Stabilization of Raw Rice Bran using Ohmic Heating

Ohmic heating experiments for heating of raw rice bran were conducted using a Teflon cylindrical cell. Electrical conductivity (EC) values were evaluated for ohmic heating of rice bran at 20, 30, and 40 % moisture content (w.b.), by applying voltage gradients between 44 and 72 V/cm. The EC increased significantly with increase in temperature and moisture content but the variation in EC was not significant with the variation in voltage gradient. The linear temperature and moisture content-dependent EC relations were obtained. EC values for rice bran at 20 % moisture content were in the range 0.01-0.06 S/m within the entire temperature range of 25-100 degrees C. Whereas, they were observed to be 0.04-0.14 and 0.08-0.23 S/m, respectively, for rice bran at 30 and 40 % m.c., w.b. An ohmic heating system having a capacity of 10 kg/batch was developed and evaluated for its performance. Ten kg rice bran was hydrated and heated by flow of electric current through it. The treated sample was observed to be stable even after 75 days of storage in comparison to raw rice bran sample. The % free fatty acid (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. The FFA concentration of the ohmically heated samples increased very slowly in comparison to raw rice bran samples during 75 days of storage. The peroxide value and acid value of ohmically heated samples after 75 days of storage were 4.7 meq/kg and 9.34 %, respectively. Results showed that ohmic heating is an effective method for rice bran stabilization.