On food and cooking the science and lore of the kitchen ( PDFDrive ) 1008

for energy, and produce carbon dioxide gas and alcohol as by-products of that metabolism The overall equation for the conversion that takes place in yeast cells is this: C6H12O6 2C2H5OH + 2CO2 (1 molecule of glucose sugar yields 2 molecules of alcohol plus 2 molecules of carbon dioxide) In making beer and wine, the carbon dioxide escapes from the fermenting liquid, and alcohol accumulates In making bread, both carbon dioxide and alcohol are trapped by the dough, and both are expelled from the dough by the heat of baking In an unsweetened dough, yeasts grow on the single-unit sugars glucose and fructose and on the double-glucose sugar maltose, which enzymes in the flour produce from broken starch granules A small amount of added table sugar in a dough will increase yeast activity, while a large amount decreases it (see sweet breads, p 546), as does added salt Yeast activity is also strongly affected by temperature: the cells grow and produce gas most rapidly at about 95ºF/35ºC In addition to providing carbon dioxide gas to inflate the dough, yeasts release a number of chemicals that affect the dough consistency The overall effect is to strengthen the gluten and improve its elasticity Forms of Baker’s Yeast Commercial yeast is sold to home and restaurant cooks in three common forms, each a different genetic strain of S cerevisiae with different traits Cake or compressed yeast is a moist block of fresh yeast cells, direct from the fermentation vat Its cells are alive, and produce more leavening gas than the other forms Cake yeast is perishable, must be kept refrigerated, and has a brief shelf life of one to two weeks Active dry yeast, which was introduced ... of chemicals that affect the dough consistency The overall effect is to strengthen the gluten and improve its elasticity Forms of Baker’s Yeast Commercial yeast is sold to home and restaurant cooks in three common forms, each a different genetic strain... Yeast activity is also strongly affected by temperature: the cells grow and produce gas most rapidly at about 95ºF/35ºC In addition to providing carbon dioxide gas to inflate the dough, yeasts release a number of chemicals that affect the dough... common forms, each a different genetic strain of S cerevisiae with different traits Cake or compressed yeast is a moist block of fresh yeast cells, direct from the fermentation vat Its cells are alive, and produce more leavening gas than the