Abstract

Soybean milk was fortified with calcium salts to increase its calcium contents and improve its nutritional value. The addition of calcium fortifiers gave rise to a significant drop of pH and a marked rise of calcium ion concentration. Addition of calcium salts to soy milk had a pronounced negative effect on its heat stability against heat-induced and calcium-induced coagulation. Tri-sodium citrate was added to improve the heat stability of Ca-fortified soy milk as a result of lowering ionic calcium concentration and increasing pH. Twenty five millimolar (25 mM) calcium lactate, calcium chloride and calcium gluconate were added to soy milk with no coagulation when 0.7, 1.2 and 1.4% tri-sodium citrate were added in combination. Dialysis was applied to investigate how pH and ionic calcium changed at high temperature and evaluate the influence of sterilization on certain properties of Ca-fortified soy milk. The pH and calcium ion concentration significantly decreased at high temperature but recovered after cooling.

Key words: Soy milk, calcium, calcium salts, tri-sodium citrate, heat stability.