The potential of ohmic heating for pectin extraction from orange waste

The effect of voltage gradient, pH and S/L ratio during ohmic heating up to 90 °C on the heating rate, system performance coefficients (SPCs), yield, and quality of pectin was investigated. The results showed that the rate of heating was increased with increasing of voltage gradient (from 5 to 30 V/cm) and decreased with decreasing of pH (from 4 to 1.5). With increasing of voltage gradient and decreasing of pH and S/L ratio, SPC was increased and the highest SPC was 84.4%. The yield of pectin was increased sharply from 1.17 to 10.69 g/100 g d.m. by decreasing of pH from 4 to 1.5. Finally, the highest SPC and yield of pectin with good quality (high DE and galacturonic acid) were obtained at the voltage gradient of 30 V/cm, pH of 1.5 and S/L ratio of 1:20 g/ml. Practical applications Ohmic heating technology has a good potential to extract some components from plant waste because it heats the material rapidly with high energy efficiency (SPC) in comparison to the conventional heating, therefore it can be an appropriate alternative method for extraction of pectin industrially. In addition to obtaining the highest pectin with good quality, determination of ohmic heating rate (or time of heating) and SPC at different conditions is necessary to design the industrial ohmic extraction.