Unraveling the flavor variation mechanism of wheat bran insoluble dietary fibers during different dynamic solid-state fermentation patterns: identification via E-nose, GC-MS, and GC-IMS combination with fingerprinting

To investigate the influence of microbes on flavor attributes during solid-state fermentation of wheat bran insoluble dietary fiber (IDF), this study constructed CK (unfermented IDF), NF (native fermented IDF), YF (yeast fermented IDF), LF (Lactobacillus plantarum fermented IDF) and MF (mixed fermented IDF) systems and studied their flavor profiles change during dynamic processes (12-48 h). The E-nose results indicated that the sensor response values of flavor compounds in the samples were increased as fermentation progressed (especially in the YF and MF groups). Also, the GC-MS findings verified that co-fermentation promoted flavor release and enhanced compound species. Cluster analysis validated E-nose results, while O2PLS-DA selected 8 flavor compounds with prominent VIP scores. Moreover, GC-IMS verified the differences in flavor formation in IDF, confirming a more balanced fermentation hypothesis in MF. Also, the fingerprints were compared and differentiated in the distribution of the 75 flavor compounds featured in different fermentation groups. This flavor formation and conversion pattern may be attributed to synthesizing and releasing flavor compounds during co-fermentation by degrading bran and utilizing its products. The production of this complex flavor is related to its components' interactions. Obtained results are expected to enhance whole grain flavored food development and high-value utilization of IDF.