by David Chapman [1]
Why the geologists’ love of beer is more profoundly interwoven than the stereotype suggests.
Earlier this month, the West Midlands Regional Group [2] of the Geological Society hosted a talk delivered by the aptly named Professor Alex Maltman [3]. Professor Maltman gave a talk on the impact of geology on the taste of some of our best-loved alcoholic beverages.
He argued that the much-hyped role of geology in the processes of wine and whisky making, in fact pales in comparison to the role of geology in the brewing of beer, where it has a much more direct impact on taste.
Traditionally, wine and whisky labels are rich in information on the geology of the source area. Claims of being able to “taste the minerals” and “smell the rocks” are all too common. However, much of the information is purely descriptive and offers no explanation as to how it might actually affect taste, argues Professor Maltman. Wine, for example, is thought to be directly affected by the rocks and minerals of the vineyard. On the face of it this seems like a reasonable assumption, doesn’t it? A successful wine vineyard must have particular physical properties [4]: suitable topography, for good airflow; a slope angle that provides maximum exposure to sunlight; and the correct soil colour, for the desired amount of heat insulation. All of these properties are directly affected by geology and therefore must affect wine taste, mustn’t they? Well, not exactly. During the talk Professor Maltman pointed out that all plants, from corn to carrots, are affected by the physical characteristics of the ground they’re grown in, but you don’t see books on the geology of your favourite vegetables! In any case, modern farming techniques such as irrigation, land moving and airflow controls all supersede the role of the natural geology.
Professor Maltman cited studies that show that the proportions of inorganic vine nutrients in wine are unrelated to vineyard chemistry. Even if they were related, the levels present are below the required concentration to be tasted by humans. Perhaps the importance of geology in wine making is more of a marketing ploy than a scientifically viable discipline, and that anyone claiming to have a ‘hint of granite’ in their glass has simply been fooled by the whole charade.
Geology’s role, it seems, is similarly oversold when it comes to whisky. The main assertion concerning the role of rocks on whisky taste is its role in affecting the water, or more specifically whether that water is ‘hard’ or ‘soft’: a factor mainly controlled by carbonate content. The effect again seems to be negligible. During distillation water is driven off, so it seems unwise to have any faith in its ability to affect taste.
Beer, however, is different. Beer has a range of classic, historic tastes that owe their signature flavours to the rocks beneath our feet.
In the late 19th Century, Burton-on-Trent – famed for its water as well as its beer – had 35 commercial breweries, yet a population of only 30,000. Burton [5] was making the best beer – and for good reason. The hydrochemistry of the Burton water was perfect for beer brewing. During a process known as ‘mashing [6]’, the conversion of starches to sugar is most effective within a pH range of 5.4-5.8; Burton falls within this range and its highly mineralised water gave it a crisp, hoppy beer taste. The geology below Burton is characterised by Permian-Triassic rocks, rich in gypsum [7] (calcium sulphate). This calcium sulphate not only gives the beer a distinctly hoppy taste, it also makes the beer stable, and allowed it to be exported around the world; in some cases as far as India, and so the name India Pale Ale [8] was born. Other breweries started to, and still do, add calcium sulphate to their beer and the process became known as ‘Burtonisation’.
Elsewhere, beer brewers were developing new tastes, and geology was at the forefront of the process once more. In Pilsen, Czech Republic, the pH of the water was also found to be appropriate for the effective conversion of starches into sugar. However, the late Proterozoic metamorphic rocks of the area did not lend themselves to producing the kind of mineralised water that had made the Burton beers so good. The low mineral content, ‘soft’ beer, produced a clear, pale beer variety, and became known as Pilsner, defining the classic lager taste. In Munich beer brewers found the water to be too highly mineralised. The high carbonate content made the water alkaline.. The brewers found a solution that involved roasting the brewing cereals, which produced phosphic acid and would bring the pH down to the required level. This technique produced dark beers, now recognised as stout. This process was echoed closer to home, where – owing to the thick limestone bedrock – Dublin brewers were faced with an even higher carbonate content. The roasting process was intensified and this led to the production of a thick, dark beer with a distinctly burnt taste: now one of the world’s most famous beers, Guinness.
As opposed to wine and whisky, where similar tastes are produced on vastly different lithologies, distinctive geology produces distinctive tasting beer. As iterations of the world’s most consumed alcoholic beverage were created, geology was providing unique ingredients that defined classic tastes. These tastes were then exported and imitated the world over.
It’s easy to imagine how an opulent society of wine and whisky lovers was seduced by the romance of a drink defined by the earth on which it grows. The sheer amount of literature on the subject reflects the popularity of the fantasy but, unfortunately, the science doesn’t quite agree. Beer is the only drink that is truly defined by its geological roots and yet it has received little academic attention.
So whether it’s wine, whisky or beer you enjoy this New Year, remember that if you really want to taste the geology, beer is the only way to do it.
