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Microbiology Production of Bread

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on 6 April 2015

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Transcript of Microbiology Production of Bread

~The word "yeast" comes from Old English gist, gyst, and from the Indo-European root yes-, meaning "boil", "foam", or "bubble"
Growth Problems
~Liquid and/or other ingredients were too cold – slowed down yeast activity
~Too much salt was used which will inhibit or slow down yeast activity
~Too much sugar or not enough will inhibit or slow down yeast activity
~Rise temperature was too low or too high
~If bread is allowed to rise to more than double its size, the gluten will stretch to the point of collapse and will no longer be able to hold the gas bubbles that provide necessary structure for the loaf
How to Make Bread
~ 3 primary ingredients flour, liquid, and yeast are used to make a variety of breads
Science Behind Yeast
The Microbiology of Bread
Preferred Conditions of Growth
~ Yeast can be grown in either liquid medium or on the surface of a solid agar plate
is a microscopic fungus consisting of single oval cells that reproduce by budding, and are capable of converting sugar into alcohol and carbon dioxide.
1. Measure Ingredients
2. Pre-Ferment*
3. Mixing and Kneading
4. Proofing
5. Punching Down and Turning Dough
6. Second Proofing*

~There are more than 500 species of yeast
~3 different types of yeast used for baking fresh yeast, instant yeast, active dry yeast
~Yeasts are sac fungi, class Ascomycetes.
~Commercial yeasts belong to the Saccharomycetaceae family.

"Types of Yeast for Baking." Bread Cakes And Ale. N.p., 05 Mar. 2015. Web. 01 Apr. 2015.

Work Cited
Commercial Yeast Production
Other Uses
"How to Make Bread Epicurious.com." Epicurious. N.p., n.d. Web. 01 Apr. 2015.
"Yeast Production." Yeast Production. N.p., n.d. Web. 02 Apr. 2015.
~ Yeast cells will grow on a minimal medium containing dextrose (glucose)as a carbon source and salts that supply nitrogen, phosphorus, and trace metals.
~ Asexual (common)
- called fission or budding, the parent cell divides to form a new daughter cell that is an exact copy of parent cell
~ Sexual (rare)
- only happens to haploid yeast cells
- two haploid cells become long and thin before they join together and fuse their nuclei together to create a diploid.This begins to bud and form a colony of diploid yeast cells that return to haploid states when environmental conditions become hostile.
~ Growth Rate Factors
- include food availability, pH, temperature, and removal of waste products

~ Saccharomyces telluris prosper at 41 to 95 °F
~ Yeasts grow best in a neutral or slightly acidic pH environment.
~Common media used for the cultivation of yeasts include potato dextrose agar or potato dextrose broth, Wallerstein Laboratories nutrient agar, yeast peptone dextrose agar, and yeast mould agar or broth
~Egyptians yeast-raised bread, as well as drawings of 4,000-year-old bakeries and breweries
~In 1680, Dutch naturalist Anton van Leeuwenhoek observed yeast, didn't know it was a living organism
"Understanding Microbes." BBC News. BBC, 2014. Web. 02 Apr. 2015.
~In 1857, French microbiologist Louis Pasteur proved that alcoholic fermentation was conducted by living yeasts
~late 18th century, two yeast strains used in brewing had been identified
Why is Yeast Important in Bread?
Yeast Cell Structure

~ Makes Bread Rise
- enzymes in yeast and flour break down starch into simple sugars.
- yeast metabolizes simple sugars releasing CO2 into existing air bubbles in the dough.
~ Strengthens Bread Dough
- like kneading, yeast helps develop the gluten network (molecule-by-molecule kneading)
- with every Co2 bubble released, the protein and water molecules move about connecting to form more gluten
~ Fermentation Generates Flavor in Bread
- Fermentation breaks down large molecules into smaller, flavorful ones
- yeast use sugars to produce alcohol and flavorful byproducts such as organic acids and amino acids
~ Other Baking Goods
(pastries and cakes)
~ Brewing Beer
~ Nutritional Supplement
~ Wine Making
~ Eating
(yeast extract paste)
7. Dividing and Reshaping Dough
8. Shaping
9. Final Rise
10. Glazing*
11. Stenciling and Slashing*
12. Baking
13. Cooling, Slicing, and Storing
Khazin, Roman. "Five Different Uses for Yeast." EHow. Demand Media, 13 Apr. 2011. Web. 05 Apr. 2015.
Chu, Micheal. "Baker's Yeast." Atom 10. N.p., n.d. Web. 05 Apr. 2015.
By: Claudia Waddingham and Nicole Clark
"Common Problems with Possible Solutions." Red Star Yeast. N.p., n.d. Web. 05 Apr. 2015.
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