Intro to Fermentation

Question 1

What is Fermentation and what is it caused by?

Answer 1

It is a process where a sugar gains electrons and releases energy with out the use of O2 or as a terminal electron acceptor in the electron transport chain. It involves bacteria and yeast breaking down substrates often involving release heat in the process of effevesence. This is done during food processing involving yeast and bacteria

Question 2

How was fermentation used in ancient times? Who discovered fermentation?

Answer 2

Fermentation was first observed by the Chinese in 7000BC and the ancient Egyptians used it to make fruit wine. Its a naturally occuring progress used to preserve food and was discovered by louis pasteur who was the first to make the observation that microbes could lead to the spoilage of food.

Question 3

What are some examples of fermented food and drinks?

Answer 3

1. Kefir 2. Saurkraut 3. Yogurt 4. Bread 5. Wine 6. Beer 7. Kiminchi 8. Vinegar

Question 4

What are some examples of microbes involved in fermentation?

Answer 4

1. Streptococcus thermophillus(required by law) 2. L. acidophillus, L. Subspecies, Bifido-bacteria(probiotics)
2. Bifidobacterium, lactobacillus, leuconstoc, streptococcus(kefir)
3. Saccharomyces cerevisiae
4. Acetobacter aceti
5. Pediococcus, Leuconstoc, klebsiella, enterobacter

Question 5

Describe the bacteria behind fermentation

Answer 5

Lactic acid lowers the pH of the food making easier for fermenting bacteria to work more efficiently it also makes it possible for secondary fermenters to grow. The low pH also causes the clumping together of proteins leading to the production of a gel along with exposure to heat. The longer you heat a food and incubate the bacteria the thicker the gel that will form.

Question 6

Differences between yogurt and kefir

Answer 6

1.Yogurt: Solid
Kefir: Liquid
2. Different starter cultures
3. Yogurt: subjected to heat treatment (causes proteins to unwind and reform into a gel matirix when cooled down),
Kefir: Not subjected to anything (different structural form)

Question 7

What are the aseptic techniques used in lab?

Answer 7

1. Switch on bunsen burner while working
2. Dispose of any equipment which touched biological material
3. Sterilize all equipment
4. Wear goggles at all times

Question 8

Describe the Methods for the Kefir Experiment:

Answer 8

1. Add 25ml of commericial kefir to milk. 2. Stir the mixture 3. Label as Kefir culture 4. Place paper towel over jar lid and secure with rubber band
2. Incubate at 25 degrees celsius for 24 hours
3. Refrigerate for 1 week

Question 9

Describe the Methods for the Yogurt Experiment

Answer 9

1. Heat milk at 80 degrees celsius for 30 minuites.
2. Cool milk down to 45 degrees celsius
3. Add 1 spoon of yogurt to milk and then mix them
4. Place paper towel over jar lid and them together using a rubber band
5. Incubate at 25 degrees celsius for 24 hours

Question 10

Purpose of quality assurance experiment

Answer 10

To create dilution schemes for yogurt and kefir in an effort to visualize the bacterial cultures generated from each.

Question 11

Steps of the yogurt and kefir dilution scheme

Answer 11

1. Add 900 ul of peptone water to first of 6 test tubes.
2. Added 100 ul of yogurt or kefir to 1st test tube, vortexed for 3-5 seconds and then transferred 100 ul to the next and repeated the procedure.
3. Labled petri dishes based on the degree of dilution, and labled two for each one.
4. Transferred 100 ul from each pipette into each petri dish and spread plated them
5. Turned the petri dishes upside down and incubated them 25 degrees celsius for 24 hours.
6. Refrigerated them for a week.

Question 12

Materials

Answer 12

1. Micropipette
2. Petri dishes
3. Milk
4. Kefir
5. Yogurt
6. TSA
7. Water bath: maintain kefir and yogurt samples in
8. Thermometer: monitor the temperature of incubation for kefir and yogurt samples