News from the Vineyard - Science of Olfaction

Victoire Chabert
July 1, 2022

Today I wanted to present an article from my uncle Patrick Essa, who leads the Domaine Buisson Charles estate with my aunt Catherine and their son, my cousin and oenologist Louis. Patrick is passionate about wine and his writing skills prove it. I propose that you learn more through one of his texts that he published last April and that could allow you to know more about the aromatic olfactory notes.

“A short while ago, I mentioned in these columns the aromatic deviations, empyreumatic and roasted, that affect white wines. As I delved deeper into my sensory memory, I had the idea of memory, I had the idea to list here the main defects that can be found in the wines made from Chardonnay of the Côte de Beaune. Indeed, the wine lover - who is not always a beginner of course - does not have the chance to observe the birth and evolution of its scents and aromas and can be led to confuse them with an aromatic complexity to be linked in priority to the grape variety or the terroir.

These varietal and/or terroir-specific notes can thus be parasitized by the balance of the harvested fruits and/or the residues of the vinification and maturation which are almost systematically "impure". These two poles that could be qualified as "natural" and "artificial" are opposed and lead the winemakers to make choices that tend towards a magnetic" orientation that marks their wines significantly. In a more insidious way, the wines produced since time immemorial have always been at the crossroads of these two orientations and are culturally singled out by them. Those who do not understand that the terroir alone cannot explain the image that characterizes an appellation will always try to find "extra natural/artificial" accents in the wines he tastes because these indelible accents carry in them a part of the implementation that observe those who who make them.

To clarify my point about the roasted drifts that a bottle can carry, I listed in my previous article a number of perceptions - not exhaustive - that affect the wines

Here, I will start from the aromatic note to better try to explain its genesis and its different perceptions and interpretations in the finished wine during olfaction.

1- The iodized olfactory note: this scent, which can be discreet if it comes from a slightly botrytized "wet" harvest, is often invasive in wines marked by non-noble rot, known as "grey". Impossible to eradicate without using pure lees - possible when the same appellation is produced on different climates and some are not affected by rot. Frequently impacted years: 1981, 2001 and 2010.

2- The "apple" olfactory note (of green or warm apple): the must or wine has taken on air between alcoholic fermentation and malolactic fermentation or the latter has lasted a very long time at a slow pace. This last case frequently occurs in musts with high acid potential. Impacted years: 1994, 2008.

3- The "vegetal" olfactory note: the scents of cut hay, sage or iris come from a maturation without sun in a late year combined with a slightly too loose settling. Thick skins, quite high degrees but rarely exceeding 13, small desiccation of the berries by the wind. The pressings of these berries often give little juice and the wine turns to gentian flower on the nose. Years: 1991, 2004, 2011.

4- The "waxy" or "honeyed" olfactory note: an overripe harvest, not very acidic and sometimes marked by a real botrytis. Often the sign of a premature evolution unless the color remains golden with green reflections. The wine starts its life under glass with scents of mirabelle plum and then evolves more or less quickly towards aromas close to mead. Year 1983, 2006.

5- The olfactory note of "candied orange": a year of botrytis which is often combined with pronounced golden colors. Very aromatic when young, sometimes refining with ageing but never on the most noble fresh notes. The viscous texture can seduce. Year: 1989, 1992, 1995.

6- The olfactory note of white truffle: from raisined and/or wilted grapes. Not unpleasant if discreet but unfortunately often combined with low acidity: 2003.

7- The toasted olfactory note: see the text written about it in my previous review.

8- The "buttery" olfactory note: fresh or rancid, it is due to a lactic bacterium working during the MLF, oenococcus oeni, which generates during a tumultuous fermentation a metabolite precursor of aroma, the diacetile. All years can be impacted, but curiously, especially highly concentrated musts marked by intense malolactic fermentation.

9- The olfactory note called "reduced": heady nasal nebula which evokes in turn the sulphuric wick or which goes under its evolving form H2S towards the famous mercaptan, a thiol which smells the egg punaie. It is the worst organoleptic deviation. It is generated by muddy lees which come from fruit marked by residual sulphurs combined with containers which do not allow any micro-oxygenation. It must imperatively be circumscribed before bottling by treatment with copper. Its olfactory "residue" is the blackcurrant bud.

10- The "asparagus" olfactory note: massive addition of sulfite at bottling and slow combination with the so-called total SO2 part under glass. The free SO2 generally remains at a high level. The wine ages well but is lean and not very complex.

