How much soybeans can be added to wheat flour and how should they be added?
About 10 % soybeans can be added to wheat. But soybeans should first be roasted in a pan for 10 minutes on high flame and then added to wheat and ground to inactivate trypsin inhibitor. The roasting makes the whole protein in soybeans digestible. Since we cook roti only for a minute it is not enough to make the trypsin inhibitor in soy inactive. Adding soybeans means 20 % fat too, so the shelf life of wheat flour reduces. It is better to add defatted soy flour because it is heat treated and the trypsin inhibitor is already inactivated. And since there is no fat there is no question of rancidity or reduced shelf life.
