EFFECTS OF DIFFERENT HEAT TREATMENTS ON LIPOXYGENASE ACTIVITY AND THE OXIDATIVE STABILITY OF WALNUT OIL

The study was aimed to know the effects of different heat treatments on lipoxygenase activity and the oxidative stability of walnut oil after the complete lipoxygenase losing activity. The Yunnan Santai walnuts were treated by dry heating, microwave heating and steam heating, and walnut oil was made by pressing after lipoxygenase inactivated with dry heat method, then Schaal oven test was used to accelerate the oxidation of walnut oil. Oxidative indexes such as POV, iodine value, CGV and TBA were determined and analyzed. It was shown that three methods can significantly inactivate lipoxygenase. The enzyme was completely inactivated by 120°C dry heating 30 min and microwave 12 min treatments. The enzyme deactivation retarded the development of oxidative rancidity, and can extend the shelf-life of walnuts.