11- The amylic note which marks the wines having fermented at low temperatures in large inert containers. Aromas of "scotch glue" that oversimplify the olfactory pole of the wine by giving the illusion of white fruit notes when aired. It is often coupled with residual sugars and the absence of malolactic fermentation. Not to mention doses of CO2 gas.

To produce a white wine free of all these scents is a challenge as the vintages, by their characters, characterize the wines but it is undoubtedly necessary to seek discrete expressions that do not dominate the ultimate finesse that comes from the note of terroir combined more or less frankly with those of the grape.

We also consider that the wines should not be under the influence of the container in which they were vinified. The sweetness of a woody wine should never dominate the balance of the fruit. Similarly, neutral containers such as stainless steel should not produce residual reducing effects and should only enhance the freshness of the initial aromas without erasing them with sulphurous accents.

Among the most used terms in the wine literature, I think that "reduction" follows very closely to "minerality". A somewhat nebulous term often used incorrectly, it is one of those used to justify gustatory odors that are as varied as they are misunderstood, and if for a long time it was synonymous with defects and unpleasant odors, it is curiously becoming one of the vectors necessary for a happy conservation.

Is the hunt for the natural organoleptic qualities of a product now going to involve a search for living things that do not smell like roses? One could believe it sometimes if I judge some wines that are born on olfactory registers expressing themselves on the grilled match - white wines - or cabbage - red wines - for example. What exactly is the origin of this reduction? Is it the simple effect of a liquid loaded with alcohol placed in an anaerobic environment or is it the result of some process linked to the wine making process? As is often the case, reality is more complex than it seems and the causes of its development are multiple. But let's not be mistaken, it is not a path taken serenely by a winemaker wishing to use its benefits.

It is a frequent consequence of fermentation in containers with little or no oxygen permeability. It can have multiple origins and is, whatever one may say, always to be monitored in terms of its intensity because it can irreparably spoil a wine.

Following the cycle of conception of a wine, the first element that could generate reducing effects has to do with the phytosanitary treatment program used by the producer on his vine plants, because it can leave sulfur residues on the fruits and in the musts. The same is true for wines from soils with high nitrogen deficiencies. Thus, we observe with constancy vintages regularly impacted by significant reducing phenomena while according to the same procedures, other vines located next to them seem never to be affected. A frequent headache linked to the balance of the soils - and above all to their geological and cultural history - which very often leads the producer to be the follower of his wine rather than its instigator, even if this may delight "by default" the supporters of reductions under glass as a "freshness" argument.

An analysis of the soils and their composition crossed with a reflection on the possible amendments is necessary here to understand the causal relations at the origin of their "functioning" and consequently to optimize their incidence.

Once the grapes are in, the vatting stage for the reds and pressing for the whites is essential. It is necessary to manage the white or red vintages according to an essential parameter, the oxidation of the vacuolar juices released. The musts obtained are then fragile and oxidizable and must be protected. For this purpose, an aqueous solution mixed with SO2 (sulfur dioxide) is most of the time used. This anti-oxidant product has the effect of covering the fermenting musts by preventing their redox potential - see below for an explanation of the term - from dragging them to the dark/oxidative side of the force.

If all fermentative activity consumes oxygen, for any cell in aerobiosis, which breathes, as for any cell in anaerobiosis, which ferments, there is recovery of energy stored in the form of phosphorylated compounds. This oxidation energy is essential for the growth of the cell and then for its aging.

The fermenting wine is also marked by its oxidation-reduction phenomena due to the effect of oenological treatments. The birth of a must occurs at the pressing. At this technological stage of elaboration, the future wine released by the berries is under the influence of atmospheric oxygen and this oxygen is a substrate of choice for polyphenol-oxidases whose activity is very detrimental to its aging potential. The winemaker must act by a reductive treatment of the musts with a sulphite solution according to doses that he will interpret according to the characteristics of his press juice. Inhibited by these reductive treatments, the different enzymes - tyrosinase and laccase - will not be able to generate casse brune which considerably reduces the complexity of the phenolic compounds. The must, during its settling and racking, will even be able to dissolve a few milligrams of oxygen that the yeasts, true "electron factories", will consume and reduce in order to multiply better. It is therefore obvious that the first steps in the treatment of a must for its transformation into wine correspond to oxidation phases followed by reduction phases.

