Yeast Fermentation and Reproduction
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Questions and Answers

Match the following yeast characteristics with their descriptions:

Yeast cells = Very small single-celled microorganisms Yeast fermentation = Breakdown of sugars for energy Yeast reproduction = Budding Yeast enzyme = Breaking sugars into smaller molecules

Match the following yeast features with their functions:

Scars on yeast cell = Result of previous buddings Amylase = Breaking down starch into sugar Zymase = Many enzymes in yeast for sugar breakdown Bud = Enlarges and eventually pinches off from mother cell

Match the following yeast processes with their outcomes:

Glycolysis = Breakdown of sugars to carbon dioxide Fermentation = Production of carbon dioxide and alcohol Bread baking = Expanding dough during early stages Yeast reproduction = Increasing yeast cell population

Match the following yeast additives with their uses:

<p>Malted barley flour = Adding amylase in lean doughs Amylase = Breaking down starch into sugar Zymase = Breaking down sugars in yeast Yeast = Fermentation process</p> Signup and view all the answers

Match the following yeast discoveries with their discoverers:

<p>Proof that living yeast is necessary for fermentation = Louis Pasteur Discovery of zymase = Unknown Understanding of glycolysis = Many scientists Yeast's role in bread baking = Ancient bakers</p> Signup and view all the answers

Match the following yeast characteristics with their aspects:

<p>Tiny enzyme machines = Breaking down sugars Microorganisms = Small size Reproduction by budding = Yeast cell growth Lack of amylase = Inability to break down starch</p> Signup and view all the answers

Match the following yeast processes with their descriptions:

<p>Fermentation = Breakdown of sugars into carbon dioxide and alcohol Glycolysis = Many steps in sugar breakdown Budding = Yeast cell reproduction Enzyme reactions = Breaking down sugars into smaller molecules</p> Signup and view all the answers

Match the following yeast outcomes with their results:

<p>Carbon dioxide production = Leavening of dough Alcohol production = Evaporation during baking Yeast reproduction = Increased yeast population Sugar breakdown = Energy for yeast cells</p> Signup and view all the answers

Match the type of yeast with its characteristic:

<p>Active dry yeast = More vigorous than compressed or active dry Instant yeast = Can be added directly to dough without hydration Fresh compressed yeast = Not commonly used in pizza or tortilla production</p> Signup and view all the answers

Match the type of yeast with its usage:

<p>Active dry yeast = Best used in pizza or tortilla production Instant yeast = Should not be used in doughs with long fermentation time Fresh compressed yeast = Preferred by professional bakers</p> Signup and view all the answers

Match the type of yeast with its ratio to fresh compressed yeast:

<p>Active dry yeast = Same amount as instant yeast Instant yeast = One-quarter to one-half the amount of fresh compressed yeast Fresh compressed yeast = Same amount as active dry yeast</p> Signup and view all the answers

Match the type of yeast with its storage instructions:

<p>Unopened Instant yeast = Will last up to one year at room temperature Opened Active dry yeast = Should be refrigerated for several months Opened Instant yeast = Should be frozen for long-term storage Unopened Active dry yeast = Will last for several months at room temperature</p> Signup and view all the answers

Match the type of yeast with its initial dough temperature:

<p>Active dry yeast = Between 21°C and 35°C Instant yeast = Between 70°F and 95°F Fresh compressed yeast = Between 41°C and 46°C</p> Signup and view all the answers

Match the type of yeast with its drying process:

<p>Active dry yeast = No drying process Instant yeast = A gentler fluidized bed process Fresh compressed yeast = No drying process</p> Signup and view all the answers

Match the type of yeast with its effect on dough:

<p>Active dry yeast = Produces extensible dough Instant yeast = Leads to overproofing Fresh compressed yeast = Produces dense loaves</p> Signup and view all the answers

Match the type of yeast with its popularity among bakers:

<p>Active dry yeast = Popular among home bakers Instant yeast = Preferred by professional bakers Fresh compressed yeast = Popular among professional bakers</p> Signup and view all the answers

Match the characteristics of yeast with their corresponding type:

