BIO250L+V2+Lab+6 straighterline assignment PDF

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Lab 6 Food Microbiology

BIO250L”

Student Name: Access Code (located on the underside of the lid of your lab kit): AC-XC9QOE “Pre-Lab Questions” 1. Escherichia coli is one of the most common causes of foodborne illness, yet it is also a common microorganism found within the human gut. What explains this disparity? Some E. coli illnesses contain virulence factors which are considered to be foregin structures. These virulence factors are responsible for causing infection in the host.

2. There are several foods and beverages listed in this lab that are created through the actions of microorganisms. Name five of the foods and the specific microorganisms that are used to make each of them. Cheese: lactococcus, yogurt: lactobacillus, Fruit: E.coli, bread: saccharomyces cerevisiae, milk: listeria monocytogenes

3. Using an online research tool such as the A-Z index on the CDC website, explain why Listeria monocytogenes is a major threat to pregnant women and their developing fetuses, who are ten times more likely to get sick than other demographic groups. This is a major threat to pregnant women because this illness can be based through the placenta and harm the fetus.

“EXPERIMENT 1: Assessing the Bacterial Load of Milk with Methylene Blue

Results Tables Table 1: Time Required for Methylene Blue Color Change

0 hours

Start Time/Date (Step 10) 8:00 AM

End Time/Date (Step 11) 8:30 AM

Time Elapsed (End Time-Start Time) 30 MINS

1 hour

8:00 AM

9:00AM

1 HOUR

Milk Sample

Lab 6 Food Microbiology

BIO250L”

3 hours

8:00 AM

11:00 AM

3 HOURS

4 hours

8:00 AM

12:00 PM

4 HOURS

Post-Lab Questions 1. On average, which sample took the least time to become white? Why do you think this was the case? The 4 hour sample since it was at room temperature the longest.

2. On average, which sample took the most time to become white? Why do you think this was the case? The zero hour sample

3. How does refrigeration affect the number of bacteria present in milk? Refrigerated milk has a lower number of bacteria because bacteria doesn’t thrive in cold environments.

4. How does pasteurization affect the number of bacteria present in milk? Pasteurized milk destroys pathogenic bacteria so there is very little bacteria present.

5. What differences, if any, would this assay show if performed using raw (unpasteurized) milk? The color of the milk would change at a faster rate.

6. What differences, if any, would this assay show if performed using milk that was past its expiration date and had an off-putting odor? More bacteria would present so the color would change rapidly.

Lab 6 Food Microbiology

BIO250L”

Insert a photo of your tubes. Include your name and access code handwritten in the background of

your photo.

“EXPERIMENT 2: Yogurt Preparation

Lab 6 Food Microbiology

BIO250L”

Data Tables Table 2: Yogurt pH Results Sample (Step #)

pH

2

7

6

7

10

6

14

5

4 15

Post-Lab Questions 1. Make a graph of the pH changes over the course of the experiment. Insert it below. How does the pH change at each step? Why?

Lab 6 Food Microbiology

BIO250L”

The pH decreased due to lactose degeneration.

2. What attributes does lactic acid confer to yogurt? Lactic acid makes yogurt have a soft texture and taste.

3. How does the consistency of the milk change during the production of yogurt? What facilitates this change? Milk thickens because of lactic acid being added during production.

4. What are the breakdown products of lactose? Galactose and glucose are the breakdown products.

Insert a photo of your pH strips. Include your name and access code handwritten in the background of

Lab 6 Food Microbiology your photo.

BIO250L”...