Hydrogen sulfide production during early yeast fermentation correlates with volatile sulfur compound biogenesis but not thiol release

Microorganisms: The Key Regulators of Wine Quality

Nowadays, microorganisms are recognized as pivotal regulators of winemaking processes, influencing the color, aroma, and taste of wine. Regardless of the type and quantity, the metabolic activities of them during fermentation significantly impact the final quality of wine. They metabolize sugars and other organic compounds, producing a diverse array of metabolites that enrich the wine's flavor profile. From esters that contribute to fruity aromas to pigments that affect color, the delicate balance of microbial activities is essential for creating the wine's unique character. Still, different species may produce distinct metabolites, leading to the complex and defining sensory attributes of wine. Skilled winemakers meticulously manage fermentation conditions to guide these metabolic pathways, ensuring the final product achieves desired sensory qualities different from other wines. However, no specific reports provide a detailed and comprehensive overview of the effects of microbial species. The effects of dozens of microorganisms on wine quality were summarized in this paper, including yeast and lactic acid bacteria with positive effects and acetic acid bacteria and mold with negative effects. In addition, the paper delves into microbial interactions and their synergies within fermentation, revealing how these complex relationships shape the sensory and chemical properties of wine. By providing a scientific basis for microbial selection and fermentation regulation, this paper not only supports winemakers in optimizing production processes and improving wine quality but also highlights the importance of microorganisms in responding to environmental changes and consumer demands, thereby ensuring the sustainable development and core competitiveness of wine production in the future market.

Flavor characteristics and formation mechanisms in spirits: A case study in whisky

Alcoholic beverages are a crucial segment of the global food industry, with water and ethanol serving as their foundational components. Trace compounds, though present in minute quantities, significantly influence the flavor complexity and sensory quality of these beverages. Understanding the flavor formation mechanisms in alcoholic beverages has emerged as a key research area. Whisky, a global esteemed spirit, is discussed thoroughly in this review with regard to its diverse flavor characters and distinctive flavor formation mechanisms. Chemical compositions and their organoleptic contributions were generalized, highlighting the intricacies of flavor development. Furthermore, flavor formation patterns and potential compound interactions were proposed based on various production processes, including raw material selection, fermentation, distillation, and aging. Additionally, non-volatile compounds were thoroughly reviewed on their gustatory and olfactory implications, emphasizing their subtle yet significant contributions to the overall sensory experience. The review also discusses sensory interactions among diverse flavor compounds, offering insights into the complex interaction and suggesting future research directions in whisky flavor analysis and other alcoholic beverages. Instrumental analysis techniques and authentication methods are reviewed, providing valuable perspectives for advancing the analytical landscape. This comprehensive overview pioneers an understanding of whisky's flavor profile and underlying flavor formation mechanisms, while proposing innovative concepts for flavor interaction investigations, serving as a pivotal reference for future research.

Insights into the relative contribution of four precursors to 3-sulfanylhexan-1-ol and 3-sulfanylhexylacetate biogenesis during fermentation

The desirable wine aroma compounds 3-sulfanylhexan-1-ol (3SH) and 3-sulfanylhexyl acetate (3SHA) are released during fermentation from non-volatile precursors present in the grapes. This work explores the relative contribution of four precursors (E-2-hexenal, 3-S-glutathionylhexan-1-ol, 3-S-glutathionylhexanal, and 3-S-cysteinylhexan-1-ol) to 3SH and 3SHA. Through the use of isotopically labelled analogues of these precursors in defined fermentation media, new insights into the role of each precursor have been identified. E-2-Hexenal was shown to contribute negligible amounts of thiols, while 3-S-glutathionylhexan-1-ol was the main precursor of both 3SH and 3SHA. The glutathionylated precursors were both converted to 3SHA more efficiently than 3-S-cysteinylhexan-1-ol. Interestingly, 3-S-glutathionylhexanal generated 3SHA without detectable concentrations of 3SH, suggesting possible differences in the way this precursor is metabolised compared to 3-S-glutathionylhexan-1-ol and 3-S-cysteinylhexan-1-ol. We also provide the first evidence for chemical conversion of 3-S-glutathionylhexan-1-ol to 3-S-(γ-glutamylcysteinyl)-hexan-1-ol in an oenological system.