What enzyme does yeast produce that ferments the sugar? What are the products of fermentation?
Zymase
ethnol, CO2 an other by-products
What is the name of the yeast mostly used in bread makin? Why?
Saccharomyces Cerevisae
For good qualities that are important in baking:
- Good CO2 production
- Development of desirable flavour
- Adequate keeping qualities
What are the 3 types of yeast?
Compressed yeast
Active dry yeast
Instant yeast
What are the characteristics of compressed yeast?
- Fresh
- Requires refrigeration
What are the characteristics of active dry yeast?
- Dehydrated
- Rehydrated at 43-63 degrees (higher temp kills the yeast, lower temp , leaching of ells into liquid, which softens bread dough)
What are the characteristics of instant yeast?
Added directly to dry ingredients
What are the optimal temperature and pH for fermentation of the dough?
30-35 degrees
pH slightly acid: 4-6
What enzyme hydrolyzes larger chains of starch in flour?
Flour amylase
What are the 2 types of flour amylase, and what do they do?
alpha-amylase: catalyzes conversion of starch to random smaller pieces
beta-amylase: catalyzes conversion of starch to maltose
What are the 2 enzymes produced by the yeast to hydrolyze sugars? What do they do precisely?
Maltase: maltose–> 2xglucose
Invertase: sucrose–> glucose +fructose
What are the products of yeast fermentation when NO oxygen is present?
Ethanol and carbon dioxide
What are the products of yeast fermentation when oxygen is present?
Carbon dioxide and water (???)
What are the main ingredients in bread making?
Yeast Sugar Flour Water Salt
What are some optional ingredients in bread making?
Shortening, fat, milk or other liquids, sugar and eggs
What is the effect when only a small amount of sugar is added?
If small amount (less than 8% of weight of flour),
provides substrate for immediate gas production by yeast
What is the effect when larger amount of sugar is added?
- Inhibits yeast activity (too high osmotic pressure)
- Tenderizes dough, by interfering with gluten development
- Browning due to Maillard reaction (???)
What is the role of flour in bread?
Wheat flour provides proteins (gliadin and glutenin) which form gluten complex during hydration and mixing
What is the role of the liquid in bread making?
Liquid in bread is necessary to hydrate prots and starch, so there is guten developmentd (and gelatinization???)
Why is milk the most common liquid used in bread making? What do you have to watch out for when using milk?
- Add nutrients
- Gives finer texture
- Improves crust and crumb color and flavor
Watch out!!!
Whey softens the dough and decreases volume, therefore, milk must be heated before using to denature whey prot
Why is the role of salt in bread making?
- Improves taste of bread?
- Stabilizes yeast fermentation (slows activity)
- Changes rheological properties of the dough
- Has firming effect on gluten
- Increase water hilind capacity of dough
- Increase mixing requirements for the dough - Also influence firmness
When too much salt is added to the dough? what does happen to firmness?
If too much salt= too firm
What is the effect of adding a small amount of fat or eggs to the dough?
If added in small amount ( less than 3% of weight of flour)
- Increases loaf volume
- Gives more uniform and tender crumb
- Improves slicing properties (less crumbly)
- Enhances keeping qualities (decrease staling)
What are the 3 types of leaveners? Give exemples of each
Biological ( yeast, bacteria)
Chemical ( Baking soda, baking powder)
Mechanical ( steam, air)
Name some additives or dough conditioners.
- Calcium and ammonium salts
- Oxidizing agents ( K and Ca bromates and iodates)
- Surface active agents
- Enzymes (protease)
- Antimolding agents ( sodium and calcium propionate)
- Fibers
- Antioxidants
