amanatsu (Citrus natsudaidai)
ingredient / ingredient-amanatsu
甘夏
Amanatsu (Citrus natsudaidai) is a cultivar selected in Tsukumi City, Oita Prefecture, as a bud sport of natsumikan (natsudaidai), officially named Kawano Natsudaidai. It was included in a Kumamoto comparative analysis as a citrus in the "bitter-type" group containing abundant naringin and limonin.
On this page (9 sections)
Reading the bitterness
Amanatsu (official cultivar name: Kawano Natsudaidai) was found in the early Shōwa period as a bud sport of natsumikan in Yutaka Kawano's orchard in Kami-Aoe, Tsukumi City, Oita Prefecture. Compared with ordinary natsudaidai, citric acid decreases earlier and it is described as ready to eat from early March. Other sources give 1935 as the discovery year and 1950 as the registration year, but these specific years could not be confirmed in Oita's official materials themselves.
A 2005–2007 fiscal-year survey by the Kumamoto Prefectural Technology Center of bitter compounds in 8 citrus cultivars described amanatsu (Kawano natsudaidai), together with 「大橘」 (Ōtachibana), Kawachi bankan, and banpeiyu, as 『苦味系』 (in translation: "bitter type"), containing abundant naringin and limonin in juice and peel. Unshu mikan, ponkan, shiranui, and sweet spring were described as 『非苦味系』 (in translation: "non-bitter type"), centered on narirutin and hesperidin.
In the detailed section, bitter limonin compounds were explicitly named in the juice of ponkan, banpeiyu, and sweet spring, but the text did not explicitly mention amanatsu juice. Limonin was described as present in the peel of all 7 cultivars except unshu mikan, while nomilin was detected only in Kawachi bankan peel. The summary classification and detailed description do not fully agree, so both are recorded as stated.
The survey reports no change in bitter-compound content after heating, while odor produced during heating was strongest in unshu mikan and weakest in amanatsu among 8 cultivars. This odor difference concerns smell and is separate from bitterness strength. Public information mainly concerns whether classifications are present; actual naringin and limonin amounts could not be confirmed.
Sources for this overview
Checked for this overview: The discovery history as a bud sport was confirmed.
Checked for this overview: The classification among 4 bitter-type cultivars and its basis was confirmed. / The discrepancy between the summary and detailed limonin descriptions was confirmed. / The distinction between heating-related odor and bitter compounds was confirmed.
Other names: 川野夏橙 (ja)
Follow the connections
amanatsu (Citrus natsudaidai) →is derived from→ Citrus natsudaidai
amanatsu (Citrus natsudaidai) →contains→ naringin →is associated with→ bitterness
amanatsu (Citrus natsudaidai) →contains→ limonin →is associated with→ bitterness
Hypotheses and recipe candidates for this entry are on the Japanese page.
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (4)
Scope: An account in official materials from Oita Prefecture
Note: Discovered in the early Showa era as a branch sport (bud mutation) of natsumikan (natsudaidai) at Kawano Yutaka's summer-citrus orchard in Kami-aoe, Tsukumi City, Oita Prefecture. Its citric acid drops faster than ordinary natsudaidai, and it is ready to eat from early in the 3rd month (March). The specific year given in other sources — "discovered in 1935, registered as 'Kawano natsudaidai' in 1950" — could not be confirmed in Oita Prefecture's own official materials.
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ingredient-amanatsu —is_derived_from→ ingredient-natsumikanScope: Kumamoto Prefectural Industrial Technology Center research, 2005-2007 fiscal years, 8-variety comparison
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ingredient-amanatsu —contains→ compound-naringinScope: Kumamoto Prefectural Industrial Technology Center research, 2005-2007 fiscal years, 8-variety comparison
Note: The summary and detailed sections of the source material do not match in their enumeration of varieties; both are recorded as stated.
