Beer production in ferment: John Shepherd reports on the appliance of science by brewers

A SENSITIVE thumb was once the most important tool in any head brewer's kitbag, but today's producers of ales and lagers need to be equipped with a good understanding of physics and chemistry to keep pace with the industry's technological advances.

The chemical composition of beer has been known for a very long time - recipes for medicines dissolved in beer have turned up on 4,000-year-old Sumerian tablets.

But there have been big innovations in production techniques this century, starting in the 1930s with keg beer. By pasturising the product to kill off the yeast, brewers were able to increase its shelf life significantly.

Barrels of real ale, or 'living' beers, have a life of a few days once the barrels are tapped, and in any case start to deteriorate about 40 days after they are brewed.

Keg beers, however, can still be used for up to nine months after production. Watney's, which eventually gave us Red Barrel, invented keg beer and soon discovered the export potential for long-life beers.

The brewers also tinkered in the 1930s with the idea of putting beer into cans. The first recorded beer in a tin was made by the Felinfoel Brewery in Llanelli, Wales. It had a screw top, much like the ones found today on tins of metal polish.

But it is really only in the past 30 years that brewers have harnessed 20th century scientific breakthroughs. These have improved farming yields for barley and led to the pioneering gas-filled widget which delivers beer from a can with that just-served-by-the-landlord taste.

Brewers were placed on a steep learning curve when British drinkers acquired a liking for lager. The modern methods cultivated on the Continent for producing lager forced a radical rethink.

Until then, the UK industry had ambled along with tried and trusted formulae handed down through the centuries. Lager overhauled the working practices of head brewers, who acquired the skill to judge the temperature in fermenting tanks simply by dipping their thumbs in the liquid.

Brian de la Salle, supply and operations director for the Whitbread Beer company, said: 'Lager brought about a big change in the '60s. It particularly made us look at big-volume output of beer.'

It was the difference in fermentation processes for lagers and ales that captured the brewers' minds. Ales were fermented in long oblong tanks, whereas yeasts used in lagers went about their business at the bottom of upright conical vessels.

Brewing capacity took on a new meaning. Ales were, and still are to a large extent, produced in small batches to ensure consistent flavour, but lagers can be produced in much bigger quantities.

Conical tanks also give the brewer better temperature control - an important aspect in a business dependent on fussy yeasts that will only perform their duty of converting starch into alcohol under the right conditions.

Lager also involves a high- gravity brewing process and is therefore a more dilutive product - 1,000 barrels from the fermenting tanks can be turned into 1,300.

There was no holding the brewers. Revelling in a period of rising beer consumption, they burst into the 1970s with big tin cans in the shape of Party Four's and Party Seven's - each name reflecting the amount of pints.

But because beers were assuming the taste of a tin, many take-home drinkers stayed loyal to bottled products for longer than the brewers had bargained for. Once it was discovered that the problem could be solved by lining tins with a high-quality food resin, the six-pack took off.

The breakthrough also opened the door to automated high-speed packaging lines, not only for tins but for barrels of beer which, after all, are just large tins. Output per man has increased over the past 10 years from 2,500 barrels to 4,000.

There were more production efficiencies to go for, however, and the brewers pushed the tin manufacturers for innovations that would reduce unit costs.

To begin with, the makers reduced the price of a can by using less material. Ideas for saving on the use of materials are still being developed today; the two-piece can with a steel body and an aluminium lid is rapidly being replaced with an all-aluminium one.

And more and more tinned beers now come complete with one of two types of widget, otherwise known as the draught-flow system that makes a beer look and taste like a pint pulled in a pub.

Both types of widget work on pressure when the can is opened. One releases nitrogen, and the other simply releases a pressurised jet of the same beer in the rest of the can. Both have the same softening effect on the beer, achieved by the displacement of some of the carbon dioxide.

It took Whitbread two years to develop its widget, but the cost of the in-house research and expenditure has been more than rewarded. The Boddington's beer brand, which it only bought in 1988, is now a top-selling bitter.

Away from the brewhouses, which have now taken on that computer-controlled clinical look, the industry has been a big gainer down on the farm.

Pesticides and fertilisers have of course improved crop yields, but more recent breakthroughs have also improved barley strains.

The barley seed performs the first stage of the breakdown of starch by producing amylase, an enzyme. Brewers hoodwink the seeds into thinking it is summer, and then stop the germination process by boiling the seeds.

After filtering, the brewer is left with the wort, to which is added hops to add flavour and act as a preservative. After this stage, the yeast can do its duty and break down the sugar.

Messing about with the genetic chemistry of yeasts is likely to become common practice in the industry.

Yeasts have numerous different properties, reacting differently at different temperatures and according to where they are placed in fermentation tanks. Yeasts used for lager work at the bottom of the tank, whereas the ones used for ales work best on the surface.

But improvement in the working power of yeasts would be a boon for the brewers. If they could be developed to carry out the full process of breaking down starch - known as saccharification - then the brewers would not have to add costly enzymes to help the ones produced by the barley.

(Photographs omitted)