Deciphering layer formation in Red Heart Qu: A comprehensive study of metabolite profile and microbial community influenced by raw materials and environmental factors

Environmental-origin microbiota significantly influences Chrysanthemum Red Heart Qu (CRH_Qu) stratification, but their microbial migration and metabolic mechanisms remain unclear. Using high-throughput sequencing and metabolomics, we divided the stratification of CRH_Qu into three temperature-based stages. Phase I features rising temperatures, causing microbial proliferation and a two-layer division. Phase II, characterized by peak temperatures, sees the establishment of thermotolerant species like Bacillus, Thermoactinomyces, Rhodococcus, and Thermoascus, forming four distinct layers and markedly altering metabolite profiles. The Huo Quan (HQ) layer, developing from the Pi Zhang (PZ) layer, is driven by the tyrosine-melanin pathway and increased MRPs (Maillard reaction products). The Hong Xin (HX) layer evolves from the Rang layer, associated with the phenylalanine-coumarin pathway and QCs (Quinone Compounds) production. Phase III involves the stabilization of the microbial and metabolic profile as temperatures decline. These findings enhance our understanding of CRH_Qu stratification and offer guidance for quality control in its fermentation process.