Sanbokan: Japan’s rare, sour citrus fruit

Tom Schiller

Tokyo: When you think of Japanese cooking, chances are you may not think of citrus. But Japan produces some of the most diverse varieties of citrus in the world, and, after salt, the acidic juice from sour citrus is the single most important seasoning in the Japanese pantry.
It finds its way into condiments like ponzu marinades and fermented chilli yuzu kosho; it is used to brighten the flavour of almost every dish – including sushi and sashimi – and it is made into an infinite variety of preserves, desserts and drinks.
Today, thanks to its ideal growing conditions, Wakayama remains Japan’s top citrus-producing prefecture. Straddling the Earth’s temperate and sub-tropical zones, the region benefits from long, hot summers and winters just cool enough to ripen citrus.
And because Wakayama is a peninsula that juts out into the Pacific Ocean, it catches the heavy rainfall caused by the warm Kuroshio Current that flows up from the South Pacific along Japan’s eastern coastline, making the region the wettest semi-tropical area in the world.

As a result, Wakayama is commonly referred to within Japan as “The Fruit Kingdom”. And among the prefecture’s myriad varieties of juicy sweet mandarins, oranges and tangelos – and distinct lemon-like yuzu, lime-looking sudachi, mandarin-esque jabara, grapefruit-sized hassaku and bitter-orange daidai – one rare citrus stands out: the exceedingly sour and bitter, yet exquisitely delicious, sanbokan.

With its thick peel and unmistakably pronounced nipple, the sanbokan is instantly recognisable. It has a taste that is somewhere between a blood orange and a bitter grapefruit. Scientists have no idea how this unique citrus formed. Most say it’s a variety of orange. Others that it’s related to Japan’s ethereally fragrant yuzu. Some even say it’s a type of lemon. But according to legend, it comes from a single tree that grew inside the castle of the former feudal lords who ruled Wakayama prefecture until 1867.
I first heard about sanbokan from Shigeru Muroi, chef-owner of the Michelin-starred kaiseki restaurant Muroi in Kyoto, who told me that it’s his favourite citrus because, though very tart, it also has a sweet richness. He uses it when it’s in season each winter to finish his multi-course meals with a sophisticated, palate-cleansing flourish. Muroi also told me about the sanbokan legend: a samurai allegedly found the fruit growing wild sometime between 1818 and 1829 and brought the tree to the castle. Wakayama’s ruler restricted its cultivation and distribution so only those in the castle could taste it, and this “secret fruit” became part of the bracing diet of the feudal lord of Wakayama and his samurai followers.

As a citrus lover who has travelled widely across Japan enjoying its many unique varieties, I ventured to Wakayama to learn more about the largely unknown sanbokan and taste it for myself.
It was easy to see why Wakayama Castle, which sits imposingly on a hill in the centre of Wakayama City, was the most important military outpost of the Tokugawa Shogunate that ruled Japan during the Edo period (1603-1867).
Built at the end of the 16th Century, the castle was the fortress of the Kishu-Tokugawa family, one of three branches of the ruling Tokugawa samurai clan. Their mission was to protect Japan’s Honshu island mainland and the new capital at Edo-Tokyo from invasions from the south; in particular, a possible rebellion by the feudal lords of south-western Japan, who only nominally accepted Tokugawa authority.

The Kishu-Tokugawa lords of Wakayama restricted the cultivation of the castle-bound sanbokan until the late 19th Century. But in recent generations, local farmers have been propagating and spreading saplings of sanbokan and cultivating its fruit for broader consumption.
Yoshinori Kodama is one of these farmers. His farm, Kannonyama Fruit Garden, is located in Kinokawa, about 24km east of Wakayama City in a wide river valley. It’s a family business that was started 110 years ago, and Kodama is the sixth generation to tend the orchards that cascade down the mountainside. Kodama grows more than 100 fruit varieties, and in addition to citrus, he harvests Wakayama’s famous plums, persimmons, pears, peaches and grapes. According to Kodama, the only fruit that can’t be grown in Wakayama are bananas and pineapples.

Since taking charge in 2013, Kodama has reinvented the business and now mainly sells his produce online. He has also opened the garden to visitors, building a shop-cafe and guesthouse in the orchards where people can buy fruit and saplings, enjoy fruit-based desserts and spend the day picking fruit or stay longer as farmhands. Kodama began farming sanbokan three years ago because of the growing demand for it. He told me that it’s one of the easiest citrus trees to grow because it’s a “traditional Japanese tree, an old-time tree, and not a hybrid, which makes it strong and not prone to disease.”
Kodama described sanbokan as “very sour like a lemon, but a lemon with a king’s taste”, which he explained was a “well-balanced combination of sour, bitter and sweet tastes”. Its season runs from January through mid-May, becoming sweeter and fuller in flavour towards the end of the season. He said those who buy sanbokan are accomplished home cooks and restaurant chefs who appreciate its unique flavour.

