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Wine yeasts and their role in wine fermentation has attracted researchers’ interest in the last few years, given the potential of yeasts to solve new winemaking industry challenges. F1000Research author, Roberto Peréz-Torrado, discusses his recent analysis of the molecular adaptation of two yeast strains to low temperatures and explains how this information will be useful for winemakers.

Wine yeasts

Yeast has become an essential agent in the process of wine fermentation, as it allows the conversion of sugars into ethanol among many other bioconversions, including the production of flavours and aroma compounds.

A dozen different yeast species are frequently identified at the beginning of the grape must fermentation. These yeasts can be found around the winery environment, on the grape surface, on the winery tools and instruments and they end up mixed in the must after the whole process of grape harvest and must preparation.

Then, a complex battle starts for the consumption of the resources that includes the generation of antimicrobial compounds. At the end of the fermentation only one or two species are found, including one of the most dominant species, Saccharomyces cerevisiae, which thrives because of its high fermentative capacity and ethanol resistance.

Consumers tend to prefer wines with new and more complex aromas

Complex aromas

The wine industry is always looking to improve their products and one of the most important issues is the wine’s aroma. Consumers tend to prefer wines with new and more complex aromas, which is why wineries want to develop new strategies to obtain the perfect aroma in wine.

One of these strategies is to ferment wine at low temperatures. This decrease in the fermentation temperature promotes the production of aroma compounds by the yeast cells and reduces the evaporation of aroma compounds, which, due to their intrinsic nature, tend to be volatile.

Theoretically, this would be the perfect way to keep the aroma, however there is a problem with this approach. The S. cerevisiae cells become ‘stressed’ at lower temperatures and this slows down the wine fermentation process. Other species from the same genera, such as Saccharomyces bayanus or Saccharomyces kudriavzevii, can deal with low temperatures. They have an optimal growth temperature around 10 ºC lower than S. cerevisiae. Unfortunately, S. bayanus and S. kudriavzevii have poor fermentative power and the aroma production is not of the highest quality. Another possibility is to use hybrid organisms between S. cerevisiae and S. kudriavzevii or S. bayanus. These hybrids can, in some cases, show the best characteristics of the parental species.

Hybrids can, in some cases, show the best characteristics of the parental species.

Natural hybrids

In fact, there are a few natural wine hybrids that are used in cold fermentations and in countries which are use to colder climates than the Mediterranean wine-growing regions. The knowledge about these hybrids could be essential to understand the complex interactions that occur between the yeast cells. Global transcription studies are a good starting point to gain insights into the molecular interactions and how the different alleles express and regulate the alleles from the genomes of other yeast species.

The results of this study revealed that complex interactions that occur in the hybrids are far from a simple addition of one genome to the other. We’ll need to perform more detailed and precise studies to solve the puzzle related to the genome interactions in wine hybrids.