<p>Osmophilic yeast = Grows well in high-sugar environments Regular yeast = Takes time to adapt to high-sugar environments Compressed yeast = Comes as moist cakes or blocks Active dry yeast = Sold in vacuum-packed jars or pouches</p> Signup and view all the answers

Match the yeast types with their storage conditions:

<p>Compressed yeast = Refrigerated or frozen Active dry yeast = Room temperature, refrigerated, or frozen Sourdough starter = Fed and cared for daily Instant yeast = No specific storage condition</p> Signup and view all the answers

Match the yeast characteristics with their effects:

<p>High sugar content = Increases osmotic pressure in dough Osmophilic yeast = Produces CO2 and alcohol quickly Regular yeast = Takes time to adapt to high-sugar environments Sourdough starter = Affects flavor of bread</p> Signup and view all the answers

Match the yeast forms with their moisture content:

<p>Compressed yeast = 30% yeast, 70% moisture Active dry yeast = Less than 10% moisture Instant yeast = No specific moisture content Sourdough starter = Variable moisture content</p> Signup and view all the answers

Match the yeast handling methods with their effects:

<p>Crumbing compressed yeast = Uneven distribution of yeast Dissolving compressed yeast = Even distribution of yeast Using active dry yeast = Longer shelf life Caring for sourdough starter = Microorganisms grow and adapt</p> Signup and view all the answers

Match the yeast types with their suitability:

<p>Osmophilic yeast = Sweet, rich doughs Regular yeast = Lean doughs Compressed yeast = Most bread recipes Sourdough starter = Traditional, naturally fermented bread</p> Signup and view all the answers

Match the yeast characteristics with their effects on bread:

<p>Sourdough starter = Variable flavor Osmophilic yeast = Faster fermentation Regular yeast = Slower fermentation Compressed yeast = Consistent results</p> Signup and view all the answers

Match the yeast forms with their contents:

<p>Compressed yeast = Moist cakes or blocks Active dry yeast = Dry granules Instant yeast = No specific form Sourdough starter = Flour, water, and microorganisms</p> Signup and view all the answers

Match the yeast handling methods with their purposes:

<p>Feeding sourdough starter = To maintain microorganisms Storing yeast = To preserve yeast activity Dissolving compressed yeast = To prepare yeast for use Crumbling compressed yeast = Not recommended</p> Signup and view all the answers

Match the yeast characteristics with their effects on fermentation:

<p>Osmophilic yeast = Faster CO2 production Regular yeast = Slower CO2 production Sourdough starter = Variable fermentation rate Compressed yeast = Consistent fermentation rate</p> Signup and view all the answers

Match the following factors with their effect on yeast fermentation:

<p>Temperature of dough = Increases yeast fermentation rate Amount of salt = Retards yeast fermentation Amount of sugar = Increases yeast fermentation rate up to 5% pH of dough = Has no effect on yeast fermentation</p> Signup and view all the answers

Match the following types of sugar with their fermentation rate:

<p>Sucrose = Fermented rapidly Maltose = Fermented slowly Lactose = Not fermented at all Fructose = Fermented rapidly</p> Signup and view all the answers

Match the following yeast characteristics with their description:

<p>Yeast activity = Increases with temperature up to 120°F Yeast death = Occurs at 140°F Optimum fermentation = Occurs at 78°F-82°F Yeast dormancy = Occurs at 32°F-34°F</p> Signup and view all the answers

Match the following preferment characteristics with their description:

<p>Preferment with low salt = For short fermentation Preferment with high salt = For long fermentation Preferment with no sugar = For lean yeast doughs Preferment with large amount of sugar = For rich, sweet doughs</p> Signup and view all the answers

Match the following antimicrobial agents with their effect on yeast fermentation:

<p>Calcium propionate = Slows yeast fermentation Cinnamon = Has no effect on yeast fermentation Most spices = Have strong antimicrobial activity Yeast = Increases yeast fermentation rate</p> Signup and view all the answers

Match the following yeast amounts with their effect on fermentation:

<p>Small amount of yeast = Prevents yeasty flavor Large amount of yeast = Adds yeasty flavor Optimum amount of yeast = Balances flavor and fermentation rate No yeast = Stops yeast fermentation</p> Signup and view all the answers

