Page last updated at 10:14 GMT, Tuesday, 4 August 2009 11:14 UK

Molecular trap makes fresher beer

Beer pouring (AP)
The process can be applied to beer, milk and other beverages

A material that could lead to beer with significantly longer shelf life has been designed by researchers.

The approach works by removing riboflavin, or vitamin B2, which causes changes to beer's flavour when exposed to light passing through the bottle.

Scientists at the Technical University of Dortmund designed a polymer "trap" with tiny crevices that capture the riboflavin molecules.

The technique could be applied to other beverages such as milk, they said.

Because such riboflavin-containing beverages tend to be stored in translucent containers, they are more prone to the effects of light on their long-term storage.

In a process called photo-oxidation, ultraviolet light can strip off charged atoms that can go on to degrade other chemicals or proteins in the drink, ultimately affecting its flavour and shortening its shelf life.

Lock and key

Borje Sellergren of the Technical University of Dortmund made use of a technique called molecular imprinting to design a solution to the riboflavin problem.

The process involves chemically designing a riboflavin-shaped cavity into a polymer by moulding it around riboflavin molecules and then removing them.

These polymer cavities are then made in high quantities, selectively trapping riboflavin when dunked into a vat of beer or milk.

The idea mimics biological systems such as antibodies which are targeted in a similar "lock-and-key" way for mopping up bacteria or viruses.

The work was commissioned by Dutch brewery Heineken, but the concept is not just limited to those drinks, Dr Sellergren told BBC News.

"The technology itself is more generic than we've shown here," he said.

"There are a number of examples where this kind of absorbance can be used for the removal of specific unwanted compounds in food - flavours, impurities, pesticides, and spoilage agents as we've shown here."

"The next step is to demonstrate for the brewery industry and food industry that we have this capability now."

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