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Production of low alcohol wines by non-Saccharomyces yeast

by | Oct 28, 2020 | Oenology

Project Number

Project title
Production of low alcohol wines by non-Saccharomyces yeast

Project leader
Jolly, N P

Team members
Jolly, N P
Vries, F
Erten, H
Van Breda, V
Ohlson, S
Hoff, J
Booyse, M

Objectives & Rationale
The objective of this project was to explore the use of non-Saccharomyces yeasts in aerobic production technology to produce low-alcohol wines.

Twenty-four yeasts were obtained for investigation, 22 non-Saccharomyces, a Saccharomyces cerevisiae laboratory yeast, and an S. cerevisiae commercial reference yeast also used for co-inoculation. Laboratory-scale trials were conducted in previously frozen grape must. Sugar used for one percent ethanol formed was calculated from sugar and alcohol measurements. Both aerated and standard fermentation conditions were investigated. The project was concluded with small-scale winemaking trials over two vintages.

Key Results
Non-Saccharomyces yeasts show greater variability in sugar consumption compared to the S. cerevisiae reference yeast. Some non-Saccharomyces yeasts consume considerably more sugar than S. cerevisiae for the production of 1% ethanol under laboratory conditions during co-inoculated fermentations. Cellar trials using aeration in comparison to standard fermentation showed shorter fermentation times, increased biomass formation, more sugar utilised for ethanol produced, but reduced wine quality. The same yeasts under standard fermentation conditions also showed increased use of sugar, but neutral or positive effects on wine quality.

Conclusion and Discussion / Recommendation
The yeast selection for this trial was based on previous work and published sources. The yeast can be mostly considered “non-conventional” amongst non-Saccharomyces yeasts associated with wine research. A Candida zemplinina yeast showed higher sugar utilisation for ethanol produced in comparison to the S. cerevisiae reference. This is accompanied by increased biomass production under aerated conditions, but reduced wine quality. However, under standard fermentative conditions increased sugar utilisation is achieved without negative effects on wine quality.

Jolly, N P, Kritzinger, H and Du Plessis, Z. 2014. Production of low alcohol wines by non-Saccharomyces yeast. Presentation at the Winetech Winemaking Techniques and Practices Programme Workshop. 2 October 2014, Stellenbosch, South Africa

Jolly, N P, Mehlomakulu, N, Nortje, S, Erten, H, Hoff, J, Minnaar, P, Booyse, M. 2016. An aerobic approach to wine production with non-conventional yeasts. Paper presented at the 38th South African Society of Enology and Viticulture Conference, 23-25 August, Somerset West, South Africa

Jolly, N, Mehlomakulu, N, Nortje, S, Erten, H, Hoff, J, Booyse, M. 2017. Aeration and non-conventional yeasts for wine production. Paper presented at the 33rd International Specialised Symposium on Yeasts (ISSY33). 26-29 June, University College Cork, Ireland

Jolly, N P, Varela, C, Pretorius, I S. 2014. Not your ordinary yeast: Non-Saccharomyces yeasts in wine production uncovered, FEMS Yeast Research, v. 14 (2) (p. 215-237)

Jolly, N P, Varela, C, Osmond, G, Pretorius, I S. 2014. Role of non-Saccharomyces yeasts in wine production, Wines and Vines, Mnth Jul v. 95 (7) (p. 52-57)


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