Abstract
We compared the behavior of five kinds of coagulants on gelation of soybean proteins on the basis of breaking stress of Tofu (soybean curd) prepared by using different amounts of coagulant obtained by puncture and compression tests. The acid-type coagulant such as glucono-δ-lactone (GDL) or L-ascorbic acid (LAA) requires a lower concentration, as compared with the salt-type coagulant such as calcium sulfate (CaSO4), Magnesium chloride (MgCl2), or a bittern, to form a Tofu gel of the largest breaking stress, beyond this concentration the gel was rapidly disaggregated. On the contrary, the maximum breaking stress of Tofu prepared by salt-type coagulant, CaSO4, MgCl2, or bittern, slightly decreases with increasing coagulant concentration over a wide range. The behavior of CaCl2 on heated soybean milk is intermediated between those of acid-type and another salt-type coagulants even though CaCl2 belongs to a class of salt-type one. Based on the observations from the coagulability and texture of Tofu gel formed, the most suitable concentration, above which the poor taste develops, for each coagulant was determined. When the GDL-MgCl2 mixtures were used as a coagulant, the behaviors of them were divided into three types depending on the range of compositions. The mixed coagulants of the composition between 0.18 and 0.37 mole fraction of MgCl2 showed a synergistic effect of mixing acid-type coagulant with salt-type one, and the behaviors of which composed of either below 0.18 or over 0.37 mole fraction of MgCl2 were identical with those of the individual coagulant, GDL or MgCl2, respectively.
