Physicochemical properties and aroma characteristics of broad bean koji produced by disk starter propagation technology

In this study, the physicochemical properties and aroma characteristics of broad bean koji in the disk starter propagation system (DSPS) were studied by comparing with those in the incubator koji-making system (IKS) and the traditional koji-making system (TKS). The total acid content, amino acid nitrogen content, spore numbers and enzyme activities in the DSPS were significantly higher than those in the TKS and IKS. Among the 194 volatiles detected by GC×GC–MS in these three processes, 133, 159 and 123 appeared in DSPS, TKS and IKS, respectively. Fourteen volatiles were identified as aroma-active compounds by GC–O–MS, of which 10 compounds with OAVs greater than 1 were identified as key aromas. The koji qualities in different systems presented differences gradually with the incubation continuing by PCA analysis. The quantity of physicochemical properties associated with enzyme activity in the DSPS, IKS and TKS was 23, 17 and 22 respectively by the correlation analysis. The results indicated that a better quality of broad bean koji could be obtained in the DSPS.