onion
ingredient / ingredient-onion
玉ねぎ（たまねぎ） / onion (tamanegi) / Allium cepa L.
On this page (5 sections)
Short definition
A vegetable of the genus Allium in the family Amaryllidaceae. Raw onion is mainly discussed for its pungency, but sensory evaluations in Japanese cooking science report that long frying produces bitterness in addition to sweetness and sourness.
A reader-facing overview for this entry is in preparation. What has been checked, and its sources, can be followed from the claim cards below.
Other names: タマネギ (ja), 玉葱 (ja)
Structured claims — open a section to read each claim's confidence, evidence and limits
Sensory (3)
Scope: 1 commercially available Hokkaido onion cultivar, "Kita-momiji". 200 g of 1 mm slices were fried in 20 g of soybean oil (high heat at 250°C for the first 5 minutes, then low heat at 170°C). 9 trained members of a food science laboratory judged for each sample whether each item was "recognized".
Note: The data are judgments of whether an item was recognized, not a scale of bitterness intensity. Frying for 60 minutes or more turns the onion brown to dark brown and also gives a burnt smell; this is prolonged heating, more extreme than a typical home sautéed onion. The main text describes a "balance of bitterness" in onion soup made with onion fried for 50 minutes, but because bitterness was recognized in Table 1D only at 60 minutes or more, the table was given priority.
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ingredient-onion —has_perceived_bitterness_affected_by→ "Frying time. In a taste evaluation of 18 samples of sliced Hokkaido onion fried for up to 70 minutes, 7 or more of the 9 panelists recognized "bitterness" only in the sautéed onion fried for 60, 65 and 70 minutes (not in the shorter-fried samples). In onion soup made with the same sautéed onion, bitterness was also recognized only in the 60 to 70 minute samples."Scope: 6 onion soups (bases: chicken bouillon, homemade consommé, water, instant chicken consommé, instant beef consommé). 5 soups with sautéed onion (CB-FO, CO-FO, W-FO, ICC-FO, IBC-FO) and 1 soup with deep-fried onion (IBC-DO). 13 faculty and staff in cooking science (aged 20 to 60, women).
Note: Deep-fried and sautéed onion differ at the same time in cooking conditions (deep-frying: oil at 8 times the weight, preheated to 160°C, 120°C after the onion was added, 10 minutes, 9% added to the soup; sautéing: in butter over high and medium heat, 165 minutes of total heating, 17% added), so the difference cannot be attributed to "deep-frying" alone. The authors attribute it to browning (the amino-carbonyl reaction) but did not measure the reaction. The main text gives no numerical value for the correlation coefficient with the a and b values (it says only "since they correlate").
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ingredient-onion —has_perceived_bitterness_associated_with→ "Onion soup containing deep-fried onion (sliced onion fried in oil) (instant beef consommé plus deep-fried onion) was rated significantly more bitter, on a 7-point scale by 13 panelists, than the 5 other soups containing sautéed onion (1% level). The bitterness ratings correlated with the colorimeter a and b values, and the authors infer that browning during heating is involved. Among the 5 soups containing sautéed onion, there was no significant difference in bitterness."Scope: 13 Hokkaido onion cultivars (12 yellow onion cultivars and the red onion "Kurenai"). The bitterness of sautéed onion made by frying sliced onion in oil was rated by 12 members of a food science laboratory on a 5-point scale from -2 to 2, with "Sarari" as the control.
Note: The significance level is 10% (p<0.1), a weak association that is not significant at the 5% level. The phenol content of the bulb is about 150 mg/100 g in the red onion and 70 to 100 mg/100 g in yellow onions. Bulbs with high total phenol showed a color with stronger green and yellow tones. The pungency of raw onion and the effects of soaking in water or of heating time are not addressed. On the same page of the original, the same "r=0.631, p<0.1" is also given for the correlation between the color rating of sautéed onion and the b* value, so there may be a transcription error. The number of correlation points (n) is not stated in the original.
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ingredient-onion —has_perceived_bitterness_associated_with→ "In Hokkaido yellow onions, the higher the total phenol content of the bulb, the higher the tendency for the bitterness rating when sautéed (correlation coefficient r=0.631, p<0.1)."Mechanism and receptors (1)
Scope: Compounds isolated by sensory-guided high-performance liquid chromatography fractionation from processed onion (Allium cepa). Based on the abstract.
Note: Abstract only. The abstract does not show which processing (cutting, heating, storage) produces them or in what amounts. The amounts in home cooking by roasting or sautéing, and their correspondence to the bitterness of sautéed onion, have not been checked. The formation pathway is the authors' proposal.
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ingredient-onion —has_bitterness_attributed_to→ "As the cause of the bitter off-taste of processed onion (Allium cepa), sensory-guided fractionation found a new group of sulfur compounds that are derivatives of 3,4-dimethylthiolane S-oxide (allithiolanes A to I, 9 groups). These have an unpleasant bitterness, with detection thresholds in the range of 15 to 30 ppm."