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. Cate Gillon/Getty Images hide caption toggle caption Cate Gillon/Getty Images The Salt When The Microbes Are Happy, The Brewer Is Happy February 8, 2013 Yeast are demanding little critters. To make good-tasting beer, brewers have to pamper them like pedigreed pets. A new report says it's all about the microbiology. Brewers say they use science to keep their charges happy.