Individual variation in PROP status, fungiform papillae density and responsiveness to taste stimuli in a large population sample

Despite considerable research investigating the role of responsiveness to PROP and of variation of fungiform papillae density (FPD) on the tongue in food perception and acceptability, these relationships remain unclear, which may be a function of these relationships typically being investigated using small sample sizes. In the present work, this topic is explored in a large adult population sample. Data from 1150 subjects (39% male; 18-60 years) enrolled in the Italian Taste project were analysed. Sensitivity to the bitterness of solutions of 0.0032M PROP was assessed on a gLMS. FPD was manually determined from digital images of the tongue.Quartile limits of the percentile distributions of PROP ratings and FPD values were used for classification. Solutions of tastes (sweet; sour; bitter)were prepared to be moderate/strong on a gLMS. Four foods had tastants added to produce four variations in target sensations from weak to strong (pear juice: sweetness, sourness; chocolate pudding:sweetness, bitterness, astringency; bean puree: saltiness, umami; tomato sauce: pungency, sourness). FPD showed a normal distribution. PROP bitterness ratings followed a bimodal distribution, and the quartile limits were in good agreement with arbitrary cut-offs used in previous studies to categorize subjects as non-tasters (NT) and super-tasters (ST). Females gave ratings to PROP and showed FPD that were significantly higher than in males. Both indices significantly decreased with age. No significant correlations were found between PROP ratings and FPD considering the whole population, or by grouping subjects by gender or age. FPD positively affected taste intensities (solutions and foods) in NT only. Taste intensities for STs with the lowest FPD were significantly higher than for those ST with the highest FPD. Results on a subset of cases indicate that ST with PAV/AVI haplotype and high papillae density show taste responsiveness similar to ST with PAV/PAV haplotype and low papillae density. Responsiveness to PROP positively affected all taste intensities in subjects with low FPD while there were no significant effects of PROP in high FPD subjects. These data highlight a complex interplay between PROP status and FDP and the need of a critical reconsideration of their role in food perception and acceptability.