Colloids and aromatics

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Stewart Johnson
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Colloids and aromatics

#1 Post by Stewart Johnson » February 10th, 2014, 9:24 pm

Hi Clark. Can you elaborate on this subject. I gather that your model of good colloidal structure also binds/stabilizes/sequesters aroma molecules -- good and bad. My question is, how and when are these molecules unbound/volatilized and perceived by the taster?
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Clark Smith
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Colloids and aromatics

#2 Post by Clark Smith » February 10th, 2014, 9:53 pm

Stewart Johnson wrote:Hi Clark. Can you elaborate on this subject. I gather that your model of good colloidal structure also binds/stabilizes/sequesters aroma molecules -- good and bad. My question is, how and when are these molecules unbound/volatilized and perceived by the taster?
Sequesters is the right word. There's not necessarily any covalent binding. When phenolic structures stack, small, volatile phenols (and other aromatic ring compounds) like to inter-collate between the stacked rings like a Dagwood sandwich because they have an affinity for each other and because water repels them into the hydrophobic regions inside the colloids composed of tannin and pigment. These include oak constituents like vanillin, eugenol (cloves) and guaiacol (char) as well as pyrazines (vegetal aromas) and microbial characters like 4-ethyl phenol (bandaid) and 4-ethyl guaiacol (cured meat).

As long as the structure remain intact, the aromas will continue to be integrated in this way. Poorly made wines with unskillful élevage techniques or excessive hangtime tend to fall apart in a few short years, resulting in a dry, grainy mouthfeel and the release of these volatiles. This will also occur when the wine is heated.

Fixed color is thought to be the key to colloid longevity because it caps the ends of the short polymers and prevents them from elongating and precipitating. The key to fixed color is the skillful use of oxygen to polymerize the color when the wine is very young.

It's hard to describe the perception of integrated aromas. Bearnaise sauce doesn't smell or taste like the individual elements that comprise it: tarragon, mint, onion and vinegar -- but rather like a single united bearnaise-y thing. In the same way, the aromatic elements of an integrated wine are all pleasant, but they interact with one another and support the central fruit components like supporting actors. It's similar to an orchestra or band all playing together in a strikingly soulful way.
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