Making the perfect coffee only uses two procedures:
Before we look at foaming milk, let’s first look at the importance of fresh milk.
Here we will talk about cow’s milk, and later we’ll look at milk alternatives.
What are the main components of cow’s milk? Sugars, fats and proteins – making milk one of the most complex and complete foods there is. However, milk will have different characteristics at different times of the year, and the composition will vary slightly from breed to breed. Should your milk supply come solely from a local farm, you may find some times of the year when its foaming abilities alter, whereas when buying bulk processed milk, these changes in characteristics are minimised.
The milk sugar lactose is made of two sugars; glucose and galactose. The level of lactose usually is around 5%.
Lactose is minimally affected by ageing.
Full fat 4% (often blue top in UK), semi skimmed 2% (often green top in UK) and skimmed 0.1-0.3% (often red top in UK).
Milk also contains cholesterol; this is generally located in the cores of the fat globules around 24mg.
Fat is minimally affected by ageing.
The milk proteins are the agents used for foaming.
Protein is the main factor determining the quality and stability of the foam. The concentration of beta-lactoglobulin (the predominant whey globular protein found in bovine milk) varies throughout the year. It depends on the cow’s lactation cycle, related hormone changes, and the growing season.
The protein levels in the grass-fed cows are a significant factor in the protein levels of the milk produced and hence the quality of your froth.
The periods of low protein production by the cow are those of early lactation (February to April) and late lactation (September to December). These are months when the milk will not give such good quality froth, but which could be improved with correct feeding.
Storing milk at 4˚C and lower will give it up to 10 days shelf life. Check the date on the container.
You may well remember driving along a country road and being held up by a farmer moving his herd from the field to the milking parlour. All around the country, this is happening, usually twice a day. After the cows have been milked, the farm will await the arrival of the milk tanker to remove their produce. These, often smaller lorries, will meet up with large tankers that will take all the milk in bulk to a central processing plant. Super herds often have more than 1000 cows, and the cows are trained to milk themselves. The cow wears a collar with a chip in it. It walks to the milking parlour as it becomes uncomfortable with the amount of milk it’s carrying and starts to eat the food in the trough.
Meanwhile, a robot sprays the udders with disinfectant and attaches the milking machine to the teats. When the milk flow slows, the milking device automatically releases, disinfects again, and the cow returns to the field. This process takes around three days to train the cow, putting milk production in one cow up by as much as 40%. The milk will be pasteurised and sent to the bottling plant, refrigerated and transported to supermarkets. Cutting the time of distribution by up to 2 days gives your milk at least an 8-10 day shelf life.
This process is a relatively mild heat treatment and has a minimal effect on milk’s flavour and nutritional value.
The HTST (high-temperature short time) method is the most popular method in the UK and the milk must not reach less than 71.7°C for 15 seconds before cooling to below 10°C.
What makes filtered milk different to other pasteurised milk?
Following the pasteurisation process, milk is finely filtered (usually through ceramic filters) to make it purer and because this removes more of the bacteria that turn milk sour, it lasts a lot longer too.
The prolonged life of sterilised milk is obtained at the expense of flavour changes due to the caramelisation of lactose and a loss in nutritional value (approx 50% vitamin loss). A continuous flow method is used and the milk is pressurised in a heat exchanger at a temperature of around 108°C, which is used for cartons.
This process involves heating the milk to a very high temperature for a short time, normally 132°C for one second.
This is where milk is heated to 71.7°C and forced through minute valves, breaking up fat globules and ensuring their uniform distribution. This gives a creamier taste to the milk and aids digestion.
Protein levels in milk alternatives
Goat’s 3-4%
Soya 3-4%
Almond 2%
Oat 2%
Coconut <1%
Hazelnut <1%
Rice <1%
Protein is the component needed for foaming, not fat or sugar.
Bacteria consume protein during milk’s shelf life. Therefore, the longer the remaining shelf life, the better-quality foam you will produce.
Fat will add to the quality of the drink in both mouthfeel and taste.
So, the next time the milk doesn’t appear to be foaming too well, check its shelf life, not the top’s colour.
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