Dietary fibre characteristics and antioxydant activity of sesame seed coats

The dietary fibre contained in the seed coats (testae) of sesame, by-products of the dehulling processes during the manufacture of sweetened sesame paste (halaweh), were evaluated with two assays: the AOAC enzymatic-gravimetric method and the enzymatic-chemical method. Functional properties and antioxidant activity of sesame seed coats were also determined. The total, insoluble, and soluble dietary fibre contents measured were significantly higher using the AOAC method, than with the enzymatic-chemical method. The dietary fibre contained high amounts of neutral sugars (15.11 g/100 g seed coat dry matter), insoluble uronic acids (10.52 g/100 g seed coat dry matter), and lignin (5.42 g/100 g seed coat dry matter). Physical property analyses showed a high positive correlation between particle size reduction of seed coat, water holding capacity, and oil holding capacity; however, there was a negative correlation with bulk density. Sesame testae showed a relatively high polyphenol content (9.9 mg/g of seed coat dry matter). Aqueous methanol, ethanol, and acetone extracts of seed coats yielded similar polyphenol levels (75 mg/g of extract), higher than those found in aqueous extracts (52.7 mg/g of extract). Aqueous organic solvent extracts possessed higher antioxidant activity than water extracts. Our results suggested that sesame seed coats can be used in the preparation of low calorie, high fibre, and antioxidant-rich foods.