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ingredient-amanatsu —contains→ compound-limoninScope: Naringin in the flesh (juice sacs), segment membrane and peel of Kawano natsudaidai was compared between the portion extracted with water after complete grinding and the total amount obtained by heating after grinding.
Note: This result differs from the earlier explanation (Nakabayashi's theory, cited by Tsusaka 1965) that 40 to 70% of the naringin in natsumikan is in an insoluble or bound form that becomes soluble on heating. Bessho et al. and Manabe et al. (1964, natsumikan) also reported that more than 90% of the amount found after heating dissolved out by grinding alone, with the insoluble or bound form being only a part.
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ingredient-amanatsu —has_composition→ compound-naringinSensory (1)
Scope: Fresh and frozen fruit of Kawano natsudaidai (flesh of varying degrees of bitterness). A panel of 12 judged the flesh as "ordinary, clearly bitter, or extremely bitter (unsuitable for eating)" and this was matched against naringin in pressed juice (modified Davis method).
Note: The panel was 12 people, which the author also notes is small. Read from Figure 4, in a sample with about 20 mg% naringin all 12 panelists judged it "ordinary"; at about 28 mg%, 10 judged it ordinary and 2 clearly bitter; in samples at about 45 to 50 mg%, 8 to 7 judged them clearly bitter; and at about 70 mg% all 12 judged it extremely bitter (read by eye from the figure, so the horizontal axis values are approximate). This is a correspondence between the bitterness of the fruit itself and naringin in pressed juice, not an experiment that shows a threshold concentration of naringin.
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ingredient-amanatsu —has_sensory_response→ "The naringin amount in juice pressed from the flesh of Kawano natsudaidai with a manual juicer agreed relatively well with the sensory test of the bitterness of the flesh: at around 50 mg% (mg% = mg per 100 g) bitterness was clearly perceived (the limit accepted as a commercial product), and at 63 mg% or more many panelists judged it unsuitable for eating. The mean for fresh fruit was about 24 mg% (ordinary bitterness), and the strongly bitter frozen fruit was about 74 mg%."Mechanism and receptors (1)
Scope: Flesh of Kawano natsudaidai (1 tree aged 17 years; fresh fruit harvested on January 13 and stored at 4°C, and frozen fruit). Naringin in juice prepared from fresh and frozen flesh by complete grinding, pressing and extraction (modified Davis method) was compared with a sensory test of the bitterness of the flesh by a panel of 12.
Note: This is an experiment that measured bitterness by sensory test and matched it against naringin. It is a study of the effect of freezing, not of flesh with the membrane removed or of the effect of cooking. "It comes out of the membrane when chewed" is the author's interpretation and not an experiment that directly measured dissolution from the membrane (the data that all panelists judged even the juice sacs of frozen fruit, rinsed with water, to be bitter and inedible support the interpretation). The samples in this report are Kawano type (corresponding to amanatsu), and it cannot be taken as the same for hassaku or natsumikan. The introduction states that natsudaidai and hassaku become bitter from winter cold damage.
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ingredient-amanatsu —has_perceived_bitterness_affected_by→ "The strength of bitterness in the flesh of Kawano natsudaidai (amanatsu) did not correspond to the total amount of naringin extracted by completely grinding the flesh, but corresponded to the amount of naringin released by hand pressing (squeezing). Naringin by complete grinding was almost the same in fresh and frozen fruit, 67.3 and 69.9 mg% (mg% = mg per 100 g), but by pressing it differed greatly, 23.7 mg% in fresh and 73.0 mg% in frozen fruit, and the bitterness was normal in fresh fruit and "extremely bitter" in frozen fruit. The author considered that what determines bitterness is the naringin released when the flesh is chewed with the teeth: in fresh fruit, little dissolves from the segment membrane (especially the stalks of the juice sacs), which holds much naringin, but when freezing makes the membrane fragile, a large amount dissolves out of the membrane and gives strong bitterness."