Biological leaveners yeast bacteria yeasts produce

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Biological leaveners: yeast & bacteria. Yeasts produce CO2 during fermentation. Yeasts become activated when they are hydrated in water at an optimal temperature, mixed in, and dough is kneaded and allowed to sit in a warm place as CO2 generated by growing yeast makes dough rise. Harmless bacteria that generate CO2 are also used as leavening agents in breads such as sourdough or salt-rising breads. These depend on a “starter”. Chemical leaveners: baking powder and baking soda. Baking soda chemically yields CO2 in the presence of moisture and an acid. Baking powder is baking soda with the acid already added, so it is not necessary to add an acidic ingredient to the flour mixture to produce the CO2. 7) How are quick breads typically leavened? With air or steam, or chemically with CO2 generated by baking soda and/or baking powder. 8) Why does an over-mixed quick bread get too tough? Over-mixed quick bread results in undesirable gluten development, causing bread to be dense and heavy. 9) What are baking soda, baking powder and cream of tartar composed of? 10) What are the general steps in making a yeast bread? Yeast bread is made by mixing ingredients into a dense, pliable dough that I kneaded, allowed to rise by fermentation, and then cooked by baking, steaming, or frying. Normally at least 2.5-3 hr operation. 11) What factors affect the growth and survival of yeast? pH, temperature, nutrients/concentration of nutrients (i.e. presence and concentration of sugar, etc.) 12) Regarding optimal fermentation, at what temperatures are yeasts activated, slowed down, and killed? Yeasts are activated between 60-100F degrees, slow down below 50F, and die above 140F. 13) Define the following terms from Chapter 17, 19 & 20: a. yeast bread: bread made with yeast (a single-celled fungus that is able to ferment sugars and used for producing food products such as bread/alcohol), which produces carbon dioxide gas through fermentation, causing bread to rise b. quick bread: leavened with air, steam, and or CO2 from baking soda or powder
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c. crumb: cell structure within a baked product’s interior, revealed when it is sliced & affects texture. Based on cell shape, size, and thickness. d. Gluten: the protein portion of wheat flour with the elastic characteristics necessary for structure of most baked products e. knead: work dough into elastic mass by pushing, stretching, and folding f. stream: division of milled flour based on particle size g. bread flour: long-patent white flour made primarily from hard winter wheat.
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  • Summer '17
  • Tracy Grgich
  • Flour, Graham flour

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