the juice electrical conductivity. The variation in electrical conductivity of lab-squeezed juice of orange, pineapple and tomato fruits purchased from different retail markets were measured and modeled in terms of juice properties, such as total soluble solids and pH. EC of all juices had a linear variation with temperature as they were heated continuously to 80°C. EC of juice was affected by fruit maturity: 9-months old oranges had lower EC value of 0.392 S/m at 25°C, whereas 12 months old oranges had 0.475 S/m. The electrical conductivity of lab-squeezed orange juice from fresh fruits from different locations showed a 10% variation in the mean value of 0.343 S/m at 25°C and 0.971 S/m at 80°C. Mean electrical conductivity values for pineapple and tomato juice at 25°C, were 0.295 S/m and 0.504 S/m with maximum variations due to location at about 20% and 18.3%, respectively. These variations in EC of juices studied were observed to be higher at higher temperatures. The observed electrical conductivities for three juices were modeled in terms of temperature and total soluble solids with very high goodness-of-fit values.