Whereas cows' milk mozzarella is pretty bland, mozzarella di bufala has an earthy - almost mossy - taste. This is in part due to the marshland of Campania around Naples, where most of the herds are reared. Originally buffalo were kept here simply because they were practically the only animals that could survive the bleak conditions. For hundreds of years the peasant farmers sold the cheese they made from the milk for next to nothing, until their product caught on with the foodies of Naples and became fashionable.
As with many Italian ingredients, things started to take off for buffalo mozzarella in the Sixties and Seventies, with the development of tourism and the arrival of an Italian trattoria on nearly every high street in this country.
Patricia Michelson started selling buffalo mozzarella in her London cheese shop, La Fromagerie, when she first opened for business seven years ago, although she says some customers still take a while to come round to the idea that it's made from real buffalo milk. "People can't quite believe that there are buffalo living in Italy," she says.
However, the cheese is now in such demand that Italy is not the only place you'll find the cattle today. In 1991 Bob Palmer and his wife imported buffalo into Britain. Now they have a herd of 200 on their farm in Warwickshire, and they produce their own buffalo mozzarella which they sell, in a coals- to-Newcastle arrangement, to an Italian wholesaler. They have also used the milk to make yoghurt and ice-cream.
Bob claims that the cattle adapt superbly to our environment. "Buffalo have different sweat glands to cows, which means they're less heat tolerant. So in many ways they are better off in a climate like ours, particularly during a summer like this one," he says.
l The best buffalo mozzarella is produced on the farms themselves, but with increasing commercialisation the milk is also dried or frozen so that cheese can be made on a larger scale in factories. Among other outlets, you can buy farmhouse mozzarella di bufala from the village of Battipaglia, just south of Naples, and from La Fromagerie, 30 Highbury Park, London N5 (0171-359 7440) for pounds 4.25 for 30g.
l Milk is not the only popular buffalo product. The meat is increasingly sought after because it is lower in cholesterol and higher in mineral content than beef - and because there has been no incidence of BSE in buffalo. You can buy British buffalo meat by mail order from Barrow Boar, Foster's Farm, South Barrow, Yeovil, Somerset (01963 440315). Supplies are still limited, so the meat is expensive: pounds 27 per kilo for rump steak.