Project Number
IWBT-B 11-01
Project title
Interaction between wine yeast and malolactic bacteria and the impact on wine aroma and flavour
Project leader
Bauer, F F
Institution
University of Stellenbosch. Department of AgriSciences. Department of Viticulture and Oenology
Team members
Du Toit, M A
Bauer, F F
Divol, B
Taillandier, P
Rossouw, D
Lerm, E
Project description
The chemical composition of the wine originates from the grapes, those produced by the yeast during alcoholic fermentation and by lactic acid bacteria (LAB) during malolactic fermentation (MLF). Alcoholic fermentation mainly conducted by Saccharomyces cerevisiae produces many metabolic by-products that are important to wine quality and style due to typical aroma compounds associated with a specific yeast strain. MLF is mainly conducted by Oenococcus oeni and is induced after alcoholic fermentation has finished. The production of certain compounds is directly related to the matrix in which the yeast/bacteria have to function, including nutrient availability, microbes present naturally or being inoculated, physico-chemical parameters etc.
Today the winemaker is challenged with new inoculation practices such as mixed yeast starter cultures containing mixes of S. cerevisiae or non-Saccharomyces, yeast and bacteria co-inoculation versus sequential inoculation, the use of Lactobacillus plantarum as pure culture or as mixed culture for MLF.
Therefore the challenge of this project to study the impact of the inoculated yeast and MLF bacteria will have on a specific grape juice composition to produce a specific wine aroma profile. The base line data generated by Prof Bauer in his project on ‘Grape juice composition and winemaking practices: Predicting flavour and aroma production by individual yeast strains and the final chemical composition and sensorial quality of wine’ for the yeast will be used and to add the complexity of the MLF bacteria into the strategy under controlled conditions. The impact of yeast and bacteria will also be assessed under winemaking conditions in must generated from a characterized vineyard (Molecular and metabolic profiling of grapevines submitted by Prof Vivier).
Therefore the overall objective of this project is to study the interaction between selected yeasts and bacteria and to predict the impact of the combinations regarding flavour and aroma compounds produced in specific juice scenarios.
Presentation(s)
Du Toit, M. 2013. Chasing varietal aromas – impact of different LAB and MLF scenarios. Presentation 24th Entretiens Scientifiques Lallemand
Du Toit, M. 2013. Inoculation times for MLF. Lallemand ML School, Hblaba Klosterneuburg, Austria.
Du Toit, M. 2013. Impact of MLF on white wine aroma. Lallemand ML School, Hblaba Klosterneuburg, Austria.
Du Toit, M. 2014. Using timing as a tool to maximise MLF – the early bug gets the prize. Thales Workshop: Bio-protection and other bugging issues. Klapmuts, South Africa.
Du Toit, M. 2014. Introduction into microbiology of malolactic fermentation from the past to the future. Lallemand Seminar: Controlled Malolactic Fermentation – More Than Just a Simple Biological De-acidification Step. Stellenbosch, South Africa.
Du Toit, M. 2014. MLF in white wine: Impact in the glass. Lallemand Seminar: Controlled Malolactic Fermentation – More Than Just a Simple Biological De-acidification Step. Stellenbosch, South Africa