Fig 1.
Effect of sucrose on the lactisole sweet water taste.
The perceived intensity of sweetness (black circles), saltiness (dark gray circles), sourness (light gray circles), and bitterness (open circles) are shown for the 5 conditions of experiment 1: (a) LAC → H2O: lactisole followed by 5 water rinses; (b) MIX → H2O: lactisole + sucrose, followed by 5 water rinses; (c) SUC → LAC: sucrose before lactisole, followed by 4 water rinses; (d) LAC→ SUC: sucrose after lactisole, followed by 4 water rinses; and (e) LAC → H2O → SUC: sucrose after lactisole and 1 water rinse, followed by 3 water rinses. Letters on the x-axis of each graph represent water rinses (W), lactisole rinses (L), and sucrose rinses (S). Letters on the right y-axes represent semantic labels of sensation intensity on the gLMS: BD = barely detectable; W = weak; M = moderate, and S = strong. The dotted line at BD serves to highlight the near imperceptibility of most tastes other than sweetness, and the number of rinses over which the SWT was clearly perceived. Vertical bars indicate standard errors (SEs) of the log10 means.
Fig 2.
Effects of different sweeteners on the lactisole sweet water taste.
Five different sweeteners (CYCL = cyclamate, FRUC = fructose, SACC = saccharin, SUCRA = sucralose, NHDC = neohesperidin dihydrochalcon) were presented in the 2 treatment conditions of experiment 2: in mixture with lactisole (a-e) or after lactisole (f-j). The data for the lactisole SWT is shown in each graph (open circles) for comparison with the SWT produced in the treatment conditions (filled circles). In graphs (a-e) L/M on the x-axis indicates that in the treatment condition the mixture was presented on the first trial. Asterisks in graphs (d) and (e) indicate significantly higher SWT on the first water rinse after the mixture compared to the SWT after lactisole alone (Tukey HSD, p<0.05). In graphs (f-j) W/S indicates that in the treatment condition the sweetener was presented on the second trial. Thus in (f-j) the data on the second trial reflects the sweetness evoked by the sweetener, and the remaining 4 trials indicate the SWT. Arrows below the x-axis highlight the large differences in suppression of the SWT during the first water rinse after each sweetener compared to the second water rinse after lactisole alone. The horizontal dotted line in each graph indicates a “barely detectable” level of sweetness. Vertical bars are SEs of the log10 means.
Fig 3.
Decay in sweetness produced by sweeteners alone across water rinses.
Main graph: Peak sweetness ratings for the 5 sweeteners of experiment 2 when presented alone and during 5 water rinses. S and W’s on the x-axis indicate exposures to the sweeteners and water rinses, respectively. The horizontal dotted line indicates a “barely detectable” level of sweetness; vertical bars are SEs of the log10 means. Inset: residual sweetness during the first water rinse expressed as a percentage of the initial sweetness reported for each of the sweeteners.
Fig 4.
Lactisole sweet water taste requires flowing water rinses.
Shown are log10 ratings of the lactisole SWT experienced on the tongue tip in experiment 3 under conditions of Still vs. Flowing water rinses. The dotted line indicates the level of “barely detectable” sweetness. Vertical bars are the SEs of the log10 means.
Fig 5.
Pre-exposure to lactisole suppresses the sweetness of sucrose and neotame in ‘still’ solutions.
Shown are log10 ratings of the sweetness of still solutions of sucrose or neotame perceived on the tongue tip when the solutions were sampled alone or following exposure to a still solution of lactisole, in which rinsing of lactisole is assumed to be incomplete and therefor results in partial suppression of sweetness. Different letters over the bars indicate significant differences in sweetness. The dotted line indicates the level of “barely detectable” sweetness. Vertical bars are the SEs of the log10 means.
Fig 6.
Lactisole sweet water taste is unaffected by prior sweet receptor activation.
Log10 sweetness ratings are shown for solutions of (a) sucrose and (b) neotame sampled with the tongue tip in 4 conditions: Suc or Neot + Lac: a still lactisole + sweetener mixture (white bars); Lac→Suc or Neot: a still solution of lactisole before a still solution of the sweetener (gray bars); Suc or Neot + Lac → H2O: a still sweetener + lactisole mixture followed by a flowing water rinse (hatched white bars); and Lac→Suc or Neot→H2O: a still solution of lactisole before a still solution of the sweetener followed by a flowing water rinse (hatched gray bars). Shown for comparison is the SWT produced by a flowing water rinse after lactisole alone (dashed line). Vertical bars are the standard errors of the log10 means (SEMs).