Physico-Chemical Changes and Stability of Nutraceutical in Rice Bran Oil During Simulated Domestic Frying

Abstract

Simulated frying studies were carried out by frying circular sheets of rice flour dough in rice bran oil, heated to 180±2°C. The total frying time was up to 8 hrs. At the end of every 2 hrs, the oil samples were drawn and physicochemical changes were determined. Results showed that the changes were markedly rapid in the initial phase of frying which is first the 2 hrs. The Lovibond colour values for 0 to 2 hrs were from 12.1±0.5 to 43.1±0.95. During the same period, peroxide value (PV), free fatty acid (FFA), anisidine value (AV), total polar material (TPM), saturated fatty acid (SFA), monounsaturated fatty acids (MUFA) and viscosity were found to increase from 0.2±0.01 to 3.5±0.05 Meq.O2/kg, 0.25±0.05 to 0.69±0.05%, 5.0±0.05 to 11.1±0.2, 1.0±0.05 to 1.9±0.05 %, 25.6±0.05 to 26.2±0.05 %, 43.7±0.01 to 43.9±0.05 % and 107±0.01 to 108±0.2 mPas, respectively. Beyond 2 hr, a gradual increase in these parameters was observed till the end of frying. Similarly, more than 50 % of the tocopherol present was lost at the end of 2 hr of frying. Marginal decrease was observed in oryzanol content from 1.6±0.05 to 1.4 ±0.05 %, polyunsaturated fatty acids (PUFA) 30.5±0.01 to 28.6±0.05 % and iodine values from 100.2±0.05 to 96.8±0.05 even after 8 hr of frying. Keywords: Rice bran oil, fatty acid, oxidation, nutraceutical, simulated frying, tocopherol, oryzanol.