Changes in the taste of japonica, hybrid, and indica brown and milled rice, stored for 10 months at low (5 degrees C, 65-70% relative humidity) and room temperatures were observed by physicochemical analyses and a novel method using a taste sensing system. During storage, some properties increased or decreased while others were fairly constant. The main taste components of cooked rice such as sweetness (sucrose) and umami tastes (glutamic acid and aspartic acid) were reduced during storage, whereas glucose and fructose increased. The increase of fat acidity and consequent decrease of the pH value of the cooking solution may contribute to the off-taste of cooked stored rice. A taste sensing system with 10 lipid membrane sensors was also used to classify new and old rice samples using principal component analysis. Fresh and room temperature stored japonica and indica rice could be clearly distinguished; however, it was not possible to differentiate the samples stored at low temperature.

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The bitterness of nine commercial antibiotics (clarithromycin, erythromycin, cefdinil, doxycycline, vancomycin, tetracycline, minocycline, oxytetracycline and bacampicillin) was evaluated in human gustatory sensation tests with nine volunteers. The bitterness of 0.1-0.3 mM solutions (or suspensions in the case of clarithromycin) of the antibiotics was then measured using an artificial multichannel taste sensor. In the sensor measurements, three variables were used to predict estimated bitterness in single and multiple regression analysis and principal component analysis: sensor output as relative value (R), the change of membrane potential caused by adsorption (C) and C/R. Particularly good correlation was obtained between obtained bitterness scores and predicted scores using C from channel 2 of the sensor (r2=0.870, P<0.005) and C/R values for channels 2 and 3 (r2=0.947, P<0.005). The taste sensor was also successful in assessing the bitterness intensity of clarithromycin powder suspensions of various concentrations. Clarithromycin has a low aqueous solubility but is the most bitter of the nine antibiotics. Sensory data from channel 3 of the sensor predicted the bitterness of clarithromycin powder suspensions and their filtered solutions well. Finally, the bitterness intensity of a commercial clarithromycin dry syrup product (Clarith dry syrup, Taisho Pharmaceutical Co. Ltd, Tokyo, Japan) was evaluated in gustatory sensation tests and using the taste sensor. In Clarith dry syrup the drug is coated with aminoalkyl methacrylate polymer using a spray congealing method. The taste sensor results confirmed that the polymer was successful in almost completely masking the bitter taste of the dry syrup product.

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