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Research note 011 — 2026-08-31

How Bitterness, Astringency, and Egumi Differ

Some people eat wild mountain greens and call them "bitter"; others call them "astringent" or "egui." All three can express an unpleasant feeling in the mouth, so they overlap in everyday conversation. As scientific language, though, they are not the same.bitterness is one of the basic tastes, alongside sweetness, saltiness, sourness, and umami — a basic taste being a broadly distinguished category of taste sensed by the tongue. astringencyis mainly a tactile sensation felt as dryness or roughness in the mouth. Egumi (えぐみ, egumi (Japanese food descriptor)) is a Japanese word used when people put into words the character of what they are tasting, but the sensation it points to can shift depending on the food. Separating the three is not throwing away the language of cooking.It is a starting point for asking again, from one ambiguous word, where in the mouth, when, and what kind of sensation occurred.

What this page establishes

• Several studies organize astringency as an oral tactile sensation combining dryness, roughness, and tightening, treated separately from bitterness.
• The individual differences in astringency explainable by the degree of salivary protein recovery are measured to hold only for part of the aqueous-solution experiments, and the astringency of solid foods is measured not to be predictable by the same index.
• Taking EGCG repeatedly for 2 weeks is measured to lower the bitterness rating even at the same concentration, but the change in salivary protein alone does not fully explain the mechanism.
• Pungency is a chemesthetic sensation mediated by nerve sensors that carry pain and heat, and is treated as a route separate from the basic tastes, but whether pungency changes how the basic tastes are perceived has not yet been confirmed.

The short answer

Bitterness

One of the basic tastes. It mainly involves a group of bitterness sensors on taste-sensing cells, the human TAS2R receptor family. That said, how it is perceived shifts with the kind and concentration of the bitter substance, what else is present, and prior eating experience.

Astringency

An oral tactile sensation combining dryness, roughness, a tightening pucker, and the urge to purse the lips. Changes in oral lubrication from saliva matter, but they alone cannot explain the astringency of every food.

Egumi

A Japanese word used in cooking talk and in sensory evaluation of food. There are examples where it points to a harsh, throat-catching quality on the tongue or throat, but it is not treated as pointing to the same single taste, or the same mechanism, across every food.

Pungency

A form of chemesthesis received by the trigeminal nerve, which mainly carries pain, heat, and touch from the face and mouth to the brain — as with capsaicin from chili peppers or the irritation from garlic. Its sensing mechanism differs from that of the basic tastes.

Clues for telling them apart in the mouth

This is not an organ map for self-diagnosis. Bitterness and astringency occur together, and each affects the judgment of the other's intensity. The point is not to decide by location alone — "if it's on the tongue, call it bitterness; if it's in the throat, call it egumi" — but to describe them by combiningquality, location, onset, and fade.

Egumi is not a vague word that science leaves out

Egumi has examples defined precisely enough to use in experiments. A study published in 2025 titled 「米飯の官能評価用語体系」 (in translation: "Terminology System for Sensory Evaluation of Cooked Rice") — a difficult-sounding name, butsensory evaluation means examining the appearance, aroma, taste, and texture of rice using the senses of sight, smell, and mouth, and aterminology system is a"dictionary of evaluation terms" for recording and comparing those characteristics with the same words. Here, cooked rice (米飯) means rice that has been cooked — in other words, what is commonly called gohan (ご飯). In this study, atrained panel — people trained to put taste characteristics into words by the same procedure — examined 60 samples of 32 rice varieties that had been cooked, plus 36 kinds of commercially prepared rice such as kept-warm, frozen, and packaged rice, and sorted the results, together with words gathered from the literature, into 120 terms. Among them, 「苦味がある」 (in translation: "has bitterness") is placed as a basic taste felt on the tongue, while 「えぐみがある」 (in translation: "has egumi") is placed, in a separate item, as a harsh, throat-catching feeling as if aku were clinging to the tongue or throat.

