Studies on the dehulling and screw pressing of soybean to obtain optimally processed soyflour.

500 g samples of soya beans were sprayed with 2, 4, 5 or 10% water, allowed to equilibrate for 15 min, dried for 5, 10, 15, 20 or 25 min at 50-60 degree C and dehulled in a coffee grinder. Addition of 2% water gave optimum dehusking; larger quantities caused excessive uptake of water by the cotyledons. Drying for 15-20 min gave optimum yield of whole, unhusked seeds; longer drying periods caused discoloration and damage. In a 2nd expt., effect of cooking and pressing on nutritional value of soya flour was investigated; direct injection of steam for 2 min followed by cooking for 20 min at 4.2 kg/cm-2 steam pressure inactivated the trypsin inhibitor and removed the beany flavour. Composition of the soya flour included: moisture, 7.6%; protein, 49.0%; fat, 18.5%; ash, 3.2%; available lysine, 4.9%; total lysine, 5.6%; methionine, 1.4%; and cystine, 1.2%.