Effect of compound sequence on bitterness enhancement.

Area of Science:

• Sensory Science
• Food Chemistry
• Psychophysics

Background:

• Carry-over effects, where prior stimulus exposure influences subsequent responses, are crucial in sensory perception.
• Understanding these effects is vital for accurate taste evaluations and product development.

Purpose of the Study:

• To investigate the nature and occurrence of carry-over effects for specific bitter compounds.
• To quantify how previous bitter taste experiences alter the perception of subsequent bitter stimuli.

Main Methods:

• A time-intensity procedure was employed to assess bitterness ratings of six compounds (caffeine, denatonium benzoate, limonin, naringin, quinine, sucrose octa-acetate).
• Subjects evaluated paired sequences of compounds, with controlled rinsing protocols between stimuli to isolate carry-over effects.
• Concentrations were standardized to be approximately equal in perceived intensity.

Main Results:

• Significant carry-over (sensitization) effects were observed for all tested bitter compounds.
• Key bitterness parameters—maximum intensity, rate of onset, and total perceived area—increased when a compound was presented second in a pair.
• The degree of sensitization and susceptibility varied significantly between compounds.
• Caffeine demonstrated the strongest enhancing effect on other compounds' bitterness while being least susceptible to enhancement itself.
• Quinine and denatonium benzoate exhibited the most pronounced bitterness enhancement, irrespective of the preceding compound.

Conclusions:

• Carry-over effects significantly influence the perception of bitterness, leading to heightened responses.
• Sensitization to bitterness is compound-specific, with varying degrees of susceptibility and enhancement.
• Caffeine, quinine, and denatonium benzoate play distinct roles in modulating bitterness perception through carry-over mechanisms.