Depth Study

Question 1

What is the aim of the inquiry question?

Answer 1

To determine the most effective method for sterilising milk products to prevent illness and reduce economic pressure on governments and individuals

Question 2

What is the purpose of the inquiry question?

Answer 2

• Before milk food safety standards were introduced in 1924, almost 25% of foodborne illnesses in the US were due to untreated dairy products - now 1%
• 838.8 times more likely to experience an illness and 45.1 times more likely to be hospitalized from raw milk
• Raw milk can contain microbes that cause diarrhoea, vomiting, and even kidney failure
• Raw milk can contain salmonella, E.coli, and cyptosporidium
• People getting sick means the government must spend money on treatment and they cannot go to work to make money - negatively impacts economy and personal income

Question 3

What is the hypothesis?

Answer 3

If the temperature of the raw milk increases, then the number of microbial colonies will decrease because high temperatures cause cell death and damage to reproduction

Question 4

What is the scientific backing to the hypothesis?

Answer 4

• If temperature higher than microorganism’s optimal temperature, enzymes and proteins denature & become non-functional
• optimal temp for raw milk microbes is ~35℃
• high temperatures cause phospholipids to become excessively fliud, causing membrane to lose structural integrity and rupture
• allows intracellular fluid to leak and extracellular toxins/organisms to damage/kill cell
• High temperatures have increased kinetic energy which damages 3D structure of enzymes - loss of function
• loss of enzyme function prevents cellular reproduction (binary fission) - cannot form colonies
• microbes heated to high temps more likely to die/lose protein function and cannot reproduce to form colonies

Question 5

What are the controlled variables and why are they important?

Answer 5

• All 6 plates are from the same agar plate batch - different batches have different amounts of nutrients/microbes
• Both samples are from the same batch of raw milk - different batches have different amounts/types of microbes
• Sterilised inoculating loop & thermometer - prevents microbes being transferred between trials
• Agar plates incubated at 30℃ - microbes grown under same conditions & prevents growing human pathogens
• Agar plates sealed with tape - provides microbes with necessary oxygen & prevents growing anaerobic bacteria

Question 6

What is this?

Answer 6

test tube

Question 7

What is this?

Answer 7

Beaker

Question 8

What is this?

Answer 8

Gauze

Question 9

What is this?

Answer 9

Tripod

Question 10

How do you draw a heatproof mat?

Answer 10

straight horizontal line

Question 11

What is the dependent variable?

Answer 11

Number of microbial colonies on agar plate - measured by % cover on agar plate

Question 12

What is the independent variable?

Answer 12

Temperature of raw milk
* changed by heating milk sample in a water bath over a bunsen burner
* measured using a thermometer

Question 13

What do you include in the discussion?

Answer 13

1. Results
   - state trend
   - refer to IV and DV
2. Explain
   - use data to explain shape
   - Pasteur
   - enzymes, plasma membrane
   - denaturing due to KE
3. Evaluation
   - validity - control plate
   - reliability
   - accuracy