Match the following types of yeast with their characteristics:

<p>Instant yeast = Good for no-time doughs Fast fermenting yeast = Good for slow fermentation Yeast for lean doughs = Requires a small amount of yeast Yeast for rich doughs = Requires a large amount of yeast</p> Signup and view all the answers

Match the following factors with their effect on flavor molecules:

<p>Long, slow fermentation = Develops desirable flavor molecules Fast fermentation = Inhibits flavor molecules Temperature of dough = Has no effect on flavor molecules Amount of sugar = Increases flavor molecules</p> Signup and view all the answers

Match the following yeast fermentation characteristics with their description:

<p>Yeast fermentation rate = Is affected by pH</p> Signup and view all the answers

Match the following yeast products with their characteristics:

<p>Yeast for lean doughs = Requires a small amount of sugar Yeast for rich doughs = Requires a large amount of sugar Instant yeast = Good for fast fermentation Yeast for slow fermentation = Good for developing flavor molecules</p> Signup and view all the answers

Study Notes

Yeast Fermentation

  • Yeast fermentation is a process in which yeast cells break down sugars for energy, producing carbon dioxide and alcohol as byproducts.
  • Yeast uses the energy for survival and reproduction.
  • The rate of yeast fermentation is affected by several factors, including temperature, amount of salt, amount of sugar, type of sugar, pH of dough, presence of antimicrobial agents, and amount of yeast.

Yeast Cells

  • Yeast cells are very small, single-celled microorganisms, with approximately 15 trillion cells in one pound of compressed yeast.
  • Yeast cells reproduce by budding, and visible scars from previous buddings can be seen on the yeast cell.

Enzymes and Fermentation

  • Yeast can be thought of as tiny enzyme machines, breaking sugars into smaller and simpler molecules with every step.
  • Yeast lacks amylase and cannot break down starch into sugar, which is why amylase is an important additive in bread baking.
  • The overall process of fermentation involves multiple steps, controlled by separate enzymes, and produces carbon dioxide, alcohol, and small amounts of flavor molecules.

Factors Affecting Yeast Fermentation

  • Temperature: Yeast is dormant at 32–34°F (0–1°C), active at 50°F (10°C), and slows down at 120°F (50°C), with an optimal temperature of 78–82°F (25–28°C).
  • Amount of salt: Salt retards yeast fermentation, and the optimal amount of salt is 1.8–2.5% (baker's percentage).
  • Amount of sugar: Small amounts of sugar (up to 5%) increase yeast activity, while large amounts (above 10%) slow fermentation.
  • Type of sugar: Sucrose, glucose, and fructose are fermented rapidly, maltose is fermented slowly, and lactose is not fermented at all.
  • pH of dough: The optimal pH for yeast fermentation is an acidic 4 to 6.
  • Presence of antimicrobial agents: Certain antimicrobial agents slow or stop yeast fermentation.
  • Amount of yeast: The more yeast, the faster the fermentation, but excessive yeast can add an undesirable yeasty flavor and exhaust dough of sugars.

Types of Yeast

  • Compressed yeast: Fresh, moist cakes or blocks with 30% yeast and 70% moisture, lasts up to two weeks when stored wrapped in plastic and refrigerated, and three to four months when frozen.
  • Active dry yeast: Dried granules with less than 10% moisture, sold in vacuum-packed jars or pouches, and lasts several months at room temperature, longer if frozen or refrigerated.
  • Instant yeast: Developed in the 1970s, instant yeast can be added directly to dough without first hydrating in water, and is more vigorous than compressed or active dry yeast.

Sourdough Starters

  • Sourdough starters are prepared by mixing flour and water, allowing wild yeast and lactobacilli bacteria to ferment, and can be used to leaven bread.
  • Fresh starter does not need to be made for each new day's production, and can be saved for the next day's bread by mixing it with fresh flour and water.
  • Some bakeshops pride themselves on the number of years they have continued to bake from their original starter.

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Learn about the biological process of yeast fermentation, how yeast cells break down sugars for energy, and their reproduction process through budding.

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