Effect of Coagulants on the Quality of Soybean Curd Added With Cow's Milk

응고제가 우유 첨가 두부의 품질에 미치는 영향

Soybean curd added with 40% of cow’s milk was prepared with eight coagulants such as calcium acetate, calcium lactate, calcium chloride, calcium sulfate, magnesium chloride, glucono-delta lactone (GDL), acetic acid and lactic acid. The curd products were evaluated by the chemical composition, coprecipitation porperties, mineral content, yield, color and textural characteristics. The lowest concentrations for protein coprepitation were 0.3% (v/v) for calcium salts, 0.4% (v/v) for magnesium chloride, 0.2% (v/v) for organic acids. Turbidity and crude protein of whey were markedly decreased at these concentrations. The optimal concentrations of coagualnts used for soybean curd preperation were 1.2% (v/v) for calcium acetate, calcium sulfate and calcium lactate, 1.0% (v/v) for calcium chloride and GDL, 0.8% (v/v) for magnesium chloride and lactic acid, 0.6% (v/v) for acetic acid. It was observed that of the eight coagulants tested, calcium chloride provided a satisfactory curd in quality. Calcium content of soybean curds by the calcium salt coagulants was higher than that by organic acid coagulants. Through the examination on the textural properties by a texturemeter was found out that acetic acid treated soybean curd among the organic acids, calcium salts and magnesium chloride treated curds had very high hardness value. All the curd products prepared in this experiment had a pale yellow color as affected by the value of L (lightness), a (redness) and b (yellowness). Although the colorimetric readings showed that the soybean curds prepared with the organic acids had higher L value but lower a and b value in comparison to calcium salts and magnesium chloride treated curds.

두유에 우유를 40% 첨가시킨 두부 제조를 위하여 각 응고제별 및 첨가농도별로 두부를 제조하여 gel형성, 순물(whey)의 탁도, 단백질함량, 두부 생산량, 무기질함량, 조직특성과 색도를 비교 조사하였다. Calcium염 응고제는 0.3%(v/v), magnesium chloride는 0.4%, 유기산 응고제는 0.2% 첨가수준에서 대두와 우유 단백질의 공침전이 일어났으며 각 응고제 첨가비율에 비례하여 whey 탁도와 단백질의 유출량이 낮아졌다. 각 응고제 첨가 적정수준은 calcium acetate, calcium sulfate, calcium lactate 가 각각 1.2%(v/v), calcium chloride, gluconodelta-lactone이 각각 1.0%(v/v), magnesium chloride, lactic acid 0.8%(v/v), acetic acid는 0.6%(v/v)였으며 두부 생산량은 calcium chloride를 응고제로 사용했을 때 가장 높았다. 무기질의 함량은 calcium염 응고제가 유기산 응고제보다 Ca은 약 3.3배 많았고 K, Mg, Na, Fe도 약간 높았다. Texturemeter에 의한 우유 첨가 두부의 조직특성 조사결과 가장 단단한 두부는 acetic acid 두부이었고 calcium염 중에서는 calcium sulfate가 단단하였다. 응고제별 두부의 색도 비교에서 명도는 유기산 두부가 약간 높았고 적색도와 황색도는 calcium염 두부가 높았다.