Over the Christmas and New Year festivities I got to taste some remarkable wines, beginning on Christmas Eve with a magnum of Antonio Gaja's 'Sperss' ( which means something in his Piedmontese dialect) and a bottle of Rosemount's 'Balmoral', both of which are spectacularly good wines. I won't bore you with a list of wines that made the year's end memorable, but they did get me thinking, what makes a wine great as opposed to simply good?

The first part of the answer to that is easy; the taste. A wine should please the palate. But some cheap and commercially produced wines can please the palate and not even their makers would call them great, so there's more to it than pleasing the palate. A great wine doesn't just please: like a lover it should also intrigue you, surprise you with nuances, excite the pleasure centres in your brain, please the eye, linger tantalisingly as a taste sensation and lastly it should leave you wanting more. We have, thankfully, a shorthand for describing this phenomenon, we call it 'complex'.

This complexity doesn't come easily to wine and it's mostly a product of age and maturation in the bottle. That means that a wine has to be well-structured to begin with, or it won't survive the aging process. There's a natural ingredient in grape skins called tannin, which acts like a preservative. There's much more in red wine than white, and when it's in a young wine it has an almost sour taste, but it's what gives a wine the structure to age well. It's present in large quantity in oak, so putting wine in new oak barrels is a way of introducing tannins to wines that are naturally low in them. Its preserving effect allows a wine to age without going off and lets some of the subtler flavours emerge with the passing of time and blend into a harmonious unity.

Keeping wines for aging is keeping your capital tied up, so older, aged wines are more expensive than young ones. But apart from price there are clues that can give you an idea of whether a wine maker rates his own wine. Is it a well-printed label? Is the bottle heavy and well-made? Does it have a good, long cork? Does it have a metal capsule around the top rather than a plastic one? Rarely do wine-makers add these expensive things to a poor wine.

Wine of the Week

Almaviva, Concha y Toro, 1998

A truly remarkable wine from South America, a joint venture between Concha y Toro and Baron Philippe de Rothschild. Drinking it now is almost certainly infanticide, it's a wine that will improve enormously with age, yet even in its youth shows greatness. Complex (see above) and sinuous it can hold its own with any of the great Bordeaux chateaus. Expensive, but still value for money.

Available Superquinn, RRP €66.55