Pasteurisation
A process of moderate heating (usually 72°C for a few seconds) designed to destroy pathogenic micro-organisms in a food while preserving its qualities as far as possible, invented by Louis Pasteur.
Pasteurisation, developed by Louis Pasteur in the 19th century (initially for wine), briefly heats a food to kill pathogenic bacteria and extend its shelf life, without fully sterilising it. Milk is the emblematic case: heated to about 72°C for 15 seconds (the HTST method).
Not to be confused with sterilisation (UHT treatment, about 140°C): pasteurisation kills pathogens but leaves harmless micro-organisms, hence a shorter shelf life (pasteurised milk = refrigerated, a few days; sterilised UHT milk = ambient, several months).
An original angle (the safety/nutrition trade-off): pasteurisation is a compromise. It has saved countless lives (bovine tuberculosis, brucellosis, listeriosis from raw milk), but it has a moderate nutritional cost: a slight loss of vitamin C and B vitamins, and destruction of the natural enzymes and probiotics of raw milk.
The raw versus pasteurised milk debate illustrates this trade-off:
- Raw milk: intact microbiota and enzymes, potentially better tolerated by some, but a real health risk (especially for children, pregnant women and the immunocompromised)
- Pasteurised milk: safe, nutritionally almost equivalent, but « depleted » of microbial life
Pasteurisation also destroys the probiotics in shop-bought fermented foods, a key point: pasteurised sauerkraut no longer has live probiotics. For probiotic benefits, look for « unpasteurised ».