Thermal processing principles

Question 1

What is the purpose of thermal processing?

3 answers

Answer 1

1 - achieve microbial safety and preserve quality by applying heat

2 - extend shelf life

3 - used as a cooking process (ie. canned soup)

Examples: blanching, pasteurization, sterilization

Question 2

What are the 3 principles of thermal processing?

Answer 2

1 - transfer of thermal energy to food products
2 - increase temp = increase rate of microbial population reduction
3 - Less microorganisms = safer to store and consume

Question 3

To effectively apply thermal processing, what do you need to know?

Answer 3

1 - The type of microorganism
2 - know the time and temp it will take to kill the target microorganism

Question 4

List examples of target organisms

Answer 4

E. coli, Salmonella, Clostridium botulinum

Question 5

1 -Which pathogens are killed at 60C?
2 - Where can they be found (produce)?

Answer 5

1 - E.coli, Listeria, Salmonella
2 - Cilantro, spinach, coleslaw, raw eggs

Question 6

1 - Which pathogens are killed at 100C?
2 - Where can they be found (product)?

Answer 6

1 - C. botulinum spores
2 - Canned meat, soups, vacuum packed foods

Question 7

Describe the necissary steps of thermal processing:

Answer 7

1 - Identify target microorganisms
2 - Identify the effect of heat on the target MO’s
3 - Collect time / temp data
4 - Apply time / temp data to a specific food/package

Question 8

What is the D-value?

Answer 8

• D value = Decimal reduction Time
  -The time required to* reduce* number/concentration by **90% **at a temperatrue

Question 9

What is the Z-value?

Answer 9

The temp change required to decrease D value by 90% (a factor of 10)

Question 10

What does a higher D value mean?

Answer 10

• More time needed to reduce the same number of MO’s at a centrain temp

MO’s are more heat resistant

Question 11

What does a higher z value mean?

Answer 11

• more temp change needed to reduce the same processing time (D-value)

MO’s more heat resistant

Question 12

(1)What is the F value?
(2) Define it.

Answer 12

1 - Thermal Death time

2 - Time required for a food product to be heated to get a specified decrease in concentration at a temperature

Question 13

What do you call the specific decease for MO’s?

Answer 13

Sterilization value (SV)

Question 14

Thermal processing design

What factors do you need to consider when assessing how to destroy microorganisms?

Answer 14

• Temp (thermophiles / mesophilles etc)
• pH -> which MO’s survive in low acid foods (pH > 4.5) or high acid foods (pH < 4)
• Oxygen requirements -> Aerobic/anaerobic

Question 15

What do you have to consider during thermal process design?

Answer 15

1 - target microorganisms
2 - compositions of food products
3 - physical properties of food products

- ensure safety
- preserve quality (texture, taste etc)

Question 16

What conditions does C. botulinum survive under?

Answer 16

• anaerobic
• low acid
• mesophile

Question 17

Thermal processing design

What do you have to consider about the composition of foods?

Answer 17

• acidity levels
• amount of moisture + fat

Question 18

What do you have to condiser about the physical properties of foods?

Answer 18

• viscosity
• solid vs. liquid

Question 19

With regards to food quality, what can thermal processing change?

Answer 19

Flavour, colour, texture, heat sensitive nutrients

Question 20

What is the key to thermal processing?

Answer 20

Determining the differences in thermal resistance between microorganisms and quality factors to maximise food safety and minimize loss of nutrients, functionality and flavour