Rare Italian white truffles cost over $4000 per kilo - here's why real truffles are so expensive

• Truffles are one of the most expensive foods on the planet.
• The most prized varieties could cost you over $4000 per kilo.
• The English Truffle Company finds autumn truffles across the South of England, alongside truffle hunting experiences and truffle dog training.

The luxury cousins of the mushroom, truffles are an indulgent food enjoyed across the world. But these fragrant fungi will cost you.

In 2014, the world's largest white truffle was flown to New York, accompanied by a security guard, and sold at auction for $61,000. Discovered in Italy, this gigantic fungus weighed almost 2 kilos.

So what is it that makes them so expensive?

There are a lot of types of truffles. There at least 40 species, many of which aren't edible - and new species have been discovered as recently as 2018.

You've probably seen luxury truffle products in supermarkets or fancy restaurants. But the unique truffle flavour you recognise might not be real truffle at all. Cheap truffle oil often hasn't been anywhere near a real truffle.

Many cheaper truffle products use 2,4-dithiapentane, a synthesized compound containing one of the main aromatic compounds in foot odor - guaranteed to give it that that "earthy" taste.

Real truffles are seasonal and pricey, with a short shelf life. They were originally sniffed out using truffle pigs, but these days dogs are much more common truffle-hunting companions. These fungi can be found across the world, but they all require a very specific climate to grow. While different varieties may have somewhat different requirements, one thing is certain: You can't have truffles without trees.

Even when you have exactly the right conditions, truffles aren't guaranteed. And hunting them is a labour-intensive process. Once you know where to look, you have to sniff out and dig up each truffle by hand, and they can be tricky to find. It may take a while, but finding a good one can make it worth the work, a 80g truffle can be worth over $100.

Truffles also have a short season, often appearing for only a few months of the year. And even when you do get your hands on them, they have a very short shelf life. After just five days, the pungent truffle smell will have halved.

You can farm many truffle varieties, besides the rare Italian whites. Many people have been successful in setting up truffle orchards, but it's not easy. Trees need to be planted in the right soil conditions, inoculated with truffle fungus, and often irrigated constantly. It can take as long as six years before you get a good truffle harvest, and there's no guarantee that the fungi will grow at all.

These days, farming has taken over as our primary source of truffles - and today, 70% of the world's truffles are cultivated.

Through the loss of woodland and climate change, the number of wild truffles has decreased significantly. Since the 19th century, production in France has fallen from over 1,000 tonnes a season to just 30 tonnes. And climate change could mean that truffles will disappear altogether in the future.