Sequential Fermentation with Selected Immobilized Non-Saccharomyces Yeast for Reduction of Ethanol Content in Wine

Abstract

The average ethanol content of wine has increased over the last two decades. This increase was due to consumer preference, and also to climate change that resulted in increased grape maturity at harvest. In the present study, to reduce ethanol content in wine, a microbiological approach was investigated, using immobilized selected strains of non-Saccharomyces yeasts namely Starmerella bombicola, Metschnikowia pulcherrima, Hanseniaspora osmophila, and Hanseniaspora uvarum to start fermentation, followed by inoculation of free Saccharomyces cerevisiae cells. The immobilization procedures, determining high reaction rates, led a feasible sequential inoculation management avoiding possible contamination under actual winemaking. Under these conditions, the immobilized cells metabolized almost 50% of the sugar in 3 days, while S. cerevisiae inoculation completed all of fermentation. The S. bombicola and M. pulcherrima initial fermentations showed the best reductions in the final ethanol content (1.6 and 1.4% v/v, respectively). Resulting wines did not have any negative fermentation products with the exception of H. uvarum sequential fermentation that showed significant amount of ethyl acetate. On the other hand, there were increases in desirable compounds such as glycerol and succinic acid for S. bombicola, geraniol for M. pulcherrima and isoamyl acetate and isoamyl alcohol for H. osmophila sequential fermentations. The overall results indicated that a promising ethanol reduction could be obtained using sequential fermentation of immobilized selected non-Saccharomyces strains. In this way, a suitable timing of second inoculation and an enhancement of analytical profile of wine were obtained.

The aptitude of commercial yeast strains for lowering the ethanol content of wine

“…Previous studies (Canonico, Comitini, Oro, & Ciani, ; Contreras, Curtin, & Varela, ; Contreras et al, ; Gobbi et al, ; Varela, Barker, Tran, Borneman, & Curtin, ) have reported a significant reduction in ethanol yield (0.3%–1.7% v/v) when using non‐ Saccharomyces and S. cerevisiae strains in co‐inoculated or sequential cultures. The use of M. pulcherrima co‐inoculated with S. cerevisiae in the pilot‐scale production of Merlot wines resulted in 1.0% v/v lower ethanol content compared to wines fermented by S. cerevisiae alone (Varela et al, ).…”

“…At lower levels (below 50 mg/L), acetaldehyde can contribute pleasant fruity aromas to a wine. As for comparison, Varela et al (2017) and Canonico et al (2016) reported that wines produced with M. pulcherrima showed higher concentrations of ethyl acetate, total esters, total higher alcohols, and total sulfur compounds Table 1. a,b,c different letters for the results in every specific day of alcoholic fermentation indicate significant differences between values (p < .05) and benzyl alcohol (9.7-11.2 mg/L) were detected in wines produced by the activity of S. cerevisiae, in both individual and sequential inoculations (samples CER, MET+CER, and MET+BAY+CER).…”

“…The activity of T. delbrueckii resulted in an ethanol concentration of 0.8%-0.9% v/v in the early days of fermentation. The highest ethanol production rate with a pure culture of T. delbrueckii was achieved between the third and sixth days of fermentation.Previous studies(Canonico, Comitini, Oro, & Ciani, 2016;Contreras et al, 2014;Gobbi et al, 2013;Varela, Barker, Tran, Borneman, & Curtin, 2017) have reported a significant reduction in ethanol yield (0.3%-1.7% v/v) when using non-Saccharomyces and S. cerevisiae strains in co-inoculated or sequential cultures. The use of M. pulcherrima co-inoculated with S. cerevisiae in the pilot-scale production of Merlot wines resulted in 1.0% v/v lower ethanol content compared to wines fermented by S. cerevisiae alone Contreras et al (2014).…”

Wine aromatic compound production and fermentative behaviour within different non-Saccharomyces species and clones

“…Other authors (Canonico et al . ) have shown that the M. pulcherrima yeast species is a good candidate for this purpose.…”

Yeasts found in vineyards and wineries

“…Besides having a role in shaping wine flavour profile, M . pulcherrima has also shown potential as a mixed starter culture for reducing alcohol concentration during wine fermentation (Canonico et al ., ; Contreras et al ., ; Quiros et al ., ).…”