Everyday Chemistry from A to Z

All life is chemistry: B for Butter

Donauchem

B for butter

Nowadays, butter is made from pasteurised cream. In a centrifuge, the milk is skimmed in a few seconds. Due to the density of the different components of the milk, they separate: skimmed milk and cream remain. It takes more than 20 litres of milk to make one kilogram of butter.

The cream is then briefly and gently heated to about 85°C (= pasteurised), cooled and then stored for between seven and 20 hours to mature. This process inactivates germs and enzymes and thus prevents the formation of undesirable flavours. Depending on the type of butter, lactic acid bacteria are added. The cream is then whipped in butter-making machines and the butter is separated from the buttermilk. Subsequent kneading makes the mass smooth and fresher tasting. It can then be shaped in moulding machines and finally packaged for sale.

There are different types of butter:

  • Sour cream butter
  • Sweet cream butter
  • Milk-soured butter
  • Salted butter

as well as various types with reduced fat content:

  • Three-quarter-fat butter
  • half-fat butter and
  • Milk fat with X %.

The chemistry of milk fat Milk fat consists of triglycerides, each of which is made up of a glycerol molecule as the basic building block and three attached fatty acids (ester bond). The fatty acids are carboxylic acids with carbon chains of different lengths and mobility. They determine the properties of the fat molecule. The special feature of milk fat is that it contains more than 400 fatty acids. This broad fatty acid pattern allows countless triple combinations in the fat molecule; milk fat is therefore considered "polymorphic".

From a chemical point of view, the production of butter is a phase reversal: the oil-in-water emulsion "milk" becomes the water-in-oil emulsion "butter". The fat content of the finished butter is at least 82 percent.
The diverse fatty acids of butter melt in the range from -8° to +70° C. That is why butter reveals its flavours depending on the temperature.

The fat is spreadable at room temperature. Of the short-chain fatty acids, it is mainly butanoic or butyric acid (4 C atoms) that is interesting in terms of taste. In fresh butter, it is mostly present in bound form. The few free molecules provide a pleasant freshness. However, if too much butyric acid is released (e.g. incorrect storage), the butter tastes old and rancid. Other free fatty acids and precursors of fatty acids such as aldehydes also contribute to the taste of butter.

Donauchem GmbH
www.donauchem.at

Related Links:
www.chemie-schule.de
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Donauchem

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