Unearthing the Essence of Japanese Citrus (Part 1)

This article is part one of the two-part series on the unique Japanese citrus becoming increasingly popular globally. In this part one, we will discuss Kabosu and Yuzu. 

Kabosu and yuzu are two prized Japanese citrus fruits; each celebrated for theirKetan Shah, president, Esha Flavor Solutions, LLCCourtesy of Esha Flavor Solutions unique flavors and culinary versatility. Kabosu, native to Ōita Prefecture, is characterized by its tart, lemon-like juice and fresh fragrance. Typically harvested green, this fruit is a staple in the regional cuisine of Ōita, enhancing grilled fish, sashimi, hot pot, and serving as a substitute for vinegar in many dishes. Kabosu's history in the region stretches back centuries, with some trees believed to be up to 300 years old. Today, kabosu juice finds its way into a diverse array of foods, drinks, and even fish feed, which helps produce specialty seafood unique to the area.

Yuzu, closely related to kabosu, is equally beloved for its powerful aroma and sharp, citrus flavor. Harvested when yellow and fully ripe, yuzu is a key ingredient in Japanese culinary traditions, lending brightness to sauces, soups, sweets, and beverages. Its distinctive fragrance and acidity make it an irreplaceable element in Japanese kitchens, and its influence has spread globally, inspiring chefs and food enthusiasts worldwide.

Kabosu

Kabosu (Citrus sphaerocarpa) is a citrus fruit produced by an evergreen, broad-Kabosu is closely related to yuzu and is valued for its tart, lemon-like juice.Picture Partners at Adobe Stockleaf tree in the Rutaceae family. Highly regarded in Japan, particularly in Ōita Prefecture, kabosu juice is widely used to enhance the flavor of various dishes, especially cooked fish, sashimi and hot pot dishes.

Description

Kabosu is closely related to yuzu and is valued for its tart, lemon-like juice, which is sometimes used as a substitute for vinegar in Japanese cuisine. The fruit grows on a flowering tree equipped with sharp thorns and is typically harvested while still green, although it will turn yellow if allowed to fully ripen. Kabosu is sometimes mistaken for similar citrus fruits like sudachi, but it can be identified by the slightly raised torus shape at the apex, where the pistil has fallen off.

Origin

Kabosu is believed to be a hybrid between ichang papeda and bitter orange. The term "kabosu" did not appear in literature until the mid-Showa period. According to legend, cultivation in Ōita Prefecture began when a doctor named Sogen brought a kabosu seed or sapling from Kyoto during the Edo period. Notably, some kabosu trees in Ōita are older than those found elsewhere in Japan, leading to the belief that kabosu may be native to the region. In Usuki, there are numerous trees estimated to be 200 years old, with some believed to be as old as 300 years. 

The 1960s saw an increase in kabosu cultivation in Ōita, and the fruit began to be shipped to other prefectures. Prefectural promotion in the 1970s fueled further growth, making kabosu a well-known Ōita specialty throughout Japan by the 1980s and 1990s.

Usage

Kabosu juice is notable for its sourness and unique fragrance. It is commonly used with sashimi, grilled fish, ponzu for hot pot and as a vinegar alternative in Japanese dishes. In Ōita Prefecture, it is also incorporated into miso soup, noodles and shōchū, where a few drops of juice provide additional flavor. When squeezing kabosu, cutting it into vertical quarters and pressing with the peel side down helps prevent seeds from entering dishes or drinks. 

Kabosu juice is an ingredient in a wide array of products, including condiments, beverages (both non-alcoholic and alcoholic), frozen desserts, snack foods, traditional Japanese wagashi and pastries. Furthermore, when added to fish feed, kabosu's polyphenols help prevent discoloration and odor in fish meat, resulting in specialty products like Kabosu Buri (Japanese amberjack) and Kabosu Hirame (summer flounder) in Ōita.

As of 2018, Ōita Prefecture produced approximately 99% of all kabosu in Japan.yamasan at Adobe Stock

Production

As of 2018, Ōita Prefecture produced approximately 99% of all kabosu in Japan. The fruit is grown across most areas of the prefecture, particularly in Usuki, Taketa, Bungo-Ōno and Bungotakada. 

In 2007, total kabosu production in Japan was 5,185 tons, with Ōita contributing 5,019 tons, Aichi Prefecture 144 tons and Miyazaki Prefecture 17 tons. The main production district of Ōita accounted for 97% of national output. 

Production volumes can vary year to year: 2009 was especially productive, yielding about 6,587 tons in Ōita, while 2010 and 2011 saw 3,623 and 5,273 tons, respectively. Kabosu is typically in season from August to March; however, storage methods and greenhouse cultivation enable year-round availability.

Kabosu Essential Oil Composition

The essential oil derived from kabosu features a complex and rich profile of aromatic compounds, contributing to its distinctive fragrance and sensory qualities. The following table lists the major and minor components identified in kabosu oil, including their retention times (RT) and relative percentages:

Yuzu

Overview

Yuzu (Citrus × junos), is a citrus fruit and plant belonging to the Rutaceae family and originates from China. Traditionally cultivated across East Asia, yuzu has more recently been grown in countries such as New Zealand, Australia, Spain, Italy and France. It is believed to have arisen in central China as a hybrid between the mangshanyeju, a subspecies of mandarin orange, and the ichang papeda.

