Over the past few years Brettanomyces or Dekkera (Brett for short) have been spreading rapidly throughout wineries in Australia causing much unwanted wine taint, specifically in the form of volatile phenols or ‘sweaty leather’. Brett yeasts are a natural component of the winemaking process, which makes it almost impossible to eliminate completely and unsurprisingly they find themselves in winery air, on cellar walls, drains, pumps, transfer lines and other pieces of equipment. The two most important stages for Brett contamination in winemaking occur during malolatic fermentation and ageing in used barrels. Brett’s slow growing characteristics are best suited to the conditions created after alcoholic fermentation is completed and where the surfaces are not cleaned and sanitised correctly, leaving residual sugars and allowing Brett to proliferate.
The real issue here is how to combat Brett proliferation in your winery. A report in the South African Journal of Enology and Viticulture outline the five key areas for the spread of Brett, which are;
- Recent trends in some winemaking styles - such as wines with higher pH values and residual sugar;
- Trends in winemaking practices - decreased use of filtration and SO2;
- General poor cellar hygiene along with improper cleaning and sanitisation of barrels - a critical source of Brettcontamination of wine;
- The spread of Brett between wineries and regions due to the use of contaminated barrels which are traded in the second hand barrel market; and
- Importation of Brett contaminated wine from other affected wineries.
The first two points are winemaking practices, and as we are hygiene specialists not winemakers, we’ll leave those decisions up to the experts and enjoy the end result! The last two points are about good winery management. That is making sure you know what you are putting into your cellar and where you are getting your produce from, that’s just good practice. Knowing when Brett infected products or wine is in your winery will enable to you to take steps to manage their spread, and limit any damage that may occur. There are many different ways to manage Brett in your wines once they are there, some of which are outlined in this Wine Monthly article, but we believe that prevention is better than a cure and that brings us to point 3 - poor hygiene. As dull as it may sound, it’s serious business and it can cost you dearly if you don’t take it seriously.
Research into Brett has shown that it is able to form significant biofilms on what appear to be clean surfaces, and these biofilms are a major source of Brett propagation throughout a winery. The formation and adherence of Brett has been shown to increase with increasing pH of wine, and sulphur dioxide is known to slow down the rate of Brett growth in solution (which is why it is so commonly used in modern winemaking). A good summary of biofilms and effect of cleaning and sanitising can be found here. However these are merely control solutions after infestation, rather than a method to eliminate harmful microbes from your wines. Another source of Brett contamination is in oak barrels. A 2013 study by Guzzon, Nardin, Micheletti, Nicolini and Larcher outlined the use of ozone as ‘a highly effective sanitising agent without interfering with the profile of the phenolic substances extracted from oak’.
When we talk about hygiene, what we are really talking about is your hygiene procedure, which includes all aspects from cleaning, sanitation and scheduling. It’s important to have a thorough hygiene procedure in your winery to limit the spread of all microorganisms, not just Brett. Cleaning is a very important part of any winemaking process, however a clean surface is deceptive as it can still harbour microorganisms such as Brett that can taint your wine if left unattended. This is where sanitisation is most important and is something that needs to be addressed in a serious and systematic way so that you can ensure the quality of your wine. Think of sanitation like insurance for your wine. If you do it properly, then you can be safe knowing that there won’t be any hidden surprises along the way to achieving your final product. Just remember, sanitation alone will not cure a Brett infestation, as sanitation will not destroy the biofilms that Brettutilises to grow, but using the right cleaning agent, followed by correct sanitation will provide you with the best possible counter-attack to Brett infestations. The last and probably most important step is to develop a hygiene procedure within your winery, and then stick to it. If you take hygiene seriously, then you shouldn’t have to spend much time worrying about the scourge of Brett in your winery, which means you can spend more time making great wine!
Oelofse, A, Pretorius, IS & du Toit, M 2008, ‘Significance of Brettanomyces and Dekkera during Winemaking: A Synoptic Review’, South African Journal of Enology and Viticulture, vol. 29, no. 2, pp. 128-144
Barata, A, Laureano, P, D’Antuono, ID, Martorell, P, Stender, H, Malfeito-Ferreira, M, Querol, A & Loureiro, V 2013 ‘Enumeration and Identification of 4-Ethylphenol Producing Yeasts Recovered from the Wood of Wine Ageing Barriques after Different Sanitation Treatments’, Journal of Food Research, vol. 2, no. 1, pp. 140-149
Patterson, T 2012, There’s No Subsitute for SO2 (Yet), Wines and Vines, http://www.winesandvines.com/template.cfm?section=columns_article&content=103719&columns_id=24
Joseph, L, Kumar, G, Su, E & Bisson, L 2007 ‘Adhesion and Biofilm Production by Wine Isolates of Brettanomycesbruxellensis’, American Journal of Enology and Viticulture, September 2007, vol. 58, no. 3, pp. 373-378
Guzzon, R, Nardin, T, Micheletti, O, Nicolini, G, & Larcher, R 2013 ‘Antimicrobial activity of ozone. Effectiveness against the main wine spoilage microorganisms and evaluation of impact on simple phenols in wine’, Australian Journal of Grape and Wine Research, June 2013, vol. 19, no. 2, pp. 180-188