It’s a drink that’s been with us for millennia. But how has science shaped today’s pints? Chris Baraniuk discovers a world of secret yeasts, strange brews and ‘glass widgets’.

Venture through a dank railway tunnel, then turn on to a small industrial estate in south east London and you’ll find yourself at a fine example of a British brewery. But there are no rambling roses or tumble-down ancient buildings crying of English tradition here. The Kernel brewery is little more than five years old and the beer produced in this urban hideaway combines old traditions with new thinking – and a little experimentation.

“We rely on that process of hypothesis, experiment and result,” says brewer Toby Munn. “We can create our own little experiment and do all kinds of different things, which is fun.”

Munn shows off the fermentation tanks, where yeast gradually turns sugars into alcohol over several days, and a room full of barrels and large French “fouders”, which were previously used in wine-making.

There is also a lab, not much bigger than a walk-in wardrobe, but its size does no justice to its significance. A microscope takes pride of place, but nearby are other instruments for measuring the density of liquids and a curious looking contraption for acceleration of the fermentation process by the gentle heating of beer.

Making beer is sometimes seen as something of an art, but once you get to larger scales, science is vital. Whether you’re an up-and-coming outfit like Munn’s or a multinational brand like Guinness or Budweiser, the key to succeeding as a brewery is shrewd scientific analysis of your product and some clever chemistry.

Repeat trick

For starters, a lot of thought goes into making beer taste the same worldwide, especially among multi-national brands. The yeast, for example, must be consistent, says Chris Giles, owner of Surebrew, a firm which provides chemical analysis and yeast storing services for breweries. “You can freeze that culture down and preserve it as a snapshot of what they want. Then we supply back every three to six months so they can brew beer in the same style with the same flavour profile.”

Guinness, for example, stores its yeast strain in liquid nitrogen vapour – at an undisclosed location.

Gearoid Cahill, a Guinness brewer, says that the firm takes many things into account to make the beer taste consistent. The water used in the production for Guinness is tested for levels of calcium as too much or too little can inhibit the enzymes that turn the malt’s starch into sugars. (Malt is simply cereal grain, which is germinated in water but stopped from further germination by being dried in hot air. The sugars that come out of the malt are what the yeast is able to turn into alcohol, among other substances, during fermentation.)

Then there’s the distribution. Guinness is characterised by the beer’s texture and the famous white, creamy head that forms at the top of a pint. This is achieved by nitrogen bubbles which are forced into the beer via pressurised taps in pubs. After pouring, the nitrogen comes out of solution again, just like carbon dioxide does in sparkling water for example. But it’s at this point that the specific properties of nitrogen are capitalised on.

“Because it’s not very soluble, when it comes back out the bubbles don’t grow at all, they initiate to a very small size,” says Cahill. And that explains the smooth, creamy texture in contrast to the frothy foam that crowns a pint of lager.

The company also says it takes responsibility for the cleaning of Guinness lines and taps in Irish pubs, which is perhaps why some people say the stout tastes better there than anywhere else.

More innovative, perhaps, is how the beer’s texture is achieved when no special tap can be used. Cans of Guinness and a number of other brands have a “widget”, which is simply a ball with a small bit of beer inside. When the can is opened, the contents depressurise which forces the widget’s payload out through a pinhole.

“It’s like a bullet of Guinness passing through Guinness, if that makes sense,” says Cahill. “And that physical disruption to the beer actually triggers the nitrogen to come out of solution and form this swarm of bubbles. They will then rise very slowly to the top.”

For similar reasons, some glasses in pubs made by lager brands such as Fosters now feature laser-etched concentric shapes on their base to aid the production of carbon dioxide bubbles that rise to form a head. The circles encourage the gas to nucleate at one point in the liquid, meaning bubbles are more likely to form.

This isn’t all just for show, either. The precise level of carbon dioxide or nitrogen dissolved in beer can have a dramatic impact on its taste, according to Joanne Hort at the University of Nottingham’s research microbrewery.

“An increase in carbonation can cause a decrease in sweetness,” she explains. “So the same two beers with the same amount of sweetness can be perceived quite differently by the consumer if they have different levels of carbonation.”

The bottle in which a beer is stored can also make a difference, and beer companies have had to innovate to make sure it doesn’t affect taste. Ever drunk beer out of a clear glass bottle? You’ll have been able to do so because of the cultivation of “light-stable hops”. Beer is most often sold in brown or green glass bottles, which protect the liquid from light exposure that can damage flavour.

Full experimentation

Having said all that, some smaller brewers still pride themselves on the unpredictability of their manufacturing process, because it promises to reveal whole new tastes. Munn says he is a self-confessed fan of the Belgian “Lambic” beers, which come from Pajottenland near Brussels. These are made by taking the wort (the sugary liquid that turns into beer after fermentation) and leaving it overnight in large dishes, where it gathers yeast and bacteria from the air.

“They call it spontaneous fermentation,” explains Munn. “There’s something quite romantic about how they do it, it’s very much in touch with where they are.”

Knowing that yeast is ubiquitous and that there are thousands of strains, others have taken to novel approaches for harvesting wild yeast from the environment. A US company called Rogue Ales brews one of its beers using yeast cultivated from the beard of the chief brewer.

And a London-based brewer, James Rylance, says he has lately been trying to gather wild yeast from orchards and caves. Who knows, perhaps one of these strains will make the perfect beer?

“It’s only in the past few hundred years we’ve had a good understanding of bacteria and yeast,” notes Rylance. “The old word for yeast was literally ‘God is good.’ And that was all very linked up with mysticism and mythology. These practices were originally developed through trial and error.”

Perhaps the most talked about yeast of the moment is a strain called brettanomyces. It’s been present in brewing cultures for centuries, but has recently been popularised as a primary strain for beer-making by young brewers like Colorado-based Chad Yakobson. Yakobson is one of a handful of brewers attempting to popularise “sour beers”, which are made with brettanomyces.

The yeast delivers a beer which can be less susceptible to contamination or oxidisation and has a characterful, slightly sour flavour that sometimes pairs particularly well with certain foods, for instance cheese or saltier dishes. Unlike many beers, its quality can improve drastically with age, which is why breweries like The Kernel are buying up old wine barrels to play with.

“Some of these beers are like wine and have the ability to age 10 or 20 years. They just keep getting better,” says Yakobson.

Still, all this creativity and spontaneity must be balanced with careful methodology and rigour, says Chris Giles. The joy of brewing is discovering a great beer, but the secret is in knowing how to produce it consistently time and time again. It’s an endeavour on which larger breweries have spent millions, and one that every smaller outfit aspires to. But if anything, science has helped level the playing field for those who want to take their first steps.

“Brewing is an art,” says Giles summing it all up, “but there’s a hell of a lot of science behind it these days.”

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