Time-dependent variation in oral irritation subqualities of capsaicin solution: Using Time-Intensity-Rate-All-That-Apply (TI-RATA) and temporal Check-All-That-Apply (TCATA) methods

Most of the previous studies characterizing the time-dependent perception of capsaicin have used the Time -Intensity (TI) analysis to highlight temporal variation in perception of overall oral irritation or its specific subquality, especially "warm/hot" or "burning." Little attention has been paid to how multiple subqualities of oral irritation for capsaicin-containing samples can be perceived over an evaluation period. This study aimed at determining the time-dependent characteristics of capsaicin-induced oral irritation subqualities and their vari-ations as a function of habitual spicy food consumption. In Study 1, 50 participants first rated oral irritation intensities of capsaicin solutions using the TI analysis over 600 s, then assessed the presence and intensities of seven subqualities - "burning", "itching", "numbness", "stinging/pricking", "tickle", "tingling", and "warm/hot", using a Rate-All-That-Apply (RATA) analysis. The results of TI-RATA analysis revealed four dominant sub -qualities - "burning", "stinging/pricking", "tingling", and "warm/hot", in terms of selection proportions and perceived intensities by participants. In Study 2, using the Temporal Check-All-That-Apply (TCATA) analysis, the same participants traced the presence (or absence) of the four dominant subqualities (determined from Study 1) of capsaicin solutions over a period of 600 s. The results of TCATA analysis revealed that participants' initial perception of the more algogenic sensations (i.e., "burning" and "stinging/pricking") were slower in occurring and lasted for a shorter period, while the milder sensations (i.e., "tingling" and "warm/hot") lasted longer than "burning" and "stinging/pricking". There were no or little effects of habitual spicy food consumption on the time -dependent perceptions of oral irritation and its subqualities, respectively, in Studies 1 and 2. In conclusion, our results support and extend the notion that overall oral irritation and its subquality perception vary over time. This study also shows that the TI analysis can be supplemented with the TCATA analysis for greater under-standing of the temporal dynamics of oral irritation perception of capsaicin solutions.