bitter adaptation
concept / concept-bitter-adaptation
苦味順応
Bitter adaptation is a change in response during continued exposure to a bitter stimulus. Record it with the stimulus, temperature, and mixture state.
On this page (5 sections)
Reading the bitterness
Bitter adaptation is a change in perceived intensity during continuing exposure to a bitter stimulus. A 2017 study presented 4 bitter substances—quinine, caffeine, naringin, and denatonium benzoate—to the tongue tip at 4 solution temperatures (10, 21, 30, and 37°C; 3-second presentations after 0, 3, or 10 seconds of pre-exposure), then collected bitterness ratings on a generalized Labeled Magnitude Scale (gLMS). It reports 33 participants in experiment 1 (18 women, 15 men) and 38 in experiment 2 (25 women, 13 men). Temperature affected initial bitterness and adaptation, but differently by substance. Quinine adaptation was temperature-dependent; caffeine adaptation was not. For naringin and denatonium benzoate, temperature affected initial bitterness only, not adaptation itself.
The researchers discuss whether suppression of bitterness at 10°C might be explained by temperature sensitivity of TRPM5, an ion channel involved in bitter reception. They note, however, that prior in vitro TRPM5 thermal responses rose monotonically with temperature, unlike the inverted-U temperature response observed here, particularly for initial bitterness of quinine, naringin, and denatonium benzoate. This compares known TRPM5 biochemistry with psychophysical data; it does not directly test other receptors or peripheral and central mechanisms.
Another study had 14 trained assessors rate 9 bitter stimuli—caffeine, quinine, L-phenylalanine, L-tryptophan, urea, naringin, sucrose octaacetate, and 3 hop extracts—by time-intensity measurement (continuous ratings for 90 seconds, swallowing after holding in the mouth for 10 seconds, 3 repetitions). Profiles split into 2 groups: caffeine, quinine, L-phenylalanine, L-tryptophan, and urea had fast onset and decay, whereas naringin, sucrose octaacetate, and hop extracts had slower onset, intensified after swallowing, and decayed more slowly. Only the abstract has been checked.
Sources for this overview
Stimulus-Dependent Effects of Temperature on Bitter Taste in Humans
Checked for this overview: Used the experimental results for temperature-dependent bitter adaptation. / Used the discussion of inconsistency with the TRPM5 hypothesis.
Common bitter stimuli show differences in their temporal profiles before and after swallowing
Checked for this overview: Finding that 9 bitter stimuli split into 2 time-intensity profile groups.
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
Sensory (2)
Scope: Caffeine, quinine, naringin, and denatonium presented to the tongue tip at 10, 21, 30, and 37°C
Note: For quinine, temperature affected adaptation, but this was not the same for caffeine and others.
Show data
concept-bitter-adaptation —has_perceived_bitterness_affected_by→ "The combination of stimulus compound and solution temperature"Scope: Layer: solution. Time-Intensity method with 14 trained assessors (90 seconds of continuous ratings, 3 repetitions, swallowing after 10 seconds in the mouth).
Show data
concept-bitter-adaptation —has_perceived_bitterness_affected_by→ "When 14 trained assessors rated 9 bitter stimuli (caffeine, quinine, L-phenylalanine, L-tryptophan, urea, naringin, sucrose octaacetate (SOA), and 3 hop extracts) by Time-Intensity measurement (continuous ratings for 90 seconds, swallowing after 10 seconds in the mouth, 3 repetitions), profiles split into 2 groups: caffeine, quinine, L-phenylalanine, L-tryptophan, and urea with fast onset and decay; naringin, SOA, and hop extracts with slow onset, an increase after swallowing, and slow decay."