By Penny Carmichael, on 14 October 2013
- Article by Jack Humphrey
Following last year’s successful talk the CPS have again decided to dedicate a night to the science of beer. I do hope it becomes an annual event. Not only is the brewing process highly scientific it also gives the Society a chance to sample lots of different beers graciously donated by the Fuller’s brewery. Also donated by the brewery was their brewing manager Derek Prentice. Derek has 40 years of experience in the brewing industry and he spoke warmly and enthusiastically about the science of brewing. He focused on the contribution of the ingredients to the flavour of the finished product.
As it makes up over 90% of the beer, the mineral content of the water used has a strong effect on taste. The mild flavour of calcium is generally preferred by brewers whereas carbonate ions aren’t. However, carbonate is better tolerated by darker beer styles which explains the popularity of these beers in the chalky basin cities of London and Dublin. An acidic pH is also preferred for optimal keeping properties. Derek explained that when relocating a brewery the water is very carefully analysed in order to reproduce the same taste with different water supplies.
Barley gives beer it’s claim to be “liquid bread” and is the most popular grain used in brewing. Barleycorn is the seed of the barley grass and contains all the nutrients needed for the plant to grow. The process of malting recreates the germination process by soaking the barleycorn in water. This encourages the natural enzymes to break the starches down into sugars and the proteins down into amino acids. This process is then halted by kiln drying. The temperature of the drying affects the flavour of the malt. Pale malts used for bitters and pale ales and lagers are dried at low temperatures to retain the enzymes for the later brewing process. This kind of malt has a neutral flavour and is used as the “base malt”. Darker colours and richer flavours can be obtained with higher temperature drying, creating dark or chocolate malts which can be mixed with pale malt.
A weed closely related to the cannabis plant, Hops are a relatively recent addition to the beer recipe. The sweetness of the malted grain was traditionally balanced by a mixture of herbs and plants called gruit. It was only when it was noticed that hops-flavoured beer spoiled less frequently than the gruit beer that hops caught on. As well as antimicrobial effects, Hops also gives beer its characteristic bitterness and improves foam.
For brewers, yeast is the biochemical powerhouse that performs the much needed conversion of sugars into ethanol. The strain of yeast used is important for the flavour and style of beer. The classic brewer’s yeast Saccharomyces cerevisiae is a top-fermenting yeast that is so called because it forms a form at the top of the brewing liquor and produces sweet fruity. Lager yeasts such as Saccharomyces Pastorianus create drier tasting beers as they are able to ferment the more complex trisaccharide sugars.
The goal of the brewing process is to create alcohol from sugar using yeast. To further break down the starch and proteins the malt is milled into small particles called grist. The grist is then mixed with warm water to activate those retained enzymes. This porridge-like material is then boiled to sterilise it before the yeast is added. The volatile aromatic compounds from the hops are driven off at this point so are replaced later. Any other ingredients such as honey for honey beers can be added at this point.
Following Derek’s talk was a tasting session of seven different beers, including two “vintage” beers that had been aged before bottling. There was an enthusiastic response to all of them (although one of the younger vintages at 8.5% was undrinkable in this author’s opinion) and it was apparent just how varied beer can be. A highly entertaining talk. Bring on next year!
This talk was given in memorial of Catherine Side 1954 – 2012, who held an MSc in Brewing and gave the talk last year.