Wild yeasts may improve wine from warmer climates
A research team led by the University of Adelaide has found yeasts that naturally occur on grapes may improve wines produced in warmer climates — despite the fact that the use of these ‘wild’ yeasts during the production process has mostly been discouraged by winemakers.
As explained by Dr Ana Hranilovic, a recent PhD graduate from the university’s ARC Training Centre for Innovative Wine Production, “Intentional over-ripening of grapes, as well as rising global temperatures due to climate change, produces excess sugar in grapes, which is converted to ethanol during fermentation. This results in highly alcoholic wines.
“Highly alcoholic wines may not necessarily be a good thing,” she continued. “Wine fashions change as consumers’ tastes change but also these wines can lack acidity, be different in flavour and lead to a higher cost to the consumer in the form of higher taxes.”
‘Fixing’ such wines can be difficult or costly — for example, boosting acidity for a ‘fresher’ taste and to reduce the risk of bacterial spoilage adds to the production costs. The good news is that these problems may be solved through the use of different yeasts — yeasts which winemakers have always tried to suppress during production.
“These yeasts don’t always improve wine as they can cause different off-flavours,” Dr Hranilovic said.
However, Dr Hranilovic has discovered that certain strains of naturally occurring yeasts have beneficial effects in wine production. She revealed, “The yeast Lachancea thermotolerans produces high levels of acidity in the form of lactic or ‘good’ acid. This type of acid improves the wine by giving it a soft, mellow taste.
“But Lachancea thermotolerans, and other similar yeasts, cannot be used on their own as they are not capable of consuming all the grape sugars. They must be used in conjunction with the typical ‘wine yeasts’.
“We now need to do more research into how different blends of yeasts affect the taste and the quality of wine.”
Dr Hranilovic’s research was supported by the University of Bordeaux, Charles Sturt University through the National Wine and Grape Industry Centre (NWGIC), CSIRO and Laffort Oenology. It has been published in the journal Scientific Reports.
“This important research shows a potential new way for oenologists to improve the quality of wine grown in warm climates using different strains of naturally occurring yeasts,” said Professor Vladimir Jiranek, Head of the Department of Wine and Food Science, University of Adelaide.
“The ultimate aim of the research is to produce a simple method of blending different strains of yeasts to improve the quality of wine.”
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