Calcium fortification in soybean milk and in vitro bioavailability

Abstract

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 cow's 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 cow's milk. Calcium bioavailability in fortified soybean milk was evaluated by an in vitro Miller's method that involved a simulated human gastrointestinal digestion followed bymeasurement of dialysable calcium. Calcium ranked dialysis percentage was calcium carbonate fortified soybean milk (19 ± 0.7%) > cow's 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 cow's 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. © 2000 Academic Press.