A tool for catching mice in wine: development and application of a method for the detection of mousy off-flavour compounds in wine

Over the past two years, the AWRI has received 69 wine samples suspected of being affected by mousy off-flavour. The character has been mostly observed in white wines. Possible reasons for this could be the increased use of white winemaking techniques such as high grape solids ferments and extended lees ageing to add textural components to white wine, and higher pH, lower sulfur dioxide and minimal clarification or filtration practices. 

Mousy character is an off-flavour in wine that has been described as similar to the smell of caged mice. Although generally infrequent, its detrimental effect on wine quality can cause economic loss to wine producers and, in severe cases, can render wine unpalatable. Mousy off-flavour is a unique wine fault which, due to its chemical nature in wine pH, is rarely perceived by aroma but instead is detected retronasally after affected wine is swallowed or expectorated. There is a wide variation in the ability or sensitivity of individuals to perceive this character, with some tasters unable to perceive it at all. This creates problems for wine producers if they do not have the ability to detect the character during production and therefore do not take remedial action. 

The compounds responsible for this off-flavour in wine reportedly include 2-acetyltetrahydropyridine (ACTPY), 2-acetylpyrroline (ACPY), 2-acetylpyridine (AP) and 2-ethyltetrahydropyridine (ETPY). However, the contribution and importance of these individual compounds to mousiness in spoiled wines has not been demonstrated. The unavailability of a practical and reliable method for the detection and quantification of mousy-related compounds in wine has impeded objective measurement of mousy-affected wines and further research in preventing or reducing the occurrence of this fault in wine. 

The authors have recently developed a HPLC-MS method for the quantitation of ACTPY, ACPY and AP in wine. The method is simple and rapid and requires only filtration and basification for sample preparation. The analytical run time is approximately 17 minutes for one sample. Precision and accuracy tests confirm that the method is highly reliable and robust. The AWRI has implemented the developed method as a tool for the investigation of wines suspected of being affected by mousiness. A description of the method development and its application to off-flavour investigations will be presented and discussed.

Authors: Yoji Hayasaka, Geoff Cowey, Adrian Coulter

The Australian Wine Research Institute, Hartley Grove cnr Paratoo Road, Urrbrae, South Australia 5064, Australia 

Email: yoji.hayasaka@awri.com.au

Keywords: Off-flavour, Mousiness, HPLC-MS, Wine fault 

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