Effects Of Soybean Protein Coagulating Properties On Tofu

The effects of heat treatment on soymilk denaturation of different protein content and different heat treatments were studied by differential scanningcalorimetry (DSC).the gel properties of tofu effeced by soymilk denaturation were also studied, the best proteases for soymilk coagulating were selected, the impact in the processing of soymilk coagulating by proteases and the Hydrolysis of soy proteins treated with Alcalase were investigated to study the coagulating properties and mechanisms of protease-treated soymilk coagulum. using protease and CaCl₂ to make tofu. The main conclusions were obtained as follows:1. The effects of heat treatment on soymilk denaturation of different protein content. were studied by differential scanningcalorimetry (DSC). Transition behavior of soymilk was studied by DSC. in DSC heating curves, when soymilk protein contents were above 2.5%; the transition observed at around 70℃is attributed to the denaturation of 7S (β-conglycinin) and the transition at around 90℃is to 11S (glycinin). The denaturation temperature increased with the increasing soymilk protein content. The DSC heating curves in different heat treatments soymilk. indicated that when the heating temperature is below their denaturation temperature, the protein fractions cannot completely be denatured after heated.2.The propertiesof hardness,cohesiveness,gumminess of tofu made of different heat treatments soymilk were studied ,the result indicated that high temperature treated soymilk producted gels of higher hardness, gumminess,however,the Cohesiveness showed no significantly different with the high temperature treated soymilk.3. Most of proteases used in this study, Alcalase, papain and bromelain have stronger activity of soymilk coagulating. acidic proteases had no cogulating activity. For these proteases, the optimal temperatures to coagulate soymilk were usually about 20℃higher than that to hydrolyze soy proteins. The coagulum from soymilk treated with Alcalase had a smooth mouth feel and bitterless taste. hower, comparing with gel from soymilk treated with CaCl₂.it was of low strengthness and high adhesiveness, and moreover, the whey could not easily drain from the coagulum.4. Glycinin treated with Alcalase was more easily to form cogulum thanβ-conglycinin treated with Alcalase, and the glycinin coagulum was stronger thanβ-conglycinin.5. The adding proportion of Alcalase and CaCl₂ used to make tofu was: 0.15%CaCl₂ and 10SCU/100mL Alcalase were used.