M.C. González

Formation of pyranoanthocyanins by Schizosaccharomyces pombe during the fermentation of red must

Schizosaccharomyces pombe is a non-Saccharomyces yeast strain that can ferment grape musts with high sugar contents - but it also has other metabolic and physiological properties that render it of great interest to wine biotechnologists. This work compares the production of pyranoanthocyanins by S. pombe, Saccharomyces cerevisiae and Saccharomyces uvarum during fermentation. Total pyranoanthocyanins ranged from 11.9 to 19.4 mg/l depending on the strain of S. pombe used. On average, S. pombe produced more pyruvic acid than did either Saccharomyces species; as a consequence it also formed more vitisin A-type pigments. S. pombe 938 produced the largest quantity of vitisin A (11.03±0.82 mg/l). The formation of large amounts of pyranoanthocyanins intensifies the post-fermentation colour of wines somewhat, a phenomenon that helps them maintain their colour over ageing as the natural grape anthocyanins become degraded. Some of the S. pombe strains showed hydroxycinnamate decarboxylase activity, which favours the formation of vinylphenolic pyranoanthocyanins. Fermentation with S. pombe therefore provides an interesting way of increasing the overall pyranoanthocyanin content of red wines, and of stabilising their colour during ageing.

Effect of Saccharomyces strains on the quality of red wines aged on lees

Ageing on lees involves ageing the wine in contact with yeast cells after fermentation. If combined with the addition of oak chips, it can soften the wood flavour and increase the aromatic complexity of wine. The aim of the present work is to optimise both ageing techniques through selection of an adequate Saccharomyces cerevisiae strain. The study lasted 6 months and content of polysaccharides, anthocyanins, proanthocyanidins, volatile compounds, colour parameters and sensory analysis, were periodically evaluated. Among the strains tested, G37 showed the highest release of polysaccharides (24.4±5.5 mg l(-1)). Vanillin, syringaldehyde and furfuryl alcohol increased with ageing time in 7VA2 treatment. The wine aged with CTPL14 strain presented fewer monomeric and oligomeric proanthocyanidins (12.4±0.6 and 83.4±8.3 mg l(-1), respectively), and showed the lowest astringency and bitterness sensations. Results show an improvement in the sensory profile of the red wine aged with a combination of these two techniques.

Formation of polymeric pigments in red wines through sequential fermentation of flavanol-enriched musts with non-Saccharomyces yeasts

Non-Saccharomyces yeasts may contribute to enrich wine aroma while promoting the formation of stable pigments. Yeast metabolites such as acetaldehyde and pyruvate participate in the formation of stable pigments during fermentation and wine aging. This work evaluated the formation of polymeric pigments in red musts added with (+)-Catechin, ProcyanidinB2 and ProcyanidinC1. The non-Saccharomyces yeasts used were Lachancea thermotolerans, Metschnikowia pulcherrima and Torulaspora delbrueckii in sequential fermentation with Saccharomyces cerevisiae and Schizosaccharomyces pombe. Use of Lachancea thermotolerans led to larger amounts of polymeric pigments in sequential fermentation. (+)-Catechin is the flavanol prone to forming such pigments. The species Metschnikowia pulcherrima produced higher concentration of esters and total volatile compounds. The sensory analysis pointed out differences in fruitiness and aroma quality. The results obtained strengthen the fact that metabolites from non-Saccharomyces yeasts may contribute to form stable polymeric pigments while also influencing wine complexity.

Theoretical considerations about usage of metabolic inhibitors as possible alternative to reduce alcohol content of wines from hot areas

The present review describes a number of metabolic inhibitors capable of redirecting the glycolytic pathway in winemaking yeasts of the species Saccharomyces cerevisiae, leading to an increase in yeast biomass production and the excretion of secondary metabolites alongside a desired reduction in wine alcohol content. The main application of these inhibitory molecules lies in the preparation of reduced-alcohol wines from grapes grown in hot areas.

Effect of Lachancea thermotolerans on the Formation of Polymeric Pigments during Sequential Fermentation with Schizosaccharosmyces pombe and Saccharomyces cerevisiae

Anthocyanins in red grape musts may evolve during the winemaking process and wine aging for several different reasons; colour stability and evolution is a complex process that may depend on grape variety, winemaking technology, fermentative yeast selection, co-pigmentation phenomena and polymerization. The condensation of flavanols with anthocyanins may occur either with the flavylium ion or with the hemiacetal formation in order to produce oligomers and polymers. The kinetics of the reaction are enhanced by the presence of metabolic acetaldehyde, promoting the formation of pyranoanthocyanin-type dimers or flavanol-ethyl-anthocyanin structures. The experimental design carried out using white must corrected with the addition of malvidin-3-O-glucoside and flavanols, suggests that non-Saccharomyces yeasts are able to provide increased levels of colour intensity and larger polymeric pigment ratios and polymerization indexes. The selection of non-Saccharomyces genera, in particular Lachancea thermotolerans and Schizosaccharomyces pombe in sequential fermentation, have provided experimental wines with increased fruity esters, as well as producing wines with potential pigment compositions, even though there is an important reduction of total anthocyanins.

Effects of ultrasound treatment on the phenolic fraction of a red wine aged on lees

Sonication is an emerging non-thermal technology useful to disrupt cell wall and increase polysaccharides release when applied to red wines aged on lees. At the same time, ultrasound treatment may cause changes in the composition of the wine, both in the phenolic and aromatic compounds. In this work, we evaluated the influence of ultrasounds treatment (frequency: 50 KHz; ultrasonic power: 200 W; acoustic energy density: 0.02 W cm−3) on polyphenols content and colour parameters of a red wine (Vitis vinifera L. cv. Tempranillo) by comparing different ultrasound treatments, lees dosages and yeast species. In general, total anthocyanin content and total polyphenol index decreased in wines treated with ultrasounds and high lees dosage, and hue increased as a result of oxidation associated with the sonication process. Regarding the effect of the yeast species, anthocyanins loss was smaller in Saccharomyces cerevisiae and Schizosaccharomyces pombe.