Lipid Oxidation and Tocopherol Contents Change in Full-fat Soy Flour during Storage

Lipid oxidation and the tocopherol content of full-fat soy flour during storage were investigated. Lipid oxidation of full-fat soy flour was evaluated by p-anisidine (PAY) and conjugated dienoic acid (CDA) values. HPLC was used to determine tocopherol contents of soy flour. Full-fat soy flour in a tightly-sealed serum bottle was stored at $20^{\circ}C$ and at $60^{\circ}C$ in the dark or with light for 24 days. The CDA and PAY of soy flour increased as storage time increased. The highest values were observed in soy flour stored at $60^{\circ}C$ under light, with light exerting a higher effect on CDA and PAY than high storage temperature. Tocopherols, which were initially present at $318.81\;{\mu}g/g$, did not show much difference with storage time in soy flour stored in the dark at $-20^{\circ}C$. However. there was a big loss in tocopherol contents of soy flour during storage in the dark or with light at $60^{\circ}C$. Tocopherol contents were lower in soy flours stored with light at $60^{\circ}C$ than those in the dark at the same temperature. Light also resulted in a higher decrease in the tocopherol content of soy flour than high storage temperature.