What is pasteurization?

Summary

Pasteurization is a food-preservation method in which food is heated to a specific temperature for a set time. It destroys most microorganisms and enzymes that can cause spoilage, while generally changing the food less than cooking does. The required temperature and duration vary depending on the food and its acidity.

Louis Pasteur’s experiments helped establish that microorganisms cause fermentation and spoilage rather than appearing spontaneously. In his swan-neck flask experiments, boiled infusions remained free of visible microbial growth when airborne dust was kept out. Microbes appeared after dust entered.

Methods and examples

• Orange juice: Because it is acidic, it is commonly heated to about 95–98°C for 10–30 seconds. This mainly inactivates enzymes that could shorten its shelf life.
• Milk: The video describes heating milk to around 60°C for 20–30 minutes or 72°C for 15 seconds. UHT milk is heated to about 140°C for 2–3 seconds. Higher-temperature treatments generally allow milk to keep longer; UHT milk can last for months.
• Cheese: Some cheeses are made from raw milk and aged, while others use pasteurized milk. Raw-milk cheeses can contain pathogens such as Salmonella, Listeria, and E. coli. The video notes that rules differ across countries and that raw-milk cheese has raised particular concerns for young children and people with weakened immune systems.
• Honey: Pasteurization is used mainly to slow granulation and keep honey smooth, rather than to make it safer. Honey’s low moisture and high acidity make it difficult for bacteria to thrive. Heating is sometimes paired with filtration, which can remove pollen.
• Eggs: Pasteurized eggs can reduce the risk from raw eggs, especially for people more vulnerable to foodborne illness. However, pasteurization can affect taste and make egg whites less suitable for whipping into stiff peaks.

Researchers and sources

The researchers and sources mentioned include Louis Pasteur and the U.S. Food and Drug Administration (FDA). The video also refers generally to unnamed experts.