Sterilization

Question 1

What is commercial sterilization

Answer 1

• no MO’s survive
• 12D process
• F (processing time) = 12 x D (thermal death time)

Question 2

List the factors you need to consider for commercial sterilization

Answer 2

1 - Product characteristic
2 - MO’s thermal behaviour
3 - Packaging
4 - Heating/cooling medium

Question 3

elaborate on these factors to consider:

Product characteristic

Answer 3

1 - pH
2 - heat resistance of MO’s/spores
3 - heating/cooling characteristics
4 - water activity (aw)

Heating/cooling characteristics = conduction/convection, thicknes, phase

Question 4

elaborate on these factors to consider:

MO’s thermal behaviour

Answer 4

Time : Temp depends of D (time) and z (temp)

Question 5

elaborate on these factors to consider:

Packaging

Answer 5

shape, material, size

Question 6

elaborate on these factors to consider:

Heating/cooling medium

Answer 6

Water, steam, air

Question 7

What is the main target of sterilization?

Answer 7

Clostridium botulinum (low acid foods)

remember: low acid = high pH

Question 8

List the following about C. botulinum

1 - pH it grows in
2 - oxygen requirement
3 - water activity
4 - where it can be found in food
5 - where it can be found in the environment and how it contaminates

Answer 8

• low acid (4.5 < pH)
• anaerobic
• Aw > 0.94
• badly processed/home canned foods
• soil -> soil contact can cause spore contamination

Spores are heat resistant

Question 9

1) What toxin does C. botulinum produce?
2) How do you destroy this toxin?

Answer 9

1. Botulinum toxins = intoxication
2. T > 100 C for **10 min **

Question 10

What are considered extreme health hazards for C. botulinum?

Answer 10

Canned and vacuum packed foods with a high pH (low acid)

Question 11

What is the minimum heat treatment to destroy C. botulinum spores?

Answer 11

• 121 C for 2.45 min (Fo = 2.45min)
• z = 10 C

Typically aim for 3 min

Question 12

How can you tell a product is at risk for having C. botulinum?

Answer 12

Swelling in sealed containers

Question 13

What is the “cold point”?

Answer 13

The slowest heating point

PLEASE remember to see additional info on slides

Question 14

Name which kind of particles fit into the following:

1) Convection
2) Combination
3) Conduction

Answer 14

1. Fluid foods (apple juice) / discrete particles in liquid (peas in brine)
2. Particles in viscous liquid (Cream corn)
3. Heavily matted foods / very viscous liquids(spinach, pumpkin) / solidly packed foods (meat; fish)