Abstract
Using novel non-Saccharomyces strains is regarded as an effective way to improve the aroma diversity of wines to meet the expectations of consumers. The non-Saccharomyces Hanseniaspora vineae and Metschnikowia pulcherrima have good aromatic properties useful for the production of table wine. However, no detailed information is available on their performances in icewine fermentation. In this study, simultaneous and sequential fermentation trials of indigenous M. pulcherrima CVE-MP20 or H. vineae CVE-HV11 with S. cerevisiae (SC45) were performed in 50-L fermenters of Vidal icewine, respectively. The results showed that SC45 cofermented with different non-Saccharomyces strains could generate a distinct aroma quality of icewine compared with four S. cerevisiae strain monocultures as evidenced by principal component analysis (PCA). Mixed fermentation of MP20/SC45 produced higher contents of acetate esters and β-damascenone with lower C6 alcohols relative to SC45 monoculture. Interestingly, HV11/SC45 generated the highest amounts of C6 alcohols [(Z)-3-hexen-1-ol and (E)-3-hexen-1-ol], higher alcohols (isobutanol, isopentanol, and 2-phenylethanol), acetate esters (2-phenethyl acetate and isoamyl acetate), cis-rose oxide, β-damascenone, and phenylacetaldehyde. Compared with simultaneous inoculation, sequential inoculation could achieve higher aroma diversity and produce higher intensity of fruity, flowery, and sweet attributes of icewine as assessed by calculating the odor activity values (OAVs). Our results verified the desired enological characteristics of H. vineae strain in icewine fermentation and also demonstrated that using indigenous non-Saccharomyces and Saccharomyces strains is a feasible way to improve aroma diversity of icewine products, which could provide an alternative way to meet the requirement of wine consumers for diversified aromatic quality.
Highlights
Icewine is a dessert wine that is made from grapes, which have been left on the vine until weather conditions are cold enough to freeze the grapes
The results of fermentation trials showed that both non-Saccharomyces strains can well multiply and persist in initial stages of icewine fermentation, they were gradually dominated by S. cerevisiae
Our data showed that HV11 had better growth profile than that of MP20 and a higher growth rate and cell number were observed during fermentation, which was consistent with previous results that H. vineae has a higher ability to adapt to harsh conditions of wine fermentation compared to other non-Saccharomyces species (Viana et al, 2011)
Summary
Icewine is a dessert wine that is made from grapes, which have been left on the vine until weather conditions are cold enough to freeze the grapes. Compared to table wine yeast, icewine yeast is challenged by more extreme stresses during alcoholic fermentation especially high sugar concentrations (above 35 Brix) and low fermentation temperature (15–18◦C), which lead to reduced cell growth, prolonged fermentation time, and lower-than-desired alcohol levels (Kontkanen et al, 2004). These stresses can induce significant changes of yeast metabolism and the production of metabolites including acetic acid, glycerol, and aromatic compounds, and affect icewine quality (Heit et al, 2018). Several works have confirmed that different commercial S. cerevisiae strains could produce diversified aromatic profiles during icewine fermentation and lead to different sensory characteristics (Erasmus et al, 2004; Crandles et al, 2015; Synos et al, 2015)
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