It is the same for the rest of the elaboration, during the maturation and then, in the final phases, during the last steps that precede the bottling: the racking and the possible fining and filtering. This succession of oxidation and reduction defines from the beginning of the fermentations a REDOX potential which is the expression of the electrical activity which is automatically generated by fermentations and oxidations. Expressed in millivolts, it sanctions the functioning of the must according to its evolution between its two poles and obviously it can be analyzed and controlled by the winemaker whose strategy aims at never leading it to extremes.

Thus, during the maturation process, the game consists in preserving a reducing matter without it evolving towards a heavy reduction which would strongly impact the wine's scents, or even its matter itself. In particular when the reducing wine evolves towards the famous defective nose of mercaptan which can be assimilated to the smell of punished egg.

Without going towards these compounds, the excessive reductive markers that pull the Redox potential down - the top being here oxidation - are commonly the notes of green asparagus and grilled matches in whites and blackberry, viandox then blackcurrant bud and cooked cabbage in red wines. Grilled in the whites and iridescent notes and animality in the reds are thus - at high intensity - serious defects that should never be blamed on a possible expression of terroir.

The winemaker has simple remedies to eradicate these harmful olfactory expressions as soon as they appear or in a later, more curative mode. I am not going to list them here, but you should know that it is not necessary to preserve a reductive material for a wine to keep well. It is not necessary to over-sulphite a juice with an oxidative tendency to fossilize it... It is all a question of balance.

In the absolute, a very fine toasted nasal line underlining an ageing carried out on the middle line of the Redox potential associated with an olfactory volatility conferred by an imperceptible but present CO2, authorizes a lively and relaxed wine matter to face time by embracing fresh scents and by preserving an overall purity absolutely essential to the expression of a well born wine... Or rather a good nose!

How can we accept that obvious deviations are taken for aromatic complexity by sharp palates while explaining that a residual note of maturation is most often the result of an unfinished work?

To illustrate my point, I will try to isolate what generates this famous toasted note that would sign the noblest aromas of a couple of advanced winemaking / maturation in the world of white winemakers. Of what order are they:

The "sulphurous" toasted note: more or less intense perception on the Swedish match and the rubbed flint. Most of the time, it is sulfur residues that have been spread for a long time and at a late stage by dry spraying. Leachable by rain, these repeated applications end up impregnating the skins of the grapes and they durably mark the musts during vinification and maturation. Impure.

The "roasted" note: an artifice of an ageing process carried out with a generous proportion of new, heavily heated wood. It "peanuts" or "caffeine" or even gives off a smell of "toast" depending on the heaviness of its imprint... always vulgar. An impurity that many people love and even seek. The ageing in large barrels has a clear tendency to amplify this phenomenon.

The "roasted" note: discreet nasal scents that evoke fresh hazelnut and apricot skin - or grape skin - gilded in the sun. A sign of right maturity without botrytis, it ennobles the wine. Pure.

The "reduced" toasted note: it appears during the maturation when the proportion of lees is a little high compared to the micro-oxygenation potential of the container. Fine notes during a well-managed maturing process that wishes to be little interventionist on sulfites, it can irremediably mask the finest aromas of white wines - and in particular those that are floral - if it is too marked. Pure if it only traces finely during maturation. Impure as soon as the wine is under glass because a single racking should be enough to make it disappear. Highly impure when combined with the "match" toast that leads the taster to feel an unpleasant olfactory note of "firecracker" after use.

The toasted "praline": the ultimate and fresh note of hazelnut lignifying, it evokes the limit between the fruit and the vegetable and marks the terroirs most capable of bearing great grapes at full maturity without too many natural degrees. Lost if the fruit meets under-ripeness, overload of yield or excess of alcohol, this noble toast is delivered only in great years. The last one was for example in the Côte des blancs, 2009, but we could evoke 1999, 92 or 89,82,79,76 and 73. Pure.

The "toasted vanilla/coconut" note: heavy note brought by the over-ripeness of the fruit and a very present woodiness. Less unpleasant than the match or the empyreumatic roasting at first sight, it is undoubtedly worse because it signals an unbalanced matter. Impure.

Therefore, be aware that the toasted expression of a white Burgundy must always be retained and that if it is superimposed "in front" of the aromatic spectrum of the wine, it spoils it irreparably. Its olfactory place is therefore naturally subjacent, subtle and infinitely discreet.”

-Patrick Essa