See also Pasteurization in the Dairy Science and Technology Education website.
Many people assume that all dairy products in Canada, including cheese, are made from pasteurized milk. Not so; several alternatives are possible as outlined below. Note, however, that the Food and Drugs Act and Regulations, recognizes only two types of cheese with respect to milk heat treatment, namely, fully pasteurized milk and raw milk. That is, if the milk is not fully pasteurized the resulting cheese is considered raw milk cheese.
1. No heat treatment results in raw milk cheese which has more flavour. Raw milk cheese by law must be "held at 20C or more for a period of 60 days or more from the date of the beginning of the manufacturing process, " Food And Drugs Act And Regulations, Sections B.08.030 and B.08.043. The question of raw milk cheese is an ongoing concern to consumer groups and to health authorities. Suffice it to say that with respect to regulations on cheese milk heat treatments, 'one size doesn't fit all'.
2. Thermisation (63-65C, short hold) results in phosphatase positive milk which must be fully pasteurized before cheese making. The purpose is to prevent raw milk spoilage (eg. over a weekend) due to acid or protease producing bacteria.
3. Pasteurization (63C, 30 min. or 72C, 16 s) is generally considered the safest alternative, but the full flavour of traditional ripened cheese can not be achieved. Note that over pasteurization causes denaturation of whey proteins which subsequently adsorb to the casein particles. The effects are:
- Longer flocculation times
- Weak or no curd formation
- Excessive loss of fines
- Poor syneresis (moisture release)
- Coarse textured curd with reduced ability to stretch, mat and melt.
4. Heat treat (55 - 65C, 16 s) is trade lingo for subpasteurization treatment which is applied to destroy most pathogens but allow some bacteria to survive and contribute to cheese ripening. This process permits fuller flavour of cheese with better control of culture growth (i.e., acid development) than with raw milk. For current regulatory purposes, heat treat is equivalent to raw. Most aged Canadian Cheddar is safely made from heat treated milk