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only lactic acid, or heterofermentative, producing lactic acid, ethanol, energy and acetic acid. Pediococcus is known for producing diacetyl, a buttery/butterscotch character that has a similar boiling point to ethanol and is difficult to separate, while acetobacter and gluconobacter convert ethanol and glucose to acetic acid. Wild yeasts picchia and hansenula are aerobic, but can create esters very quickly before dissolved oxygen levels drop. On the anaerobic side, brettanomyces can create acetic acid, as well as flavors commonly described as barnyard or horsey. “Brett fermentations take quite a long time compared to saccharomyces cerevisiae, so that’s probably not going to be a heavy hitter. It’s probably going to be more on the acetic acid side, but it’s something to take note of.” Rhoades also noted that after fermentation is finished, the beer well/charging vessel can be a commonly missed source of contamination. “It could be finished in fermentation, it could be sitting there. That’s when you’ll typically see a crop-up of lactic acid bacteria, depending on your level of contamination,” she said. “That can be something that people might overlook, and if that’s not cleaned out regularly that can be a source of contamination. Even though you think, ‘Hey, fermentation is over, I hit my yield,’ you could have an off-flavor or not hit the brand profile if you’re not taking a look and taking care of your beer well or charging vessel.” Finally, Rhoades addressed the utility and flavor optimization of sour mashing. While defined slightly differently from distillery to distillery, it generally involves using leftover material from the previous batch, which adjusts the pH for consistency. In some cases lactobacillus is added at the beginning of fermentation, as well. The use of backset — low-pH stillage from a previous batch — does a number of positive things for a new batch. It helps to curtail contamination by starting with a lower pH, and adds a lot of essential vitamins and nutrients that were in the lysed yeast from the prior batch. “All of these really lead to flavor effects,” Rhoades said. There’s also the reuse of material and the lower demand on utilities and water, if you’re into that.” But does it make a difference in the product? Rhoades analyzed sweet versus sour mashes — the addition of backset to a mash versus water — at the Dickel distillery. The sour mash distillate had an increased concentration of higher alcohols, which she attributed to a higher amount of solids and increased yeast growth. There was also a decreased concentration of acetaldehyde and acetal. “We definitely saw very different clusters, signifying that this is actually doing something from a volatile perspective,” said Rhoades. “What we saw was that the sour mash…was significantly different from a sensory perspective.”

Gabe Toth is lead distiller at The Family Jones Spirit House in Denver and Loveland, CO. A former craft brewer, his passion for fermenting and transforming ingredients also extends to sausage and meat curing, cheesemaking, and pickling. He can be found up in the mountains or at WWW.ARTISANSPIRITMAG.COM  

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Artisan Spirit: Summer 2018  

The magazine for craft distillers and their fans.

Artisan Spirit: Summer 2018  

The magazine for craft distillers and their fans.