Effect of roasting temperature and time on the chemical composition of rice germ oil

Compositional changes of rice germ oils prepared at different roasting temperatures (160-180degreesC) and times (5-15 min) from rice germ were evaluated and compared with those of unroasted rice germ oil, The color development and phosphorus content of oils increased significantly as roasting temperature and time increased, whereas the FA compositions of rice germ oils did not change with roasting temperature and time. Four phospholipid classes, i.e., PE, PI, PA and PC, were identified. PE had the lowest stability under roasting conditions. There were no significant differences in gamma-oryzanol levels of rice germ oils prepared at different roasting temperatures and times. Four tocopherol isomers (alpha-, beta-, gamma-, and delta-tocopherol) and three tocotrienol isomers (alpha-, gamma-, and delta-tocotrienol) were identified, but no beta-tocotrionol was detectable. The content of alpha- and gamma-tocopherol in rice germ oil gradually increased as roasting temperature and time increased.