A fresh future for flat old beer
Last Updated: 12:01am BST 10/04/2007
Researchers have discovered an extraordinary potential for vintage ales. Science Editor Roger Highfield reports
A century and a half ago, their dark-brown contents would have tasted something like a barley wine. Today, however, they have changed beyond recognition, entrancing beer lovers and biotechnologists alike.
A stash of ancient beer was recently found in a vault under the streets of Burton upon Trent. The bottles were cool and still had corks and wax seals in place. "It was always rumoured that there were some vintage beers on site, but uncovering such an interesting collection is fantastic," says Steve Wellington, head brewer of Worthington White Shield, of the find.
The collection included strong commemorative ales brewed to celebrate royal marriages, visits and births. The oldest was Ratcliff Ale, created to mark the birth of a son into the Ratcliff brewing family. The beer was brewed in 1869, when Neville Chamberlain, future prime minister, was born and Charles Dickens was embarking on one of his last literary tours.
A tasting of the brews was held in London for the Guild of Beer Writers. Wellington had feared the old ales would be dreadful, but he was in for a surprise. "Contrary to a widely held belief that beer cannot age for as long as wine, most of the bottles seem to have developed subtlety over the years," he says. Although complex, they did not taste like a modern beer. They were flat, alcoholic and more like port, madeira or, in the case of his favourite - Ratcliff Ale - like a sherry.
At the tasting, wine expert Oz Clarke called the Ratcliff Ale "astonishing" and waxed lyrical about the taste of beef tea, reduced fish bouillon, jams, smoky charcoal and old leather wrapped in liquorice.
"The flavours are fantastically intense," he said. A few more bottles of the old beers are to be sacrificed later this month in another tasting at Waterstone's Piccadilly.
Today, these bottles are providing scientists with an intriguing glimpse of the complex chemistry of fermentation, a form of biotechnology that dates back thousands of years. They are fascinating because beers were never intended to last this long. Modern cask ales have a shelf life of a few weeks, where the brewer's maxim is "fresh is best".
This reflects the origins of this drink. Beer drinking, like tea drinking, first evolved as a way to slake a thirst and avoid disease: fermentation, like boiling, is a great way to kill the bugs in water. But as safe supplies of water developed, so did a taste for higher-alcohol beers, rather than the thirst-quenching, low-alcohol variety. And that change is the secret of the longevity.
"It has always been known that beers with higher alcohol levels normally age for far longer than less alcoholic beers," says George Philliskirk, of the Beer Academy, "and, as hops are a preservative, highly hopped beers such as India Pale Ales have long been known to have great ageing potential. The discovery of these bottles is remarkable, especially as the oldest beer dates back to 1869 and tastes so fresh, with attractive ripe-plum and honey flavours."
While wine makers refer to ageing as maturing, brewers refer to the same process as "staling" (as in going stale). Both are united by elaborate chemical changes. The characteristic flavour and aroma of a beer depends, in part, on raw materials, such as malt, hops and the yeast strain used to effect fermentation, the all-important conversion of sugar from the malted grain into alcohol, according to Dr Chris Bolton of Coors. Burton upon Trent, where the Ratcliff Ale was brewed, can also draw on Trent Valley springs that provide water rich in natural salts such as gypsum and magnesium that enhance flavour and maximise both malt and hop character in beers. For these beers, the hops were boiled in copper cauldrons, fired with coal, creating hot spots along with caramel flavours and brown colours.
Cask ales are only fermented once and with one yeast. But bottled beer, like these ancient ales, is fermented a second time, says Prof Katherine Smart, a Nottingham University expert in yeast fermentation. "It is not unlike what happens in the maturation of wines and Champagne," says Prof Smart, who is continuing a great tradition of women master brewers that goes back millennia.
The secondary fermentation takes place for longer than in cask beers. It may employ the same yeast as primary fermentation, thought to be the case here, or a different strain can be used to expand the palette of flavours. The yeast will carry on working for weeks, exhausting the fermentable sugars and dissolved oxygen. When the food runs out, the yeast cells draw on their reserves and turn off metabolic processes that are not strictly necessary for survival, becoming the sediment at the bottom. Finally, cellular structural components are degraded before the yeast cells die and their contents spill into the beer. The passage of yeast metabolites and cellular breakdown products in beer introduces another set of molecules which then participate in further chemical reactions, either between themselves and/or with other beer components.
The effects of this chemistry on flavour can be far-reaching. Research suggests that the breakdown of genetic materials might be implicated as "moreishness". Prof Charlie Bamforth of the University of California Davis, adds that he suspects chemical changes that give a more rounded flavour include "acetal reactions between alcohols and aldehydes".
The use of dark-brown bottles to store the beers cut the likelihood of light driving chemical reactions, while the sealed tops helped to stop oxygen from entering. But the stash of old bottles takes beer science into unknown territory, not least as oxygen always seeps in over the years.
Traditional barley wine flavours include liquorice, mouthwarming alcohol and an underlying sweetness balanced by tangy hops. But after a century, the extraordinarily chemistry within these bottles exerts a kind of magic, highlighting the decayed wood, dried fruits, molasses and other warts in their original flavour. In order to preserve these beers for years to come, Wellington and his team have embarked on a programme to recork them. Paul Hegarty of Coors Brewers, which owns White Shield, says that they now plan to lay down two pallets (about 2,000 bottles) of the beer every year to see how it ages. This marks a new dawn in boozing: the vintage beer.