Characterization of flavor profile and microbial community dynamics in naturally fermented sour watermelon

Sour watermelon (DFSW) is a distinctive fermented food that originated in Hainan, China, known for its unique and pungent flavor. Despite its cultural significance, the microbial dynamics and flavor formation mechanisms of DFSW remain poorly understood. This study employed multi-omics approaches, including HS-SPME-GC-MS and metagenomic sequencing, to analyze the physicochemical properties, volatile flavor compounds, and microbial community structure during DFSW fermentation. Results revealed that p-cresol, acetic acid, ethanol, hexaldehyde, and ethyl acetate were the dominant flavor compounds, endowing DFSW floral, fruity and spicy flavors, with p-cresol being the primary cause of pungent odors. The microbial community was primarily composed of Limosilactobacillus, Lactiplantibacillus, and Lactobacillus, which together made up over 83 % of the total abundance and were closely linked to flavor production. The correlation coefficient values (R) for Lactiplantibacillus and Lactobacillus with p-cresol, lactic acid, and acetic acid were consistently greater than 0.6. Metabolic pathway analysis highlighted the role of microbial carbohydrate and amino acid metabolism in flavor development. The synthesis of p-cresol was mainly related to the metabolism of tyrosine and L-phenylalanine, while the synthesis and metabolism of lactic acid and acetic acid were mainly related to the dominant bacterial genera in the fermentation system. These findings provide valuable insights for the biotechnological optimization of DFSW production, supporting the development of a consistent flavor profile and improved product stability.