Reality Check: Helpful Microbes

Question 1

Yeast is . . .

Answer 1

Not airborne, a typical vector of ripe fruits

Question 2

What does that flour do for the bread?

Answer 2

Nutrient source
- Complex compounds in the carbohydrates are broken down into simpler sugar
- From primary structure
- Protein impact impact strength and stability

Question 3

What does water do for water?

Answer 3

Water pH influence yeast activity
- Alkaline water reduces dough elasticity and slows microbial activity
- Activates enzymes in flour

Question 4

What does salt do for the bread?

Answer 4

Slows down microbial activity (yeast and undesirable microbes)
- leads to less sugar break down, leaving some sweetness in bread
- Salt binds on gluten - more stable

Question 5

What happens when dough rises?

Answer 5

Respiration (Glucose + O2 -> CO2 + H20)
Alcoholic Fermentation (Glucose -> CO2 +ethanol)

Question 6

What is pickling?

Answer 6

The process of preserving food by anaerobic fermentation in brine or immersion in vinegar

Question 7

Lactic Acid Bacteria

Answer 7

• Decreases pH of environment
• Preform lactic acid fermentation
• Produces EPS
• Produces broad-spectrum bacteriocin which inhibits a range of spoilage causing microorganisms and foodbrone pathogens

Question 8

Spontaneous fermentation

Answer 8

Relies on microbial inoculation from microbes that happen to be present in air and on the food that is being fermented

Question 9

What is water used in pickling?

Answer 9

Provides high water activity for microbes to grow
- reduces vegetable oxygen exposure which is needed for fermentation and inhibits fungus and mold growth

Question 10

Why is salt used in pickling?

Answer 10

Slows microbial growth
- LAB grows extremely well in salty environment, thus encouraging LAB growth

Question 11

Why are cucumbers used in pickling?

Answer 11

Have high water activity
- outsider reduces rate of spoilage and microbial penetration
- microorganisms convert carbohydrates and sugars into biomass acid and carbon dioxide

Question 12

Why are tannins used in pickling?

Answer 12

Class of compounds that bind and precipitate proteins and other amino acids
- Inhibit pectinase enzymes (in cucumber) from softening and breaking skin down

Question 13

What is a SCOBY?

Answer 13

Symbiotic Culture of Bacteria and Yeast
- Biofilm formed from symbiotic relationship between acetic acid bacteria and osmophilic yeast

Question 14

What does the yeast do in kombucha?

Answer 14

Preforms alcoholic fermentation resulting in carbon dioxide and ethanol

Question 15

What is the bacteria in kombucha and does does it do?

Answer 15

Acetic acid bacteria (AAB) - ferment sugar and alcohol to acetic acid
- preforms oxidative fermentation

Question 16

What does oxidative fermentation do?

Answer 16

Oxidizes sugar and alcohols produced by yeast, resulting in the production of acids, such as acetic acid. This increases the acidity and reduces/eliminates ethanol concentration

Question 17

What are the stages for fermentation?

Answer 17

1) Yeast produces invertase
2) Yeast ferments sugar into ethanol
3) Bacteria oxidize ethanol to produce acetic acid
4) Bacteria produces biofilm

Question 18

What is the significance of the biofilm in kombucha?

Answer 18

-ESP matrix inhibits diffusion of antibiotic or invading cells
- great place to store resources
- will use biofilm as source of nutrients when resources are limited