Yuzu fruits resemble yellow clementines with uneven skin, and their color ranges from yellow to green depending on ripeness.taiyosun at Adobe Stock

Description

Yuzu fruits resemble yellow clementines with uneven skin, and their color ranges from yellow to green depending on ripeness. The fruit is highly aromatic and generally measures between 5.5 and 7.5 cm (2 1⁄8 and 3 in) in diameter, though some fruits can reach the size of a grapefruit (up to 10 cm or 4 in, or larger).

The yuzu plant forms an upright shrub or small tree, often with many large thorns. Its leaves are distinguished by a large, leaf-like petiole, similar to those of the related makrut lime and ichang papeda and are strongly scented.

Yuzu closely resembles sudachi (Citrus sudachi), a Japanese citrus from Tokushima Prefecture that is a cross between yuzu and mandarin orange. However, yuzu eventually ripens to an orange color, unlike sudachi, and there are subtle differences in the flavors of their fruits.

Cultivation

Originally growing wild in Tibet and central China, yuzu was introduced to Japan and Korea during the Tang dynasty and continues to be cultivated there. The plant grows slowly and typically takes ten years to bear fruit, although grafting onto karatachi (P. trifoliata) can shorten this period. Remarkably, yuzu is relatively frost-hardy due to its Ichang papeda ancestry and can survive winters as cold as −7 °C (19 °F), unlike many more sensitive citrus species.

Varieties and Similar Fruits

Japan cultivates an ornamental yuzu variety known as hana yuzu for its flowers. The sweet yuko variety, only present in Japan, became severely endangered in the 1970s and 1980s, prompting extensive efforts to revive it in southern Japan. Another Japanese yuzu variety, shishi yuzu, is characterized by its knobby skin.

Dangyuja, a Korean citrus fruit from Jeju Island, is often considered a type of yuzu due to its similar shape and flavor, though it is genetically a pomelo variety.

Production and Culinary Uses

Japan's domestic yuzu production was about 27,000 tons in 2016. Although yuzu is rarely eaten fresh, it is a staple ingredient in Japanese cuisine. Its aromatic zest and juice are used similarly to lemons in Western cuisines. The fruit’s flavor is tart and fragrant, reminiscent of grapefruit with mandarin orange notes.

Yuzu is a key ingredient in ponzu, a citrus-based sauce, and yuzu vinegar is alsoThe essential oil derived from Yuzu features a complex and rich profile of aromatic compounds.Tsuboya at Adobe Stock produced. The fruit is commonly combined with honey to create yuzu hachimitsu, a syrup used for yuzu tea and as a component in alcoholic beverages like yuzu sour. Yuzu kosho (also yuzukosho, "yuzu and pepper") is a spicy Japanese condiment made from yuzu zest, chili peppers and salt.

The fruit is also used to make liquors, such as yuzukomachi and wine, and is featured as a garnish for dishes like chawanmushi (savory egg pudding) and miso soup. Yuzu is used alongside sudachi and kabosu and is incorporated into various sweets, such as marmalade and cake, as well as the flavoring in many snack products, including Doritos.

Yuzu in Korean Cuisine

In Korea, yuja is primarily used to make yuja-cheong (yuja marmalade) and yuja tea. Yuja-cheong is made by sugaring peeled, depulped, and thinly sliced yuja, while yuja-cha (yuja tea) is prepared by mixing hot water with yuja-cheong. Another common dessert is yuja-hwachae (yuja punch), a variety of hwachae (fruit punch). Yuja also appears in Korean-style Western dishes, such as salads.

Cultural and Other Uses

Yuzu is celebrated for its strong aroma, and its skin oil is marketed as a fragrance. In Japan, bathing with yuzu on Tōji, the winter solstice, is a tradition dating back to at least the early 18th century. Whole fruits are floated in hot bathwater, sometimes enclosed in cloth bags, releasing their scent. The fruit may also be halved, allowing its juice to mix with the water. The yuzu bath, known as yuzu yu or yuzu buro, is believed to prevent colds, treat skin roughness, warm the body, and relax the mind.

Yuzu in Western Countries

In the early 21st century, yuzu gained popularity among chefs in the United States and other Western nations, notably featured in a 2003 New York Times article. The U.S. Department of Agriculture restricts the import of fresh yuzu and most citrus plants, including both fruit and trees, to prevent the spread of crop diseases. However, due to its introduction to California in 1888, yuzu is cultivated and available for sale within the United States.

Yuzu Essential Oil Composition

The essential oil derived from Yuzu features a complex and rich profile of aromatic compounds, contributing to its distinctive fragrance and sensory qualities. The following table lists the major and minor components identified in Yuzu oil, including their retention times (RT) and relative percentages: