Effect of salt and citric acid on electrical conductivities and ohmic heating of viscous liquids

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 a pparent viscosity of 0.2 Pa.s at 20C and 300 s(-1) A voltage of 150 V was a pplied in a static ohmic heating cell to study the effect of hydrocolloid a nd salt on electrical conductivity (EC) and temperature profile at their pH . The pH levels were modified by citric acid addition and the combined effe ct of hydrocolloid, salt and citric acid was investigated. At low salt conc entration, carrageenan and xanthan had shortest heating times and highest E Cs. This was followed by pectin. Starch was the least effective, having slo west heating rates and lowest ECs. At 1% concentration, the salt effect ove rcame that of hydrocolloid giving similar temperature profiles and ECs. The effect of citric acid addition was present but negligible.