Chemical consequences of three commercial strains of Oenococcus oeni co-inoculated with Torulaspora delbrueckii in durian wine fermentation.

This work evaluated for the first time the chemical consequences of three commercial strains of Oenococcus oeni co-inoculated with Torulaspora delbrueckii in durian wine fermentation. Compared with the control (yeast only, 5.70% v/v ethanol produced), samples co-inoculated with T. delbrueckii and O. oeni PN4 improved ethanol production (6.06% v/v), which was significantly higher than samples co-inoculated with Viniflora (4.78% v/v) or Enoferm Beta (5.01% v/v). Wines co-fermented with the respective latter two oenococci contained excessive levels of ethyl acetate (>80mg/L) that were likely to affect negatively wine aroma. In addition, they led to significantly higher acetic and lactic acid production relative to PN4. O. oeni PN4 seemed to be the most suitable strain to co-inoculate with T. delbrueckii for simultaneous alcoholic and malolactic fermentation in durian wine by contributing moderately increased concentrations of higher alcohols, acetate esters and ethyl esters that would have positive sensory impacts.

Lu Y ，Chua JY ，Huang D ，Lee PR ，Liu SQ ... -  《-》

Biotransformation of chemical constituents of durian wine with simultaneous alcoholic fermentation by Torulaspora delbrueckii and malolactic fermentation by Oenococcus oeni.

Lu Y ，Chua JY ，Huang D ，Lee PR ，Liu SQ ... -  《-》

Influence of the dominance of must fermentation by Torulaspora delbrueckii on the malolactic fermentation and organoleptic quality of red table wine.

Torulaspora delbrueckii can improve wine aroma complexity, but its impact on wine quality is still far from being satisfactory at the winery level, mainly because it is easily replaced by S. cerevisiae yeasts during must fermentation. New T. delbrueckii killer strains were selected to overcome this problem. These strains killed S. cerevisiae yeasts and dominated fermentation better than T. delbrueckii non-killer strains when they were single-inoculated into crushed red grape must. All the T. delbrueckii wines, but none of the S. cerevisiae wines, underwent malolactic fermentation. Putative lactic acid bacteria were always found in the T. delbrueckii wines, but none or very few in the S. cerevisiae wines. Malic acid degradation was the greatest in the wines inoculated with the killer strains, and these strains reached the greatest dominance ratios and had the slowest fermentation kinetics. The T. delbrueckii wines had dried-fruit/pastry aromas, but low intensities of fresh-fruit aromas. The aroma differences between the T. delbrueckii and the S. cerevisiae wines can be explained by the differences that were found in the amounts of some fruity aroma compounds such as isoamyl acetate, ethyl hexanoate, ethyl octanoate, and some lactones. This T. delbrueckii effect significantly raised the organoleptic quality scores of full-bodied Cabernet-Sauvignon red wines inoculated with the killer strains. In particular, these wines were judged as having excellent aroma complexity, mouth-feel, and sweetness.

Ramírez M ，Velázquez R ，Maqueda M ，Zamora E ，López-Piñeiro A ，Hernández LM ... -  《-》

Induction of simultaneous and sequential malolactic fermentation in durian wine.

This study represented for the first time the impact of malolactic fermentation (MLF) induced by Oenococcus oeni and its inoculation strategies (simultaneous vs. sequential) on the fermentation performance as well as aroma compound profile of durian wine. There was no negative impact of simultaneous inoculation of O. oeni and Saccharomyces cerevisiae on the growth and fermentation kinetics of S. cerevisiae as compared to sequential fermentation. Simultaneous MLF did not lead to an excessive increase in volatile acidity as compared to sequential MLF. The kinetic changes of organic acids (i.e. malic, lactic, succinic, acetic and α-ketoglutaric acids) varied with simultaneous and sequential MLF relative to yeast alone. MLF, regardless of inoculation mode, resulted in higher production of fermentation-derived volatiles as compared to control (alcoholic fermentation only), including esters, volatile fatty acids, and terpenes, except for higher alcohols. Most indigenous volatile sulphur compounds in durian were decreased to trace levels with little differences among the control, simultaneous and sequential MLF. Among the different wines, the wine with simultaneous MLF had higher concentrations of terpenes and acetate esters while sequential MLF had increased concentrations of medium- and long-chain ethyl esters. Relative to alcoholic fermentation only, both simultaneous and sequential MLF reduced acetaldehyde substantially with sequential MLF being more effective. These findings illustrate that MLF is an effective and novel way of modulating the volatile and aroma compound profile of durian wine.

Taniasuri F ，Lee PR ，Liu SQ 《-》

Using Torulaspora delbrueckii killer yeasts in the elaboration of base wine and traditional sparkling wine.

For still wines, killer strains of Torulaspora delbrueckii can be used instead of non-killer strains to improve this species' domination during must fermentation, with an ensured, reliable impact on the final wine quality. The present work analysed the usefulness of these killer yeasts for sparkling-wine making. After the first fermentation, the foaming capacity of T. delbrueckii base wines was very low compared to Saccharomyces cerevisiae base wines. Significant positive correlations of foaming parameters were found with the amounts of C4-C16 ethyl esters and proteins, and negative with some anti-foaming alcohols produced by each yeast species. There were, however, no evident positive effects of polysaccharides on those parameters. The organoleptic quality of the T. delbrueckii base wines was judged inappropriate for sparkling-wine making, so that the following second-fermentation experiments only used a single assemblage of S. cerevisiae base-wines. While second fermentation was completed with inoculation of S. cerevisiae (both alone and mixed with T. delbrueckii) to yield dry sparkling wines with high CO2 pressure, single inoculation with T. delbrueckii did not complete this fermentation, leaving sweet wines with poor CO2 pressure. Yeast death due to CO2 pressure was much greater in T. delbrueckii than in S. cerevisiae, making any killer effect of S. cerevisiae over T. delbrueckii irrelevant because no autolysed cells were found during the first days of mixed-inoculated second fermentation. Nonetheless, the organoleptic quality of the mixed-inoculated sparkling wines was better than that of wines single-inoculated with S. cerevisiae, and showed no deterioration in foam quality. This seemed mainly to be because T. delbrueckii increased the amounts of ethyl propanoate and some acids (e.g., isobutyric and butanoic), alcohols (e.g., 3‑ethoxy‑1‑propanol), and phenols (e.g., 4‑vinylguaiacol). For these sparkling wines, no significant correlations between foaming parameters and aroma compounds were found, probably because the differences in foaming parameter values among these wines were fairly small. This is unlike the case for the base wines for which there were large differences in these parameters, which facilitated the analysis of the influence of aroma compounds on base-wine foamability.

Velázquez R ，Zamora E ，Álvarez ML ，Ramírez M ... -  《-》