Changes in isoflavone contents and composition of sufu (fermented tofu) during manufacturing

Sufu is a fermented tofu product which is popular in China. Manufacturing procedures of sufu significantly affected the isoflavone contents and composition of sufu. The recovery of isoflavones in sufu from soybean was 16.9%. The loss of isoflavones was mainly attributed to the preparation of tofu and salting of pehtze (fresh bean curd overgrown with mould mycelia). The isoflavone composition was altered during sufu processing. The levels of aglycones increased, while the corresponding levels of glucosides decreased. “Former fermentation” corresponded to the fastest period of isoflavone conversion. The isoflavones in sufu, in the form of aglycones and in the form of glucosides, accounted for 99.7% and 0.3% of the total, respectively. The changes in the isoflavone composition were significantly related to the activity of β-glucosidase during sufu fermentation, which was affected by the NaCl content.