Mouse sound

Wine taint is a well-known problem in winemaking and is caused by harmful microorganisms. The substances 2-acetyltetrahydropyridine (ACTPY), 2-ethyltetrahydropyridine (ETPY) and 2-acetyl-1-pyrroline (ACPY) are mainly responsible for the wine defect. In contrast to almost all other wine defects, mousiness cannot be eliminated by fining, but can only be avoided proactively and preventively in the production process.

Infection with microorganisms is promoted by processes with which wine producers react to a market that demands more individualized wines and to which wineries are increasingly willing to experiment: Processes that increase the texture of wines are therefore being used, particularly for red wine, but also for white wine. For example, wines are increasingly fermented spontaneously instead of using pure yeast. The use of sulphurous acid (_SO2) to kill microorganisms is increasingly being minimized. In order to achieve drinking maturity and marketability more quickly, wine maturation is made more oxidative. To avoid atypical ageing (UTA), longer maceration times of up to five days are used before alcoholic fermentation or the wine remains on the lees for several months. These oenological factors increase the risk of contamination by harmful microorganisms and promote the development of a mousy hue. In addition to these oenological measures, the effects of climate change and increasingly hot years promote the occurrence of harmful microorganisms. In recent decades, a steady increase in the pH value of the must has been measured. On the one hand, this provides optimal living conditions for the microorganisms; on the other hand, the molecular _SO2 content decreases exponentially with increasing pH values. Sensory pronounced mouse tones with marker substance contents far below the threshold value also indicate that other aroma substances contribute to the mouse tone and that there are synergistic interactions with other aroma substances and off-notes. The same applies to the microbial causes of mouse taint, which have been insufficiently clarified in the past due to the available identification methods.

Against this background, the aim of the research project is to use modern sequencing methods (next-generation sequencing) to determine viable-but-not-culturable harmful organisms, to develop a knowledge-based minimization strategy to avoid the false note "mice" and to develop recommendations for practical action.

The research project is funded as a cooperation project with the Institute of Viticulture and Enology (Dr. Pascal Wegmann-Herr) from the funds of the industrial joint funding (Federal Ministry of Economics and Climate Protection via AiF) via the Forschungskreis der Ernährungsindustrie e.V. (FEI). Project number: AiF 21642 N