between the sugar maltose and the amino acid proline And it begins the process of clarifying the brew by coagulating large proteins and causing them to bind with tannins from the barley hulls, form large masses, and precipitate out of the solution When boiling is finished, the wort is strained, then cooled and aerated OPPOSITE: Making beer Beer is made in two basic ways Ales are fermented in less than a week at a warm temperature and matured for days, while lagers are fermented for more than a week at a cold temperature and matured for weeks Fermentation With boiling, the brewer has finished transforming the bland barley grain into a rich, sweet liquid Now the yeast cells transform this liquid into beer, which is far less sweet, but more complex in flavor There are two basic methods for fermenting beer, and they produce distinctive results One is rapid fermentation at a high temperature with ale yeasts (strains of Saccharomyces cerevisiae) that clump together, trap the carbon dioxide gas that they produce, and rise to the wort surface The other is slow fermentation at a low temperature with lager yeasts (Saccharomyces uvarum or carlsbergensis) that remain submerged in the wort and fall to the bottom when fermentation is over These are often called “top” and “bottom” fermentations Top fermentation is usually carried out at between 64 and 77ºF/18–25ºC and takes two to seven days, during which the yeasty foam is skimmed off several times Because the yeast layer at the top has a good supply of oxygen and is inevitably contaminated by other airborne microbes, including lactic-acid bacteria, top-fermented beers are often relatively acidic and strong in flavor Bottom fermentation goes on at distinctly lower temperatures, 43 to 50ºF/6–10ºC, takes six to ...results One is rapid fermentation at a high temperature with ale yeasts (strains of Saccharomyces cerevisiae) that clump together, trap the carbon dioxide gas that they produce, and rise to the wort surface... produce, and rise to the wort surface The other is slow fermentation at a low temperature with lager yeasts (Saccharomyces uvarum or carlsbergensis) that remain submerged in the wort and fall to the bottom when fermentation is over... when fermentation is over These are often called “top” and “bottom” fermentations Top fermentation is usually carried out at between 64 and 77ºF/18–25ºC and takes two to seven days, during which the yeasty foam is