jamie goode's wine blog

I have been busy. Very busy.

For two weeks each April, I do what most normal people do, and work a 9-5, with a commute.

I commuted into London for 15 years, but I easily forget how tiring it is, and how little energy it leaves you for the other stuff (in my case, family time, walking the dogs, sport, keeping fit, playing guitar – and, of course, this website).

Robert Joseph, one of the co-founders of the IWC 30 years ago, and Tim Atkin

This week we have been awarding medals, after spending last week sifting out the un-medalworthy wines. A few wines rejected in week one are put back into week two – either by the co-chairs, who think the panels missed them, or by the organizer to see how reliable the panels are – a sort of test.

Judges’ briefing

There’s also a county game going on at Lords this week: Middlesex versus Derbyshire. So during the breaks we’ve been able to watch a few overs. The foreign judges just don’t know what to make of cricket.

Sadly, county cricket doesn’t draw big crowds. It does mean you get to sit in the best seats in the house, though. The section we sat in had brand new padded seats installed this week.

One of the nice aspects of judging is socializing with people you wouldn’t normally bump into. The wine trade is full of lovely people, and we take time to share a beer at the end of each day.

Below are two of my judges from yesterday, Paul Braydon and Terry Threlfall. Terry is from Vancouver, and Paul is from Manchester (red, not blue, alas, but he’s a good guy).

Two vineyards 100 m apart. One treated with herbicide, the other allowed to grow a cover crop.

So where are we up to with soils and wines?

We began by exploring the ideas of minerality, and how soils might be having a direct effect on wine quality, even though science seems to indicate that soils impact upon wines rather indirectly. We explored the idea that what is perceived as minerality might actually be a result of ‘reduction’. And then we looked at the way that the root environment affects above-ground growth through hormone signalling.

Now let’s think about the issue of soil biology, and how this could be affecting the vine.

‘The extent, health, and physical and chemical environment of the roots must be a major key to the best ripening and terroir expression.’

John Gladstones, Wine, terroir and climate change (Wakefield Press, 2011).

Vine roots respond to the conditions of the soils they are growing in. First of all, a large permanent framework of roots is established, followed by a network of finer lateral roots, and finally even finer tertiary roots which are vital for uptake of water and nutrients. Nutrient uptake by the roots can be both passive and active. As the vine takes up water, it will usually take up whatever is dissolved in that water. But if it lacks specific nutrients, it can take them up actively, if they are present in the soil. There are some situations where the vine is fooled, though, by mineral ions that look quite similar, such that a deficiency of one can occur when there’s an abundance of another. And, for example, in soils with a lot of limestone, chlorosis can be a problem. This is because in limestone-rich soils, vines find it very difficult to take up iron, which is needed for photosynthesis, as a vital component of the green-coloured chorophyll pigment. As a result, the leaves turn a yellow colour and are diminished in their ability to carry out photosynthesis, the process of transforming light into energy.

A special layer of material called the Casparian strip surrounds the root endodermis, the layer of cells that circle the vascular tissue. This strip contains suberin, a waxy, rubbery material that is impermeable to water. Thus water and solutes entering the roots have to pass through plasmodesmata (pores in the cell walls) and therefore through the cytoplasm of root cells, before they can be transmitted to the rest of the plant. This gives the vine a level of control to what is taken up. The plasmodesmata are significant because they allow direct communication between the cytoplasm of adjacent plant cells, through the otherwise rigid cellulose cell walls.

