>Regarding "How and Why WIne Ages" you seem to have provided an incomplete
>explanation when you put it down to tannin. The white wines of Germany and
>Alsace are noted for their longevity and they have no contact with oak. It
>would appear that high levels of acidity, alcohol or sugar can also provde
>ageing capability. Is this not so?

The explanation I gave was meant to be simple, not comprehensive.

To say that Alsatian wines are noted for their longevity, is a bit of an overstatement. The great single vineyard Rieslings of Alsace certainly are best when aged longer than other Alsatians; however one does not look to them to age longer than say 15 - 20 years (not even Jancis Robinson expect more out of them).

The TBAs and the other better sweet Rieslings of Germany are again a style of Riesling that ages longer than its contact with wood suggests (they have a very slight oak contact in large oak containers).

In both cases it is primarily the acids that preserve the wine, rather than actually allowing it to change through bottle aging (tertiary aging). In this case aging is more a function of balancing the caramel flavors of oxidation with the freshness of the acidity. Once the balance swings towards the oxidation away from the acidic freshness, these wines are usually considered 'over the hill'. The residual sugars too play their part in disguising any off tastes that develop with age. A sweet wine can be amazingly out of balance, but as long as the sugar is high enough, these off flavors are below threshold.

Alcohol alone can not sustain wine. Look at white Port or white Armagnac. In both cases these 'wines' are missing tannins (the Port from the grape, and the Armagnac from the oak) and in both cases these are raw, simple wines, best consumed young.

Sugar alone can not sustain a wine. Look at the California sweet wines. Few have any real longevity, although they may have amazing amounts of residual sugar. In fact the longet lived sweet wine is by far Sauternes. I have had Ch. d'Yquem going back to pre-phylloxera. Sauternes is oak aged.

Acidity alone certainly can't preserve a wine, or allow it to age. Look at Beaujolais or Muscadet. Plenty of acidity here, but these wines are best exceptionally young. Some of the Cru Beaujolais do indeed age somewhat; however that is because the Gamay in those cases is treated like Pinot Noir.

The other notable wine that follows your Riesling model is the great Chenin Blancs of Coteaux du Layon. These sweet Chenins can reach amazing age; however again it is not so much aging as it is slow decay.