Pasteurization Does not Destroy the Nutritional Value of Milk

In Canada, pasteurization of milk destined for consumption is mandatory under the Food and Drug Regulations.² Pasteurization is a protective measure to ensure consumers’ health.³

Invented in the 19^th century by microbiologist Louis Pasteur, pasteurization involves heating milk below its boiling point for a short time. This type of process destroys nearly 100% of pathogenic bacteria, yeast and mould, and 95% to 99% of other non-pathogenic bacteria. Pasteurization also inactivates enzymes that cause rancidity.⁴

There are different types of pasteurization methods for white milk classified according to the temperatures and times used:^6,7

The most common pasteurization method for white milk is 72° C for 15 seconds. It allows large quantities of milk to be processed in a short period of time. Ultra-high-temperature pasteurization requires the combination of a temperature of 140° C for four seconds and sterile packaging, which significantly increases the shelf life of milk.^6,7

The effects of pasteurization on nutritional value

Although the benefits of pasteurizing milk are well established, some consumers wonder if this type of thermal process destroys some of the nutrients. Researchers in Ontario looked into the question and published a systematic review and meta-analysis of 40 studies.⁵ The results show that milk pasteurization decreases its concentrations of vitamins B₁, B₂, B₁₂ and C, and folate. Following pasteurization, milk is still a source of thiamine (vitamin B₁) and an excellent source of vitamin B₁₂. A significant decrease in riboflavin (vitamin B₂) was observed; however, pasteurized milk remains an excellent source of riboflavin.⁵ As for other vitamins, the effect on the nutritional value of milk is not significant since vitamin C and folate are found at relatively low levels prior to pasteurization. In addition, vitamin D fortification has been mandatory since 1975 for pasteurized milk sold in Canada, making it an excellent source of this vitamin, unlike raw milk, which contains only a very small amount.

Some may also question what effects pasteurization has on the proteins and enzymes present in milk. It is well established that whey protein, particularly β-lactoglobulin, is partially denatured during heating. However, denaturing whey protein does not affect the nutritional value of milk.^8,9 About 10% of these proteins are denatured during pasteurization and 70% during ultra-high-temperature processing.⁸ There is a misconception that raw milk is easier to digest because it contains “active” enzymes, which are deactivated by pasteurization.¹⁰ Although some enzymes are denatured by pasteurization, the same phenomenon can also occur during digestion due to the presence of acids in the stomach. Importantly, the enzymes found in milk are not required for digestion.¹¹