Microwave-Assisted Stabilisation and Storage Stability Study of Rice Bran Oil from Different Varieties

Rice bran is a by-product from milling process of paddy rice to produce refined rice, however until today, there was limited utilisation of rice bran even though rice bran has the ability and potential to become of the major supplementary sources that function as food agent substance. This is due to the instability of rice bran as it will become unstable due to the hydrolysis and oxidation process. The oxidation process, mainly due to the oil presence in the rice bran, releases substances that is unsuitable for consumption. Immediate extraction of the oil from the rice bran is needed as it will be hydrolysed into free fatty acids (FFA) and glycerol by the activity of lipase enzymes. The stabilisation of rice bran can be done by controlling the lipase activity. This process could indirectly prevent the rice bran from being oxidised. Studies have shown that the lipase enzymes in the rice bran can be inactivated depends on the temperature and duration of heat exposure (stabilisation) as well as the moisture content. In this study, the effect of microwave-assisted stabilisation of rice bran was investigated on the quality of rice bran oil (RBO) extracted. Different varieties of rice bran were used in this study which was from lowland, upland and Bario. Extraction of the rice bran was performed using soxtherm extractor and quality of RBO was determined by analysing its properties in terms of crude RBO yield, moisture content and free fatty acid content. Storage stability of the rice bran was evaluated until 40 d. The results demonstrated that the Bario rice bran showed decrease of oil yield from 0 - 40 d with a difference of 48.9 %, followed by the lowland rice bran by 48.7 %. The upland rice bran oil gives the higher different percentage of 64.2 % during the storage. An increase of moisture content was observed during the storage for all stabilised and unstabilised rice brans. Free fatty acid contents show increase amount in almost all types of rice bran range from 2.5 to 11.9 %.