OHMIC HEATING SYSTEM FOR STABILIZATION OF RICE BRAN

Ohmic heating is an alternative to conventional heating. Ohmic heating has internal energy generation within its system. Major factors which influence ohmic heating include: 1) the electrical conductivity of the food substance, 2) the time that the substance is subjected to the heating, 3) the electric field strength and constancy, and 4) the temperature dependence of electrical conductivity. An ohmic heating system (Fig.1) having a capacity of 10 kg/batch was fabricated. It consists of a HDPE cylindrical container of 300 mm diameter. The bottom electrode was fixed and the upper electrode was placed on top of the material after filling the cylindrical chamber. The electrodes were made of stainless steel. A step-up isolation transformer having a rating of 10 kW and output of 450 V, 50 Hz AC was used to supply electrical power to the system. The hydrated rice bran having a moisture content of ~30 % (w.b.) was filled into the container and the upper electrode was securely placed. The electrodes were then connected to the electrical supply. The heating of rice bran started immediately and the temperature rose to around 100 ^oC in ten minutes. The heated rice bran was taken out from the system and dried. The FFA of treated and raw rice bran was measured at regular intervals. The % FFA in treated (ohmically heated) bran was observed to be 4.77 % after 75 days of storage whereas it was 41.84 % in case of raw bran. Ohmic heating effectively checked the development of FFA in rice bran. The peroxide value and acid value of ohmically heated samples after 75 days of storage were 4.7 meq/kg and 9.34 % respectively.