In our previous lesson, we discussed reduction faults. In this lesson, we will turn our attention to microbial faults. There are other important microbes that can cause strange odors in wine. A particularly bad one is, unfortunately, one that is ubiquitous in wine cellars around the world. Have you ever smelled any of the following in a wine? Barnyard, stable, smoky, manure, Horsy or Wet horse blanket, Wet dog, Rancidity, Band-Aid or medicinal smell, sweaty, cheesy, leathery, pharmaceutical, spicy, ammonia, mouse droppings burnt bean or compost. A lovely set of aroma descriptors. So these are caused by spoilage yeast called brettanomyces. It's often called simply Brett, standing for brettanomyces, by tasters or wine makers. Brettanomyces is familiar in the world of wines and other beverages. It's a small yeast. Wine makers call it a spoilage yeast, but actually it's used in certain beer fermentations. Brettanomyces bruxellensis, for example, is one of the main species that is used in making certain types of Belgian ales. It's also the one that is implicated in the spoilage of wine. And given enough time, in the wine, it creates any one of those lists of smells I just named for you. Before I go any further, don't worry too much about this, if you are involved with a winery. Brettanomeyces is very easily controlled, or I should say, prevented by good sanitation practices. And fortunately it's also fairly sensitive to sulfites, or sulfur dioxide. So, you should be able to keep bread under control and not have it become a problem. If it does become a problem though, there are a couple of ways that it shows itself. For example, there is a compound called 4-ethylphenol, sometimes abbreviated as 4-EP. And if we pick up a wine and swirl it and smell something that resembles Band-aids, or camphor disinfectant or menthol, a medicinal kind of smell. And if it's anything other than a really minute background smell it may be the indication that Brettanomyces has grown in this wine and possibly tainted this wine. Again, the name of that is 4-ethylphenol or 4-EP. There's another compound that is also noticed from time to time, and that is 4-ethlguaiacol, or as we abbreviate it, 4-EG. This is the one that smells like barnyard, or compost, or burlap, or a sweaty horse blanket. And it also has a smoky smell. If you take or gather a residue from smoke, the smoke odors are also guaiacols. So it's very possible that if your vineyard was in the vicinity of a forest fire, in the weeks leading up to harvest. Possible that your grapes could have coal compounds from the forest fire smoke sticking to their grape skins, and therefore getting into the wine as the wine is made. So what you think is Brettanomyces, smokiness, might actually be another fault that Al mentioned in passing called smoke taint. Smoke taint is very severe in some years, in some areas, where there have been forest fires. One vintage that I recall is 2008, in the California North Coast, where there were fires in July that lasted weeks and weeks, and the prevailing winds blew that smoke right into Vineyards in Mendocino, and Lake County, and Napa county. And quite a few wines smelled like they'd been barbecued. So we have to be careful about that. However, if the smell really asserts itself we may also to suspect the activity of the spoilage yeast called brettanomyces. And in that case the smell is probably 4-ethylguaiacol. So we don't necessarily have to find one or the other. We can find them both. We can have a smokey, mentholy, band-aidy kind of wine. Sounds delicious? The reason I mentioned these two compounds is that they're the ones that can be measured rather easily in a laboratory test. And so if we suspect that we have a problem with this microorganism in our winery, we can actually have wines tested for the presence of 4-EP or 4-EG. When they're at the sub threshold level before they get bad enough to be smelled, and then we can take some kind of corrective action. In this lesson we discussed microbial faults. In our next lesson we will turn our attention to cork taint.
