A new method, not patented and therefore available to wineries, makes it possible to detect the amount of acetic bacteria in wine by predicting the increases that affect the aroma, the result of acescence. It is based on the sense of smell, is simpler and more effective than the current ones and is the result of Alejandro Parra Manzanares’ doctoral thesis at the University of La Rioja and the Dolmar Tentamus Laboratory.

The thesis, ‘The Detection of Acetic Bacteria in Wines: Problems and Development of a Rapid Predictive Test‘, directed by Ana Rosa Gutiérrez Viguera and Isabel López Alfaro, was developed at the Department of Agriculture and Food of the UR and the Institute of Vine and Wine Sciences (ICVV: Government of La Rioja, CSIC and UR); the Research Group ‘Management and Control of Vinification’ (GESVIN) and the Dolmar Tentamus Laboratory (Gimileo, La Rioja).

Excess acetic acid in wines causes consumer rejection and compromises their quality. The presence of these bacteria is common in wines, generally in the form of residual populations.

The problem arises when these microorganisms multiply in excess and form large quantities of acetic acid. It is a concern for wineries to control the presence of acetic bacteria and avoid further increases in volatile acidity, especially during storage of finished wines.

However, the lack of simple and effective analyses led Alejandro Parra Manzanares to focus his thesis on the development of a liquid culture medium for the early detection of acetic bacteria based on olfactometry.

Until now, wineries could analyse the acid concentration through traditional solid cultures, although these often led to false negatives; or through PCR, an expensive technique that, moreover, has to be performed by a third party.

In this sense, the new method – which is not patented, so wineries and producers can use it freely – has been contrasted with the results obtained with PCR but, unlike the latter, it is simple and cheap: the winery only needs a refrigerator and a cooker to predict the risk of acetic acid in its wines.

A sample of wine for analysis is placed in the culture medium, heated to 30° and checked daily by smell until the concentration of acetic acid and the resulting vinegar aroma is detected.

By checking the day on which the smell appears, it is possible to know the amount of acetic acid bacteria initially present in the wine sample and the danger of acescence.

The results of this research – in which Alejandro Parra Manzanares, Ana Rosa Gutiérrez Viguera, Isabel López Alfaro, Lucía González Arenzana and Aroa Ovejas Gálvez participated – were published in the article ‘Development and Validation of a New Method for Detecting Acetic Bacteria in Wine’ available in the journal Food.

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