Why are truffles popping up on the McDonald’s menu?

Meera Cortesi is cross about truffle oil. Really cross. ‘Never, never, never order truffle oil!’ she barks down the phone. ‘It’s got no truffle in it. It’s pure chemical, artificially re-created essence of truffle. It’s designed to give us the notion of truffle as opposed to anything that is really truffle.’ 

Cortesi, a 48-year-old banker-turned-truffle dealer, has been buying and selling truffles for 17 years, but it’s only recently that truffle oil has become so massive. Seriously, the stuff is everywhere. Pubs flog truffle chips and truffle mac and cheese; Pizza Express has truffle dough balls; McDonald’s sells truffle mayo; and in Sainsbury’s you can get gold-packaged truffle Marmite for £4.50. 

In fact, things got so bad that, last December, French authorities intervened. ‘You get things that say “natural truffle flavour” that have no truffle in them at all,’ said the head of the French truffle federation, Alain Ambialet, in a statement. ‘They contain things like cabbage and beetroot instead.’ Shoppers, he warned, were being ‘misled’. 

You can tell a real truffle by its smell, says Michelin-starred chef Chris Galvin. The 64-year-old is pro real truffles (‘in the kitchen we call them black diamonds’) and anti fake truffle oil (‘I just cannot eat it’). 

That distinctive aroma is partly caused by androstenone, a musky chemical that – if you ever wondered – makes female pigs want to mate. Scientists reckon 25 per cent of humans don’t smell androstenone at all; 35 per cent of us like it; and 40 per cent are keenly sensitive to it (in other words, think it smells revolting). 

This makes sense. When I ask Galvin to describe the smell of truffles, his voice goes all dreamy: ‘That’s the million dollar question. It’s smouldering and meaty. It’s almost…’ He pauses. ‘Colourful! I think truffles have a deep, black, velvety smell.’ Interesting, because I think truffles smell like feet. 

Still, good or bad, velvety or hoof-like, we agree that truffles are pungent. ‘I once got off the tube at Piccadilly Circus and could smell truffles everywhere,’ says Galvin. ‘I walked quicker and quicker and the smell got stronger and stronger. Eventually, I caught up with this man carrying a canvas bag. He turned around and it was Thierry Laborde, who’s a well-known chef. I said: “Have you got truffles in your bag?” And he said: “Yes!” I mean, can you imagine what that smell must have been like on the tube?’ 

It’s risky carrying around real-deal truffles in a flimsy tote bag: these fungi aren’t cheap. Galvin buys black truffles for ‘around £1,000 a kilo’ and white truffles for ‘£4,000 a kilo and upwards’. The world’s most expensive truffle sold for $330,000 (£160,000) at a charity auction in 2007. It came from Tuscany, weighed 1.5kg and was bought by a casino owner, Stanley Ho. Curiously, Damien Hirst also bid for it over the phone from Cornwall, but he bowed out at $130,000 (£63,000); apparently the Brit artist bellowed down the line, ‘I’m walking down a beach. F*** it!’, and hung up. 

Truffles have always been popular. The ancient Sumerians snacked on them in 3000 BC; the ancient Egyptians slathered them in goose fat and ate them raw; and the Roman emperor Nero called them a ‘delicacy from the Gods’. Napoleon thought truffles were an aphrodisiac (unlikely) and Lord Byron kept one on his desk because he was convinced the smell inspired creativity (the proof is in the poems). 

They’ve always been hard to source, too. Truffles need very specific conditions to grow: the temperature has to be cool and damp, the soil slightly acidic, and the rainfall has to come at precisely the right moment in the growth process. Italy and France have the most suitable climates for this, China and Australia are fine, and Britain produces the odd truffle in summer. But these are finicky fungi: you can’t plant them just anywhere, turn on the sprinkler and cross your fingers. 

Also, unlike mushrooms, truffles grow underground, attached to the roots of trees. So, while mushrooms are spread because their spores get blown about by the wind, truffles are spread because animals – pigs and boars mostly – eat them in one place and then deposit their dung in another. It means that, unless a pig eats one and then decides to walk for miles before defecating, truffles tend to stay in one spot. 

And being underground means truffles are difficult to find. For a long time, farmers used pigs to sniff them out, but the animals are greedy and hard to train: they would find the truffles and eat them immediately. In 1985, Italy banned truffle pigs and, wisely, switched to dogs. (Although canines have their own problems, too: this month The New York Times reported that Italian truffle hunters were trying to kill their rivals’ dogs with poisoned tennis balls.) 

Now comes the really complicated part: once a truffle is out of the ground, you have only about 20 days to eat it. That’s because the fungi are around 70 per cent water, and when exposed to the air they start to sweat. Every day truffles lose around 3 per cent of their weight; after about five days, the aroma and flavour will have halved. 

Galvin buys truffles in small quantities only, so he can be certain he will sell them. Most restaurants shave thin slices of fresh truffle on to food; at some establishments, customers’ plates are weighed and they’re charged by the gram. 

To make his truffles last, Galvin has a few tricks. Apparently, if you store truffles in a container with eggs or rice, their flavour will spread and you can make truffly scrambled eggs or truffly risotto. But not all chefs are so cautious. In 2004, London restaurant Zafferano spent £28,000 on a 700g truffle from Tuscany – only to put it in the kitchen safe, where it turned mouldy. On hearing the news, the Tuscan truffle association requested the restaurant send the rotting truffle back to Italy so that it could be given a formal burial. 

Still, Galvin thinks that drama is part of the truffle’s appeal. ‘They’re quite mythical,’ he says. ‘You can’t count on them. You don’t know how bountiful the season is going to be.’ These days, most farming is engineered, mechanised, precise – but not truffles: ‘I like that we’ve got the mystery left.’