Throughout Wakayama prefecture, sanbokan is widely available as jellies, jams, marmalades, candied peels and juices. But perhaps the best known sanbokan product in Japan is Misuzuame, made by the company Iijima Shoten in Japan’s northern Nagano prefecture where it is considered a traditional sweet. Misuzuame are a jelly candy made by mixing fresh apricot, grape, peach, apple and sanbokan with mizuame, a Japanese sweetening syrup, and kanten, a gelling agent made from seaweed.
Iijima Shoten invented Misuzuame in 1919. After World War Two, the then-head of the family-owned company, Shinsaburo Iijima, visited Wakayama, and, according to Hiroyuki Tanaka, head of Iijima Shoten’s business department, “Shinsaburo fell in love with the taste of sanbokan,” calling it “johin” (elegant). Afterwards, he added the fruit to the company’s line-up of jellies, in part because he was concerned that sanbokan might go out of existence. Not enough farmers were growing it, and he wanted to champion its cultivation and use. One result of his efforts was the planting of a sanbokan tree in the East Gardens at Japan’s Imperial Palace in Tokyo as a representative citrus of Wakayama prefecture.

Iijima Shoten obtains fresh sanbokan from farms near the city of Tanabe, located about 40 minutes south of Wakayama City by train. The fruit they use to make Misuzuame is harvested in January and February when, Tanaka said, “the fruit tastes the most sour, its unique aroma is the most fragrant, and its ethereal flavour the most transparent.”
According to Tsutomu Nomura, representative of the Tanabe branch of the Japan Agricultural Cooperatives, sanbokan remains a very rare citrus. Nomura told me that 97% of Japan’s sanbokan is still farmed in Wakayama, and the prefecture only produces 140 tons of sanbokan per year, compared to more than 12,000 annual tons of other types of citrus.
Nomura also happens to be a citrus farmer who is very proud of his trees, some of which are more than 70 years old. He said that sanbokan’s “astringent flavour is what all citrus used to taste like before much of it was hybridised to meet the popular demand for sweeter fruit,” adding that sanbokan is an “acquired taste”.

Citrus season was just getting underway when I arrived in Wakayama, and the region’s many farmers markets were already selling the kind of early sweet hybrid mikan mandarins that Nomura was talking about, including Hina no Hi, Yura N and one simply known by its hybrid symbol V2. They are the runup to mikan mandarin’s peak season in December, the prize of which is the Kishu-Mikan, a tiny, intensely sweet and juicy type of unshiu mandarin called satsuma. Traditionally, they are enjoyed while sitting at a kotatsu low table, and there is a particular way of peeling them so that the fruit resembles a flower.
It was too early for sanbokan, but I got my chance to taste its juice at Mikan no Ki, a shop in the old town of Arida, which lies at the centre of Wakayama’s citrus growing area. Mikan no Ki is housed in the renovated warehouse of Ito Farm, an orchard that specialises in bottling fresh additive-free citrus juice. The sanbokan juice was sweeter and more balanced than I expected, albeit still very sour and bitter. It had a faint orange taste – Meyer lemon like. It was surprisingly pleasurable to drink, which may be due to the fact that Ito Farm uses sanbokan picked in March and April when they’re riper and sweeter. Still, I realised that what makes Sanbokan unique is that it’s an edible sour citrus; one that does not need the addition of sugar to be palatable and delicious.

In fact, sanbokan is both eaten as fresh fruit and used as an acidic seasoning. It’s easy to peel, and once its large seeds are removed, it’s cut into chunks and served. Because it’s so high in citric acid, it’s also used by chefs to season winter’s rich seafoods, often taking the place of lemon. One way it’s used takes advantage of sanbokan’s large orange-like size: the fruit is cut in half, its flesh scooped out and the shells used as bowls, which are filled with such delicacies as chawan mushi (a seafood egg custard), steamed cod milt and fugu blowfish.
My final stop was back in Wakayama City to spend time in the garden at Wakayama Castle. I wasn’t expecting to find the legendary sanbokan tree because the castle was almost completely destroyed during World War Two and rebuilt in the 1950s. The garden, called the Nishinomaru Teien, is designated as “A Place of Scenic Beauty” by Japan’s Agency for Cultural Affairs. Reached by a covered bridge that crosses a moat, it’s truly a secret place; a powerful composition of massive rocks set around a serene pond that is surrounded by lush foliage.

The garden’s unusually masculine and refined design reminded me that the samurai who once lived here were not only warriors but also highly cultured devotees of Japan’s more esoteric arts and cuisine. Noh theatre, waka poetry and sumi-e ink-wash painting all flourished under their patronage, as did Zen Buddhism and its refined vegetarian cuisine.
The flavour profile of sanbokan fit the samurai aesthetic and culinary interests perfectly: invigorating yet nuanced, and soul-satisfyingly delicious. The appreciation of sanbokan by Wakayama’s samurai rulers also reflected their connoisseurship. They discovered the most delicious of Japan’s ancient sour citrus in their midst and kept it for their exclusive use. Today, it seems Japan is finally awakening to the culinary potential of this rarest of fruits, and you no longer need to scale the castle walls to find it.