A test for measuring gustatory function

Abstract

Objectives/hypothesis: The purpose of this study was to determine the usefulness of edible taste strips for measuring human gustatory function.

Study design: The physical properties of edible taste strips were examined to determine their potential for delivering threshold and suprathreshold amounts of taste stimuli to the oral cavity. Taste strips were then assayed by fluorescence to analyze the uniformity and distribution of bitter tastant in the strips. Finally, taste recognition thresholds for sweet taste were examined to determine whether or not taste strips could detect recognition thresholds that were equal to or better than those obtained from aqueous tests.

Methods: Edible strips were prepared from pullulan-hydroxypropyl methylcellulose solutions that were dried to a thin film. The maximal amount of a tastant that could be incorporated in a 2.54 cm2 taste strip was identified by including representative taste stimuli for each class of tastant (sweet, sour, salty, bitter, and umami) during strip formation. Distribution of the bitter tastant quinine hydrochloride in taste strips was assayed by fluorescence emission spectroscopy. The efficacy of taste strips for evaluating human gustatory function was examined by using a single series ascending method of limits protocol. Sucrose taste recognition threshold data from edible strips was then compared with results that were obtained from a standard "sip and spit" recognition threshold test.

Results: Edible films that formed from a pullulan-hydroxypropyl methylcellulose polymer mixture can be used to prepare clear, thin strips that have essentially no background taste and leave no physical presence after release of tastant. Edible taste strips could uniformly incorporate up to 5% of their composition as tastant. Taste recognition thresholds for sweet taste were over one order of magnitude lower with edible taste strips when compared with an aqueous taste test.

Conclusion: Edible taste strips are a highly sensitive method for examining taste recognition thresholds in humans. This new means of presenting taste stimuli should have widespread applications for examining human taste function in the laboratory, in the clinic, or at remote locations.

Fig. 1

Edible taste strips are readily formed from pullulan-HPMC polymers. This figure is an image of a clear pullulan-HPMC edible film that formed from a 3.25% polymer solution containing 87.5% pullulan and 12.5% HPMC by weight. The clear film is then cut into 2.54 cm × 2.54 cm pieces for psychophysical testing.

Fig. 2

Human taste recognition thresholds for the sweet tastant sucrose that were obtained with edible taste strips. Various amounts of sucrose were incorporated into 2.54 cm × 2.54 cm edible taste strips. (A) Graph represents the number of subjects that could detect the tastant in strips containing differing amounts of sucrose. (B) Cumulative frequency distribution of taste recognition thresholds for sweet taste that was obtained with edible taste strips.

Fig. 3

Human taste recognition thresholds for the sweet tastant sucrose that were obtained from a standard sip and spit test using a 10 mL sample volume. (A) Graph represents the number of subjects that could detect a tastant in solutions containing varying amounts of sucrose. (B) Cumulative frequency distribution of taste recognition thresholds for sweet taste that was obtained with an aqueous test.