As I wandered through the crowded Farmers’ Market on Sunday morning in Kochi in Shikoku, admiring the persimmons and queuing up for the fluffiest sweet potato fritters, I noticed a pervasive aroma drifting on the mild November air. It was an energising fragrance that hinted at bergamot and grapefruit. “Oh, yuzu!” exclaimed my Japanese companion, sniffing the air in delight. “Can you smell it? It reminds me of my childhood. We always put whole yuzu in our baths during the winter solstice.”

We pushed our way through the crowd of local shoppers to discover trays of leafy golden yellow citrus fruit. It was hard to believe that the heavy scent was emanating from them. They were slightly bigger than a satsuma, but rounder and with a rougher skin. They looked beautiful, neatly displayed beside crates of pale lemon bottled yuzu juice. October and November are peak yuzu season in Japan.

The origins of yuzu are shrouded in mystery. It is thought to be a hybrid between the Ichang papeda C. ichangensis, a wild, hardy papeda, native to southwestern and west-central China and the mandarin (also known as satsuma) C. reticulate which evolved in Vietnam, south China and Japan. No one knows whether the yuzu originated in China and then spread into Korea or the opposite, but all agree that it was introduced into Japan via the Korean peninsula during the Nara period (710-794AD). Today, Japan is the biggest producer and consumer of yuzu in the world. Most is grown in Shikoku, Kyushu and Kyoto.

Driving through Kochi Prefecture in Shikoku on the way to Umaji, a tiny mountain village famous for its organic yuzu orchards, small, unruly yuzu trees, laden with golden fruit, are everywhere. Every house has its own tree and higher up towards the dark cedar forests, there are narrow terraces of yuzu orchards. Parked near each were small white pick-up vans laden with crates of freshly picked yuzus.

Kochi prefecture currently produces almost half of Japan’s yuzu. Its warm marine climate, cool nights and high rainfall are perfect growing conditions for yuzu trees. I was travelling to meet Mr Hiroyuki Shimota, a member of Japanese Agriculture Umaji Village Co-Operative, which was formed in 1948, when the villagers depended on forestry for their livelihood.

He was picking yuzu on his steeply terraced orchard. The dewy morning air was filled with tiny dancing insects. Crickets sang in the grass and yellow butterflies fluttered through the trees. Music from Mr Shimota’s van’s radio resonated across the valley and far below a river burbled through the village.

Using long clippers, Mr Shimota deftly cut the fruit from their thorny branches. He paused and dropped them on to a pile beneath the tree. “My father, like everyone in the village, grew rice and worked in forestry. Then in 1961 the government passed a law on fruit promotion and development. We were discouraged from continuing in forestry, so the village co-operative voted to cultivate yuzu as we already had trees growing around our houses. We decided to grow them organically as we all had several jobs and couldn’t spend too much time tending them.”

He pruned a few branches thoughtfully and pulled some trailing lichen from the bark of his tree. “The old, ungrafted trees give the best-flavoured fruit. They can be planted from seed, but I mainly buy grafted trees from Japan Agriculture as they have larger, better looking fruit.” Fresh yuzu juice is similar to a lemon in sourness but has a complex floral flavour with hints of grapefruit.

Over the years he felled some of the forest to build higher terraces to grow more yuzu trees. They can withstand temperatures as low as -9C but the cool wet climate and organic farming methods meant that Umaji’s fruit couldn’t compete with the large, flawless yuzu sold at market.

Slowly, the village developed their own brand and manufactured their own products to add value to their fruit. They created their own bottled ponzu sauce, made from yuzu juice, vinegar, soy, mirin, kelp and bonito flakes; yuzu vinegar for vegetable sushi, Gokkun (Gulp), a honeyed soft drink, and yuzu kosho—a spicy salted fermented yuzu paste seasoned with sansho peppers.

Nothing was wasted. In April and May, once the fruit has set, the flower petals are picked and turned into cosmetic products, as are the pips—an oil rich by-product of juicing. Crucially, they marketed their products as being homely and natural.

For centuries, Japanese mothers had served homemade ponzu with their winter nabemono (things-in-a-pot) and added aromatic yuzu zest to their soups, simmered dishes and relishes. However, the Japanese government’s drive in 1961 to promote home-grown fruits, led to a nationwide increase in the consumption of yuzu from pickles to sweets. Domestic cooks began to buy ready-made sauces, while chefs began to treasure fresh yuzus as a means to evoke seasonality in their food.

Golden ripe yuzu conjure up late autumn and winter in Japan, while the verdant aroma of grated or finely sliced green (unripe) yuzu zest added to summer salads and sashimi creates a sense of cool, green freshness. Green yuzu juice is too bitter to use.

Keiji Miyabe, executive chef of Wadakura in the Palace Hotel, Tokyo, explains: “Yuzu used to be a really popular ingredient in home cooking, but now it’s mainly used in restaurants. When I was child growing up in Kumamoto in Kyushu, neighbours often shared home-grown produce like yuzu. My grandmother would make a big nabe (Japanese hot pot dish) and serve it with soy sauce mixed with yuzu juice. The fruit didn’t look beautiful, but it tasted delicious.”

Inspired by such memories, he mixes the finest white shoyu with yuzu juice and serves it as a dip for sashimi; or steams savoury egg and yuzu juice custards in yuzu shells with propagule and mountain caviar to evoke a wistful wintery feeling.

As Japanese chefs began to use more yuzu in their cooking, an increasing number of French chefs such as Pierre Hermé and Michel Bras opened shops and restaurants in Japan. Inevitably, awareness of the aromatic properties of yuzu spread into French cuisine. Hélène Darroze, of the eponymous two-Michelin-starred restaurant at the Connaught in London, fell in love with its taste 10 years ago. “I’m a big fan of Japanese food and noticed that yuzu was used a lot on Japanese menus. It’s a taste that you appreciate more and more with time. It adds the perfect touch of acidity to dishes, such as with caviar, oyster and sea urchin or chestnut mousse with yuzu foam.’

She buys fresh yuzus from Baches Nurseries in France, but other chefs, such as Martin Zahumensky, head chef of the recently opened Urban Coterie in Shoreditch are sourcing fresh yuzu from Japan for dishes such as Orkney scallops, radish and apple, where the scallops are marinated like a ceviche in the zest and juice of yuzu.

In the last two years, the popularity of yuzu in Britain has rocketed with chefs adapting it to their own style of cooking. Yuzu juice is now sold by supermarkets such as Waitrose, but as the Economic Section of the Embassy of Japan explains: “in order to export fresh yuzu to the EU, exporters have to be inspected by EU officials and get approval for each farm, clarifying that there are no significant diseases, so the number of farms currently exporting yuzu is very limited.”

Yuzu producers, such as Umaji village, have noticed increased demand, and neighbouring villages, such as Kitagawa, are now exporting their fruit to Europe. Sitting in the homely Umaji Community Centre, sipping a yuzu-flavoured beer after a delicious meal, redolent with yuzu, I find it impossible to imagine my world without yuzu. It’s simply too good.

Umaji Community Centre:

www.umaj.gr.jp/lodging.php#new_house

palacehoteltokyo.com

www.japancentre.com sells fresh yuzu and yuzu products.

www.seejapan.co.uk