A comparison of milks from humans, cows, sheep and goats reveal a near perfect food specific to each species. Over countless generations, humans have successfully exploited the secretions of mammary glands to feed both the poorest communities and raise the nutritional profile for the more fortunate.
A Quick History
Early hunter-gatherers eventually realised there was more to animals than just meat and skin, but milk was an unstable food commodity, unless it was quickly processed and stored. With butter and cheeses hitting primitive menus, the range of transportable goods increased and trade between communities was suddenly enriched. The advent of hygienic milk production and selective breeding ensured the development of the dairy industry in recent times, although the ravages of bovine tuberculosis had to be overcome first. During the Depression in the 1930s, and following the Second World War, the emphasis on fresh milk as an essential food, particularly for children, significantly improved the quality of the UK diet for decades. The memory of that daily third of a pint distributed during school break may have faded, but this is the average amount we now consume on a daily basis in the UK. (1)
Nutritional Analysis of Milk
Cow's milk contains nearly all the constituents of the perfect food, with only a few nutrients in short supply. These include modest and variable amounts of iron, vitamin C and vitamin D. Untreated cow's milk contains the most vitamin C, but subsequent pasteurisation removes the bulk of this. Summer milk will contain more iron and vitamin D compared to winter milk. Most animal products carry little in the way of carbohydrates, but milk contains a large proportion of carbohydrate in the form of lactose. This sugar is not as sweet as sucrose, but provides useful extra energy, easily absorbed by the human gut. Reduced fat milk is a relatively recent innovation, produced in response to increasing awareness of dietary guidelines for fat intake (2). Unfortunately, this has led to reduced milk consumption for some people, and it is vital that essential calories, calcium and riboflavin intake in children is not compromised by well-intentioned public health programmes.
The contribution of milk to the nutritional needs of adults is significant, with 10% of our energy needs, 16% of our protein and 14% of our fat requirements coming from dairy products (2). We also collect around 24% of our saturated fat this way too...so it's not all good news.
The amount of fat in one pint of full cream milk is 23g, compared to 10g in semi-skimmed and 1.2g in skimmed varieties, with the result that fat-soluble vitamins (A, D and E) are correspondingly reduced as fat content decreases. In contrast, the proportion of water soluble vitamins (B and C) and minerals rises as the fat content diminishes, so skimmed milks contain more calcium, drop for drop than full cream milk.
All this changes when we process the milk, which does not keep fresh for long - owing to the large numbers of naturally occurring Lactobacillus bacteria present. At room temperature, these will cause the milk to go sour within a few days, so early man had to find a solution.
How to Increase the Shelf Life of Milk
Back in Medieval Times, they had no fridges or freezers, so how might one extend the life of a daily pint? Here are a few empirical suggestions based on simple food science:
- If you leave milk around too long, it goes sour, as the Lactobacilli produce more waste products in the way of lactic acid. Here lies the basis of yoghurt production, first exploited centuries ago in South East Asia and Turkey. "Modern" yoghurts are but a pale comparison these days, with large amounts of added sugar and fruit disguising the distinctive "bite" of soured milk.
- Try shaking it up and then churning it to break down the tiny fat droplets - this produces butter when the fat re-forms into a solid workable mass.
- You could leave it separate out and claim the fat on the top layer, which can be sold as single cream or double cream with 18% and 48% fat respectively. Modern UHT treatment ensures a longer shelf life.
- Clotted cream is very naughty with a mighty 60% fat content. All you have to do is first scald the milk in a pan to separate the fat more efficiently .
- If you coagulate the protein in milk using rennet, you have the basis of a cheese, better left to ferment in its own time, and well worth the wait. The protein in milk is casein, which traps unusually high concentrations of calcium in such a way it does not precipitate out within the milk.
- Casein also has a non-culinary use, in the manufacture of plastics, including knitting needles!
Choose Your Cow Carefully
Not all cows are equal. The cream content of the milk from Channel Island cows, along with those in South Devon, leaves the rest standing, or possibly lying down. These efficient herbivores convert the meagre nutrients in grass into milk containing 27% fat, which is 4% up on normal full cream milk, but it does not stop there. What about making some Jersey Clotted Cream?
References:
- Food Standards Agency (2008). Manual of Nutrition. London TSO.
- Fox B. & Cameron A. (1995) Food Science, Nutrition and Health. Arnold.
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