Nitrogen extractability of sesame (Sesamum indicum L.) seed and the preparation of two protein isolates

Nitrogen extractability from sesame flour in water is greatest using a flour: solvent ratio of 1:40 and an extraction time of 15 min. At pH 4.0‐6.5, <10% nitrogen is extracted, whilst >90% is extracted at pH 11.0. In the presence of NaCl (0.5‐1.0M) nitrogen extractability is greatest at pH values > pH 4.0. The two sesame protein isolates produced were bland‐tasting, light‐coloured and contained approximately 95% protein. The alkali isolate (extracted in water at pH 10.0 and precipitated at pH 4.0) was readily solubilised and showed a good protein recovery (60%). The salt isolate (extracted in 1M NaCl at pH 6.0 and precipitated at pH 4.0) was less soluble and showed a lower protein recovery (50%). The sesame products were extracted sequentially using various solvents. Sesame flour proteins were mainly salt‐soluble (67%), alkali isolate proteins mainly water‐soluble (41%) and alkali‐soluble (41%), and salt isolate proteins mainly alkali‐soluble (35%). The amino acid composition of the sesame products is described. Oil‐expelled cake showed poor nitrogen extractability (53% at pH 11.0 in water) and was, therefore, a poor source for protein isolate production.