Isolation of endosperm protein and aleurone cell contents from wheat, and determination of their amino‐acid composition

The techniques of air classification, and differential centrifugation in non‐aqueous media, have been combined to isolate from flour (a) endosperm protein and (b) aleurone cell contents. The amino‐acid composition of the isolated protein has been determined and compared with that of the total protein complex in the parent flour. The results show that in the isolated protein fraction the proportion of the glutenin/gliadin group of proteins is higher than in the parent flour. This was observed in the material obtained from both a strong and a weak flour. It is suggested that this partial segregation occurs in the air classification process. The protein fractions isolated from the weak and strong flours were closely similar in their overall amino‐acid composition. The amino‐acid composition of the protein contained in the isolated aleurone cell contents has also been determined. The composition is quite different from that of the main endosperm proteins and resembles, in this respect, some of the soluble protein fractions which have been previously isolated from flour. A notable feature of the composition is a relatively high content of arginine.