How do vine roots take nutrients from the soil? One of the key concepts here is cation exchange. Roots are able to exchange hydrogen ions, which they pump out, for the cations attached to the negatively charged soil particles such as clay and humus. Clay often carries a negative charged, whereas humus – decayed organic material – can carry both negative and positive charges, and so can hold both cations and anions. Cation exchange capacity (CEC) refers to the number of positive ions (such as calcium, magnesium, iron and the nitrogen-containing ammonium ion) that the soils can hold. When clay and humus have a negative electrical charge they are able to hold onto positively charged ions. Generally speaking, CEC correlates positively with soil fertility, because it determines how many plant nutrients the soils can hang on to. Soil pH also affects CEC: more acid soils (lower pH) have a lower CEC than more alkaline soils (high pH). One way to increase CEC is to increase the organic content of soils. This has the benefit of both increasing CEC, and thus fertility, and also increasing soil texture. Without organic material or clay, soils find it hard to retain nutrients. For example an excessively sandy or gravelly soil will allow mineral ions to be rapidly leached from the soil by rainfall.

So where do the mineral ions (nutrients) come from in the first place? It is not really from the bedrock, which would be the intuitive assumption on many. Some mineral ions might be bedrock-derived, but these would largely be in the subsoil. Low levels can come from rain, and some can come from the weathering of larger soil particles such as stones and rocks, but the bulk of soil nutrition will come from decaying organic material.

To get a better handle on this I spoke with Tim Carlisle, who has studied soil science, but also has a deep understanding of wine from his current employment as a wine merchant. ‘We need to then look at the microbial activity in soil,’ he states. ‘This affects the speed and ability of soil to break down organic matter into mineral ions that can be used by plants – and also aids the uptake of ions by plants. Because of this, no discussion about soil should exclude them, because whatever the terroir is, the level of microbial activity is an important and always overlooked element.’

Carlisle points out that there are many factors that influence this microbial activity, but primarily water, food and oxygen. ‘Oxygen is more available in a loose uncompacted soil,’ he says. ‘A soil that is overly compacted has little oxygen and so little microbial activity – the same is true of a waterlogged soil – which Is one reason why porous bedrock and/or slopes are important, not just because of vine stress but because the microflora and fauna don’t get drowned.’ The term microflora refers to the bacteria and fungi in the soil. Their existence also governs the level of microfauna, which refers to soil organisms ranging from single-celled protista to small arthropods and insects, through to nematodes and earthworms.

‘The food they need is organic matter. If you visited a conventional agriculture wheat field you’d find that there was very little organic matter in the soil, and as a result very little microbial activity, which is further diminished by crop spraying – hence the vicious cycle of needing to use tons of fertiliser.’

During his studies of soil science, Carlisle looked at the effect of fungicides, herbicides and insecticides on the soil microbes. He did this two different ways. First, he took microbes from the soil, grew them in culture, and then studies the effects of dilute agrochemicals on their growth. ‘What I found in this was that fungicides over herbicides and insecticides kill off not just fungi (which includes yeasts and moulds),’ says Carlisle, ‘but also a high proportion of bacteria, and actinomycetes (I didn’t do anything with algae), but also that herbicides and insecticides also killed off a proportion of all types of microbe, and restricted growth of others.

He also studied the overall microbial activity in the soil. ‘What this showed up was that untreated soil was healthier than anything with any kind of treatment, including one that was sprayed with fertiliser,’ reports Carlisle. ‘If you think about it, minerals are essentially the excretion of microbes. Too much excretion to soil will poison them and so spraying with fertiliser actually caused a check in microbial activity – it continued but at a lesser rate.’ He adds, ‘the thing that was by far the most interesting from a viticulture perspective was that one of the samples was sprayed with copper sulfate, which is permitted in organic viticulture. This sample was the one in which microbial activity was reduced by the most.’

This raises interesting questions. Clearly, soil life is important. And this soil life can be affected by vineyard treatments. It poses a problem for organics and biodynamics: while these approaches aim to encourage soil life, the fact that they need to rely on copper – a traditional but toxic remedy for fungal disease – is at odds with this approach. But then conventional remedies, such as the use of systemic fungicides, are also problematic.

So, to continue our look at soils and vines, and the making of vines. In part 4, we are going to be focusing on vine roots.

