(AcademicWino) - The use of oak barrels in wine fermentation and aging is common, as it is known to increase wine aromatic complexity and improve overall wine quality. One downside to using oak barrel in winemaking is the fact that it costs more money to produce an oaked wine than it does to produce a wine made in stainless steel tanks. As a result of this cost differential, some wineries as well as home winemakers ultimately choose to use alternatives to oak barrels that give similar aromatic and quality characteristics to the finished wine without the high costs.

One alternative approach is to use oak chips, staves, cubes, et cetera,in stainless steel tanks. In fact, I have a carboy of wine sitting in my cellar right now that’s soaking up the oaky glory from some oak shavings. Passing countless tiny oxygen bubbles through the wine (microoxygenation) allows for even more extraction of the oak flavor from the chips into the wine, reducing the amount of time needed in production and allowing the winery to get their product out faster to the consumer.

Another alternative, one of which we’ve described before on the blog, is to instead apply oak extracts directly to the grapevine. Theoretically, and as seen in studies, the resulting wines made from grapes sprayed with oak extract during the growing season retain the characteristics of these extracts, thus eliminating the need to age the wines in relatively expensive oak barrels or the need to use oak chips and the like.

These alternatives are not without their faults, however. For example in regards to oak chips, some winemakers have complained of too much variability between batches. Perhaps one batch was cut slightly larger than another batch, thus decreasing the oak-to-wine surface area and reducing the amount of oak flavor extracted. This lack of consistency could mean one tank of wine doesn’t extract enough oak flavors, while a different tank may extract too much.

To combat this over-extraction of oak flavor from using inconsistently cut oak chips, some researchers have suggested aging wine over the lees. Yeast, which makes up the vast majority of the lees, has been shown to mitigate overly excessive oak aromas from wines, and also has been shown to reduce other undesirable sensory characteristics, including those associated with ethyl-phenol and ochratoxin-A levels.

A new study published in the journal Food Chemistry has come up with a completely novel way to impart oak flavor in wines without actually using any oak barrels or oak chips. Building upon the knowledge that yeasts are relatively amenable to absorb varies compounds, and the fact that some wines use aging on the lees techniques to improve aromatic complexity, researchers have developed a way to inject oak flavor into yeast prior to fermentation and aging and have that yeast, or now “wood-aromatized yeastbiomass”, act as the conduit through which the wine obtains its oak flavors and aromas.

Brief Methods

Quickly: The yeasts used in this study were the wine yeasts Saccharomyces cerevisiae(G37), the wine was made from Tempranillo grapes (Vitis vinifera) from Spain, and the wood sources used were acacia, chestnut, cherry, and American oak. Need more details, just ask!

To infuse the wood into the yeasts: Each of the wood sources went through an extraction process. After extraction, 10g of freeze-dried S. cerevisiae yeasts were added and left to soak up the extracts and dry over a period of time. After the joint drying process, the new “wood-aromatized yeast biomass” was washed prior to being added to the wine.

One gram of wood-aromatized yeasts was added to 500mL of wine, with each type of wood serving as a separate treatment. Untreated yeasts were used as controls. All treatments were performed in triplicate.