Estimation of pH of Soymilk on the Properties of Soy Protein Lipid Film

The effect of various concentration of sodium hydroxide (alkali) on the pH of soymilk, protein-lipid film formation yield, chemical composition and boiling resistance was studied. Film yield increased as the pH of the soymilk increased above its natural pH (6.5). Film yield was found to be more at 0.4(v/v) and 0.5(v/v) percent of NaOH concentration in the soymilk than at 0.1, 0.2 and 0.3 per cent. Maximum protein incorporation was found at 0.2, 0.3 and 0.4 per cent levels of alkali incorporation than at 0.1 and 0.5 per cent. Whereas, the fat incorporation was less at 0.2, 0.3 and 0.4 per cent than at 0.1 and 0.5 per cent due to the less holding capacity of protein towards non-polar lipids at higher pH. Carbohydrates and minerals were also higher as the protein has the capacity to hold more polar groups at higher pH. Boiling resistance of protein-lipid films decreased as the percentage of alkali incorporation into the soymilk increased.