CHEMICAL-CHANGES IN PECAN OILS DURING OXIDATION

Chemical changes that occur during oxidation of pecan oils were investigated. During oxidation, the tocopherol concentration of the oils decreased and the oils discolored, changing from yellow to reddish and eventually becoming colorless. Changes in color were followed by a rapid increase in rancidity products and a corresponding decrease in linoleic acid concentration. Introduction of exogenous beta-carotene into decolorized pecan oil increased oxidative stability. Addition of the autioxidant tocopherol to the oil increased oxidative stability by a significant amount over that of beta-carotene. Keeping time of pecan oils could be increased by 50% with the addition of 800 mug gamma-tocopherol.gm-1 oil. Linoleic acid concentration appears to be the primary endogenous factor in the degradation of pecan oils after harvest. Endogenous tocopherol concentrations in pecan kernels were low and not closely related to the potential keeping time of the oil. The results suggest that the oxidative stability of pecan kernels may be proportional to the percent linoleic acid in the oil. Percent oleic and linoleic acid, tocopherol content, and keeping time were determined for 70 cultivars and unnamed selections of pecans.