Sudachi (Citrus sudachi; Japanese: スダチ or 酢橘) is a small, round, green citrus fruit of Japanese origin that is a specialty of Tokushima Prefecture in Japan. It is a sour citrus, not eaten as fruit, but used as food flavoring in place of lemon or lime. Genetic analysis shows it to be the product of a cross between a yuzu and another citrus akin to the koji and tachibana orange.
Cultivated for centuries in parts of Japan, and perhaps nearly as well known as another sour citrus, the yuzu in that country, it has been considered an "indispensable companion" to eating matsutake mushroom. The ponzu (ポン酢, "pon vinegar"), the squeezed citrus juice used as an alternative to vinegar uses sudachi among other bitter oranges (kabosu or yuzu juices, and daidai) as an ingredient.
The fruit is also the specialty and symbol of the prefecture of Tokushima, which produces 98% of the fruit sudachi in Japan. The top producing communities are the township of Kamiyama-cho and the village of Sanagouchi-son, which placed 1st and 2nd place according to 2008 statistics with a combined share of almost half of the prefecture's annual production. The plant has white flowers which bloom in May and June. The fruits form in bunches, or tight clusters, and are harvested in the fall. Though sudachi fruits will eventually develop a yellow-orange rind color, they are normally harvested and used while still green. They contain large smooth seeds, containing a green polyembryo.
The sour sudachi is not consumed as whole fruit, but normally squeezed like a lemon or lime to flavor food. A half-slice of this fruit is served as garnish with many traditional Japanese dishes which include fish, soba, udon, nabe, and even some alcoholic beverages. It is considered to have a zestier flavor and aroma than lemons or limes. It also boasts a higher calcium and ascorbic acid (vitamin C) content than lemons. Sudachi flavored products (such as ice cream, vodka coolers, ice pops, and soft drinks) can also be found in Japan, particularly in Tokushima Prefecture, where the fruit is sold cheaply. The actual fruit is regarded as a delicacy in other parts of Japan, and is often expensive. Compared to the related kabosu, sudachi is much smaller at 20-25 to 40 grams as compared to 100 to 140 grams.
Its species name was published by Mitsutaro Shirai (1933), but most modern scientists, even while still using this nomenclature by habit or as legacy, do not consider it as a bona fide species, but a cultivar or a hybrid of uncertain parentage. Recent genetic analysis has confirmed its status as a hybrid, with one parent being the yuzu, and the other an unidentified relative of two native-Japanese cultivars, the koji and tachibana orange.
The sudachi was classed within the Papeda subgenus in the Swingle scheme, and in the more complicated Tyozaburo Tanaka scheme within the Eusmocitrus or true yuzu subgenus, under the Osmocitrus or yuzu section.
The flavonoid eriocitrin abundant in lemon and lime juices is present in comparable concentrations in sudachi juice, but is lacking in yuzu or kabosu juices. Also, neoeriocitrin (characteristic in bergamot daidai) is found in sudachi juice and rind. Eriocitrin is an antioxidant reported to combat lipid peroxidation and like neoeriocitrin is said to block the formation of lipoxygenases involved in allergies and atherosclerosis.
Also, the flavonoid narirutin is said to be the active chemical in the Wakayama Prefecture specialty citrus jabara juice that is said to diminish the effects of pollen allergies. The jabara advertises that it contains 6 times the narirutin in yuzu, but sudachi juice also contains about 3 times as much as yuzu juice (20.1 mg per 100 ml, vs. 6.6 mg). This substance is quite abundant in the rind of yuzu and kabosu.
The ability of the sudachi to promote the body's calcium absorption has been studied as well.
In 2006, a Tokushima University research team published a report which suggests that the fruit may be effective in lowering glucose levels in diabetic patients. The team gave rats sudachi zest over a one-year period and found that their glucose levels were lowered, with signs of improved health in the rats.
- Tanaka & Taninaka (1960), p. 10
- Okuyama, Masuaki (奧山益朗) (2001). Mikaku hyōgen jiten 味覚表現辞典 [Dictionary of sense of taste expressions]. Tokyodo Shuppan. p. 224.
戦前から松茸には欠かせないものとして、徳島から近い都市へ来ていたが [Since before World War II, the sudachi has been considered indispensable to [the eating of] matsutake mushrooms, and had been shipped to cities near Tokushima]
- Schmadel (2012), Dictionary of Minor Planet Names, p. 815
- MLIT (2015). "Bunka-no-Mori Tunnel: anticipated effects of the opening of the tunnel (2)" 文化の森トンネル:今回の開通により期待される効果② (PDF)., citing 2011 Ministry of Agriculture figures for Tokushima's 98% share and 2008 data from Tokushima no Engei for shares within the Prefecture.
- Miller, Kevin. "Sudachi Tree". Sudachi. Archived from the original on 2007-05-21.
- Wardowski, Wilfred F.; Nagy, Steven; Grierson, William (1986). Fresh citrus fruits - 150. AVI Pub. Co.,. p. 150. ISBN 9780870555190.
Sudachi bears small fruit (20-25 g) and is traditionally grown in Tokushima Prefecture. The fruit are harvested only at the green stage and are served in cut halves as a garnish.
- Tanaka & Taninaka (1960), p. 12
- Iuchi, Akira; Hayashi, Katsuo; Tamura, Katsuhiro; Kono, Toshitaka (1996). "Technique of quality control for Sudachi (Citrus sudachi Hort. ex Shirai) juice by high pressure treatment". In Balny, Claude; Hayashi. Technique of quality control for Sudachi (Citrus sudachi Hort. ex Shirai) juice by high pressure treatment. High Pressure Bioscience and Biotechnology. Mitsuo Miyashita, Swapan K. Chakraborty. Elsevier. p. 387. ISBN 9780080544618.
