The order in which foods or bitter stimuli are tasted may change the perception of a later bitter stimulus itself. In a study pairing and tasting in sequence 6 bitter compounds—caffeine, denatonium, limonin, naringin, quinine, and sucrose octaacetate—the first stimulus affected the later one in every pairing. It altered peak bitterness, the speed of its onset, and cumulative bitterness over time, producing either a carryover effect that strengthened the later stimulus or adaptation that weakened it. Which effect occurred, and its magnitude, differed by compound.
The same phenomenon has been observed with actual drinks. In a test with 16 participants (7 women and 9 men), chicory bitterness was rated lower after drinking roasted coffee. In the reverse order, tasting roasted coffee after chicory did not change the bitterness of the coffee. The authors explain this asymmetry by proposing that roasted coffee activates a broader combination of receptors than chicory's bitter constituents, desensitizing the receptors mainly stimulated by chicory in advance. This is the authors' interpretation linking receptor-level experiments and sensory evaluation, not an independently established mechanism.
Lang R; Lang T; Dunkel A; Ziegler F; Behrens M / 2022 / journal article / full text checked
Checked for this overview: Checked replication of the effect of consumption order on the bitterness of a later stimulus. / Checked the asymmetric effect of reduced chicory bitterness after coffee.
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chicory →— perceived bitterness is a…→ consumption sequence
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Sensory (2)
consumption sequence can change The maximum intensity, rise rate, and time-intensity area of the following bitter stimulusestablished
Scope: 6 compounds tested in paired order
Note: Magnitude and susceptibility were compound-specific. Reproduced across 2 systems, aqueous solutions and actual beverages. The direction of the order effect is compound-dependent.
All 6 compounds showed carryover or sensitization, and the magnitude and susceptibility were compound-specific.
Limitations: Panel size is not stated in the abstract (full text needed, unchanged). However, the matching criteria for stimulus concentrations, the number of pairs presented in 1 session, and the rinsing procedure are given in the abstract and are supplemented by the related record.
Reproduces, with an independent design, the phenomenon that consumption order changes the perceived bitterness of a following stimulus, and adds that the effect is asymmetric. Verbatim: "the bitterness of chicory was rated lower after roasted coffee consumption. Evaluation of this stimulus pair in opposite sequence revealed no change in the bitterness of roasted coffee after chicory consumption." The authors relate this to roasted coffee's broader pattern of receptor activation overlapping with, and desensitizing, the receptors that chicory compounds act on.
Limitations: Because this uses actual food rather than the single-compound solutions of Cubero-Castillo 2001, the comparison is at the level of phenomenon, not compound. The direction here is suppression of the second stimulus, whereas the earlier study reported both carryover and sensitization depending on the compound. The effect size and statistics for the order comparison are not captured in the verbatim.
chicory — perceived bitterness is affected by: consumption sequencesupported
Scope: Human order-effect test using chicory, coffee substitute, and roasted coffee.
Note: The effect is specific to the tested foods and the order design.
Verbatim: The line-up consisted of 16 individuals (7 women, age 36 +/- 12 years; 9 men, age 37 +/- 10 years). The order effect was asymmetric. verbatim: the bitterness of chicory was rated lower after roasted coffee consumption. Evaluation of this stimulus pair in opposite sequence revealed no change in the bitterness of roasted coffee after chicory consumption. The authors attribute this asymmetry to roasted coffee activating a broader set of receptors (including TAS2R43 and TAS2R46) and chicory lactones selectively acting on receptors that desensitize first.
Limitations: As a crossover order effect, a panel of 16 is a small sample, and the effect size and statistical value of the order comparison are not included in verbatim. The desensitization explanation is the authors' interpretation linking receptor assay findings to sensory results and is not an independently verified mechanism.