Discussed methods of microbial control focusing on:
Cold (Refrigeration vs. Freezing)
Pressure (Pascalization)
Desiccation (Drying, Lyophilization)
Cold
Refrigeration
Inhibits Metabolism
Bacteriostatic effect: slows microbial growth
Does not kill organisms
Freezing
Below -2°C
Can kill some microbes, but not all
Psycrophilic organisms thrive at these temperatures
Ultra-Low Temperature Freezing
Dry ice freezers: -70°C
Liquid nitrogen tanks: -196°C
Pressure (Pascalization)
Used in food industry, particularly juices and meats
Denatures Proteins
Causes cell rupture similar to heat
Maintains food quality better than heat
Pressure Levels
100 to 800 Megapascals (MPa)
Sea level atmospheric pressure: 0.1 MPa
800 MPa ≈ 116,000 psi
Effectiveness
Kills vegetative cells, viruses, parasites
Less effective on spores
Desiccation (Drying)
Moisture Removal
Necessity of Water for Metabolism
Drying slows metabolism
Examples: raisins, jerky
Hypertonic Environment
Salt or Sugar Addition
Reduces water activity
Example: honey, jams, canned goods
Term to Know: Plasmolysis
Removal of moisture from living cells
Lyophilization (Freeze-Drying)
Process
Rapid freeze-drying under vacuum
Removes moisture while freezing
Used in labs for preserving DNA and bacteria
Conclusion
Covered cold, pressure, and desiccation as methods of microbial control. Each method has unique applications and effectiveness depending on the type of microorganisms targeted.