EVALUATION OF BITTERNESS OF CAFFEINE IN HOT CHOCOLATE DRINK BY CATEGORY, GRAPHIC, AND RATIO SCALING

Perceived intensity of bitterness of caffeine (0.5 - 1.6 g/100 mL) and of quinine HCI (0.5 - 1.6 g/L) added to hot cocoa gave similar response distributions with concentration by category scales (CS) and magnitude estimation (ME). Using caffeine additives, CS and graphic analogue scales (GS) gave similar bitterness response functions. Parabolic functions provided the best fit between concentration and ratings for CS, GS and ME. The data demonstrated no difference for ME of bitterness intensity between free or fixed moduli. Hedonic responses also were not modified by whether the modulus was free or fixed, however, greater ME values were ascribed to lower concentrations in the series when the reference was 4 g/L than when it was 2 g/L caffeine. CS intensity response distributions were similar between a series with a larger number of low levels versus a series with a larger number of high levels across the same concentration range. The results indicate that ME may be inappropriate for scaling of degree of liking, independent of type of modulus.     

EFFECT OF EXPOSURE TO THE AROMA OF A PRELOAD ON SUBSEQUENT INTAKE OF A FOOD WITH THE SAME AROMA

We tested the hypothesis that exposure to an aroma through a food or beverage in the first part of a meal (preload) would reduce the consumption of a food with the same aroma in the second portion of the meal, because of olfactory-specific satiety. In a first experiment, 35 young, normal-weight adults participated in 2 lunch sessions during which they consumed a fixed preload of either ranch-flavored or plain potato chips and sparkling water, followed by ad libitum consumption of a pasta salad with ranch dressing and sparkling water. In the second experiment, 33 subjects consumed a fixed preload of either lemon-flavored or plain sparkling water and pasta salad with ranch dressing, followed by ad libitum consumption of lemon-flavored yogurt and plain sparkling water. No difference was observed in the amount of food consumed (corrected for session order effects) as a function of prior exposure to ranch flavor in the chips or lemon flavor in the water. We conclude that exposure to a preload aroma may not have a significant effect on subsequent intake of a food with the same aroma.     

TIME-INTENSITY PROPERTIES OF SWEET AND BITTER STIMULI: IMPLICATIONS FOR SWEET AND BITTER TASTE CHEMORECEPTION

Interindividual differences in sweet and bitter taste sensitivity were investigated using time-intensity (TI) measurements and multivariate statistics. TI profiles were obtained in triplicate from 25 subjects for 23 sweet and/or bitter stimuli first matched to be approximately equi-intense to 200 mM NaCl. Sweet stimuli, except for the larger sweeteners, were less persistent, and required less time to reach maximum intensity than bitter stimuli. The results of principal component (PCA) and cluster (CA) analyses of the stimuli X subjects matrices for maximum intensity (Imax), time to maximum intensity (Tmax), total duration (Tdur), and area under the curve (Area) suggest that sweet and bitter stimuli do not share common receptors; and that there are at least two receptor mechanisms each for sweet taste (one for sugars and other small compounds, and the other for large sweeteners) and bitter taste (one for PTC/PROP and one for other bitter compounds).     

COMPARISON OF NEW AND EXISTING METHODS FOR THE CLASSIFICATION OF INDIVIDUALS ACCORDING TO 6-N PROPYLTHIOURACIL (PROP) TASTER STATUS

We developed an alternative method for the determination of 6-n propylthiouracil (PROP) taster status that is based on the comparison of intensity ratings of PROP solutions with intensity ratings of visual, tactile, and kinesthetic (physical) stimuli. We then compared the classification obtained with this method to those derived from traditional approaches. One hundred and forty-two subjects rated the perceived intensity of 0.000032, 0.00018, 0.00032, 0.0018, and 0.0032 M PROP, and 0.01, 0.032, 0.1, 0.32, and 1.0 M NaCl, as well as five levels each of perceived roughness of sandpaper, grayness of shades, and thickness of honey and water mixtures on the Labeled Magnitude Scale (LMS). Ratings for 0.00032 M PROP and 0.1 M NaCl were also compared in a one solution test. Subjects were classified as PROP nontasters, tasters or supertasters by all three procedures. Seventy-six percent of panelists were classified in a similar way by the physical stimuli and NaCl procedures, while 70% percent of panelists were classified similarly by the physical stimuli procedure and the one solution test, as well as by the NaCl procedure and the one solution test. Only 65% of panelists were classified similarly by all three procedures. Further, in replicate ratings of PROP solutions, supertasters' evaluations of PROP at all concentration levels decreased significantly (P < 0.01) from the first to the second rating. It is evident from these findings that the method used to determine PROP taster status can greatly influence the outcome of any investigation of PROP taster status on other phenotypes.     

TIME INTENSITY PROFILES OF FLAVOR POTENTIATORS (MSG, IMP, GMP)

This research characterized the time-intensity (TI) profiles of monosodium glutamate (MSG), disodium 5'-inosinate (IMP), and disodium 5'-guanylate (GMP). Twenty subjects rated total taste intensity of single solutions of 2.5, 5 and 10 mM MSG, 0.63 and 2.5 mM IMP and GMP, and some of their mixtures, using the TI method. The profiles generated were atypical of other taste modalities. Time to maximum intensity waslong (16–20s), followed by a plateau at maximum intensity, and a persistent aftertaste (50–96s duration). Maximum intensities of the samples varied (p < 0.001), with mixtures of 10 and 5 mM MSG with 2.5 mM IMP or GMP yielding the highest intensities. Similar differences were found for total duration and area under the curve. These results indicate that flavor potentiators may increase total flavor during consumption. Synergism between flavor potentiators was demonstrated.     

ELIMINATING ARTIFACTS IN THE STUDY OF SINGULARITY/MIXEDNESS OF TASTE STIMULI

Taste stimuli with a single solute were not judged as tasting equally singular; this confirmed earlier results, except in this study the possibility of the results being caused by trigeminal effects was virtually eliminated. Binary mixtures were generally perceived as more mixed than single solute stimuli, indicating a degree of analytic mixing. However, a caffeine/KCl mixture was perceived as more singular tasting than some single solute stimuli, indicating a degree of synthetic mixing. A preliminary examination was made of the hypotheses that the perceived mixedness of a taste mixture might be determined by a summation of the mixedness of its components or alternatively by latency effects.