Yeast population dynamics during spontaneous fermentation of icewine and selection of indigenous Saccharomyces cerevisiae strains for the winemaking in Qilian, China

Abstract

BACKGROUND: Icewine produced in China is becoming popular, but there is only limited knowledge available on the yeast population that occurs during fermentation and also on the selection of indigenous Saccharomyces cerevisiae strains for its production. In this work, we first investigated yeast species and the evolution of yeast population in spontaneous fermentations of icewine produced in the Qilian region of China and then analyzed the biodiversity and important enological properties of S. cerevisiae isolates. RESULTS: Seven species of five genera including S. cerevisiae, S. uvarum, Torulaspora delbrueckii, Hanseniaspora uvarum, Lachancea thermotolerans, Metschnikowia aff. fructicola and H. osmophila were identified by the colony morphology on Wallerstein Laboratory Nutrient medium and sequence analysis of the 26S rRNA gene D1/D2 domain. Saccharomyces cerevisiae, H. uvarum and L. thermotolerans were the dominant species, representing almost 87% of the total yeast isolates. Microvinification with seven preselected S. cerevisiae strains were performed on Vidal. All selected strains could complete fermentations, and the enochemical parameters were within the acceptable ranges of the wine industry. W5B3 produced higher amounts of ethyl hexanoate and ethyl octanoate than other strains. R3A10 was a low volatile acid producer and the corresponding icewine presented the highest values on some odorants including ⊎-damascenone, 1-octen-3-ol, ethyl 2-methylbutyrate, and isoamyl alcohol. Vidal icewines fermented with R3A10, R3A16 and W5B3 were well accepted by the judges because of superior sensory quality. CONCLUSION: Three indigenous strains (R3A10, R3A16 and W5B3) could be used as starters and could potentially improve the regional character of the icewine in Qilian.

Effects of Simultaneous Co-Fermentation of Five Indigenous Non-Saccharomyces Strains with S. cerevisiae on Vidal Icewine Aroma Quality

“…Both M. pulcherrima YC12 and R. lusitaniae QTX15 significantly increased the concentrations of heptanoic acid, hexanoic acid, and nonanoic acid; and R. lusitaniae QTX15 also significantly increased the concentration of acetic acid. A high concentration of volatile acetic acid can produce a cat urine taste in wine, which deleteriously affects the aroma quality [ 2 ]. Canonico et al [ 61 ] reported that the concentration of acetic acid in beer produced by mixed fermentation was significantly higher than that produced by pure culture with T. delbrueckii .…”

“…The colonies of S. cerevisiae F33 were smooth and creamy white, whereas those of H. uvarum QTX22 and R. lusitaniae QTX15 were smooth and green, those of S. crataegensis YC30 and P. kluyveri HSP14 were white with flocculent folds, and that of M. pulcherrima YC12 was milky white, and could be easily discriminated from S. cerevisiae F33 in mixed cultures on WL media. Fermentation rate was calculated as the loss of CO 2 (g/L) within 24 h during the fermentation [ 2 ]. After fermentation, all wine samples (350 mL) were centrifuged for 8 min (4000× g , 4 °C), and the cell-free supernatants were stored at −20 °C and used within 6 months for analysis.…”

“…Delaying harvesting increases the concentrations of sugars, acids, aroma compounds, and some non-volatile substances in the grapes, intensifying the flavor characteristics. The methods of freezing grapes, low-temperature maceration, and fermentation technology better maintain the aroma substances in the wine [ 2 ]. The current research on icewine has mainly focused on the identification of characteristic flavor substances [ 3 ] and the analysis of the dynamic changes in yeast populations during fermentation [ 2 ].…”

“…The methods of freezing grapes, low-temperature maceration, and fermentation technology better maintain the aroma substances in the wine [ 2 ]. The current research on icewine has mainly focused on the identification of characteristic flavor substances [ 3 ] and the analysis of the dynamic changes in yeast populations during fermentation [ 2 ]. However, relatively few results have been reported on the influence of mixed fermentation with non- Saccharomyces and Saccharomyces yeasts on the enhancement in icewine flavor quality.…”

Deletion of YLR358C Contributes to Reduce Cell Wall Integrity in Saccharomyces Cerevisiae

“…Yeast cell wall polysaccharides have been used as thickeners, emulsi ers, preservatives and anticoagulants in food additives to improve the avor and stability of food [21][22][23]. In addition, yeast mannoprotein has several advantages in improving wine quality, it can prevent turbidity, reduce astringency, retain aroma components, and stimulate the growth of lactic acid bacteria [24]. Therefore, mastering the role of genes related to the cell wall of S. cerevisiae can modify the characteristics of yeast and optimize the fermentation process, which is of great signi cance to the food, medicine and fermentation industries [25].…”