Inducible desensitization to capsaicin with repeated low-dose exposure in human volunteers

Oral Somatosensory Sensitivity in the Clinical Assessment of Gustatory Dysfunction

OBJECTIVE

Food perception has multimodal contributions by taste, smell, and somatosenses. The objective of this study was to investigate oral somatosensory function in patients with gustatory dysfunction.

METHODS

This case-control study was conducted from May 1, 2022 to June 30, 2023 at a tertiary smell and taste clinic. Patients with gustatory complaints and controls were recruited. All participants underwent tests for gustatory function (taste spray, taste strips), oral mechanosensation (letter recognition) and oral irritation (chili powder: 1, 2, 5 and 7 mg). Primary outcome measures were Taste Strips scores, size of oral letter recognition, and self-rated oral irritation intensity.

RESULTS

There were 43 patients with gustatory dysfunction and 26 controls. Patients with gustatory dysfunction had significantly lower Taste Strips scores compared to controls (8.0 [7.0-12.0] vs. 13.0 [12.0-15.0], p < 0.001). Patients with gustatory dysfunction rated significantly lower oral intensities of chili at 2 mg (11.4 [4.8-25.2]% vs. 28.6 [23.8-44.8]%, p = 0.002), 5 mg (26.2 [10.0-42.9]% vs. 48.6 [39.0-69.5]%, p = 0.005) and 7 mg (39.5 [24.8-68.1]% vs. 68.6 [50.5-90.5]%, p = 0.008) compared to controls. There was no significant difference in the size of oral letter recognition between patients and controls. Among patients with gustatory complaints, 21 (52.5%) scored ≥ 9 on Taste Strips (considered a normal score); These patients perceived lower oral intensities with 2 mg of chili compared to controls (14.3 [4.8-39.5]% vs. 28.6 [23.8-44.8]%, p = 0.066).

CONCLUSION

Altered gustatory perception may be related to changes in chemesthetic sensitivity. Clinical assessment using lower concentrations of chili could be considered in patients with subtle gustatory dysfunction.

LEVEL OF EVIDENCE: 2

Overview of mouthfeel from the perspective of sensory scientists in industry

Mouthfeel is vital in consumer acceptance of foods and beverages. Despite the critical role mouthfeel plays in product development, the concept is often poorly understood and subject to various interpretations. Within this review, five topics of interest are discussed to provide a better understanding of the mouthfeel attribute-the definition, the perception, the importance, the influencing factors, and the methods of measurement of mouthfeel. Mouthfeel encompasses multiple attributes. Although mouthfeel attributes perceived through physical and chemical perceptions, such as cooling and heating, are understood as mouthfeel, attributes perceived through mechanoreceptors, such as creaminess and thickness, are more challenging due to varying opinions on texture and mouthfeel. Other factors, like food composition and temperature, are also vital in understanding the overall effect of mouthfeel in food and beverages. Including all perceived attributes and factors is important for consumer acceptance of products and for developing consistent evaluation of products. Other topics to consider include the dynamic aspects of oral processing and cultural backgrounds as these topics create additional intricacies in defining and understanding mouthfeel perception. Despite the lack of instrumental methodology available to measure mouthfeel attributes, trained panelists can be used to predict facets of mouthfeel in the eating experience. When designing sensory testing for trained panelists, experimental conditions and a product-specific lexicon are important factors to consider. Overall, understanding of the mouthfeel attributes and their role in consumer preference for different types of food and beverages continues to evolve.

"Spicy Touch": Cross-modal associations between hand-feel touch and capsaicin-induced oral irritation

The influence of extrinsic hand-feel touch cues on consumer experiences in food and beverage consumption is well established. However, their impact on trigeminal perception, particularly the oral irritation caused by capsaicin or spicy foods, is less understood. This study aimed to determine the existence of cross-modal associations between hand-feel touch and capsaicin-induced oral irritation. This study investigated whether these potential associations were driven by the sensory contributions of the hand-feel tactile materials (measured by instrumental physical parameters) or by affective responses (evaluated through hedonic scales and the self-reported emotion questionnaire, EsSense Profile®, by consumers). In our study, 96 participants tasted a capsaicin solution while engaging with nine hand-feel tactile materials, i.e., cardboard, linen, rattan, silicone, stainless steel, sandpaper (fine), sandpaper (rough), sponge, and towel. They subsequently rated their liking and emotional responses, perceived intensity of oral irritation, and the congruency between hand-feel tactile sensation and oral irritation. Instrumental measurements characterized the surface texture of the hand-feel tactile materials, which were correlated with the collected sensory data. The results revealed that unique cross-modal associations between hand-feel touch and capsaicin-induced oral irritation. Specifically, while sandpapers demonstrated high congruence with the sensation of oral irritation, stainless steel was found to be least congruent. These associations were influenced by both the common emotional responses ("active," "aggressive," "daring," "energetic," "guilty," and "worried") evoked by the hand-feel tactile materials and the capsaicin, as well as by participants' liking for the hand-feel tactile materials and the characteristics of the surface textures. This study provides empirical evidence of the cross-modality between hand-feel tactile sensations and capsaicin-induced oral irritation, opening new avenues for future research in this area.

Targeting TRPV1 for Cancer Pain Relief: Can It Work?

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