CHEMISTS at the US Department of Agriculture in Washington DC have determined the structure of casein, a protein in milk. The team used two techniques, small-angle X-ray scattering and nuclear magnetic resonance, to analyse the molecule. 'We found that casein is truly unique,' says Helmut Pessen, one of the team. 'Its molecular structure is very loose, and it contains at least 10 times as much water as any other protein.'
Molecules of casein join together in spherical units, or micelles (above). The biggest micelles are one-tenth of a micrometre across. A single micelle is shown (inset); the bar represents 30 nanometres.
The characteristics of casein make it impossible to crystallise, so the researchers were unable to use X-ray crystallography, the technique normally used to analyse proteins. The team hopes that food scientists will be able to exploit the new knowledge to improve cheese-making.
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