SUMMARY
Proteins were extracted with a yield of up to 90% from wheat flour and finely powdered untoasted soya flour, with a 3M urea solution at 4°C. The urea-extracted protein contained, on hydrolysis, higher amounts of ammonia than a commercial soya protein isolate. Amino acid analysis by ion-exchange chromatography of soya proteins isolated with 3M urea showed that, on an ammonia-free basis, the urea-extracted proteins were comparable to a commercial soya protein isolate. Both had an amino acid composition comparable to that of a commercial solvent-extracted 50y0-protein soya meal. The urea-extracted proteins from wheat flour and soya flour retained their functional properties in bread-making. Extraction with 3M urea was lowered in coarsely ground soya meals and was reduced substantially by heat-treatment of soya products. Dispersibility in 3M urea at 4°C was found to be a useful parameter to evaluate the extent of heat damage to plant proteins.
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.1965.tb01848.x/abstract