Several taste substances were tested in aqueous solutions; tannic and tartaric acids were found unsuitable as a standard substance for the taste identification. Monosodium glutamate, sodium hydrogen carbonate and potassium chloride were often identified as salty substances even when the subjects were able to distinguish between the tastes. They probably identified the taste as salty owing to the lack of proper terms, and unsufficient experience with tasting monosodium glutamate and sodium hydrogen carbonate as substances possessing defined tastes different from the salty taste.
The AMADORI product was prepared from D-glucose and L-alanine after HASHIBA. The browning process was investigated by determining the absorbance at 520 nm, in aqueous solutions at 110 "C for 5-8 h. Because of the limited access of oxygen and its low solubility in the reaction medium, the browning proceeded after zeroth order kinetics with the maximum browning rate at pH = 8-9. The browning rate remained unaffected by additions of sodium sulphite, rutin. propyl gallate (except when present at high levels), iron(I1l)chloride or copper(1I)chloride but decreased in presence of L-cysteine or iron(I1)chloride. Hydrogen peroxide bleached the pigment but did not inhibit the subsequent browning of reaction products. Under experimental conditions the solution of AMAWRI product did not darken with substantially greater rate than the solution of D-glucose and L-alanine. Lower additions of D-glucose to the solution of AMADON product moderately increased the reaction rate while additions of L-alanine or L-hydroxyproline moderately decreased the browning rate.
The browning rate of HEYNS rearrangement products at 110 "C under free access of oxygen is slower that that of AMADoRI rearrangement products. The maximum browning rate was observed at pH = 8.0. The browning was accelerated by Fe(II1) and Cu(I1) ions. The presence of Fe(I1) ions, propyl gallate, and rutin caused lag periods but had no pronounced effect during the subsequent browning. Hydrogen peroxide bleached the melanoidin pigments but did not destroy the browning precursors. Sulphites inhibited the browning reaction. Fluorescence spectra differed from those of the respective AMADOR! products.
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