Research note 059 — 2026-09-16
When daikon tastes bitter, which part should you use? Grated vs. simmered
The short answer
To make grated daikon less bitter, grate the upper part near the neck.
To try at home
- Grate the upper part (the side near the leaves). In a test where 20 people compared the head, middle, and tail of 3 cultivars, the upper part was less bitter and less pungent than the tip, and sweeter with more umami.
- The tip is more bitter and pungent. Instead of discarding it, use it on days when you want that bite (for example, with grilled fish).
- The middle ranked between the upper part and the tip for bitterness.
- For simmered dishes, try simmering with a little oil from the start. In a test where 30 people compared simmered dried shredded daikon, the version simmered with rapeseed oil scored significantly lower for "daikon bitterness" (oil was not added after cooking).
Not yet known
- How bitterness differs by part once daikon is simmered has not been measured (there is a cooking record of using the upper part and parboiling with rice).
- How bitterness changes with standing time after grating. Only the pungency of karami (pungent) daikon has been measured.
When daikon tastes bitter, raw grated daikon and a cooked simmered dish give different clues. What a direct sensory trial can answer is the difference by part in grated daikon. Across a comparison of three cultivars, the tail end was more bitter and more pungent than the head end, and weaker in sweetness and umami. For simmered dishes, there is a cooking record that chooses the top part and parboils it with rice, but it is not a comparison that measured bitterness.
On this page (7 sections)
What this page shows
- In raw grated daikon, across all three cultivars tested — Aokubi, Mino Wase, and Shinshu Ji — the tail end was rated more bitter and more pungent than the head end.
- In the same comparison, the head end was rated stronger in sweetness and umami than the tail end.
- A cook's recipe for "ika daikon" (simmered squid and daikon) chooses the sweeter top part, parboils it with rice, then rinses it.
- The explanation for that parboiling is about egumi (harsh, rough taste) and letting the flavor settle — not a comparison of its effect on fixing a bitter simmered dish.
Grated daikon can be answered by part
One study divided daikon of the Aokubi, Mino Wase, and Shinshu Ji cultivars into head, middle, and tail sections and grated each. Twenty people — students and members of a cooking-science laboratory whose ability to discriminate tastes had been confirmed — ranked pungency, umami, sweetness, and bitterness.
Across all three cultivars, the tail end was more pungent and more bitter than the head end, and weaker in umami and sweetness. A difference by part was confirmed for all four tastes. In all three cultivars the middle ranked between the head and the tail (significance marks are given for the head and tail; the middle's position is the order of the ranks). So for someone who wants to avoid bitterness in raw grated daikon, there is direct sensory grounds for choosing the head end over the tail end.
Scope: The head, middle, and tail of 3 cultivars were grated within 2–4 days of harvest and evaluated by 20 students and cooking-science laboratory members whose ability to discriminate tastes had been confirmed. Significance marks are given for the head and tail; the middle's position is the order of rank sums.
Note: A result for raw grated daikon. This does not measure the difference between parts in cooked daikon or the bitterness of a finished simmered dish.
Show data
ingredient-daikon-radish —has_perceived_bitterness_affected_by→ "Part of the root. In a ranking test by 20 panelists comparing the grated head, middle, and tail of 3 cultivars (Aokubi, Mino-wase, and Shinshu-ji), the tail was more pungent and bitter and less sweet and umami than the head. The differences by part were significant at the 1% level for all 4 tastes. In all 3 cultivars, the middle ranked between the head and the tail."| Part | Rating when grated | Choosing in the kitchen |
|---|---|---|
| Head end | Weaker bitterness and pungency, stronger sweetness and umami, than the tail end | A candidate for grated daikon when you want to hold bitterness down |
| Middle | Ranked between the head end and the tail end | — |
| Tail end | Stronger bitterness and pungency, weaker sweetness and umami, than the head end | A candidate when you want a stronger pungency or bitterness |
This result comes from a raw comparison of three cultivars harvested in 1988. It does not measure the difference by part in cooked daikon, or whether the same ranking holds for daikon that has been stored for a long time.
Reading pungency and bitterness separately
This sensory trial rated pungency, bitterness, sweetness, and umami separately. It cannot be decided that an operation which changes daikon's pungency also changes its bitterness by the same amount. For someone who wants to avoid bitterness in grated daikon, what this comparison lets you choose directly is the head end.
Simmered dishes, read as a cooking record
A cook's recipe for "ika daikon" (simmered squid and daikon) uses the sweeter top part of the daikon. The process is: peel it, cut it into half-moons, put it in with rice and water, bring it to a boil, parboil it over low heat, drain it in a colander, let it cool, and rinse it in water.
Scope: Ika daikon, as published in Kikkoman's 「基本の和食、おうちの和ごはん」 (in translation: "Basic Japanese Cuisine, Japanese Home Cooking").
Note: This is a cooking record, not a sensory test comparing simmered dishes made with different parts of the daikon.
