Classifying fat-taste sensitivity with repeated threshold testing and an additive-free emulsion: stability and...

Individual variability in oral sensitivity to non-esterified fatty acids (NEFAs), especially oleic acid, is well documented, yet the influence of repeated testing on threshold-based classification has been underexamined. This study aimed to investigate whether repeated evaluations, accounting for learning effects, alter the grouping of fat-taste sensitivity and how this affects fat-taste sensitivity classification. Oleic acid detection thresholds were measured using a signal-detection-based descending-block Dual-Reminder A-Not A (DR A-Not A) method with an additive-free emulsion across eight visits (four two-visit blocks) in a phenotypically similar sample of healthy young Korean women. Participants were classified as hypo- or hypersensitive relative to a 2.8 mM criterion using either a single baseline or the repeated-visits data. After repeated testing, 13 of 40 participants (∼33 %) were reclassified, whereas the remainder retained their original classification-consistent with possible practice/learning effects at the individual level. When classification accounted for these effects, PROP bitterness sensitivity was higher in the hypersensitive group; this association was not evident with single-visit classification. The use of an additive-free emulsion minimized potential confounds in fat-taste assessment. Overall, these findings suggest that brief familiarization or reference anchoring, combined with limited targeted repetition in individuals who show practice-related changes, may yield more stable classifications of fat-taste sensitivity and clearer associations with other individual traits.