🥛 Drinking milk by processing

Drinking milk by processing is a section about the kinds of milk sold in shops and how each is treated. The milk sold in shops is almost always processed. The FAO classifies it, first, by fat content — whole, standardized, semi-skimmed, low-fat and skimmed — and second, by heat treatment: pasteurized, ESL (extended shelf life), ultra-high temperature (UHT) and sterilized. Milk can also be homogenized, fortified with vitamins, lactose-free and so on. ¹

The main purpose of heat treatment is safety. Raw milk can carry Campylobacter, E. coli, Listeria, Brucella and Salmonella; according to the CDC, pasteurization sharply reduced milk-borne illness from the early 20th century on. The stronger the heating, the longer the milk keeps, but the more its taste and some vitamins change: pasteurized milk keeps for days or weeks in the fridge, UHT and sterilized milk for months without refrigeration. ¹²

Heating varies in strength. Thermization is the mildest: at least 15 seconds at 57–68 °C. It reduces microorganisms but does not replace pasteurization. Pasteurization must have an effect equal to heating every particle of milk to 72 °C for 15 seconds or 63 °C for 30 minutes ¹. In practice, homogenized milk is usually heated to 72–75 °C for 15–20 seconds ⁴.

UHT treatment runs in a continuous flow at 135–150 °C, typically for 2–10 seconds, and with aseptic packaging gives a commercially sterile product. Sterilization takes longer: 110–140 °C for 20–30 minutes ¹. Tetra Pak explains UHT's advantage this way: at high temperature the killing of bacteria rises much faster than chemical changes ⁶.

In the EU, drinking milk is divided by fat: whole at least 3.50%, semi-skimmed 1.50–1.80%, skimmed no more than 0.50% ⁵. UHT milk is not only cow's: FAO mentions goat's in the UK and Italy, and buffalo in India, the UK and Egypt ¹.

UHT milk or pasteurized milk? Both are heat-treated for safety, but the stronger the heating, the longer the milk keeps and the more its taste and some vitamins change. Pasteurization is at least 72 °C for 15 seconds or 63 °C for 30 minutes, and the milk keeps for days or weeks in the fridge. UHT reaches 135–150 °C for a few seconds and, in aseptic packaging, keeps for months unopened without a fridge. Sterilized milk is heated longer still, at 110–140 °C for 20–30 minutes. Raw milk is not heat-treated at all.

Read the treatment on the pack: "pasteurized", "ESL" (extended shelf life), "UHT" or "sterilized"; it decides where and how long to keep the milk. Pasteurized milk sits in the chilled aisle of a supermarket, while UHT and sterilized milk can stand on ordinary shelves until opened. The fat class is named too: whole, semi-skimmed or skimmed. Health authorities consider raw milk risky, so do not treat it like ordinary shop milk.

Why it matters to you. Check the treatment: it decides where and how long to keep the milk. Keep pasteurized milk in the fridge, while unopened UHT and sterilized milk can stand without cold ¹⁶. Health authorities consider raw milk risky ²³.