Wastage of valuable agricultural by- products is one of the important problems in our country. Rice bran is the most valuable by-product in rice milling factories. Rice bran is characterized by its high oil and protein contents. It also contains vitamins, minerals and many other useful chemicals. It is a potential source of vegetable oil. Rice bran is a rich source of different enzymes. The most important and crucial property of rice bran is the instability of its oil caused by a lipase system. The effect of heat treatment and storage time on lipoxidase and lipase activities was investigated in this research. This study was carried out using factorial experiment by completely randomized design with three replications. The results indicated that heat treatment time and temperature have significant effects on lipoxidase activity and the fatty acid content of bran oil. The results showed the possibility of lipase and lipoxidase renaturation and reactivation during the storage, if heat treatment time and temperature were not enough. The results also indicated that heat treatment time and temperature and the method of packaging and keeping had significant effects on the final bran moisture content. Parboiling was found to be more effective on lipoxidase activity for paddy, brown rice and bran itself. Heat treatment of bran at 110°C for 10 and 30 minutes had effect on bran enzyme activity. The lower time and temperature treatments were not enough for inactivation of rice enzymatic activity.
)