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 temperature on electrical conductivities. For each experiment, the sample was poured into the cell and heated at a constant voltage gradient of 7.24 V/cm. Voltage, current, time and temperature were logged at time intervals and used to calculate electrical conductivities as a function of temperature. Of the thickening agents examined, carrageenan gave the highest value for electrical conductivity (0.2 S/m at 25C and 1% and 1.4 S/m at 100C and 3%) followed 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 conductivities (0.06 S/m at 25C at the lowest concentration to 0.37 S/m at 100C at the highest concentration). Starch samples had the lowest electrical conductivity varying from 0.05 S/m at 25C and 4% to 0.21 S/m at 100C and 6%. Regression equations were established for each type of hydrocolloid solutions revealing a strong interaction between the concentration and the temperature and the electrical conductivity values. Major differences were observed between hydrocolloid types on electrical conductivities that were mainly attributed to their ash content.