Vine roots respond to the conditions of the soils they are growing in. First of all, a large permanent framework of roots is established, followed by a network of finer lateral roots, and finally even finer tertiary roots which are vital for uptake of water and nutrients. Nutrient uptake by the roots can be both passive and active. As the vine takes up water, it will usually take up whatever is dissolved in that water. But if it lacks specific nutrients, it can take them up actively, if they are present in the soil. There are some situations where the vine is fooled, though, by mineral ions that look quite similar, such that a deficiency of one can occur when there’s an abundance of another. And, for example, in soils with a lot of limestone, chlorosis can be a problem.

A special layer of material called the Casparian strip surrounds the root endodermis, the layer of cells that circle the vascular tissue. This strip contains suberin, and is impermeable to water. Thus water and solutes entering the roots have to pass through plasmodesmata (pores in the cell walls) and therefore through the cytoplasm of root cells, before they can be transmitted to the rest of the plant. This gives the vine a level of control to what is taken up. The plasmodesmata are significant because they allow direct communication between the cytoplasm of adjacent plant cells, through the otherwise rigid cellulose cell walls.

How do vine roots take nutrients from the soil? One of the key concepts here is cation exchange. Roots are able to exchange hydrogen ions, which they pump out, for the cations attached to the negatively charged soil particles such as clay and humus. Clay is always negatively charged, whereas humus – decayed organic material – carries both negative and positive charges, and so can hold both cations and anions. Cation exchange capacity (CEC) refers to the number of positive ions (such as calcium, magnesium, iron and the nitrogen-containing ammonium ion) that the soils can hold. Both clay and humus have a negative electrical charge, and this allows them to hold onto positively charged ions. Generally speaking, CEC correlates positively with soil fertility, because it determines how many plant nutrients the soils can hang on to. Soil pH also affects CEC: more acid soils (lower pH) have a lower CEC than more alkaline soils (high pH). One way to increase CEC is to increase the organic content of soils. This has the benefit of both increasing CEC, and thus fertility, and also increasing soil texture. Without organic material or clay, soils find it hard to retain nutrients. For example an excessively sandy or gravelly soil will allow mineral ions to be rapidly leached from the soil by rainfall.

The mineral uptake by the roots will affect the growth of the vine in significant ways.

But there’s also another important way in which vines affect the growth of vines. Significantly, root growth causes hormonal signals to be sent to the above-ground portion of the plant, and these act like instructions to tell the vine to modify its growth. Perhaps the best summary of what is happening here comes from the Western Australian plant biologist John Gladstones, in his book Wine, terroir and climate change (Wakefield Press, 2011), in which he brings together the existing literature and adds some theories of his own.

Gladstones points out that gibberellins (one of the major plant hormones) promote shoot internode growth through cell extension (the nodes are the bits of stem where the buds appear), and these gibberellins are formed in the region of cell division behind root tips. They also promote the formation of tendrils rather than fruit clusters in the newly forming lateral buds. Presumably, if conditions are good for root growth, then the vine is likely to favour vegetative growth, and gibberellins are sending up these instructions from the roots.

Cytokinins (another major plant hormone), produced in the root tips, promote new node and leaf formation, the branching of shoots, the development of existing fruit clusters and the fruitfulness of newly forming lateral buds. Gladstones observes that warm spring soils promote cytokinin dominance; cool soils gibberellins. Warm spring soils are therefore a good thing for grape production.

Abscisic acid (ABA) is probably the most interesting of the plant hormones for wine quality, though. Roots signal to the vine that water stress is coming using ABA, so that the leaves can respond appropriately, closing their gas exchange pores. ABA also acts in tension with another group of plant hormones, auxins, in controlling ripening. There’s a sort of tug of war here. The auxins, produced by developing seed, slow down berry development, prolonging the pre-veraison phase. ABA is pulling for berries to develop faster. In conditions of water stress, ABA is signalling to the berries to develop faster. A massive transfer of ABA to fruit coincides with veraison, possibly because of declining berry auxins at this stage. Therefore root moisture stress is contributing to berry ripeness. Gladstones concludes that ABA is the primary hormone imported into the grape clusters that both triggers and continues to stimulate ripening.

