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Food Microbiology Lab Straigherline Questions with Answers
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Lab 6 Food Microbiology BIO250L”Student Name: xxxx
Access Code (located on the underside of the lid of your lab kit): xxxx.
“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?
Escherichia coli contains virulence factors, they are considered foregin structures.
Virulence factors are responsible for causing infections. It is one of the most common
foodborne illnesses even though it is in our gut, that helps aid digestion only certain
strains of E.coli could cause potential harm when in consumption of contaminated food
or water.
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
Fruit: E.coli
Milk: Listeria Monocytogenes
Yogurt: Lactobacillus
Bread: Saccharomyces
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.
Listeria monocytogenes is a major threat to pregnant women because it based
through/in the placenta and can harm the fetus(es)
“EXPERIMENT 1: Assessing the Bacterial Load of Milk with Methylene Blue
Results Tables
Table 1: Time Required for Methylene Blue Color Change
Start Time/Date End Time/Date Time Elapsed
Milk Sample
(Step 10) (Step 11) (End Time-Start Time)
0 hours 1:00pm 1:30pm 30 mins
1 hour 1:00pm 2:00pm 1 hour
3 hours 1:00pm 5:00pm 3 hours
4 hours 1:00pm 6:00pm 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?
, Lab 6 Food Microbiology BIO250L”
The sample that took the least time to become white was the 4 hour sample. I think this
sample was because 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 sample that took the most time to become white was the 0 hour sample. This was
the case because it spent the least amount of time out at room temperature.
3. How does refrigeration affect the number of bacteria present in milk?
Refrigeration has an effect on the number of bacteria present in milk because when it is
refrigerated it has a lower number of bacteria. Bacteria have a harder time to grow in
cold environments.
4. How does pasteurization affect the number of bacteria present in milk?
Pasteurization of milk affects the number of bacteria present because when it is
pasteurized it destroys pathogenic bacteria and leaves it with very little bacteria present.
5. What differences, if any, would this assay show if performed using raw (unpasteurized) milk?
If the milk was raw (unpasteurized) then I think the milk would change color faster.
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?
If the milk had expired and we did this experiment, the color would change much more
rapidly.
Insert a photo of your tubes. Include your name and access code handwritten in the background of
your photo.
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