Abstract
The aim of the research was to investigate a potential application of high hydrostatic pressure (HHP) for reduction/elimination of Brettanomyces bruxellensis and Saccharomyces cerevisiae in wines. Dry red wine was inoculated with B. bruxellensis and sweet white wine was inoculated with S. cerevisiae yeast. Both wines were treated by HHP under 100 and 200 MPa for 1, 3, 5, 15 and 25 min. The culturability was determined immediately after the treatment and again after 30, 60 and 90 days of storage. The phenolic content and chromatic characteristics were evaluated spectrophotometrically immediately after the treatment and after 90 days of storage. The culturability of B. bruxellensis was not confirmed immediately after the most invasive treatment (200 MPa for 15 and 25 min). With the same parameters, only a decrease in the culturability of S. cerevisiae was observed. During storage, opposing results were observed for two yeasts treated with 200 MPa for 15 and 25 min: there was a complete reduction of S. cerevisiae in the wine treated, but the culturability of B. bruxellensis completely recovered in all wines, implying that B. bruxellensis yeast entered a viable but not culturable (VBNC) state after HHP exposure. Regarding the chemical analyses, applied process parameters induced a slight decrease of anthocyanins in red wine, while changes of total phenolics and total colour difference value were negligible. In conclusion, HHP could potentially be successful for microbial stabilisation of sweet wines and consequently assure a lower use of sulphur dioxide, while inactivation of B. bruxellensis could only be successful in the early stages of wine contamination.
Highlights
Wine production is a complex microbiological and chemical process that involves the activity of different microorganisms – primarily yeasts
During storage, opposing results were observed for two yeasts treated with 200 MPa for 15 and 25 min: there was a complete reduction of S. cerevisiae in the wine treated, but the culturability of B. bruxellensis completely recovered in all wines, implying that B. bruxellensis yeast entered a viable but not culturable (VBNC) state after high hydrostatic pressure (HHP) exposure
After the treatment, HHP was more effective for reducing B. bruxellensis in red wine, wherein its culturability was not confirmed after pressurising by 200 MPa for 15 and 25 min
Summary
Wine production is a complex microbiological and chemical process that involves the activity of different microorganisms – primarily yeasts. One of these undesirable microorganisms is Brettanomyces bruxellensis, the main spoilage yeast in red wines Contamination with this yeast negatively affects the sensory properties of wine through production of off-flavours that are often described as “barnyard”, “horse sweat” and “medicinal”. The main challenge in controlling B. bruxellensis growth is its strong ability to survive and grow in unfavourable conditions, such as low pH, high alcohol content, anaerobic conditions and very low amounts of fermentable sugars (Fabrizio et al, 2015) In stress conditions, this yeast has an ability to enter a viable but not culturable (VBNC) state, a physiological condition characterised by the inability of cells to divide on culture media, even if they are still alive and maintain metabolic activity (Agnolucci et al, 2010; Serpaggi et al, 2012; Agnolucci et al, 2017). S. cerevisiae is considered the main yeast for alcoholic fermentation, but it could negatively affect wine quality through refermentation of sweet wines and bottled wines with residual sugars
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