A recent study by Dr Hendrik Poorter and colleagues in Germany used magnetic resonance imaging (MRI) to look at root growth in potted plants. They were interested in finding out how big the pots have to be for experimental work, looking at a wide range of different pot-grown plants. The results emphasized how important root signalling is for the growth of the above-ground portion of the plant. The pot size restricted growth for a wide range of species, and doubling the size of the pot increased growth by 43%. The MRI results indicated that the plants were using their roots to ‘sense’ the size of the pot, and then signalling this to the rest of the plant.

Gladstones’ assessment of the literature on vine physiology agrees with this idea. Roots are signalling by means of hormones to the above-ground portion of the plant. The root structure is determined by soil conditions: deep soils with ample water supply prolong the phase of root development, and signal the above-ground plant to keep growing; shallower soils with limited water or a texture that obstructs root growth reduces vegatative vigour. Low vigour is best for wine quality.

More to come in part 5!

In parts 1 and 2 of this exploration of soils and wines, I looked at the issue of minerality. Do soils influence wines directly by means of root uptake of ‘minerals’ that find their way into the wine? Science suggests this is not the case, but there is a possibility that root mineral ion uptake could be having some effect, direct or indirect, on wine character.

What about a chemical explanation of minerality? That’s what we’ll explore here.

Some people use ‘mineral’ to describe aromas of wine; it’s something they get on the nose. In this case, it could be that tasters are ascribing minerality to what is in reality the presence of certain volatile sulfur compounds in the wine, also known by the term ‘reduction’. In its rawest state, reduction is caused by hydrogen sulfide, and smells of rotten eggs and sewers. This is rare in a finished wine, and wouldn’t be classed as mineral. Far more common is the presence of complex sulfides and mercaptans (also known as thiols). These sulfur compounds, like hydrogen sulfide, are produced largely by yeasts during fermentation. Their expression depends on their concentration and the context of the wine, but in some cases they can give a flinty or struck-match aroma that can be quite ‘mineral’.

There is good reason to suggest that flintiness in white wines is a result of some low level reduction. Great white Burgundies frequently show a little of this good reduction: a matchstick element to the nose is complexing. Some new world Chardonnay producers are now beginning to work out how to achieve this through winemaking practices. There’s also a link here with terroir: some sites naturally have nutrient deficiencies that can stress the yeasts a bit and cause them to produce more of these volatile sulfur compounds.

It’s tempting to assume, in the absence of good solid data, that reduction is responsible for quite a bit of minerality in wine. But it is unlikely to be the whole story, and many advocates of minerality would prefer this not to be referred to as such. ‘I believe most people confuse the “mineral” flavours like petrol, reductive notes, flint and stony aromas with minerality,’ says Olivier Humbrecht. ‘As such, it is impossible to smell minerals!’

But scientists tend to prefer this second definition of minerality because they dispute the first – the more literal definition in which minerals in the soil end up flavouring the wine. This tends to make some believers in minerality act a little defensively when discussing the subject. ‘I fully understand that when I use the term it may have no scientific validity,’ says Jasper Morris, wine merchant and Burgundy expert. ‘I have been told by enough geologists that you shouldn’t call Chablis flinty, because flint is not soluble in water and therefore it can’t have a taste. But is an image.’ Morris illustrates his point by comparing two Burgundy vintages. ‘I would use two vintages of white Burgundy to illustrate this point: 2007 and 2008. The acidity is higher in 2008, and when I taste those wines I feel that they are acid and not especially mineral. In 2007, the acidity is a little lower, but I find the wines distinctly mineral. By that, I mean that they have a fresh zingy zest to them that in my mind this puts up the single word mineral. In 2006 the wines are fat, rich and round, and some of them have enough acidity to provide balance but you don’t feel mineral when you taste the wines.’ He continues, ‘also in Burgundy, in terms of the hillsides you expect minerality in those soils which have more active limestone, and you expect less in those soils which are more clay based. For example, with any vineyard in any village which includes the words “charmes” in the name, you rarely get the concept of minerality.’ Morris is frustrated that the scientists seem to be criticising minerality, without offering an alternative explanation: ‘Scientific fundamentalists are denying that we get it right rather than offering any certainty in the other direction.’

