This milk is permeate-free!
This milk is permeate-free!

If you know me, you’ll know that I am easily annoyed by misleading statements. “Permeate free” is my latest bugbear, probably because I see that statement every time I pour milk on my cereal or into my tea at the moment.

Enjoy milk the way it should be with Dairy Farmers

The way milk should be (Pura)

Coincidentally*, both Pura and Dairy Farmers brands are owned by the same company (National Foods).

Now, there have been several chains announce that they, too, will now be producing permeate-free milk.

Cynically, I think there are probably a few people out there thinking “phew! I don’t know what they are but they sound bad so I’m glad they’re not in my milk!” (and I’d love to be shown to be wrong, although the persistence of the stickers on my milk convince me that I’m right). There are people who will believe that permeate is bad for them and should be removed on the strength of a sticker.

There are probably quite a few more people who don’t care and haven’t thought about it all.

I hope that there are a few people out there asking questions. What is this permeate stuff? Should milk be permeate free? Is this better for me? Why would the milk companies choose to make their milk permeate free?

There are some people calling “bullshit!” on permeate free products. Some are even interviewing “top scientists”** for added credibility***!

As a teacher, I see this as an opportunity for students to practise the sceptical process****. Students can ask questions, find the evidence, and take a position on whether or not their milk should be permeate-free.

What is this permeate stuff?

Cow’s milk contains fats, proteins, lactose (a sugar), other carbohydrates, fatty acids, and water. Straight from the cow’s udder, it also contains a number of micro-organisms. These micro-organisms make the milk go sour very, very quickly if left in the milk. Some are pathogenic to humans.

Milk is processed before it makes its way to the supermarket. In the past, milk has been pasteurised and homogenised. The process of pasteurisation involves heat-treating the milk to remove a large number of the micro-organisms. Homogenisation involves breaking up the clumps of cream (fat globules) to ensure that the consistency of the milk is, well, consistent.  Sometimes some fat is removed.

Industry regulators set minimum and maximum standards for the amount of fat and protein milk must have to be categorised as whole milk, trim milk, skim milk, etc. This is important because the components of cow’s milk change over the course of the year, due to changes in season, feed, availability of water, etc.

Nowadays, milk is also undergoing a process called ultrafiltration. Ultrafiltration, in addition to pasteurisation, can remove almost all of the micro–organisms in the milk, ensuring a longer shelf-life. Ultrafiltration filters out large molecules in the milk, the fats and caseins and I presume the micro-organisms, while the lactose, water, vitamins and minerals pass through the filter. The filtered material is slightly greenish, due to the presence of vitamin B, and watery. It is known as permeate. The filtered fats and caseins are known as retentate and are used to make cheeses.

Permeate is returned to the milk to boost the levels of vitamins and minerals in the milk, to reduce wastage in milk production, and keep the cost of milk production down. It is not bad for you (unless you’re lactose intolerant, in which case you wouldn’t be drinking the milk anyway!). In fact, adjusting the levels of permeate in milk is important so that you can assume that milk contains all the good things you need to stay healthy, all year round.

But don’t just believe me. Go out there and do some research

More information

Wikipedia – Milk permeate

Nutrition Australia – everything you need to know about milk standardisation


*not coincidentally at all

**one scientist from RMIT

***News Limited – now with added credibility!

****Yes, I need to define this. No, I haven’t yet. Another post?

UPDATE! 6pm Sunday 9 September 2012

A blogger I have admired on Twitter for a long time, Dr Heather Bray, wrote this about permeate-free milk a few months ago. She says that while the permeate-free milk is less watery, more whole milk will be needed to supply Australia’s demand for milk, so farmers will actually get a better deal, according to Clover Hill Dairies. I’ve also updated the paragraph above about ultrafiltration, as I had some information wrong, and some information missing. Thanks India for your comment, which helped me to dig more deeply.

It looks like my conclusions must be:
1. Permeate-free milk will result in more whole milk being purchased from farmers, but unless the dairy producers raise the price they charge for milk, I’m not sure that they’ll get enough money for it. So let’s say the jury’s out on this one, and we’re waiting for more evidence.
2. Permeate-free milk, as I understand it, will have slightly less vitamins, minerals and lactose than if some or all of the permeate were returned to it. The amounts of the vitamins, minerals and lactose in the milk will vary, too, rather than being consistent as it is in milk where the permeate is returned to it.