10: Ozone and DPCO2

Question 1

Describe how ozone can be formed.

Answer 1

1. Oxygen molecule is split into 2 oxygen radicals through corona discharge or UV radiation.
2. 3 oxygen radicals are combined to form O3.
3. Excess ozone generated will be destroyed using a destructor.

Question 2

How does ozone inactivate bacteria?

Answer 2

1. Oxidation of sulfhydryl group and amino acids of peptides, proteins and enzymes.
2. Oxidation of PUFA to acid peroxides that cause cell leakage.

Question 3

Describe the application of ozone in food processing.

Answer 3

• Water disinfection
• Surface disinfection of fruits and vegetables: Equivalent efficiency with chlorine treatment. Vacuum sanitization using ozone prevents pathogen internalization in fresh produce.
• Antimicrobial agent in meat

Question 4

Why is ozone less often used as antimicrobial agent in meat?

Answer 4

• Oxidation of lipid
• Reduced redness due to oxidation of myoglobin and oxymyoglobin to metmyoglobin
• Reduced catalase activitly
• Reduce glutathione peroxidase activity.

Question 5

What are the advantages of DPCO2 technology?

Answer 5

• Non-toxic
• Low cost
• Non-flammable
• Low critical T and P

Question 6

Describe the mechanisms of inactivation of MOs using DPCO2.

Answer 6

1. Liquefied CO2 dissolves in the extracellular liquid and forms carbonate ion.
2. CO2 diffuses into cell membrane and accumulate in the phospholipid bilayer, which distorts cell membrane and increase fluidity and permeability.
3. As more CO2 is dissolved in the cytoplasm, the intracellular pH decreases. Homeostasis is imbalanced due to too high [CO2] and distortion of cell membrane.
4. Drop in pH also causes inactivation of metabolic enzymes/
5. CO2 and carbonate ions also have direct inhibitory effect on metabolism.
6. Carbonate ions also imbalances intracellular electrolyte concentration.
7. Sudden release of pressure causes rapid transfer of intracellular materials out of the cell.

Question 7

Describe the advantages and limitations of DPCO2 as a way of cold pasteurization.

Answer 7

Adv:
- Mild temperature
- Minimum degradation of nutrient and sensory quality
- Reduce the rate of oxidation
- Automatic carbonation for carbonated beverages.
- Continuous Operation

Disadv:
- Expensive capital
- Require special high pressure equipment and accessories.