A study of spinach shows one example in which the substance of egumi separates from bitterness. So that they could compare it in the experiment, the researchers named the unpleasant sensation that remains after tasting an oxalic acid solution 「シュウ酸味」 (in translation: "oxalic acid taste"). Next, they passed the water-extracted components from the leaves through an adsorbent and split them into two liquids with different properties — separating a mixture into portions by property this way is calledfractionation. Oxalic acid and the oxalic acid taste collected on the side that flowed out with water, while bitterness collected on the side later extracted with ethanol. In other words, in this sample, the bitter substance cannot be equated with oxalic acid.

But generalizing from here to "the true identity of egumi is oxalic acid" would be a step backward. It has not been proven that the harsh, throat-catching feeling defined for rice and the oxalic acid taste of spinach are one and the same sensation. In soy sauce, there is also a study that used a single evaluation item combining astringency and egumi. Egumi is a useful word, but it can only be compared once each study has concretely decided, food by food, what it calls "egumi." Deciding the meaning before measuring, in research, is calleddefining it operationally.

Bitterness and astringency differ in the kind of sensation they are

There is a study that tested basic taste, the astringency fromtannins also found in tea and wine, and the irritation from capsaicin in chili peppers, using separate samples and separate response fields. This is not proof that "there is a single sensor that receives only astringency." But at minimum, it shows that at the stage of recording human sensation, bitterness can be treated separately from oral tactile sensations such as dryness, roughness, and irritation.

Don't explain astringency by saliva alone

Tannins are part of polyphenols, a large group of compounds that plants make, and are thought to bind with proteins in saliva and change oral lubrication. This is an important explanation in astringency research. However, the individual differences in astringency that could be explained by asalivary protein replenishmentfigure were 33% for tannic acid dissolved in water and 29% for alum. From the same figures, the astringency of a solid chocolate-like sample could not be predicted.

Moreover, the state of the mouth does not always return to normal right away. In a study of polyphenols found in cranberries, some of the change in salivary protein still remained 10 minutes later. This does not mean astringency itself lasted 10 minutes — it is a warning that the interval before the next sample is presented can move the experiment's results.

The same bitterness moves with history

After dissolving epigallocatechin gallate(EGCG) — a type of tea catechin — in water and taking it repeatedly for 2 weeks, the bitterness rating for the same EGCG was lower than after repeating water alone. But the measured change in salivary protein did not correspond in any simple way to the change in perception. A fixed value like "this ingredient is bitterness 7" leaves out the immediately preceding stimulus and weeks of experience.

The way of measuring isn't the same either

The time-intensity sensory evaluation(TI) is a method that continuously records how strong a single sensation is, from when it enters the mouth until it fades. The temporal dominance of sensations(TDS) is a method that, from candidates such as sweetness, sourness, bitterness, and aroma, chooses the one that draws the most attention at each moment. Even if bitterness was dominant late in a TDS run, that does not mean "bitterness intensity was at its maximum" or "it lingered long and strong."

Sourness has a boundary too

OTOP1 is a protein that lets hydrogen ions derived from acid into taste-sensing cells. When OTOP1 was made non-functional in mice, taste cells stopped responding to strong acidity, and the taste signal toward the brain also decreased greatly. Even so, some response to concentrated acid and the behavior of avoiding acid remained. This is an example for not connecting, with a single arrow, the substance acid, the taste sourness, pain or irritation, and avoidance behavior. It cannot be generalized directly to humans.

Pungency is closer to oral chemesthesis than to taste

TRPA1 andTRPV1 are sensor proteins that convert stimuli into nerve signals.allicin, derived from garlic, activated TRPA1 in cultured cells engineered to carry TRPA1 and in sensory nerve cells. Also, 2 people from the same family whose TRPV1 does not function due to a genetic change did not feel capsaicin in the mouth. The cell-culture experiment and the observation of these very rare 2 people are different kinds of evidence, but both show that the irritant quality should not be read back into the bitterness carried by TAS2R.

On the other hand, in a small study of 10 healthy women, even after using a capsaicin-containing gel in the mouth for 14 days, there was no statistically clear change in tests of the basic tastes. One should also be cautious about the story that "pungency always changes the basic tastes."

