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More
on terroir: a geologist speaks Those of you who have been scanning the news columns might
have seen that the concept of terroir made the big time recently. Some
of the leading news sources picked up on a press release generated by
an article in the scientific journal Geology Today by Professor
Alex Maltman from the University of Wales at Aberystwyth, entitled
‘Wine, beer and whisky: the role of geology’ (Geology Today 19:22–29).
It’s not a research piece, as such, but instead a well written
review the role of geology in influencing the flavour of each of these
three types of drink. Of course, the newspapers pulled a rather simplistic message
out this piece, running with the theme that geology proves the notion
of terroir is nonsense. But this isn’t a fair reflection of the
article’s content. Dr Maltman contacted me because he’d seen my
Harpers piece on terroir, which came out the same week, and kindly
sent me a reprint of his piece so I could see for myself. It begins by looking at the role of geology in wine
production, and the idea that flavours of the soil can be transmitted
by vine roots to the grapes. ‘It’s a seductive mental jump to
suppose that somehow flavours are being communicated between bedrock
and wine’, says Maltman. ‘Unfortunately, no one knows how this can
actually happen’. He then enters into a detailed discussion of how
geology might have more plausible effects on vine growth and,
indirectly, wine flavour. In fact, he’s clearly sympathetic to the
idea that geology is important for vine growth, and illustrates this
with diagrams of the geology of vineyards in Chablis, Corton
(Burgundy) and Sonoma County. Maltman also discusses why these effects
of geology are often dismissed by new world wine producers. He cites four main reasons. First, because of the suddenness
with which new world wine regions have ascended to fame, which means
that they haven’t had time to test the ideas. Second, because new
world winemaking has typically focused on the winery rather than the
vineyard. Third, because many new world wineries are large and grow a
wide range of different varieties, thus blurring any geological
influences. Fourthly, he looks at the geology itself. ‘It has to be
said that discussions in the popular literature are replete with
geological misunderstandings and mistakes that can hardly help in
clarifying things’, says Maltman. He then explains that many new
world vineyards are planted on flat valley floors rather than
hillsides. ‘Such areas are underlain by thick, mixed alluvial
deposits with complex soils, and hence minimal influence from the
bedrock substrate.’ These ideas fit in with the notion that terroir ‘speaks
with a quiet voice’. The effects of the soils and microclimate of a
vineyard are subtle ones, and are easily missed or lost where people
aren’t looking for them or are working in an interventionist style.
If you are growing just one or two grape varieties across your
property, then you are more likely to be in a position to spot the
site-specific effects than if you are growing several. Interestingly,
the increasing adoption of precision viticulture technologies –
where growers use spectral information gained from satellite imaging
of their properties to identify areas of homogeneous growing
conditions – could provide a short-cut to help locate areas that are
geologically and climatically uniform within each vineyard area. These
areas can then be planted and managed in such a way as to optimise
their natural characteristics. It’s also likely that for some
vineyards planted on fertile, deep soils, there will never be much of
a terroir effect. Back to Maltman’s article. He then goes on to investigate
the effects of geology on brewing and whisky. It surprised me to find
out that geology has far more of a direct influence on beer than it
does on wine. Maltman explains that this is because the chemical
properties of the water used for brewing are crucial, and depend on
the ground where the water was extracted. Burton-on-Trent, for
example, has ideal brewing water because it has a naturally balanced
blend of beneficial ions perfect for brewing pale ales. Other famous
brewing locales such as Pilsen and Budvar have suitable ground water.
Dublin is perhaps the most famous case: everyone goes on about how
Guinness tastes better when it’s made from Liffey water. Well, the
water used in Dublin Guinness is crucial, but it’s actually taken
from the Grand Canal, fed by limestone inputs. This hard water
necessitates the use of dark roasted malts, which thus dictate the
style of the beer. What about whisky? Here Maltman argues that the water used
has very little influence on the taste of the whisky, whatever the
advertising campaigns might suggest. The reasons are several, and
space doesn’t permit me to detail them here. And any water that is
added after distillation is carefully deionised, so there is no
influence at this late stage. The most likely influence of geology,
argues Maltman, is on the tap water that you may be adding to your
whisky. For those wishing to see a copy of this article, I suggest
contacting Professor Maltman directly: Professor Alex Maltman |