Incorporation of soy milk lipid into protein coagulum by addition of calcium chloride.

Lipid holding in tofu (soybean curd) has such stability that it is not released even when it is cooked. The lipid in soy milk is incorporated into the tofu with coagulation of proteins on processing by the addition of a calcium salt. In this study, the incorporation of lipid into the coagulum was examined from the association with protein. The lipid in soy milk was obtained as the floating fraction by centrifugation. The floating fraction decreased by the addition of calcium chloride prior to forming a protein coagulum. When half of the protein coagulated, all of the floating fraction became inseparable. The protein in soy milk, then, was separated into particulate and soluble fractions by centrifugation. The decrease of the floating fraction with added calcium chloride was parallel to the coagulation of the particulate protein. The association of the floating fraction and the soluble protein occurred after the new particles formed from the soluble proteins. These results indicated that the lipid incorporation took place by the conjugation of the lipid and protein particles.