Effects of gamma irradiation on soybean oil stability by enhancing tocopherol content in soybean

Soybean oil has high contents of polyunsaturated fatty acids and hence susceptible to deterioration due to the presence of lipase and lipoxygenase (LOX) enzymes. These enzymes cause the severe impact in the reduction of shelf life. Therefore it is indispensable to adopt a stabilization step to increase antioxidant levels and to decrease the activity of lipase and LOX enzymes. To carry out this study soybean varieties were irradiated by low gamma doses radiation (0.5 kGy and 1.0 kGy) and oil was stored up to 60 days at 40 °C with 45% relative humidity. Results indicated the lowest activities of lipase (20.9%) and LOX (17.1%) at 60 days of storage respectively and also observed significantly low hydrolytic (22.6%) and oxidative rancidity (64%) respectively in Bragg oil under the condition of 0.5 kGy gamma irradiation. Total antioxidants were found to be increased including lipid soluble antioxidants like tocopherols and also found low level of reactive oxygen species (ROS) deposition in Bragg seeds irradiated with 0.5 kGy which suggests that low dose of gamma irradiation is highly effective in enhancing the oil stability and also in retaining antioxidants.