The milk we drink today is the result of technological progress over the past 30 years. That means milk today is very different from what we called milk 30 years ago.
Cows generally produce milk with 3.7 per cent fat and 3.5 per cent protein. Jersey cows produce higher fat content, while Friesians have higher protein percentage. A cow at the end of her lactation will have a higher fat concentration in her milk, too.
I ran into trouble one year when quite by chance all my in-milk cows were jerseys in their last month of lactation. The result was our milk had 5.5 per cent fat content. Our cafe customers were calling me complaining that the milk wouldn’t stretch or froth properly.
Baristas were perplexed when I told them a quick fix was to use 60 per cent milk and 40 per cent water in their jugs. Effectively diluting the fat content back to 3.3 per cent.
To solve this fluctuating fat content problem, factories in the old days introduced the practice of standardisation.
Milk would go through a cream separator that uses centrifugal force to separate the heaver milk from the lighter cream. A simple calculation would ensure the correct amount of cream would be added back into the skim milk in order to give it the desired fat content.
Cream separating from milk is a natural process that milk does by itself anyway. The invention of the cream separator simply sped this process up a bit and the milk was not noticeably different.
Then one day, somebody, somewhere, for some unknown reason decided that consumers don’t like the cream sitting in the top of their milk bottle. So the process of homogenisation was introduced.
Homogenisation is the process of forcing milk at high velocity and under high pressure through a very small hole, 0.1 millimetres in diameter. This causes each fat globule to break into lots of little fat globules. These small globules stay suspended in the milk and do not rise to the top.
The advent of homogenisation is the point when we really started to get quite invasive with our milk and started modifying its constituents. But the next invention goes another step further.
The invention of ultra-filtration uses membrane filters and enables factories to separate milk components down to the molecular and ionic levels. This is where the term “permeate” comes form.
The permeate is what passes through the filter and is basically white water. The retentate is what is retained and does not pass through the filter. The retentate is the valuable bit and contains all the solids including fat, protein, etc.
In the past, standardisation was the process explained earlier using a cream separator and adding back the cream into skim milk.
Today, standardisation means the milk is deconstructed down to the molecular level. Some retentate (fat, protein and solids) is added back to the permeate (white water). This allows factories to standardise both the fat and the protein.
The levels of protein and fat are regulated in the NZ/AU Food Standards. Whole milk must have at least 3.2 per cent fat and 3.0 per cent protein. If you look at your milk bottle, you’ll find your milk has exactly those minimum percentages.
But as we know cows actually produce on average 3.7 per cent fat and 3.5 per cent protein.
Ultra-filtration allows dairy businesses to pocket the value of the 0.5 per cent fat and 0.5 per cent protein which is not included in your bottle of milk.
Faced with unhappy baristas with overly creamy, non-stretchy and unfrothy milk, I had to find a way to keep our fat content consistent. I certainly didn’t have the money to add a cream separator to our little factory.
During one milking, the ghost of Ernest Rutherford appeared to me and uttered the words, “Glen, you don’t have the money, so you have to think”.
At that moment, the process of in-paddock standardisation came to me. I’d like to think this innovation is as profound as splitting the atom but it’s simply just the way we did things 30 years ago.
We use a small herd of Jersey-Friesian cross cows so we don’t get big fluctuations in fat and protein percentages. We feed them just grass and the cows calve 365 days a year. The result is an even distribution of cows at different lactation stages, which results in a very consistent fat and protein content without all the modern machines.
To me, the best technological progress will enable us to go back in time, to the way milk and dairy was 30 years ago.