| 摘要: | This study investigated the relationship of concentration of soymilk, amount of coagulant, mixing temperature of adding coagulant, and stirring time after adding coagulant in the yield and quality of soft-tofu. Response surface methodology (RSM) was used to determine the optimum combinations of the four factors, concentration of soymilk (10~14 Brix), amount of coagulant (0.25~0.41%, W/V), mixing temperature of adding coagulant (75~91℃)and stirring time after adding coagulant (5~25 sec. for stirring speed of 285 rpm) to produce a high yield and good quality soft-tofu product. The yield, the solid and the protein content of tofu were measured. A piece of tofu was sliced into two parts, top and middle, then the textural properties of each parts were analyzed for hardness, brittleness and elasticity using an Instron Testing Instrument.
The results showed that only two factors, concentration of soymilk and amount of coagulant significantly affected the yield of tofu (p<0.05)and all factors except mixing temperature affected the solid and the protein content of tofu. However, the solid and the protein recovery, the brittleness and the elasticity of the top part of tofu were not influenced by all factors. All factors except stirring time affected significantly the hardness of the top part of tofu, and only two factors, concentration of soymilk and stirring time, affected the brittleness of the middle part of tofu.
According the results of superimposed contour plots, the optimum tofu processing area is: concentration of soymilk=11.8~12.3 Brix, amount of coagulant= 0.27~0.32%, mixig temperature=85~91℃,and stirring time=5~11.3 sec.. Using this condition to make tofu found that the coefficient of variations between predicted data and observed data were acceptable (<5%), except the brittleness of middle part of tofu (~9%). |
