EFFECT of SALT and CITRIC ACID ON ELECTRICAL CONDUCTIVITIES and OHMIC HEATING of VISCOUS LIQUIDS

Abstract

Four hydrocolloid solutions (starch, 4.3%; carrageenan, 1.7%; xanthan, 2%; pectin, 2.5%) were prepared in water with varying amounts of NaCl (0.25, 0.5, 0.75 and 1%). Hydrocolloid concentrations were adjusted to result in an apparent viscosity of 0.2 Pa.s at 20C and 300 s-1. A voltage of 150 V was applied in a static ohmic heating cell to study the effect of hydrocolloid and salt on electrical conductivity (EC) and temperature profile at their pH. the pH levels were modified by citric acid addition and the combined effect of hydrocolloid, salt and citric acid was investigated. At low salt concentration, carrageenan and xanthan had shortest heating times and highest ECs. This was followed by pectin. Starch was the least effective, having slowest heating rates and lowest ECs. At 1% concentration, the salt effect overcame that of hydrocolloid giving similar temperature profiles and ECs. the effect of citric acid addition was present but negligible.