How NIGAMI LAB records this

• Treat bitterness, astringency, pungency, shibire (tingling numbness), cooling, and sourness as separate items.
• Do not turn egumi into a single basic taste; keep it as a word specific to each food, region, and source, along with the definition used there.
• When something is recorded as "egui," do not auto-translate it into bitterness; investigate further the quality, the location in the mouth, the onset and duration, and the preparation method.
• Store sensor-protein responses, nerve responses, the intensity the person reported, the sensation most prominent at that moment, and preference as separate measurement results.
• Keep the sample, concentration, overall composition of the food, eating order, the interval before the next sample, and the experience of repeated eating as recorded conditions.
• Variation in the Japanese words egui, shibui, karai, shibire, atoaji, and koku is not erased as error; it is set aside in the hypothesis box.

An honest note

• The definition of egumi in this research targets cooked rice; the result of splitting the components into two groups targets spinach. Neither is treated as a single definition for food in general.
• There are unresolved points in the mechanism that produces astringency, and it is not explained by oral lubrication from saliva alone.
• The description of OTOP1 is from mice; the TRPA1 garlic research is mainly from cell- and animal-derived systems; the TRPV1 human result is from 2 cases.
• A result in which no difference was found is not proof that there is "absolutely no effect." The range of samples used and the number of participants is kept on the card.

Frequently asked

Is astringency determined by saliva alone?

There is research showing it cannot be fully explained by saliva alone. In liquids made by dissolving tannic acid or alum in water, the degree to which salivary protein returned to its original amount after stimulation is reported to have explained 33% (tannic acid) and 29% (alum) of individual differences in how astringency is perceived. But using the same salivary figures, the astringency intensity of a solid chocolate-like sample could not be predicted. In other words, the change in salivary protein is one factor involved in astringency, but it does not work the same way in liquids and solids, and it does not explain the whole mechanism of astringency.

Is egumi the same sensation as bitterness?

How it is treated differs by study, and it cannot simply be called the same. In a dictionary of evaluation terms for cooked rice, bitterness is placed as a basic taste, and egumi is placed, in a separate item, as a harsh, throat-catching feeling as if aku were clinging to the tongue or throat. In a study of spinach, when the components were split into those soluble in water and those soluble in ethanol, bitterness collected in the latter, and it was reported to be a substance different from the oxalic acid that has been named as the cause of egumi. On the other hand, in the evaluation of soy sauce, there are also examples where astringency and egumi are combined into a single item, and what egumi refers to changes by food and by study.

Is pungency one of the basic tastes?

In most research, pungency is treated separately from the basic tastes — sweetness, saltiness, sourness, and bitterness. Capsaicin from chili peppers and allicin from garlic are chemesthetic sensations felt through nerve sensors that carry pain and heat (TRPA1, TRPV1), a route separate from the basic-taste sensors on taste-sensing cells. There is also a report that 2 people whose TRPV1 does not function genetically did not feel the stimulus of capsaicin. However, in a small pilot study in which 10 healthy women used a capsaicin-containing gel for 14 days, no statistically clear change was seen in the judging performance for sweetness, saltiness, sourness, and bitterness, and whether pungency changes how the basic tastes are perceived has not yet been confirmed.

What is not known

• Whether astringency can be separated into the three tactile sensations of dryness, roughness, and tightening has not yet been resolved.
• Whether the sensation that was dominant at the end in TDS actually matches the most intense sensation has not been confirmed within the range of this material.
• The mechanism by which repeated intake of EGCG lowers perceived bitterness is not explained by the change in salivary protein alone, and remains unsettled.
• Whether pungency changes how the basic tastes are perceived over the long term — no material beyond a small pilot study was found.
• How far the sensation pointed to by the Japanese word "egui" is shared across foods has not yet been compared systematically.

Related: bitterness /astringency /egumi (Japanese food descriptor) /chemesthesis /hypothesis box
Topic hub: Bitterness, Astringency, and Egumi