Zachary Cartwright’s Three Minute Thesis

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Distribution of the Wine Spoilage Yeast, Brettanomyces bruxellensis, and Mitigation Strategies to Reduce Infections

Imagine sitting down to enjoy a bottle of wine with your friends and family.  When you open the bottle, you are probably expecting aromas that are fruity, floral, and nutty.  However, you smell a barnyard, a dirty gym sock, and perhaps a litter of mice.  These wine faults are likely caused by the spoilage yeast that I study in the Food Science Department here at WSU called Brettanomyces bruxellensis, or simply Brett.  This yeast is often quoted as the number one spoilage microorganism during red wine production, and the primary vector to infections is the wine aging process in oak barrels.  Therefore, my goals as a researcher were to 1) better define Brett infections among a wide range of barrel types, 2) investigate how far the yeast can penetrate into oak staves, and then 3) provide the wine industry with better steaming recommendations for removing Brett during cleaning.  To accomplish these goals, 20 infected barrels were taken apart into individual staves and studied extensively.  We found that certain barrel types (i.e. French oak and heavy toasted oak) were always more infected, that the yeast could penetrate up to an 8-mm depth in some cases, and that a minimum of 12 minutes of continuous steam was effective for yeast removal.  Alternatively, we also examined Brett survivability in the vineyard, a topic which is very controversial among wine scientists.  Here, our goals were to 1) propose one route to vineyard infections and 2) demonstrate the survivability of Brett outside for several seasons time.  To accomplish these goals, infected grape pomace samples were contained and placed in several WA State vineyards.  Pomace was our medium of choice because it is a common winery waste product that could become easily contaminated, and it is often used as a vineyard fertilizer.  After 27 months, our vineyard samples still had large viable populations of Brett with increasing populations as seasonal temperatures increased.  These results encouraged us to investigate composting trials as one way to sterilize pomace prior to being spread outdoors.  Overall, whether talking about barrels or considering the vineyard, our hope is that this research will help prevent widespread infections and stop economic losses caused by Brett so we may all continue enjoying exceptional WA State wines.