ENDOGENOUS ANTIOXIDANTS AND STABILITY OF SESAME OIL AS AFFECTED BY PROCESSING AND STORAGE

The effect of processing of coated and dehulled sesame seeds on the co ntent of endogenous antioxidants, namely sesamin, sesamolin, and gamma -tocopherol in hexane-extracted oils, was studied over 35 d of storage under Schaal oven test conditions at 65 degrees C. Seeds examined wer e Egyptian coated (EC) and dehulled (ED) and Sudanese coated (SC) vari eties. Processing conditions of raw (RW) seeds included roasting al 20 0 degrees C for 20 min (R), steaming at 100 degrees C for 20 min (S), roasting at 200 degrees C for 15 min plus steaming for 7 min (RS) and microwaving at 2450 MHz for 15 min (M). The sesamin content in fresh o ils from EC, ED, and SC raw seeds was 649, 610, and 580 mg/100 g oil, respectively. Corresponding values for the content of sesamolin in oil s tested were 183, 168 and 349 mg/100 g oil, respectively. Meanwhile, the content of gamma-tocopherol, the only tocopherol present in the oi ls, ranged from 330 to 387 mg/kg sample. The effect of processing on c hanges in the sesamin content in oils from coated seeds was low and ge nerally did not exceed 20% of the original values. On the other hand, oils from dehulled seeds underwent a more pronounced decrease in their sesamin content than the oil from coated seeds after 35 d of storage at 65 degrees C. The corresponding changes in sesamolin and gamma-toco pherol contents were more drastic. The RS treatment, which would be th e optimal to prepare sesame oil with better quality, was found to reta in 86, 80 and 60% of the sesamin, sesamolin and gamma-tocopherol, resp ectively, originally present in the seeds after the storage period. Th e loss in the content of endogenous antioxidants present in the oils p aralleled an increase in their hexanal content.