Show data
ingredient-daikon-radish —is_prepared_by→ "In a cooking record of 「いか大根」 (in translation: "squid and daikon") by a cooking expert, the upper part with its strong sweetness is used, in a composition meant to let the flavors blend."This is a cook's process record, not a trial that compared it against a condition without rice. The parboiling is explained as a step that removes excess water and egumi and lets the flavor settle. It cannot be said that "parboiling with rice makes the bitterness disappear."
Scope: The preparatory step for ika daikon by a cooking expert.
Note: This is not a controlled comparison of bitterness intensity. It is not extended to rice-rinsing water in general, or to rescuing a finished simmered dish that turned out bitter.
Show data
ingredient-daikon-radish —is_prepared_by→ "Half-moon slices 2.5cm thick are parboiled with rice and water — brought to a boil, then simmered over low heat for 10–15 minutes — and rinsed with water. The stated reason is to remove the daikon's egumi and improve how the flavor blends in."There is one test in which people compared bitterness in a simmered dish: dried shredded daikon. Simmering it with water and a little rapeseed oil from the start gave a significantly lower score for "Do you strongly sense daikon bitterness?" than simmering without oil (30 people, 5-point scale). It did not compare parts, and whether it applies directly to simmered fresh daikon has not been checked.
Scope: Samples of 50 g of domestic dried shredded daikon, 250 g of water and 3.9 g of oil in a vacuum pack, heated at 100°C for 60 minutes. 30 people chosen at random for each experiment from a trained panel group (89 people) evaluated one sample at a time on its own. Repeated-measures one-way analysis of variance and Tukey's method
Note: This is a simmered dish of dried shredded daikon, not raw daikon or a dish of thickly cut daikon simmered. The oil was put into the bag with the dried shredded daikon and water and heated from the start at 100°C for 60 minutes; it was not added afterward to the finished simmered dish. The question was a 1-item rating of "bitterness of daikon", not an evaluation by a trained panel measuring bitterness intensity on a scale. In the same report, the simmered dried shredded daikon cooked with added deep-fried tofu (aburaage) had a significantly higher overall preference than that without; in free comments on the simmered dish without aburaage, 23 of 89 people wrote undesirable tastes such as bitterness, pungency, saltiness and off-odor, whereas for the dish with aburaage there were no comments on undesirable tastes (not comments on bitterness alone). The authors consider this consistent with a report that oleic acid is involved in suppressing the bitterness of cheese.
Show data
ingredient-daikon-radish —has_perceived_bitterness_suppressed_by→ "A small amount of rapeseed oil put into the bag with dried shredded daikon (kiriboshi daikon) and water and simmered (heated) from the start. Simmered dishes of dried shredded daikon were made with no oil (a control with water added), with unheated rapeseed oil, and with rapeseed oil heated at 190°C for 7 minutes, and 30 people answered "Do you feel a strong bitterness of daikon?" on a 5-point scale (1 = not at all, 5 = very much). The means were 3.57 with no oil, 2.53 with unheated oil and 2.43 with heated oil; the 2 with oil were significantly lower than no oil (analysis of variance p<0.01, with p<0.05 between no oil and with oil in Tukey's multiple comparison). The difference between unheated oil and heated oil was not significant."How to choose in the kitchen
For raw grated daikon, use the upper side when you want to avoid bitterness. This follows directly from a result in which people compared the head end and the tail end. If you use the tail side for its pungency, you can expect the bitterness to be stronger as well.
If you are about to make a simmered dish, choosing the top part and parboiling it with rice is a candidate worth trying. But that process is not a trial that compared bitterness. From the material checked here, a re-simmering time or a seasoning amount for a finished dish cannot be specified.
Frequently asked
Is the top or the bottom of a daikon less bitter?
In a raw comparison of three cultivars, the head end was rated weaker in bitterness and pungency than the tail end, and the head end was also rated stronger in sweetness and umami. Whether the same difference holds for a simmered dish has not been checked in this trial.
Does parboiling in rice-rinse water make bitterness disappear?
The cooking record adopted here parboils in rice and plain water. It is not a comparison using rice-rinse water, and not a sensory trial that measured bitterness, so it cannot be said that "the bitterness disappears."
Can a simmered dish that has turned bitter be fixed by re-simmering?
Within the material checked here, there is no source that changed the re-simmering time or seasoning of a finished dish and compared bitterness. Nor can the difference by part measured in raw grated daikon be substituted for rescuing a finished simmered dish.
What is not known
- A trial in which people compared bitterness in a simmered dish while independently varying the daikon part, parboiling, and the presence of rice has not been confirmed.
- There is not yet a direct comparison between the difference by part confirmed in raw grated daikon and the simmered-dish process a cook has recorded.
Related: daikon
Related topic hub: Bitterness, Astringency, and Egumi
Related research notes: Rereading Kitchen Prep Through Measured Bitterness / The Science of Aku Removal Has Not Measured Bitterness
Source ledger: the source ledger
How to cite this page
Aoki, M. (NIGAMI LAB) (2026). Daikon bitterness: grated vs. simmered, by part. https://nigamilab.com/en/notes/daikon-bitterness/
Each claim card has a stable anchor (#clm-…). The dataset is CC BY 4.0; see the data page. Dataset DOI: 10.5281/zenodo.22739101