Effect of Parboiling, Heat treatment and Packaging on Rancidity development in Rice Bran

Abstract

Rice bran is an important ingredient in animal feeds. The action of lipases results in the release of free fatty acids (FFA) leading to rancidity which commences soon after milling. A study was carried out to assess the effects of two packaging materials, two stabilization treatments (microwave or simple heat treatment) and the parboiling of paddy on the rancidity process of rice bran. The experiment was conducted using a three factor factorial design. All samples were stored at incubator (at 28 °C) and analyzed for FFAs at weekly intervals for a period of 8 weeks. The results were analyzed statistically using a General Linear Model (GLM). The results revealed that three factor interactions were statistically significant (P<0.05) for 8 weeks. Therefore combination of tree factors was considered for the interpretation. According to the results, FFA content of both rice bran stored in vacuum pack and polypropylene bags remained below 12% up to 5 weeks with microwave heating and they are statistically significant with other combinations (P<0.01). Further, it was found that the simple heat treatment had increased storage time by two weeks keeping FFA amount less than 12% for both raw and parboiled rice bran when compared to untreated bran. The usual practice by Sri Lankan farmers is to store rice bran up to a maximum of four weeks in Polypropylene woven bags before use. The results of this study showed that simple heat treatment would be a cheap and easy option for farmers who use rice bran within first two weeks to keep the rice bran less than 12% of FFA while those who store for longer periods would need to use the microwave treatment to maintain the same condition.