Froth! 

The Science of Beer

Mark Denny

2009, HB, 183pp
The Johns Hopkins University Press

£13.50 delivered from Amazon

Reviewed July 2012

Mark Denny is a homebrewer and a physicist. In the Introduction he sets out his stall: “My book is unique to the best of my knowledge, in that it unites brewing with accessible physics.” I imagine that at this point many of you will move along but I rather like the idea. After all pretty much everything is physics, even beer. But if mixing physics with beer isn't for you then it gets worse—there's mathematics too. (I'm not selling this well, am I?). But panic not, the maths can be bypassed—that's what I did most of the time.

Before getting to the science Denny outlines the history of beer and brewing. Maybe he should have stuck to the science. This chapter is riddled with inaccuracies and not-quite-accurate assertions. Did Balling introduce the hydrometer into brewing in 1843? That must have surprised Baverstock you was using one in 1770. Is porter really stronger than stout? Is stout usually dry? Guinness has been so only since the 1950s and London stouts never really were. This chapter is too long and a rather out of place. This is a book about “the science of beer”—get to the science! And I hated the stupid interlude inserted to break the chapter into two.

Next up is How to Make Good Beer at Home. Still no science then. This is a very basic introduction to homebrewing but at the same time idiosyncratic and opinionated. Certainly not for the homebrewing purists. Denny advocates natural cooling of wort, plastic bottles etc. Personally I don't have too much of a problem with that but like the previous chapter this seem a bit out of place in a book about the science of beer. Who is the book aimed at? The general reader? The beginner? Or the more advanced brewer? I would have thought it was the latter in which case a homebrewing primer is an unnecessary waste of space.

There are some odd mistakes for a scientist to make like stating that crystal malt is an adjunct: the clue is in the name, surely—it's a malt. And using the yeast from bottle conditioned beer: ”Don't throw away the gunk—feed it with yeast nutrient...and pitch it into your next brew. It will go like a rocket.” Probably not.

Finally, nearly halfway through the book we get to the science. The book gets much better from here.

Yeast Population Dynamics

Quite a lots of mathematical formulae from here on but these are explained and can be skimmed over and the text will still make sense.

This chapter contains one of the best description I have read of why yeast pitching rate is important. Clear, concise, and well explained both mathematically (by formulae) and in the text. The maths can be hard and is mostly beyond me but the explanations are good.

Brewing Thermodynamics

Sounds a laugh-a-minute, doesn't it?. But, of course, temperature control is a fundamentally important part of brewing so this is relevant stuff. The chapter covers a whole range of situations such as the heat produced by yeast during respiration, heating the mash, cooling the wort, temperature control etc. Lots of good stuff.

Now it has to be said that the design of the formulae and the associated explanations is a bit poor. New terms are introduced and the explanation of what they represent can be hard to find, sometimes hidden in the text of the next paragraph. Poor book design, in fact.

One thought provoking fact: enough heat is produced by the fermenting yeast in a standard wort to boil the whole batch. Lucky that heat is lost from the fermenter then.

Bubbles

Bubbles are everywhere in brewing. You might have noticed that. I found this chapter really stimulating. They is quite a lot of abstruse science, and I am sure some of it isn't that important, but most of it was absolutely fascinating. Fermentation is discussed in some detail and we learn that a typical homebrew fermentation might generate 35 billion bubbles. See what I mean? Not terribly useful but interesting and dead good for boring the guys down the pub. Denny points out that (for the US, I think) 0.5% of all carbon dioxide emissions are produced by beer production.

Beer froth and head production turn out to be more complex that you might think. Hey, one paper on the subject received an Ig Nobel Prize. The head on a beer is a surprisingly complex and dynamic system as Denny explains. He also discusses the background to the use of nitrogen/mixed gas and also shows why it isn't terribly beneficial to beer flavour. He gives a great explanation of how a widget works. They are surprisingly simple and are, in effect, a type of sparkler. Mention is made of disproportionation, which is another good one for use down the pub, and negative bubbles (a spherical layer of gas with liquid inside and outside of the sphere.

This chapter is probably the most successful of the book and is full of fascinating insight and some interesting science.

Fluid Flow

The final “science” chapter uses its title rather liberally. Most of it is taken up with the mathematics of bulk beer distribution which is, just about, an example of fluid flow. This is the only section where I found my inability to understand the mathematics frustrating. It would have been helpful to have had the various formulae more fully explained and not to have taken so much on faith. Maybe an appendix for thickos like me could have been added?

A brief discussion of how beer is moved from cellar to bar and an appreciation of how complex the action of drinking a beer is in terms of physiology, completes the chapter.

There are a few odd assertions—are electric pumps replacing beer engines on the bars of English pubs? I'm not sure when I last saw an electric pump. I used to love watching a diaphragm pump dispensing a pint of Bank's mild when I were a lad. But then earlier in the book there was the assertion that the barrel (36 gallon) and the pin (4½ gallon) are the most common UK cask container size when the firkin (9) and the kilderkin (18) are, by far, the most common size encountered.

Final Thoughts

Not a lot to say about this chapter. Simply a summing up of what went before.

Throughout the book some of the graphs are poorly designed and sometimes inappropriate for the data they depict—line graphs where bar graphs would have been better, for example, which is rather odd for a book published by an university press.

The very simple brewing technique described is at odds with some of the science explained, especially in the thermodynamics section.

The book is a good quality hardcover, nicely printed, with a sown binding. In fact the cover is so substantial, for the size of book, that it may constitute a dangerous item. Don't try and take it onto an airplane.

Froth! is a brave attempt at a different homebrewing book. It contains some thought provoking information and certainly encourages the reader to look at things from a different perspective. But it is not a great book. Nearly half the book is not, in fact about “the science of beer”. Most of the beery science is interesting, some of it thought provoking, and some of it might even improve your brewing. Although the text is designed so that the mathematics can be missed out it is a pity that some space could not have been found to more fully explain how the formulae are derived. The mathematics is the backbone of several sections and not being able to understand it is very frustrating.

Froth! is not a book for everyone and newby brewers should avoid it if they don't want their head to explode. The more advanced and/or technical brewer will certainly get something from the book and it encourages the assessment of the brewing process from a new perspective.

So recommended (but with significant reservations) especially at £13.50 for a “proper” hardback.