Science Interviews


Sun, 7th Oct 2007

The Secrets of Beer

Professor Charlie Bamforth, University of California, Davis

Listen Now    Download as mp3 Part 1,2 from the show Brewing and Alcohol

Chris -   Now, there must be thousands of beers available worldwide and of course, beer sales are very big business. How do we actually make beer and why do we taste the tastes in beer that we taste? Well joining us to help out is Professor Charlie Bamforth. He is from the University of California at Davis, but heís also a professor of beer and brewing. Charlie, are you really Professor of Beer and Brewing?Beer

Charlie -   Yes, itís a hard life but somebody has to do it.

Chris -   I was going to say, can I have your job if you donít want it?

Charlie -   No, I think Iíve got the best job in the world.

Chris -   Haha. What does that actually involve?

Charlie -   Well basically, what I do is outreach, research and teaching.  I teach people all about the science and technology of brewing beer and we have a pilot brewery here and people can actually learn how to design and create their own beers.  I have a very active research programme.  I also have an outreach role, teaching people in California and beyond what a wonderful drink beer really is.

Chris -   I suppose you must have a queue of students outside your door, wanting to join your course.  When we actually talk about making beer whatís actually involved in the process?

Charlie -   Well, it starts in the barley fields, where youíre producing really good quality malting barley.  Then the malting barley has to be germinated in a very controlled way to soften it and to develop the enzymes that will break down the starch.  Then the malt (the germinated barley) that is produced is dried and kilned for colour and flavour.  That then goes to the brew house and is ground up and extracted with hot water.  The starch degrading enzymes, the amylases, break down the starches into sugars.  Then the liquid which is produced or extracted is boiled with hops to extract bitterness and aroma.  This is then cooled and the pitched with yeast (Saccharomyces).  And the yeast, of course, produces alcohol and some other flavours as well.  Then thereís a sort of cleaning-up process: some filtration, some stabilisation and itís packaged.

Chris -   So why is some beer flat and other beers are quite fizzy?

Charlie -   Well, yeast produces alcohol and carbon dioxide in the classic fermentation process.  It doesnít produce all the CO2 that you would want in a fairly highly carbonated beer.  For some beers some more CO2 is introduced but for other beers itís allowed to drift away.  A classic cask ale from England is fairly low in carbonation, perhaps 1.1 volume or 1.2 volume Ė something like that.  Some of the wheat beers in Germany are very highly carbonated, theyíve got three times more CO2 than liquid.

Chris -   Iíve got an email here from Gregory Staradub.  Heís on the East Coast at MIT. He says, "I sometimes brew my own beer.  When I open a bottle of beer that Iíve brewed, sometimes it behaves nicely and fizzes up all over the place but this doesnít seem to be correlated with how long the beer has spent in the bottle.  Since I reuse the bottles Iím wondering, therefore, if some bacteria have got into the beer and they keep fermenting it in the bottle.  Does this theory make sense and what other explanations might there be?"

Charlie -   Well, thereís all sorts of potential problems with brewing beer yourself.  The key secret to brewing good beer is hygiene, hygiene, hygiene.  Itís always possible that thereís residual sugar thatís not been fermented properly in the fermenter, thatís left behind in the bottle.  Sometimes they may be leakers and the CO2 may come out of the cap.  There are all sorts of possible explanations.

Chris -   And Alexis Waldo says, "what makes Guinnessģ or stout so dark, thick and foamy and so good compared to the lighter, clear beers that you get elsewhere and places like the US?"

Charlie -   Well, there are many excellent beers, some of them very light, some of them very dark.  The colour of Guinnessģ is due to roasted cereal, roasted barley.  They have a very intense heating process.  The sugars and the amino acids and the grains are cooked together to give very, very dark colours.  They give very roasted flavours.  The foam: one of the main reasons why Guinnessģ foams so well is, apart from CO2 producing foam, they use nitrogen gas to give it extremely stable foams.  The bubbles contain nitrogen gas and this is much more stable than CO2. Guinnessģ pioneered that technology.

Chris -   Now, Iíll let you off if you havenít got a clue about this one because, quite frankly, I was shocked!  This is from Kay and she says, "My daughter recently went on a school trip and she was told that in Tudor times, if beers were poured with no head on them then they would put dead mice in the beer!  Can you explain what this would achieve and why?"

Charlie -   Iíve never heard that one!  Thereís all sorts of crazy mythologies and truisms that people have handed down the ages.  Possibly one of the things with mice is that some beer can get contaminated with Brettanomyces and Brett classically has a barnyard type, sometimes called a Ďmouse urineí, type of flavour.  Maybe somethingís got lost in the telling.

Kat -   Urrghh.  So youíre down the pub and you just put a bit of mouse wee in you pint.  Anyway, we hear so many messages like alcohol is really bad for you and gives you cancer and gives you heart disease but in moderation are there actually health benefits to drinking beer?

Charlie -   Yeah, there are.  The red wine guys have made a bigger thing about this but itís just the same.  The truth is the same for beer.  One or two beers a day could stem the risk of atherosclerosis.   Itís been shown extensively, so itís actually good for you.  Beer also is a rich source of silicon.  Thereís a guy over there in the UK whoís done a lot of work on beer countering things like osteoporosis.  Beer is a significant source of several B-vitamins and antioxidants.  Beer in moderation, I stress the moderation, is a good component of a diet.

Kat -   Is the effect on atherosclerosis just from the alcohol content then?

Charlie -   The alcohol: many people now believe the alcohol is the key ingredient in cutting down the risk of atherosclerosis.  Itís not some fancy antioxidant.  People talk about resveratrol in red wine but youíd have to have a phenomenal number of bottles a day to get the amount needed.

Kat -   Excellent, Iím absolutely gasping for a pint!  Thank you very much, thatís Professor Charlie Bamforth whoís Professor of Beer and Brewing at UC Davis.

Chris -   The job that we would all kill for.


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