Enhancing wine ester biosynthesis in mixed Hanseniaspora uvarum/Saccharomyces cerevisiae fermentation by nitrogen nutrient addition.

The dynamic changes of wine ester production during mixed fermentation with Hanseniaspora uvarum Yun268 and Saccharomyces cerevisiae F5 was investigated at different levels and timings of nitrogen nutrient addition. Nitrogen additions were performed by supplementing yeast assimilable nitrogen (YAN) into a synthetic grape must with defined composition. Ester precursors and extracellular metabolites involved in ester synthesis were analyzed throughout the fermentation. Results showed that nitrogen additions covering 50-200 mg/L YAN at the point of yeast inoculation slightly affected yeast competition and ester profiles. Interestingly, when YAN was supplemented in the mid-stage, the survival of H. uvarum Yun268 was enhanced, resulting in more than a 2-fold increase in the levels of higher alcohol acetates compared to that at the initial stage. Furthermore, carbon fluxes may be redistributed in the central pathway, which contributed to the production of medium-chain fatty acids and eventually triggered a 1.2-fold elevation in corresponding ethyl ester levels.

Wine aroma response to different participation of selected Hanseniaspora uvarum in mixed fermentation with Saccharomyces cerevisiae.

Wine aroma response to a selected Hanseniaspora uvarum Yun268 strain was investigated using different inoculation strategies with commercial Saccharomyces cerevisiae yeast, namely, simultaneous fermentation (SiF), sequential fermentation (SeF), S. cerevisiae fermentation treated with extracellular extract of H. uvarum (EE), and pure S. cerevisiae fermentation (PF). Contributive volatiles in the perception of enhanced aroma traits were uncovered by partial least-squares regression. Results showed that controlled inoculation resulted into different amounts of H. uvarum Yun268, which distinctively affected the chemical and sensory profiles of wines. The concentration of aromatic compounds could be increased by H. uvarum Yun268 yeasts via high levels of ß-glucosidase activity and fatty acids. Terpenes, C13-norisoprenoids, acetate esters, ethyl esters, and fatty acids served as the impact volatiles that contributed to the enhanced aroma traits. SiF specifically increased the contents of C13-norisoprenoids, terpenes, and ethyl esters, while EE enhanced varietal volatile content rather than those of fermentative ones. However, excessive H. uvarum Yun268 in sequential inoculation elevated the concentrations of acetate esters and volatile phenols, triggering nail polish odor in Cabernet Sauvignon red wines.

Increase of medium-chain fatty acid ethyl ester content in mixed H. uvarum/S. cerevisiae fermentation leads to wine fruity aroma enhancement.

Medium-chain fatty acid (MCFA) ethyl esters, as yeast secondary metabolites, significantly contribute to the fruity aroma of foods and beverages. To improve the MCFA ethyl ester content of wine, mixed fermentations with Hanseniaspora uvarum Yun268 and Saccharomyces cerevisiae were performed. Final volatiles were analyzed by gas solid phase microextraction-chromatography-mass spectrometry, and aroma characteristics were quantitated by sensory analysis. Results showed that mixed fermentation increased MCFA ethyl ester content by 37% in Cabernet Gernischt wine compared to that obtained by pure fermentation. Partial least-squares regression analysis further revealed that the improved MCFA ethyl esters specifically enhanced the temperate fruity aroma of wine. The enhancement of MCFA ethyl esters was attributed to the increased contents of MCFAs that could be induced by the presence of H. uvarum Yun268 in mixed fermentation. Meanwhile, the timing of yeast inoculations significantly affected the involving biomass of each strain and the dynamics of ethanol accumulation.

Aroma modulation of Cabernet Gernischt dry red wine by optimal enzyme treatment strategy in winemaking.

Cabernet Gernischt (CG) is a famous Chinese wine grape cultivar, the red wine of which is known for its green trait, especially when produced from grapes cultivated in regions with monsoon climate. To modify CG wine aroma, three enzyme preparations (H. uvarum extracellular enzyme, AR2000, and pectinase) were introduced in different winemaking stages with Saccharomyces cerevisiae. Free and bound aroma compounds in young wines were detected using headspace solid-phase micro-extraction and gas chromatography-mass spectrometry, and aroma characteristics were quantified by trained panelists. Results showed that simultaneous inoculation of enzymes and yeasts improved wine aroma. Partial least-squares regression revealed that the green trait was due mainly to varietal compounds, especially C6 compounds, and could be partly weakened by fermentative compounds. Moreover, H. uvarum enzyme treatments enriched the acid fruit note of CG wine by enhancing the synergistic effect of varietal volatiles and certain fermentative compounds, such as esters and phenylethyls.