| Abstract
| - Isoflavones are novel nutraceutical constituents of soybeans, but considerable amounts are lost inthe whey during conventional tofu manufacturing. In this study, in a small-scale process, 2 mL of kojienzyme extract (soybean koji/deionized water, 1/3, w/v) was combined with 600 mL of soy milk, and30 mL aliquots were incubated at 35 °C for 0, 30, 60, 120, and 300 min, for enzyme pretreatment.After each treatment time, soy milk was heated to 85 °C, CaSO4 was added to aggregate protein,and the mixture was centrifuged to separate the solids (tofu) from the whey. The tofu yield and moisturecontents from soy milk treated for 30 or 60 min were higher than those from soy milk treated for 0(control), 120, or 300 min. The protein content of freeze-dried tofu varied in a limited range, andnative PAGE and SDS−PAGE patterns revealed slight quantitative and qualitative variations amongproducts. Soy milk daidzein and genistein contents increased while daidzin and genistin contentsdecreased as the time of enzyme pretreatment of the soy milk increased. After 30 min of pretreatment,daidzin, genistin, daidzein, and genistein contents recovered in tofu products were higher than thoseof the control. In a pilot-scale process, aliquots (3 L) of soy milk were enzyme-treated for 30 min,aggregated with CaSO4, and hydraulically pressed to remove the whey. As in pretreatments, soymilk daidzein and genistein contents increased while daidzin and genistin contents decreased. In acomparison of the control and enzyme-treated tofu products, the total recoveries of daidzin, genistin,daidzein, and genistein in the tofu products increased from 54.9% to 64.2%. When the tofu productswere subjected to a sensory panel test, both products were judged acceptable. Keywords: Tofu; isoflavone; soy milk; koji; β-glucosidase; enzyme pretreatment
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