1
Q
What are the desirable properties of baker’s yeast?
A
- High gassing power
- Good flavor development
- Stable
- Ethanol tolerant
- Cryotolerant
2
Q
What are the major ingredients and their roles in bread manufacturing?
A
- Flour: Provides protein (for dough formation) and starch (hydration and carbon sources for yeast)
- Water: Hydration
- Salt: Toughens gluten, control fermentation, impart flavor
- Baker’s yeast: Leavening, flavor formation
- Sugar: Readily fermentable sugar
- Enzymes: Increase amount of free sugar in the dough, and enhance bread quality.
- Fat: Provide soft and cake-like textures
3
Q
What are the advantages of sourdough?
A
- Preservation
- Production of anti-fungal agents
- Unique flavor and better texture
- Reduced staling rate
- Increased loaf volume
- Low GI
4
Q
Describe the symbiotic relationship of microorganisms in sourdough?
A
Lactobacillus sanfranciscensis produce acetic and lactic acids, ethanol, and CO2. Lowers pH and inhibits competing organisms
Candida milleri is acid tolerant and release free amino acids and other nutrients for Lactobacillus
5
Q
What are the major cause of microbial spoilage of bread?
A
- Yeast and mold growth: Fungal spores are widespread in bakeries due to their presence in flour.
- Spoilage organisms: Aspergillus sp, Mucor sp, Penicillium sp, Saccharocmyces cerevisiae, Bacillus sp.
6
Q
What is proofing?
A
Proofing is resting a dough and allowing it to rise before baking. Proofing is done in cabinets or rooms at 35-42C, in which yeasts continues to produce CO2
7
Q
Describe the factors affecting the growth of yeasts in bread.
A
- Temperature: Dough rises at 26-29C. Higher temperatures can accelerates fermentation and gassing rates, but also promotes the growth of microbial contaminants, such as yeasts and molds.
- Relative humidity: 70-80% is encouraged. Low humidity may cause surface drying & inhibit fermentation near the the surface.
Food Fermentation
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