Calcium Fortification in Soybean Milk and In Vitro Bioavailability

Soybean milk is a milk alternative beverage due to its inexpensive high-quality vegetable protein. Soybean milk (soybean to water, 1:8 (w/v)) contains an equal amount of protein to a comparable amount of cowʹs milk but only about one-fifth of the calcium. The objective of this study was to fortify soybean milk with calcium carbonate and tri-calcium phosphate at a similar level of calcium to cowʹs milk. Calcium bioavailability in fortified soybean milk was evaluated by anin vitro Millerʹs method that involved a simulated human gastrointestinal digestion followed by measurement of dialysable calcium. Calcium ranked dialysis percentage was calcium carbonate fortified soybean milk (19±0.7%)>cowʹs milk (17±0.8%)>tri-calcium phosphate fortified soybean milk (15±0.7%)>non-fortified soybean milk (11±2%). The relative availability of calcium from calcium carbonate and tri-calcium phosphate fortified soybean milk proved to differ significantly from that of cowʹs milk and non-fortified soybean milk. The overall acceptability, on a 9-point hedonic scale, of two types of calcium-fortified soybean milk was about 7, whereas that of the non-fortified soybean milk was about 6. The Ca:P ratio in soybean milk; non-fortified, fortified with calcium carbonate and with tri-calcium phosphate; was 1:2, 2.6:1 and 1.3:1, respectively.