Temporal Perception of Sweetness and Fruitiness and their Interaction in Model System.

Using a computerized time-intensity (TI) system, 10 judges evaluated sweetness and fruitiness of 24 solutions, varying in concentration of glucose (0.0% - 9.0%) and peach extract (0.0% - 0.6%) and presented at two solution temperatures (5°C, 25°C). The resulting TI curves were quantitated using 11 parameters. Ten parameters varied significantly across samples for sweetness; whereas, seven parameters differed significantly across samples for fruitiness. For sweetness and fruitiness, increases in concentration of glucose and peach extract, increased total time, maximum intensity, time to maximum, rate of onset, area, area before maximum, area after maximum. An additional three parameters were useful in characterizing the sweetness response: lag time, plateau time, and rate of decay. A further increase in sweetness was observed with increased peach extract for total time, maximum intensity, time to maximum, rate of onset, area, area before maximum, and area after maximum. In contrast, a further increase in fruitiness was observed with increased glucose concentration for total time, time to maximum, area, and area after maximum. For sweetness, raising the solution temperature from 5°C to 25°C significantly increased maximum intensity, the area under the curve after maximum intensity, and maximum rate of onset, while decreasing time to maximum and lag time. In comparison, temperature had no affect on the TI parameters for fruitiness. Several TT measurements were useful in contrasting the gustatory and olfactory responses. For sweetness, the maximum intensity occurred before expectoration at 6.6 sec. For fruitiness, the maximum intensity was observed after expectoration at 10.4 sec. The 3.8 sec delay in maximum intensity for fruitiness may have reflected the time required for the volatile stimuli to reach the nasal cavity via the nasopharyngeal route. Since expectoration induces nasopharyngeal turbulence, it may have aided the transfer of the odorant to the olfactory epithelium. Although the total duration of perception of sweetness and fruitiness was similar, the percentage of total perception occurring after the maximum was considerably different. The area under the curve after maximum intensity for sweetness and fruitiness represented 74% and 65%, respectively. These differences between the two perceptions were attributed to the longer time to maximum intensity, or to the shorter persistence for fruitiness compared to sweetness. For sweetness and fruitiness, the first principal components separated the solutions on the basis of concentration of glucose and peach extract, respectively. For sweetness, the second principal component, which was a function of lag time and time to maximum, differentiated the samples somewhat on the basis of temperature. All parameters except lag time, plateau time and time to maximum were highly correlated with each other; therefore, these parameters aided in characterization of the TI responses. For both attributes the rate of onset was greater than the rate of decay. These observations were consistent with adsorption/desorption principles. The degree of efficiency of stimuli removal for both sweetness and fruitiness was shown to decrease with increasing stimuli concentration.