Linda M. Kennedy

Experience-induced changes in taste identification of monosodium glutamate

Taste sensitivity for a given subject generally has been thought to be genetically determined and not plastic. Yet experience-inducible changes in human taste and olfactory sensitivities have been reported. To test a taste induction hypothesis, we exposed 17 Americans/Europeans to monosodium glutamate (MSG) in food and then compared their ability to identify MSG taste with that of 2 control groups (18 Americans/Europeans without MSG exposure and 18 Japanese). When tested on Day 11 or 12, the Americans/Europeans exposed to MSG were able to identify MSG at significantly lower concentrations than the Americans/Europeans without MSG exposure. Moreover, Japanese subjects who had prior extensive experience with MSG in Japanese food were able to identify MSG at significantly lower concentrations than the two American/European groups. The differences in identification ability between the two American/European groups challenge the notion of taste sensitivity as stable over time and support the hypothesis of an experience-inducible component in human taste.

Genetic analyses of sweet taste transduction

A genetic analysis of sweet taste transduction was initiated using fruitflies and humans. In flies, behavioral and receptor cell electrophysiology data indicate different mechanisms for fructose and glucose in or before the receptor cells. Fructose nontasters (FN) and glucose nontasters (GN) were selected from natural populations of adults and larvae. The FN are the first fructose taste variants isolated in any species. There were no significant differences between male and female frequencies for either variant type, and no observable differences in banding patterns between wildtype and FN X-chromosomes. These and preliminary cross-breeding data suggested a polygenic trait, either completely autosomal, or including coding by a defective X-chromosomal gene for which an autosomal gene(s) can compensate. In humans, psychophysical functions also indicated different fructose and glucose mechanisms. Variability analysis suggested separate signals for the monosaccharides and an additive sucrose signal. Potential GN were identified by elevated glucose thresholds.

Chemical Analyses of Hodulcin, the Sweetness‐Suppressing Principle from Hovenia dulcis Leavesa,b

The chemistry of hodulcin ( H ), the selective sweetness-suppressing principle from Hovenia dulcisl is not known. However, there are known similarities and differences between compounds from H. dulcis and ziziphins (Zs) and gymnemic acids (GAS), the selective sweetness-suppressing compounds from Ziriphus jujuba and Gymnemu syZvestre, respectively. Gymnemic acids are triterpene saponins, with a known genin structure (gymnemagenin).* Ziziphins are saponins, probably also triterpenes, yet not the same compounds as GAS.’ H. dulcis contains saponins with the same genin structure (jujubogenin) as certain saponins from Z. jujubu. 4,5 However, taste activity of the structurally identified H. dulcis and Z. jujuba saponins has not been tested. To elucidate the chemistry of taste-active H and Zs, we analyzed a partially purified preparation of H and compared it with Zs and GAS. Hodulcin was prepared similarly and found to suppress magnitude estimates of the sweetness of 80 mM sucrose 50100% in two humans. The preparations were analyzed by gradient elution reverse phase C18 HPLC (IBM Instr.; 40/60 MeOH/H,O-100% MeOH gradient, 1 ml/rnin) with a unique, automatic computer-controlled column switching system for sample isolation (IBM Instr., Valco Instr.). Elution profiles (217-nm detection) were different for H and GAS and similar, but not the same for H and Zs (FIG. 1). The H preparation was separated into three fractions, of which only one (8.513.5min retention, FIG. 1) was active (80% suppression) in blind tests on L.M.K. The major component of the active fraction ( 12.5-min retention) was isolated, concentrated, Ziziphins and gymnemic acids were prepared and found

Isolation of Variants for Fructose or Glucose Taste from a Natural Population of Hawaiian Drosophila adiastola

Strains variant in behavioral and receptor cell responses to trehalose, sucrose, glucose, and/or pyranose sugars, but not to fructose or furanose sugars, are known in the small fruitfly, Drosophila melanogaster. Genes on the X or autosomal chromosomes are involved [1–5]. Here we report variants for fructose, as well as glucose, in the larger species, D. adiastola.