Dynamic correlations between major enzymatic activities, physicochemical properties and targeted volatile compounds in naturally fermented plain sufu during production

Dynamic changes and correlations between physicochemical properties, 14 targeted volatile compounds (TVCs) and six groups of enzyme activities during eight production stages of naturally fermented plain sufu were explored. Multiple factor analysis was used to discriminate between and group the samples into three clusters: cluster I comprised tofu and pehtze; cluster II comprised dried pehtze and salted pehtze; cluster III involved the aging stages. Clusters I and II were characterised by higher enzyme activities, while cluster III was characterised by the presence of diverse TVCs. Protease and esterase were strongly correlated with most of the TVCs. Esterase, in particular, contributed to the formation of three high molecular weight esters, namely, ethyl dodecanoate, ethyl (Z)-9-octadecenoate and ethyl (Z, Z)-9,12-octadecadienoate. The enzymes found contributed to the texture and flavour of naturally fermented sufu and will provide a good guide and control for using the enzymes directly to ripen sufu products.