Peter Atkins is Professor of Geography at Durham University . His main research interest is in food and drink, with particular reference to their materiality; the stuff in foodstuffs. His work ranges from arsenic poisoning in the groundwater in Bangladesh to a history of milk. His latest book, Liquid Materialities: a History of Milk, Science and the Law was published in 2010.
What is milk? It may sound like a trivial question or an inappropriate one for a serious science blog. Why should we take any interest at all in a substance that is a matter of everyday consumption? Put on the spot, most people would say that milk is a rather dull commodity and something they take for granted. The Spanish have a saying: blanco y en botella, leche. Literally this is if it’s white and in a bottle then it’s milk. However, slipped colloquially into conversation it means it’s obvious. My purpose in this post is to show that a discussion of milk is far from obvious and indeed is something that cannot be left to dairy science alone. We need to look beyond that to understand why milk is as it is today, and ultimately, what’s at stake is the quality of all of the food we consume.
The laboratory-based analysis of milk has its origins in the late eighteenth century. In the 1790s Parmentier and Deyeux were already estimating its constituents with simple experiments. They were followed in the early nineteenth century by other French, Swedish and German scientists. But milk is a complex emulsion of fat globules and water, and a fine dispersion or suspension of casein micelles, so at the time, it was very difficult to know what was in it, given the limited techniques of organic chemistry and physics. It was eventually realised that milk was a highly variable substance; its constituents can vary among mammals and during feeding time. Its principal constituents, fat, protein and sugar, also differ from one breed of dairy cow to another.
So what? you might ask. Well, food in the nineteenth century was frequently adulterated, and milk was the most notorious example because its dense whiteness enabled the addition of small amounts of water without anyone noticing. The average pint in London in the 1870s, for instance, contained about 25% of added water. Consumers were outraged by the unreliable quality. One simple method of analysis used by the milk trade was the lactometer, which measured the specific gravity of milk, but this had to be abandoned when it was realised that, by adding water and removing some of the butterfat, it was possible to simulate the physical properties of genuine milk.
Gravimetric and volumetric chemistry eventually made progress and adulterators were brought to book under a series of Sale of Food and Drugs Acts that started in 1860. The irony was that many innocent farmers were prosecuted before anyone thought to establish a legal definition of the real thing. This came about in 1901 with the Sale of Milk Regulations. In effect, it claimed that science could determine nature’s intentions. Natural cow milk was said to contain 3.0% of butterfat, for instance, and a milk that was more watery than this was presumed to have been fraudulently manipulated.
Problem solved? Well no, because what happened if cattle were fed on very watery grass or silage? The milk they produced would be as it came from the cow, nothing added and nothing taken away. However, it would still be of a low quality, fat-wise. Legal challenges in the early twentieth century proved that almost any milk coming from a healthy cow was acceptable, as long as it was not modified later.
From 1901 to 1976 this whole milk idea remained the British consensus. Elsewhere, on the continent, a completely different approach prevailed. Countries such as the Netherlands had butter industries where it was in their economic interest to regard some extraction of fat as normal. This led to fixed, legal limits of quality, and later to the standardization of the constituents of milk. Britain’s entry into the European Community in the 1970s, meant accepting some legal definitions of foods. From 1981, it was possible for the first time to buy ‘semi-skimmed’ milk. Then, in 1933, milk with a standardized composition had to be allowed with the beginning of the Single milk market. However, it has only been since the Drinking Milk Regulations of 2008, that at last milk could be labelled with various fat levels.
When you next go to the supermarket, have a look at the dairy shelves. You’ll find an astonishing range of milk. In addition to flavoured or filtered or fortified milk, you will find milk with 0.1%, 1%, 2% and 4% fat, and the consumer in England and Wales (but not Scotland) can also choose between raw milk and heated treated milks that have been pasteurized, sterilized or ultra heat treated. There is also homogenized and organic cow’s milk, not to mention goat’s milk and soya milk.
I’m not saying that these new Euro definitions of quality are better or worse, but they are certainly different from the long history of milk in Britain. It is almost as if milk has had its own life story and we can now write its biography. It seems that most milk drinkers are oblivious to this story and are now content that it is technology that defines what is genuine and natural. We no longer feel any obligation for our diet to reflect the foibles and the cycles of nature. We are now sure that we can improve upon nature by producing a substance which has a substantial human imprint. Finally, milk still resists us by turning sour and by persisting in being an ideal medium for the spread of disease, but both of these problems are susceptible to industrial processing.