Understanding Brettanomyces behaviour to optimise the use of alternatives to SO₂ in wines

Mestrado em Engenharia de Viticultura e Enologia / Instituto Superior de Agronomia. Universidade de Lisboa

The wine world is constantly evolving, and the market is increasingly demanding with regard to the characteristics of the final product. Winegrowers must follow the trends that have been emerging in relation to winemaking methods, not only in terms of the final product, but also when talking about all the processes involved in obtaining it. As far as wine defects are concerned, one of the producers' greatest focus is Brettanomyces yeast, which is considered to have the greatest capacity to cause wine spoilage. It has been, in the last decades, a reason for great attention, since it causes great economic losses when the conditions for its establishment in the winery are met, especially when we talk about higher quality red wines that have been submitted to expensive ageing processes in wooden barrels. This yeast has the capacity to produce ethylphenols which, above certain quantities, cause highly undesirable changes in the wine's organoleptic characteristics. To date, the most used and efficient approach to dealing with Brettanomyces is the use of sulphites to prevent its growth. SO₂ is the most widely used additive in wineries for the control of this yeast. However, in recent years there has been growing concern from a number of health and food industry stakeholders about the presence of sulphites in various foods. In addition to the fact that they can be harmful to human health above certain ingested values, there is now an increasing trend towards the reduction of all chemical additives in food. The current trend has led the consumer to prefer all products that are related to organic, sustainable, natural production, words that are increasingly referred to throughout the industry. As a food product, wine has also been following this trend, which is becoming increasingly demanding and challenging. The aim of this review was to analyse most of the available alternative methods to the use of sulphites for the reduction of Brettanomyces in wine, in an attempt to minimise the amount of SO₂ to be added to the final product. Knowing how this yeast behaves, which factors influence its growth and at which stages of the winemaking process it is most likely to develop, are some of the topics. In this way, it is intended to make a synthesis of alternative methods to reduce its incidence, to understand which are the most advantageous and what still has to be done in the future to achieve the desired objectives

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