Nicholas Lander on the secrets of the best prosciutto

Thirty-five years ago Pio Tosini, who died earlier this year aged 95, lost an argument that has had a profound effect on menus all over the world.

Tosini was one of the pioneers of prosciutto, the silky air-cured ham that is equally delicious with melon, figs, draped around breadsticks or eaten on its own with an aperitif. He argued then that this ham should be marketed and sold as 'prosciutto di Langhirano', the town 20 kilometres east of Parma where its production has been pioneered and refined for the past century but he was outvoted. As a result, prosciutto di Parma, Parma ham, was born.

To this day there is still some resentment amongst Langhirano's citizens that they have been deprived of the recognition that was their due. But, after visiting what can most simply be described as 'pig city', I can report that commercially at least Langhirano's 3500 citizens have not allowed this snub to hold them back.

Virtually the entire community works either for one of more than the 100 'prosciuttofici' based here or in some associated business. The only other grand looking shop I passed, other than those which are common to all Italian towns, turned out on closer inspection to be a showroom selling machines for slicing prosciutto, salami or coppa.

Although currently in one of the two busiest periods of its year – here the six weeks pre Christmas are as busy as July and August – there is no sign whatsoever from the main street of the frenetic activity inside. This is partly because what makes prosciutto so special is just the time, up to 24 months, the hams are left to hang having been salted, massaged and cured.

But the other reason is more particular and is Pio Tosini's most long-lasting legacy to prosciutto lovers world-wide: that Langhirano's location between a small mountain range and the plains with a small stream to the north provides the ideal conditions, once the hams have been salted, to let Nature provide the cure.

The simplicity of this approach has left Langhirano with one unfortunate architectural legacy – the only distinguishing feature of the many prosciuttofici is the company name outside. Otherwise the buildings look identical: long, narrow, two stories tall with, most crucially, wide, full-length windows invariably painted green which during the spring and summer are left wide open to let the fresh air circulate.

But they remain firmly closed when the weather is not so clement – and I was there on a day when the rain was so heavy there was 100 per cent humidity – when modern air-conditioning is used to keep the hams at the correct temperature. Yet despite technology the best producers still rely on several traditional methods and in the process provide another paradox which contradicts modern medical thinking: despite a hefty part of their daily diet being taken in high-cholesterol pig products why do the citizens of Langhirano look so fit, thin and healthy?

Initially, everything inside a prosciuttofico looks highly automated, modern and ultra clean. Hams swing horizontally and vertically on inert plastic trays in and out of refrigerated rooms and the production staff, dressed entirely in white, look until they smile, highly clinical. But, ultimately, the distinctive flavour depends on three far more old-fashioned factors.

The first is human. After being salted twice, the hams rest for 24 days at one to four degrees centigrade before passing through a pummelling tunnel which takes away any excess salt and relaxes the tissue to allow the salt to penetrate evenly. Then, before they are put to rest for the next 100 days one man steps forward and squeezes the ham around the bone to ensure that, crucially, the last drop of blood is removed.

After six months the hams are hung to cure for the rest of their stay on huge wooden beams that stretch floor to ceiling and held, in the two rooms I walked around, 30,000 and 35,000 hams respectively. Introduced over 50 years ago these wooden racks have even passed muster with the US's tough food police who were ultimately convinced by the argument that as the hams were fully cured by the time they are put out to hang they cannot be adversely affected by coming into contact with wood – an argument many European cheesemakers who mature their cheeses on wooden racks would like to win.

The final touch is, however, almost medieval. Each prosciutto is serially stamped, with the number of the farmer who bred the pigs, the abbattoir and the curer. But the final stamp of the Consorzio di Prosciutto di Parma, which ultimately decides whether a ham is good enough when it is one year old, is bestowed by an independent inspector with the help of a pointed piece of horsebone, taken from the femur and about four inches long. This 'instrument' is similar to a cheese iron used to penetrate Stiltons, Cheddars or wheels of Parmesan but because it is porous bone rather than metal it is far more sensitive to the sweet aromas of the ham. Once the ham has passed this final test it receives its most conspicuous Ducal stamp and is on its way around the world.

Surprisingly the citizens of Langhirano, despite their working day preoccupied with prosciutto, seem to want to eat it at every opportunity. Lunch consisted of two trays of prosciutto and a wedge of Parmesan (whose production 45 minutes away is key as the left-over whey is fed to the pigs) and dinner at the local Trattoria La Buca began with four different salamis and more trays of prosciutto.

But, as Nicola Ghersetich, production manager at Pio Tomasi, explained, there may be more to prosciutto than just great flavours. 'Virtually everyone in this restaurant is in the business but there is nobody overweight or obese.' The prosciutto paradox, like its French counterpart, may repay further study.

Top prosciutto producers other than Pio Tomasi include Tanara, Leporati, Galloni, Bedogni and Sant'ilario.