Taints and off-flavours are one of the major concerns in the wine industry and even if the issues provoked by them are harmless, they can still have a negative impact on the quality or the visual perception of the consumer. The mousy taint was first reported in cider. It was described as a peculiarly disagreeable flavour in wine, which is closely resembling the smell of a residence of mice. In the past, it was relatively easy to control it by protecting the wine from microbial spoilage with sulphur dioxide (SO2) and high acidity.
In recent years, the frequency of the occurrence of mouse off-flavors in wines has increased. This could be caused by the significant decrease in sulfur dioxide addition during processing, increased pH or even the tendency for spontaneous fermentation in wine.
This off-flavour was associated with Brettanomyces bruxellensis or lactic acid bacteria metabolisms.Three N-heterocyclic compounds (APY, ETHP, ATHP) were described as involved in mousiness perception. Thus far, no study addressed the variability in that N-heterocycles production according to microorganism strains from different species. Twenty-five wines presenting mousy off-flavour were analysed.
In this study in total, 252 bacteria with 90.5 % of Oenococcus oeni and 101 yeast strains with 53.5 % of Saccharomyces cerevisiae were isolated and identified. Their capacity to produce mousy compounds was investigated using Stir Bar Sorptive Extraction-Gas Chromatography-Mass Spectrometry (SBSE-GC-MS) and a standardised N-heterocycle assay medium.
While four and three species of yeast and bacteria, respectively, were isolated from mousy wines, only three species of microorganisms were associated with N-heterocycles production: B. bruxellensis, Lentilactobacillus hilgardii and Oenococcus oeni. The screening was then extended to collection strains for these three species to improve their genetic representativity.
The results show that the levels and the ratios of the three N-heterocycles present huge variations according to the species. In addition, it has been shown that in most mousy wines, B. bruxellensis was not found. Finally, an interesting correlation between ATHP and ETHP was identified.
Reference article:
Moulis, P., Miot-Sertier, C., Cordazzo, L., Claisse, O., Franc, C., Riquier, L., … Ballestra, P. (2023). Which microorganisms contribute to mousy off-flavour in our wines?. OENO One, 57(2), 177–187. https://doi.org/10.20870/oeno-one.2023.57.2.7481
