Dear Clark:
I met a wino a few weeks ago who spouted a term at a lecture that described the color deficient qualities of Nebbiolo, Pinot noir and Grenache. He said that they were all “monosomething saccharides”. Do you know what the term is (and, hey, do you agree with him)?
PS: Great piece on PSs.

-Patrick

Dear Patrick:

I imagine that the term might have been “non-acylated monoglucoside anthocyanins.”

I am not aware that Nebbiolo pigment lacks acylation, but it certainly accounts for some of the peculiar color difficulties of Pinot Noir.

All Vitis Vinifera are monoglucosides (the di-saccharide pigments, illegal in Europe, mark American genera), so that part is no big deal.

This means that unlike most other flavonoid phenolics (that’s the familiar three-ring circus of chicken wire you see in all the books), anthocyanins have a fragile structure which is stabilized in the grape somehow by enzymatically tacking on a glucose sugar molecule on the “C” ring, the one in the middle containing an oxygen molecule. This glucose protects the molecule from falling apart, but is itself a highly edible goodie which is vulnerable to attack by lots of enzymes from yeasts and other microbes. So the grape in most varieties tacks an acetic acid (vinegar) molecule onto the sugar to put a big bump on it which makes it fit poorly into the active site of the yeast enzymes which are trying to attack it. Tacking on a protective acetyl group is called acylation.

Pinot lacks acylated pigments.

The other way to stabilize pigment is to incorporate it into a polymer. This takes time, so the pigment is most vulnerable in the fresh wine. It’s important to get pinot to settle clear and let it see a tiny bit of oxygen when it’s young to stimulate oxidative polymerization. Unfortunately, unlike Cabernet and Petite Sirah, Pinot Noir doesn’t readily fall clear because it lakes tannin to fine down the yeast turbidity, so it’s doubly vulnerable.

Another problem Pinot has is that it is deficient in copigmentation cofactor. Anthocyanins aren’t soluble in 13% alcohol, so they need to be extracted into little beads called copigmentation colloids. But they are positively charged, so they repel each other and won’t form beads. Thus there need to be other monomeric phenols which will help glue the bead together. Pinot Noir in most weather conditions (except, say, the Sonoma Coast) is very low in these cofactors, so its pigments won’t come out easily. This is also true for Nebbiolo in most regions, which is what makes Barolo so special.