Electrical conductivities of hydrocolloid solutions

Ohmic heating was applied to solutions of 5 hydrocolloids (carrageenan, 1-3 % w/w; xanthan, 1-3% w/w; pectin, 1-5% w/w; gelatin, 2-4% w/w and starch, 4 -6% w/w) in a static cell to study the effect of concentration and temperat ure on electrical conductivities. For each experiment, the sample was poure d into the cell and heated at a constant voltage gradient of 7.24 V/cm. Vol tage, current, time and temperature were logged at rime intervals and used to calculate electrical conductivities as a function of temperature. Of the thickening agents examined, carrageenan gave the highest value for electri cal conductivity (0.2 S/m at 25C and 1% and 1.4 S/m at 100C and 3%) followe d by xanthan (0.14 S/m at 25C and 1% to 1.1 S/m at 100C and 3%). Pectin and gelatin samples were found to exhibit lower, but similar electrical conduc tivities (0.06 S/m at 25C at the lowest concentration to 0.37 S/m at 100C a t the highest concentration). Starch samples had the lowest electrical cond uctivity varying from 0.05 S/m at 25C and 4% to 0.21 S/m at 100C and 6%. Re gression equations were established for each type of hydrocolloid solutions revealing a strong interaction between the concentration and the temperatu re and the electrical conductivity values. Major differences were observed between hydrocolloid types on electrical conductivities that were mainly at tributed to their ash content.