New Beer Head Technology
In case anyone is interested, this is from New Scientist April 1, 2000:
By Debora MacKenzie
Eat crisps, wear lipstick . . . you won't spoil the look of this beer
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--so long as drinkers are willing to stomach genetically modified beer.
"The basis of foaming in beer is the LTP1 gene," 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.
"Grease is the enemy of foam," 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.
A worse problem for brewers, says Stahl, is that quantities of LTP1 vary widely. "More is made in a dry summer than a wet one," 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's yeast. The yeast secretes so much head-producing protein, he says, that "the beer will make the same amount of foam no matter what the quality of the barley". He plans to brew his first GM beer in the autumn, but says it's not likely to go into production for a few years, given the opposition to GM food in Germany. "But unofficially, the brewers are interested," he says.