Oxidative Deterioration in Vegetable Oils: Health-Food Oils Versus Conventional Oils ¹

Storage stability of health-food and conventional vegetable oils was evaluated by determining oxidative deterioration during accelerated storage at 60 C of unused oils and room-temperature storage of unused and used (once-heated) oils. Oxidative changes were determined by peroxide value (PV), 2-thiobarbituric acid (TBA) test, measurement of weight increase, and sensory evaluation. Vegetable oils included were safflower and corn oils with (conventional oils) or without (health-food oils) added antioxidants. Health-food oils oxidized much faster by all measures than conventional oils, although composition of fatty acids was similar within each oilseed category. In addition, peak values of PV and TBA tests were higher for health-food oils than conventional oils. Differences between health-food and conventional oils increased steadily with the increase in storage time when unused oils were stored at room temperature; for used oils the steady increase was followed by a decrease after approximately 100 days. However, differences were greater with used oils than the unused within 100 days. As to the different oilseeds, safflower oils were more susceptible to oxidation than corn oils, the differences being widened by heating treatment before storage. The TBA test was more sensitive and correlated better with rancid odor development in these vegetable oils at early stages of oxidation, whereas peroxide value determination was generally more reliable for monitoring the oxidative deterioration over longer storage periods, up to certain limits.