Among sweet wines, ice wine is one of the most intriguing. Its production demands great devotion and hard work from the grower.

There is also the danger of losing all the grapes in the vineyard because the grower has to wait until the temperature drops to at least minus seven degrees centigrade.

These days, thanks to global warming, such low temperatures do not occur in Europe until January, or even February.

By then the birds, winter storms or grey rot - a destructive mould - may have ruined the entire crop.

So the grower has to watch his thermometer into the small hours of cold winter nights. If the temperature dips to the required minimum, he will wake up his family - and any neighbours willing to help - in the early hours.

They rush to the vineyard to collect bunches of frozen grapes and dash back to the winery to press them. The frozen water in the grapes must not be allowed to thaw.

Only a few drops of super sweet and unfrozen liquid in the centre of each grape will be collected.

The fermentation of the juice results in one of the world's greatest sweet wines, displaying intensive clean fruit with high refreshing acidity, mineral richness and relatively low alcohol.

Best suited for ice wine are grape varieties that have good acidity to balance their sweetness. Riesling is the most popular grape used in Europe and overseas.

The Canadians have developed a grape variety called Vidal' that is increasingly being used to make ice wine.

The Canadians have an advantage over the Europeans as their winters are colder earleir - thus reducing the risk of losing the crop.

There are less expensive freezer-made ice wines can be found in the United States and New Zealand. Such wines were also made in Canada and Australia before agreements were reached with the European Union.

A wine made from grapes from the freezer can be quite good, but it may lack the complexity of the real ice wine made from grapes which have frozen naturally and then thawed several times prior to picking.

Each time the grapes freeze, new and more complex flavours are released into the juice from the grape.

Unfortunately, it is very difficult to find ice wine in the shops or supermarkets in the Oxford area.

However, Oxford Wine Company has three different Riesling ice wines in stock.

The Mission Hill wine from the Okanagan Valley in Canada is in a small bottle and nicely packaged. It makes an ideal gift for a wine lover.

The two other ice wines are from Germany. One is from Dönnhoff, one of the top producers in the Nahe area, the other from Dr Loosen.

They say they are considering adding a less expensive cuvée from Austria to their portfolio. The Oxford Wine Company should also try get hold of some of Moldova's ice wines.

This Eastern European country gets minus 15C frosts every winter, and its winemakers, trained in Germany, will soon be introducing their cheaper ice wines to the UK market.

The cold spell in December last year enabled the German and Austrian winegrowers to make ice wine of superb quality. Let's hope that some of it will come onto the UK market!

When visiting wineries in Germany or Austria, don't fail to ask for an ice wine to taste. And if you travel by car, take some bottles home. You will find excellent ice wines for around 30 Euros.