Yeast affects several aspects of beer including the foam, or head, that forms on the of the glass. If fermentation is too vigorous, too many of the foam-stabilizing proteins may be lost.
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Yeast can be pretty demanding little buggers, despite being unicellular microscopic organisms. Brewers know they must appease them to get the beer they want.
"It's yeast-strain dependent, it's environment, it's temperature, oxygen levels," says Matt Brophy, brewmaster of Flying Dog Brewery in Frederick, Md. "There's a lot of variables that you need to have a high level of control over."
As beer drinkers demand increasingly obscure beers with ingredients like jalapenos or rhubarb, smaller and smaller breweries are stepping up to the plate. New Hampshire is one state helping these brewery startups get off the ground, with new laws that make it easier for small-scale breweries to obtain licenses and distribute their craft beers.
More and more gluten-free beers are entering the marketplace. We asked a librarian with celiac disease for her list of favorites.
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Anyone who gives up gluten, either by choice or medical necessity, will inevitably feel a twinge of regret bidding adieu to bread, pasta or pastries. But for some, the greatest hardship may be saying no to beer — especially at times like Super Bowl Sunday, when having a cold one in hand is part of many people's game day tradition.
So it's no small thing that a growing number of brewers are offering gluten-free beers that are both tasty and satisfying.
Sunday's Super Bowl - a contest between the Baltimore Ravens and San Francisco 49ers - is also a battle of craft breweries. Maryland's Flying Dog Brewery made a bet with Anchor Brewing of San Francisco. The loser must pour the winner's beer in its taproom for a week. And the loser's brewery tour guides will have to wear the winner's Super Bowl championship gear. Could be tough, but if they need a beer after all that, they're all set.