日本語版

Bitter crossing — 2026-09-06

Salty-bitter

しょっぱ苦い (shoppanigai) — our coined term

Salty-bitter refers to a taste state in which saltiness may weaken bitterness somewhat but does not itself disappear, so that saltiness and bitterness stand side by side and both remain on the tongue. It is the lab's coined term.

What this page establishes

• "Salty-bitter" is not an existing word but a term NIGAMI LAB has coined, and whether a headword of the same form exists in dictionaries has not been confirmed.
• For Italian olives, it has been reported that extending the brining period from 15 to 30 days raised the bitterness score whether the brine was 6% or 8%.
• In an experiment on bitter gourd, it has been reported that the bitterness of juice from fruit soaked in a 3.5% salt solution was almost unchanged from that of fresh fruit, while sourness fell instead.
• For the same olives, replacing the added chloride with potassium lowered bitterness, while replacing it with calcium or magnesium instead raised it — results whose direction diverges.

How it arises

Where saltiness and bitterness intertwine looks different depending on the grain of the method used to check it. Psychophysical experiments using solutions, cell-level experiments involving receptors, and sensory evaluations using actual foods can each show only a certain range. Here the layers are kept apart rather than mixed.

In solution

Saltiness and bitterness are treated as basic tastes that can be measured independently, separate from somatosensory sensations such as astringency and pungency. In a test that presented samples of sweetness, sourness, saltiness, and bitterness, and samples of astringency and pungency, on separate strips of paper with separate answer columns, this separation held up. But what this test confirmed was only whether the type of sensation could be correctly identified; it did not measure whether the intensity of bitterness itself moves when saltiness is added.

No claim has yet been confirmed here that directly examined the relationship between saltiness and bitterness at the level of receptors or other cell-level mechanisms.

In practice

In sensory evaluations of actual food, the relationship between salt and bitterness has been shown to shift with processing. For olives from Gaeta, Italy, extending the brine-fermentation period from 15 to 30 days raised the sensory bitterness score whether the packing brine was 6% or 8%.

Yet a chemical analysis of the same olive lots found that neither the packing salt concentration nor the fermentation period significantly changed the residual amount of oleuropein, the compound treated as the one responsible for bitterness. The movement of sensory bitterness and the movement of the compound's quantity do not necessarily line up in the same direction.

Exceptions and reservations

This page does not support the simplification that salting food always weakens its bitterness.

For bitter gourd, soaking fruit pieces in a 3.5% salt solution at 25 C for 60 minutes before juicing left the bitterness score unchanged from that of untreated fruit (10.6 versus 10.7 on a 15 cm line scale). What moved instead was sourness. The intuition behind salt-rubbing or bran-pickling — that applying salt draws bitterness out — is not supported within the range of this result.

For olives, the direction itself reversed depending on which chloride ion was used. Replacing part of the sodium in the packing brine with potassium chloride lowered the bitterness score, and the more it was replaced, the more the score fell. Yet in the same experimental series, adding calcium chloride or magnesium chloride became a factor that instead strengthened bitterness. Depending on what is substituted for the sodium salt, the result can reverse.

Individual differences also remain. In an evaluation using Brussels sprouts and cauliflower, participants who perceived stronger bitterness with no salt added showed a larger drop in bitterness when salt was added, while participants who had perceived little bitterness to begin with showed almost no such drop. How much salt suppresses bitterness depends on how strongly the person tasting perceives bitterness to begin with.

There are also cases where saltiness and bitterness sit in the same food and one of them simply does not move. In a comparison of growing conditions for red-leaf lettuce, bitterness was the only basic taste to show a moderate score, but changing the growing environment produced no significant difference in either bitterness or saltiness.

There are also examples where the direction runs the other way. Comparing a caffeine condition and a quinine condition matched for the same level of bitterness, only the sweetness rating fell; the ratings for bitterness, saltiness, sourness, and umami did not move. Changing which bitter compound is used does not mean the salty side automatically responds.

