Mid Atlantic Brewing News February/March 2015 : Page 6

6 Mid-Atlantic Brewing News February/March 2015 Stalking the W ild Yeast By Elizabeth Hartman Brewers, both professional and amateur, go to great lengths to keep wild microbes out of their brewing gear. But Jeff Mello, "chief yeast wrangler" for Bootleg Biology, goes to equally great lengths to put some of those bugs to work brewing beer. Although he recently moved to Nashville, Mello's curiosity with wild yeast began in his former backyard in Arlington, Va., where he isolated a promising strain he refers to as Saccharomyces arlingtonesis . It behaved similarly to domesticated brewing yeasts, creating a dry, crisp beer that was well received by the local homebrewing community. This discovery inspired Bootleg Biology’s mission to teach brewers Jeff Mello of Bootleg Biology shows off his Backyard Yeast Wrangling Tool Kit. about the potential of naturally occurring PHOTO COURTESY OF JEFF MELLO yeasts. Wild yeast is frequently associated with Second, isolate the yeast strain . Isolation a funky or sour character to beer. However, involves streaking and thinning the culture Mello, through his work with more than 25 across petri dishes of gelled wort (unfermented different wild beer). Wort produces strains, came an environment with a to a different specific pH that naturally conclusion. "If selects those microbes you isolate a wild capable of surviving yeast strain, the in such conditions. vast majority of Yeast colonies have the time it's going a distinct roundish, to come out very white shape that helps clean tasting. distinguish them from ... The flavors other microbial or mold are very earth-growth. tasting. I think Third, experiment . most people have Once isolated, a sample had a saison or those very Belgian farmhouse from the yeast colony can be cultivated, then flavors. That's the most common flavor I've used for small-batch testing. (Mello uses a found for wild strains." simple saison recipe for this purpose.) He continues, "When you're working with This process might sound complicated to wild yeast, you need to be OK with a lot of non-science majors. That's where Bootleg variability.” Flavor, color and performance will Biology steps in. Last year, Mello designed the vary between wild strains, sometimes within Backyard Yeast Wrangling Tool Kit (available the same capture area. That's part of the terroir on his website http://bootlegbiology.com) to that so intrigues Mello. help homebrewers harvest yeast, whether from Although DNA sequencing is required to the wild, bottle dregs or some other source. truly identify a yeast, you don’t need a PhD in The kits contain a mason jar for starters, microbiology to learn a lot about the yeast's pipettes, petri dishes, agar (the gelling agent) behavior, viability and flavor potential. For and labels. Step-by-step instructions, videos example, does it ferment toward the top or and photos are available on the website. bottom? How do warm or cold fermentation Mello also has established the Local Yeast temperatures affect its performance and flavor Project. With help from homebrewers across profile? Does it flocculate (form clumps) and the country, he aims to create a yeast bank settle out well, or does it remain suspended in of samples from every zip code. In exchange the beer? Based on observations like these, a for submitting a yeast sample, the brewer can brewer can decide whether to use the yeast, request a sample of another documented yeast, and for what styles. such as S. arlingtonesis . Seeking out new yeasts involves several Contributions to the Local Yeast Project steps. from mid-Atlantic homebrewers will help First, collect the yeast . The most common define the terroir of this region (to date, harvesting methods are to wipe fruit (Mello only seven yeasts from our area have been is known to travel with sterile swabs and documented, primarily from Virginia). In the vials for this purpose) or collect samples process, participating homebrewers might outside with a small lambic starter covered in discover that their future go-to strain lives cheesecloth. Either way, the sample size will closer than they think. be minute, so it needs to incubate in a warm room for a few weeks.

Stalking The Wild Yeast

Elizabeth Hartman

Brewers, both professional and amateur, go to great lengths to keep wild microbes out of their brewing gear. But Jeff Mello, "chief yeast wrangler" for Bootleg Biology, goes to equally great lengths to put some of those bugs to work brewing beer.

Although he recently moved to Nashville, Mello's curiosity with wild yeast began in his former backyard in Arlington, Va., where he isolated a promising strain he refers to as Saccharomyces arlingtonesis. It behaved similarly to domesticated brewing yeasts, creating a dry, crisp beer that was well received by the local homebrewing community. This discovery inspired Bootleg Biology’s mission to teach brewers about the potential of naturally occurring yeasts.

Wild yeast is frequently associated with a funky or sour character to beer. However, Mello, through his work with more than 25 different wild strains, came to a different conclusion. "If you isolate a wild yeast strain, the vast majority of the time it's going to come out very clean tasting. ... The flavors are very earthtasting. I think most people have had a saison or those very Belgian farmhouse flavors. That's the most common flavor I've found for wild strains."

He continues, "When you're working with wild yeast, you need to be OK with a lot of variability.” Flavor, color and performance will vary between wild strains, sometimes within the same capture area. That's part of the terroir that so intrigues Mello.

Although DNA sequencing is required to truly identify a yeast, you don’t need a PhD in microbiology to learn a lot about the yeast's behavior, viability and flavor potential. For example, does it ferment toward the top or bottom? How do warm or cold fermentation temperatures affect its performance and flavor profile? Does it flocculate (form clumps) and settle out well, or does it remain suspended in the beer? Based on observations like these, a brewer can decide whether to use the yeast, and for what styles.

Seeking out new yeasts involves several steps.

First, collect the yeast. The most common harvesting methods are to wipe fruit (Mello is known to travel with sterile swabs and vials for this purpose) or collect samples outside with a small lambic starter covered in cheesecloth. Either way, the sample size will be minute, so it needs to incubate in a warm room for a few weeks.

Second, isolate the yeast strain. Isolation involves streaking and thinning the culture across petri dishes of gelled wort (unfermented beer). Wort produces an environment with a specific pH that naturally selects those microbes capable of surviving in such conditions. Yeast colonies have a distinct roundish, white shape that helps distinguish them from other microbial or mold growth.

Third, experiment. Once isolated, a sample from the yeast colony can be cultivated, then used for small-batch testing. (Mello uses a simple saison recipe for this purpose.)

This process might sound complicated to non-science majors. That's where Bootleg Biology steps in. Last year, Mello designed the Backyard Yeast Wrangling Tool Kit (available on his website http://bootlegbiology.com) to help homebrewers harvest yeast, whether from the wild, bottle dregs or some other source. The kits contain a mason jar for starters, pipettes, petri dishes, agar (the gelling agent) and labels. Step-by-step instructions, videos and photos are available on the website.

Mello also has established the Local Yeast Project. With help from homebrewers across the country, he aims to create a yeast bank of samples from every zip code. In exchange for submitting a yeast sample, the brewer can request a sample of another documented yeast, such as S. arlingtonesis.

Contributions to the Local Yeast Project from mid-Atlantic homebrewers will help define the terroir of this region (to date, only seven yeasts from our area have been documented, primarily from Virginia). In the process, participating homebrewers might discover that their future go-to strain lives closer than they think.

Read the full article at http://mabnonline.brewingnews.com/article/Stalking+The+Wild+Yeast/1926626/245583/article.html.

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