Brief description

Pasteurization is a heat-treatment process that destroys pathogenic microorganisms in certain foods and beverages. Unlike sterilization, it does not kill all microorganisms but reduces their number to a safe level, extending shelf life without significantly altering the taste or nutritional value.

Use / Function

• Food Safety: Eliminating bacteria like Salmonella, E. coli, and Listeria from milk, juice, and other liquids.
• Disease Prevention: Historically critical in stopping the spread of tuberculosis and brucellosis via milk.
• Preservation: Slowing down spoilage by inactivating enzymes and killing spoilage-causing microbes.

Operating principle

It is based on the relationship between temperature and time:

1. Heating: The liquid is heated to a specific temperature (below its boiling point).
2. Holding: It is held at that temperature for a precise duration.
3. Cooling: It is rapidly cooled to prevent any surviving spores from multiplying.

Common methods:

• Batch (LTLT): 63°C (145°F) for 30 minutes.
• Flash (HTST): 72°C (161°F) for 15 seconds.

How to implement it

1. Preparation: Place the liquid (e.g., raw milk) in a clean Container.
2. Heating: Place the container in a water bath (to ensure even heating and prevent scorching).
3. Monitoring: Use a Thermometer to reach the target temperature (63°C for small batches).
4. Holding: Maintain the temperature steadily for 30 minutes.
5. Cooling: Place the container in an ice bath or cold water to lower the temperature quickly to below 4°C (40°F).
6. Storage: Keep refrigerated in a sealed container.

Technical level: Intermediate. Requires accurate temperature measurement.

Materials needed

• Essential: Liquid to be treated, Water for the heating bath.
• Tools: Containers (pots, bottles), Thermometer, heat source.
• Substitutes: If no thermometer is available, heating milk until it just begins to steam and bubble slightly (but not boil) can offer some protection, though it is less reliable.

Variants and improvements

• Vat Pasteurization: The traditional batch method.
• Ultra-High Temperature (UHT): Heating to 135°C (275°F) for 1-2 seconds. This sterilizes the product, allowing it to be stored at room temperature for months if packaged aseptically.

Limits and risks

• Not Sterilization: Pasteurization does not kill bacterial spores. Pasteurized products will eventually spoil and must be kept refrigerated. See Sterilization for total elimination of microbes.
• Re-contamination: If the liquid is placed in a dirty container after heating, the process is rendered useless.
• Temperature Precision: If the temperature is too low, pathogens survive; if too high, the flavor and proteins are damaged (e.g., “cooked” taste in milk).