Examples from around the world

• goya champuru (Okinawan bitter gourd stir-fry) — an Okinawan stir-fry, pairing bitter gourd with dried sardine and salty Okinawan tofu and egg.
• table olives — a drupe processed for direct eating. Brining and fermenting it in salt water does not necessarily make the bitterness itself disappear.
• uruka — a shiokara (salted, fermented preparation) made from the flesh, viscera, roe, and milt of ayu (sweetfish), cured together with salt.
• niga-uruka — a line of ayu uruka made only from the viscera, carrying the bitterness and astringency characteristic of the viscera in its name.
• shuto — a shiokara made by salting the viscera of bonito and other fish, then fermenting and aging it for six months to more than a year.

Try it at home

Narrow it to a single variable, keep the conditions to two or three, and have the same person taste them in the same order. Quantities can be approximate.

Step one: compare bitter gourd's bitterness with and without a salt solution.Split a bitter gourd lengthwise, remove the pith, and slice it thinly to a uniform thickness. Soak half in water and the other half in roughly 3.5% salt solution at around 25 C for about 60 minutes, then drain. Compare the two conditions raw, or cooked the same way, and note the bitterness intensity for each on the same scale in your own words.

Step two: compare how bitterness moves with different chlorides.Cut the same vegetable into pieces of the same thickness and soak them briefly under three conditions — no treatment, salt solution, and nigari (a coagulant containing magnesium chloride, diluted well down) — then cook them the same way. Keep the nigari within the amount stated on the product label, at a taste-testing level only. Taste the three conditions in the same order and note the bitterness intensity.

Status: candidate (to be published once a tasting-comparison record is attached).

What is not known

• No source found: no source has yet been found that examines the origin or actual usage of the term "salty-bitter."
• Not measured: the relationship between the change in the compound thought to be responsible for olive bitterness and the bitterness intensity actually perceived on the tongue has not been sufficiently confirmed from this material alone.
• Not measured: which direction bitterness moves when a household salt containing a mixture of several chlorides is used has not been measured.
• No source found: no source has been found that examined the effect of soaking in salt solution, in the same way, for bitter vegetables other than bitter gourd.

Between the dictionaries

Whether the term しょっぱ苦い, in this same form, stands as a headword in Japanese dictionaries is left unconfirmed here.

The difference from horonigai (gently bitter)(mildly bitter) lies in whether the other taste remains as a result. Mildly bitter is entered as a word for a state in which the taste that weakened the bitterness does not itself remain, and only the weakened bitterness reaches the tongue. Salty-bitter is the reverse: even when saltiness weakens bitterness somewhat, the saltiness itself remains in the result, standing side by side with the bitterness. A case where both salt and bitterness soften together belongs to the description of mildly bitter, not to this coined term.

Frequently asked

Does salt-rubbing draw the bitterness out of bitter gourd?

There is a result showing that the bitterness of juice squeezed after soaking fruit pieces in salt solution was unchanged from that of fruit soaked only in water. What moved instead was sourness. The felt sense that salt-rubbing removes bitterness is not supported within the range of this result.

Why can salted olives still taste bitter?

There is an analysis showing that changing the packing brine's concentration or the brine-fermentation period did not greatly change the residual amount of the compound treated as responsible for bitterness. The salting process itself does not necessarily eliminate that compound.

Does salting food always make bitterness disappear?

For the same olives, the direction of the effect changed depending on which chloride was added. Replacing part of the sodium with potassium lowered bitterness, but replacing it with calcium or magnesium instead raised it. There is also a report that people who already perceive bitterness strongly see a larger drop in bitterness from added salt. It cannot be said that any salt suppresses bitterness.

Related: research notes Does any seasoning remove bitterness? — Sugar and salt /Bitter Gourd's Salt-Rubbing Did Not Draw the Bitterness Out, the map of Bitter crossings, the topic hub Bitter Gourd's Bitterness.