Definition: Pasteurisation

A process that aims to destroy any pathogenic germs that may be present in a liquid foodstuff (milk, cream, fruit juice) by heating it, while altering its physical structure and biochemical elements as little as possible. The treatment of a foodstuff (milk, fruit juice, wine, beer, etc.) with heat in order to destroy any pathogenic bacteria it may contain.

Low pasteurisation involves heating milk to 63°C for 30 minutes. High pasteurisation involves heating milk to 85°C for 2 minutes or 80°C for 3 minutes. Instant pasteurisation involves heating a thin layer of milk to 75°C for 5 to 8 seconds. Various processes exist: 1) Discontinuous: low-temperature pasteurisation (LTLT) at 63°C for 30 minutes or the "holder process". 2) Continuous: closed-circuit operation protected from air and external contamination and under pressure, thus avoiding the loss of dissolved gases and oxidation - high-temperature pasteurisation or HTST (at 73-74°C; 15 to 20 seconds) - flash pasteurisation (85 to 90°C for a few seconds). In France in particular, due to the poor bacteriological quality of raw milk, temperatures of 90°C for 15 seconds are commonly applied. The milk obtained often has a slight cooked taste. The effectiveness of the treatment is checked by testing for alkaline phosphatase or peroxidase (DUPOUY test). Cream is generally pasteurised at 92-94°C for 15 to 20 seconds, as the fat forms a protective barrier against heat for the bacteria. In all cases, pasteurisation is followed by rapid cooling. The bacteriological standards in force stipulate, among other things: - For packaged pasteurised milk: less than 30,000 live bacteria/ml and a negative reaction when testing for indigenous bacteria in 1 ml at the time of delivery to the consumer. - For pasteurised milk distributed in bulk: less than 200,000 live bacteria/ml. Actinisation is a pasteurisation process that uses the thermal action of infrared rays. See flash pasteurisation.