Q: What is permeate and how is it made?

A. It's easier to deal with the second part of this question first.

Permeate is made when whole milk is filtered through a fine 'sieve' or membrane using a technique called ultra-filtration. This filtering separates the lactose (also called milk sugar), the vitamins and the minerals from the milk protein and fat.

Permeate has long been regarded as a "problem" and is mainly lactose. It's exact percentage differs from supplier to supplier but is usually in the range 65% to 85% *.

It is, however, used by some milk manufacturers to standardise milk which - according to them - allows them to ensure that their milk has a constant composition.

Permeate is NOT harmful. It's a natural by-product of milk processing, not a foreign additive as suggested by some alarmists. You're drinking permeate every time you drink milk as it's part of the milk that comes out of the cow.

            * Figures from the US Dairy Council's Reference Manual for US Whey and quoted in Dairy Foods, March 2011