Sudachi (Citrus sudachi Hort. ex Shirai) is a cultivated variety of sour orange which is grown in Tokushima Prefecture, Japan. The juice of this fruit is widely used as an acidulant instead of brewed vinegar...
- Karp, David (September 7, 2013). "Farmers Market: Sudachi, a citrus that spices up late summer and fall". Los Angeles Times.
- A discourse on Japanese names of trees (Jumoku Wamei Ko) 114, index 8. 1933
- "Citrus sudachi hort. ex Shirai". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA).
- Shimizu, Tokurou; Kitajima, Akira; Nonaka, Keisuke; Yoshioka, Terutaka (2016), "Hybrid Origins of Citrus Varieties Inferred from DNA Marker Analysis of Nuclear and Organelle Genomes", PLOS One, 11 (11)
- Shimizu, Tokurou; Kitajima, Akira; Nonaka, Keisuke; Yoshioka, Terutaka; Ohta, Satoshi; Goto, Shingo; Toyoda, Atsushi; Fujiyama, Asao; Mochizuki, Takako; Nagasaki, Hideki; Kaminuma, Eli; Nakamura, Yasukazu. "Hybrid Origins of Citrus Varieties Inferred from DNA Marker Analysis of Nuclear and Organelle Genomes". PLoS One. 11: e0166969. doi:10.1371/journal.pone.0166969.
- Tanaka, Tyōzaburō (1932), "Early existence of the Satsuma orange in Japan", Memoirs of the Faculty of Science and Agriculture, Taihoku Imperial University, 4: 12
- Tanaka & Taninaka (1960), pp. 9–10
- Miyake, Yoshiaki (2006). "Characteristics of Flavonoids in Niihime Fruit - a New Sour Citrus Fruit" (pdf). Food Science and Technology Research (Food Sci. Technol.). 12 (3): 186–193. doi:10.3136/fstr.12.186.
- Kawaii, S. (1999b). Tomono, Y., Katase, E., Ogawa, K. and Yano, M. "Quantitation of flavonoid constituents in citrus fruits. J". Journal of Agricultural and Food Chemistry. 47: 3565–3571. doi:10.1021/jf990153. also reports eriocitrin in sudachi.
- Miyake (2006), p. 186
- National Agricultural Research Center for Western Region 近畿中国四国農業研究センター (2005). "Eriojikuchiōru oyobi sono haitōtai no arakidon san tasisha kei ripokisigenāze sogai kōka" エリオジクチオール及びその配糖体のアラキドン酸代謝系リポキシゲナーゼ阻害効果 [Eriodictyol and its glucosides: their ability to block arachidonic acid metabolized lipoxygenase].
- Nogata, Yoh-ichi (野方洋一 ) (2002-09-30). "Kinōsei seibun wo kōnōdo ni ganyū suru ponka kajū no seizōhō (2)" 機能性成分を高濃度に含有するポンカン果汁の製造法 (特集 果実・果汁の機能性成分とその利用(2)) [Method to manusfacture ponkan juice with high concentrations of active ingredients (2)]. The Food industry. 45 (18): 27–34. ISSN 0559-8990. NAID 40005445401., etc.
- Nii, Yoshitaka (2004). Fukuta, K.; Sakai, K.; Yamamoto, S. "Japanese citrus fruit (sudachi) juice is associated with increased bioavailability of calcium from whole small fish and suppressed bone resorption in rats" スダチ果汁添加による小魚カルシウムの吸収促進および骨吸収抑制効果. Journal of Nutritional Science and Vitaminology. 50 (3): 177–183. doi:10.3177/jnsv.50.177. ISSN 0301-4800.
- Tanaka, Nakagawa et al. (2006), "Beneficial Effects of Long-term Administration of Citrus sudachi on blood glucose level and survival, and its constituents", Yakugaku zasshi 126 (Suppl. 3), pp. 46–47
- "Sudachi no shibori kasu ni kettōchi yokusei kōka, Tokushimadai kyōju ra happyō" スダチの搾りかすに血糖値抑制効果、徳島大教授ら発表 : ニュース : 医療と介護 [Squeezed pulp of sudachi has blood-sugar regulating effects, announces Tokushima University professors et al.]. 読売新聞（YOMIURI ONLINE）. 2006-08-30. Archived from the original on 2006-09-02.
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- Schmadel, Lutz D. (2012). "(12435) Sudachi". Dictionary of Minor Planet Names (sixth edition). Springer. p. 815. ISBN 9783642297182.
- Sudachi at Citrus Variety Collection website
- Tanaka, Naonobu (田中直伸); Nakagawa, Hiroyuki (中川博之) (October 2006). Hashida, Kazuyoshi; Sato, Masatoshi; Okuse, Yui; Taoka, Chiaki; Tomofumi, Iwanaga; Kōichiro, Tsuchiya; Takaishi, Yoshihisa. "Sudachi (Citrus sudachi) no ganyū seibun narabi ni kettōchi jōshō yokusei sayō ni tsuite)" スダチ (Citrus sudachi)の含有成分並びに血糖値上昇抑制作用について [Beneficial Effects of Long-term Administration of Citrus sudachi on blood glucose level and survival, and its constituents]. Yakugaku zasshi (薬学雑誌). 126 (Suppl. 3): 46–47.
- Tanaka, Tyozaburo; Taninaka, Tokio (1960-03-31). "A Revision of Osmocitrus, a section of the genus Citrus : Revisio Aurantiacearum XIII" (pdf). Bulletin of the University of Osaka Prefecture. Ser. B, Agriculture and biology (64): 9–13. pdf