BEER looks stale unless it has a decent head on it. But the foam is fragile
stuff: grease from a packet of crisps, or even lipstick, can destroy it. The
head can even be affected by the weather conditions when the barley used to make
the beer was growing. So brewers in Germany decided to work out how to make a
more dependable head鈥攕o long as drinkers are willing to stomach
genetically modified beer.
鈥淭he basis of foaming in beer is the LTP1 gene,鈥� says Ulf Stahl of
the Technical University of Berlin. The protein made by the gene prefers to
dissolve in fat, and hates water. When the sprouted barley is ground up to make
beer, the protein is forced into water. It escapes by forming thin films around
bubbles of carbon dioxide rising through the brew. The coated bubbles accumulate
at the top of the glass to form the foamy head. The more protein, the more
stable the head.
鈥淕rease is the enemy of foam,鈥� says John Hammond of Brewing Research
International in Surrey, because the proteins in the foam dissolve in any
passing fleck of fat rather than staying stretched around the bubbles. This is
why beer glasses must be squeaky clean, he says.
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A worse problem for brewers, says Stahl, is that quantities of LTP1
vary widely. 鈥淢ore is made in a dry summer than a wet one,鈥� he says, so any
given batch of beer may or may not make a good head. So Stahl has put the
LTP1 gene into brewer鈥檚 yeast. The yeast secretes so much head-producing
protein, he says, that 鈥渢he beer will make the same amount of foam no matter
what the quality of the barley鈥�. He plans to brew his first GM beer in the
autumn, but says it鈥檚 not likely to go into production for a few years, given
the opposition to GM food in Germany. 鈥淏ut unofficially, the brewers are
interested,鈥� he says.