Abstract
The use of selected Saccharomyces and non-Saccharomyces strains as mixed starters has advantages over pure fermentation due to achieving wine products with distinctive and diversified aroma expected by consumers. To obtain a way to improve the aroma diversity and increase the differentiation of wine product, in this study, the aromatic effect of multi-culture of indigenous Torulaspora delbrueckii (TD12), simultaneous and sequential inoculation with two Saccharomyces strains (indigenous icewine yeast SC45 and commercial yeast BDX) with different enological characteristics were investigated in laboratory-scale 20 L fermenter, respectively. The results showed that T. delbrueckii co-fermented with different S. cerevisiae strain could generate diversified physicochemical and aromatic quality of wine as evidenced by PCA. Mixed fermentation of SC45/TD12 produced higher contents of higher alcohol (3-methyl-1-pentanol and phenylethyl alcohol), ethyl esters (ethyl decanoate and ethyl butanoate), terpenes and phenylacetaldehyde with less fatty acids (hexanoic acid, octanoic acid) and acetic acid, while BDX/TD12 generated more C6 alcohol (1-hexanol) and acetate esters (ethyl acetate and isoamyl acetate). Compared to simultaneous inoculation, sequential inoculation could achieve higher aroma diversity, and generate higher intensity of fruity, flowery and sweet attributes of wine as assessed by calculating the odor activity values. The different S. cerevisiae strain and inoculation method in alcoholic fermentation could further influence the formations of aromatic compounds in malolactic fermentation. Our results highlighted the importance of S. cerevisiae strain in shaping the aromatic quality of wine in mixed fermentation, and also suggested that using different S. cerevisiae strains with distinct aromatic characteristics co-fermentation with specific non-Saccharomyces strain is a potential way to increase the aromatic diversity and quality of wine product, which could provide an alternative way to meet the requirement of wine consumers for diversified aromatic quality.
Highlights
In recent years, the consumer requirements for distinctive aromatic characteristics urge winemakers to develop a variety of ways to manipulate specific aroma compounds and increase the complexity of wine
It should be noticed that the highest populations of BDX and SC45 in sequential fermentation were comparable to those of simultaneous fermentation, suggesting that TD12 is not killer strain that secret toxin on S. cerevisiae, as reported by Velázquez et al (2015)
T. delbrueckii cells are less adapt to the grape must because in all cases, their number rapidly decreased after 2 d fermentation relative to S. cerevisiae, which were consistent with the data of previous literature (Loira et al, 2014)
Summary
The consumer requirements for distinctive aromatic characteristics urge winemakers to develop a variety of ways to manipulate specific aroma compounds and increase the complexity of wine. The multi-starter fermentations of different non-Saccharomyces species together with S. cerevisiae in a controlled manner can produce distinct aroma profiles and improve the complexity of final wine (Anfang et al, 2010; Imma et al, 2010; Cañas et al, 2011; Jolly et al, 2014). Among these non-Saccharomyces yeast species, Torulaspora delbrueckii is probably the one that is most often used in winemaking. The main explanation for these contradictory results is the difference of T. delbrueckii strain used in these studies because the aromatic effect of non-Saccharomyces in the mixed fermentation is usually strain-dependent (Renault et al, 2009)
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