Shizuko Yamaguchi and Chikahito Takahashi Central Research Laboratories, Ajinornoto Co., Inc., 1-1 Suzuki-cho, Kawasaki, Kanagawa 210, Japan

Received September 27, 1983

The taste elicited by such compounds as monosodium glutamate (MSG) is termed « umami. »1’2) « Umami » elicited by MSG has been studied extensively with respect to its nature and its intensification by various co-existing substances such as nucleotides.2~7) There are few reports avhaoilwabelvee,r, on the hedonic aspect of MSG or umami.  » In this study we characterized the hedonic functions of the taste elicited by MSG. The hedonic functions of MSG were compared with those of sucrose, NaCl, tartaric acid and caffeine representing the four basic tastes, although hey have been studied in single solution systems.8)9) The hedonic taste was rated in terms of the pleasantness perceived by panelists. This pleasantness was scored on a 9-point scale from extremely pleasant (+4) to extremely unpleasant (-4), compared with the standard. The p leasantness score of the standard was set at zero. The panelists, 20 ~40 men and women,were randomly chosen volunteers from the laboratory personnel. To avoid any bias caused by individual experience, we asked the panelists to score the samples only by the taste elicited from the samples, not by associated images. A series of test samples was presented in an increasing order of concentration. The panelists rinsed their mouths with distilled water between the trials to remove any residual taste from the preceding sample. The taste substances were reagent grade materials and solutions of these substances were given to the panelists at room temperature. All the tests were carried out in air-conditioned (20°C, 60% RH) s ensory booths. Each experiment consisted of two parts: firstly MSG and the other taste substances were rated in aqueous olutions; secondly, they were rated in food media. In the first case, single solutions of five taste substances and mixed aqueous solutions of all possible binary combinations were tested. Twenty-five series of experiments were carried out. In each experiment, a glass of standard solution and six or seven glasses of different concentrations of the test solutions were given to the panelists. For tests on single solutions, distilled water was used as the standard. For tests on binary mixtures, a solution of a single taste substance at a specific concentration was taken as the standard, and the second taste substance was added at various concentrations to this solution. The specified concentration is defined as the intermediate taste intensity between that giving no taste and that giving maximal intensity of taste.2) The specified concentrations of sucrose, NaCl, tartaric acid, caffeine, and MSG were 8.83, 0.808.,03.3, 0.06, and 0.70%, respectively. Figure 1 shows the hedonic functions of the taste substances in aqueous solutions. Points scored are mean values for pleasantness by the panelists with 95% confidliemnictes. As shown in the top row of Fig. 1, sucrose solution (sweetness) gave an exceptionally high pleasantness score over a certain range of concentrations. The highest score was obtained at 8.56%. Above this concentratthioen, score decreased and at over 34.2% sucrose, the score became negative. The other four taste substances fell into two groups: one group, containing tartaric acid (sour) and caffeine (bitter), gave a negative score even in very dilute solutions; the other group, containing NaCl (salty) and MSG (umami), gave a zero score in dilute solutions and an increasingly negative score at higher concentrations. The pleasantness scores of binary combinations of the taste substances are shown in 5 rows in Fig. 1. The standard solution at a specified concentration had a moderate taste, and the positive or negative effects of a second taste substance were evaluated as relative pleasantness scores. As in the solution alone, sucrose (sweetness) was exceptional, giving a higher pleasantness score in a tartaarcicid or caffeine solution, and a lower score in an MsSoGlution, although the effect of sucrose per se was regarded as giving a sweet taste (1st column). Besides sucrose, there were two other cases in which the pleasantness score was increased by adding a second taste substance; namely those ofMSG in tartaric acid (4th row, 5th column) and NaCl in an MSG solution (bottom row, 2nd column)’. It is well documented that dilute acid and « umami » (MSG) improve the quality of taste6>7) and this improved quality of taste may be reflected in the pleasantness score. Even in the case of MSG in tartaric acid, higher levels of MSG reduced the pleasantness score. In the case ofNaCl in MSG solution, it is also well known that NaCl and MSG have co-operative effects in enhancing the pleasantness of taste within certain concentration ranges of both substances.7~10) Our experiment confirmed that the addition of NaCl to an MSG solution improved the pleasantness score. NaCl had a favorable effect only at low concentrations, above which it gave a negative pleasantness score. On the other hand, increasing amounts of MSG added to a 0.88% NaCl solution did not significantly 1078 S. Yamaguchi and C. Takahashi Sucrose NaCl Tartaric acid Caffeine MSG 4 , , _, , , -| 3 _In a single solution 4 1 1 1 2^J 3 _In an 8.83% sucrose solution ^ 3_Ina0.88%NaClsolution 0 2- 1 it^-^*^ £ 4 I I I 1 ^ , In a 0.033% tartaric acid solution :j h\\ \\ ^ 3 _In a 0.06% caffeine solution ‘:^i4 | 1 1 1 4 I 1 . 1 ‘ 3_In a 0.70% MSG solution -4 ii i i i i i i i iiSE i i i i iT i i i iij^ i i i i i i i 2.14 8.56 34.2 0.18 0.73 2.92 0.0094 0.038 0.15 0.012 0.049 0.19 0.094 0.37 1.5 6.0 4.28 17.1 68.5 0.37 1.46 5.85 0.019 0.075 0.30 0.024 0.097 0.39 0.19 0.75 3.0 Concentration (%,w/v) Fig. 1. Mean Pleasantness Ratings as Functions of the Log Concentrations of 5 Taste Substances in Distilled Water and in the Respective Taste Solutions. Hedonic Functions 1079 1080 S. Yamaguchi and C. Takahashi Hedonic Functions 1081 press. R. Berolzheimer, « Encyclopedic Cook Book, » Culinary Arts Institute, Chicago, 1950, pp. 272, 287, 826. R. Steinberg, « Food of the World; The Cooking of Japan (Recipes), » Time-Life Books, Time Inc., New NY.ork, Y., 1969, pp. 4, 12, 101. . Hahn, « Food of the World; The Cooking of China (Recipes), » Time-Life Books, Time Inc., New York, N. Y., 1968, p. 45.