🥛 Pasteurized milk

Pasteurised milk is milk heated to a temperature below boiling to destroy disease-causing microorganisms. As defined by the FAO and WHO, pasteurisation must reliably kill the agents of tuberculosis (Mycobacterium tuberculosis) and Q fever (Coxiella burnetii). The minimum conditions are the equivalent of heating every particle of milk to 72 °C for 15 seconds in continuous flow, or to 63 °C for 30 minutes in a vat (batch pasteurisation).

The aim, in the words of the FAO and WHO, is to reduce the number of pathogens in milk to a level at which they no longer pose a significant health hazard. According to the FDA, pasteurisation does this without any significant impact on the nutritional quality of milk: it has little effect on casein and causes only limited denaturation of whey proteins, and in one study heating to 72 °C for 15 seconds changed only 1% of the immunoglobulin G.

Pasteurised milk or raw milk? Raw milk is not heated at all, while pasteurised milk is heated below boiling so that the agents of tuberculosis and Q fever are reliably destroyed; the FAO and WHO aim to cut pathogens to a level that is no longer a significant hazard. Pasteurised or UHT? Both are heat treatments, but pasteurisation is deliberately milder: it is not sterilisation, so the milk keeps for several days in the fridge and must be drunk by the date on the pack. Fresh milk simply means newly bought, not unheated.

On the pack look for the words “pasteurised milk” and a use-by date; the milk sits in the chilled cabinet of a supermarket, a dairy shop or a farm shop, not on the ambient shelf. Labels such as whole, semi-skimmed or skimmed describe fat, not heat treatment. If the pack says nothing about pasteurisation, or says raw, the milk was not heated this way. Once opened, keep it in the fridge.

Pasteurisation is not sterilisation: it reduces the number of microbes but does not remove all of them, so pasteurised milk is kept in the fridge and drunk by the date on the pack. According to the FDA, pasteurisation has little effect on most vitamins; vitamin C suffers most, but a cup of milk (240 ml) provides only about 5 mg of it, so milk is not a significant source anyway.