Paul Draper of Ridge in California is a winegrower who believes in minerality from the soil, even in the face of questioning from scientists. ‘Though I am well aware of what soil scientists say about  minerals or other elements in the soil and the impossibility of their traveling through the vine and into the wine, the roots deep enough into those minerals are effected and the wine shows that effect,’ he states. ‘I think of minerality as a wet stone quality in a wine.  Our subsoils at Monte Bello are limestone and at times are at the surface or a meter below. In other places our backhoe pits find them several meters down. Perhaps 70% of our vine roots are deep in the limestone. I have seen minerality in some shales as well so I don’t think the effect is necessarily limited to limestone. We see the most marked minerality (crushed rock, perhaps flint are other descriptors) is in our more eroded blocks where the limestone is closer to the surface. In the youngest blocks where pits have
shown considerable limestone we don’t see the minerality as yet but expect to when the roots
are deeper.’

Minerality remains enigmatic. As we begin to understand more about it, the picture seems multifactorial, with different mechanistic underpinnings for what wine tasters describe as mineral in their tasting notes. From a personal viewpoint, I used to favour the more established scientific viewpoint, assuming that much of minerality could be explained by volatile sulfur compounds. But I’m increasingly drawn to the idea that minerals in wine, derived from the soil, could be affecting wine flavour in interesting ways—and, in particular, helping to create long-lived compelling white wines. It’s a subject that deserves more attention.

In part 4, we’ll look at the interaction between plant roots and soils in more detail, and explore the strong evidence for ways in which roots might be affecting grape quality.

So the International Wine Challenge has begun. As a panel chair, I’m signed up for all two weeks of judging. I really enjoy it, working with a different panel each day. You get to meet lots of new people, as well as a chance to catch up with old friends. And because of the feedback system, most of the people tasting at the challenge are pretty good.

Last night we had a panel chairs’ dinner at the wonderful Providores, with four different wines. They deserve a mention.

Fefiñanes Albariño 2011 Rias Baixas, Spain
Such a beautiful wine. Lively and fresh with peach, pear and spice. Floral and textured with amazing precision. Pure and delicate. 93/100

Yalumba FDW(7c) Chardonnay 2009 Adelaide Hills, Australia
Very fine with lovely toast, white peach and pear notes as well as just a hint of matchstick and cabbage adding complexity. Fresh palate is fine with nice texture. Fine and expressive with lovely weight and great definition. 94/100

Viña Leyda Las Brisas Pinot Noir 2011 Leyda, Chile
Cherries, plum and spice with supple black cherry fruit and some bitter damson notes. Sweet and supple but there’s some reductive character that takes away from the elegance. Nice but could be really good without it. 90/100

Wine & Soul Pintas 2009 Douro, Portugal
Tried from two bottles: the second was better, and it’s that one I’ve produced this note from. Sweet, smooth and ripe with black cherry and spice notes and some mineral character. Ripe and sweet but fresh with real class. 94/100

And so today, it was off to Lord’s, where the wine challenge is being held for the second year in a row. We had a good day, my panel worked well, and it was enjoyable.

We finished the day with some Brewdog. Punk IPA and 5 am Saint went down very well, and after tasting a lot of wine it’s a brilliant way to wind down. I particularly enjoyed the 5 am Saint, which is rich, beautifully balance with nice hoppiness and also a bit of malty richness.