Stochastic and deterministic processes shape the fungal communities and flavor characteristics during spontaneous fermentation of abernet franc.

This study elucidates the impact of vintage climatic variation on the interplay between stochastic and deterministic processes governing fungal community assembly during spontaneous fermentation of Cabernet Franc grapes and its consequential effects on wine flavor profiles. Employing high-throughput sequencing (fungal dynamics), HS-SPME-GC-MS (volatile metabolomics), Spearman correlation (fungi-flavorant relationships), and ecological null modeling (neutral vs. niche processes), the study tracked succession across vintages. Key findings revealed vintage-driven divergence: Cladosporium dominated filamentous fungi in 2022, contrasting with significantly higher relative abundance of Saccharomyces in 2023. Volatile profiles mirrored this shift; 2022 wines exhibited elevated esters (e.g., ethyl acetate) associated with dried fruit aromas, while 2023 wines contained significantly higher levels of higher alcohols (e.g., isoamyl alcohol) linked to floral characteristics. Kazachstania and Candida were positively correlated with key volatiles. Crucially, community assembly analysis demonstrated the predominance of stochastic processes, albeit with significant deterministic influence. This research quantitatively demonstrates how vintage climate modulates the stochastic/deterministic balance in microbial assembly during spontaneous fermentation, subsequently shaping distinct wine sensory attributes. It provides a mechanistic microbial-ecological framework for understanding the terroir effect.