INFLUENCE OF PHYTATE REMOVAL AND STRUCTURAL MODIFICATION ON THE CALCIUM-BINDING PROPERTIES OF SOYBEAN GLOBULINS

The calcium-binding properties of soybean globulins that have been dea midated or enzymatically hydrolyzed after the removal of phytate were physicochemically investigated. The level of calcium was reduced from 0.32% to 0.013% and that of phosphorus was reduced from 1.1% to 0.050% by treating with cation-and anion-exchange resins. The calcium-bindin g properties of soybean globulins were described by the Langmuir equat ion, the maximum amount of bound calcium (N) and the affinity paramete r for calcium (K) being obtained for each sample. The value of N was d ecreased by the removal of phytate, while the deamidation caused the v alue of N to increase. As hydrolysis proceeded, the value of N increas ed to a degree of hydrolysis of 32%, and then decreased. Based on this result, there seems to be an optimum molecular weight of hydrolyzed s oybean globulins for the amount of bound calcium. In addition, the val ue of K for every soybean globulin sample was much lower than that of phytic acid, indicating that the globulins had proper calcium-binding properties for calcium absorption in the small intestine.