The subject matter is concerned with the early recognition of quality changes in low moisture foods. Experiments were carried out on tomato powder stored at various equilibrium moistures and temperatures between 23 and 55 °C. Using the amino acid analyser, free amino acids as well as the Amadori compounds which are formed as intermediates of the nonenzymatic browning reaction (Maillard reaction) could be determined simultaneously. In contrast to browning products the Amadori compounds are formed without an induction period and before occurence of sensory changes. Thus they may be used for early recognition of quality changes caused by the Maillard reactions. The rates at which Amadori compounds are formed depend on the production and/or storage conditions. Amadori compound formation-and their decomposition - increases with increasing moisture and temperature. The temperature coefficient (Q10 values) of these browning intermediates are highter than those of the browning reaction itself. The Amadori compounds formed vary in their equilibrium moisture dependent stability. Tagaturonγ-aminobutyric acid which is formed from galacturonic acid and γ amino butyric acid is degraded considerably faster to browning products (melanoidins) than any of the other browning intermediates. In contrast fructores-glutamic acid which in the amino acid analysis alutes at the same time with other Amadori compounds such as fructose-serine, fructose-threonine and fructose-asparagine, is particularly stable. Thus fructose-glutamic acid is particularly suitable for the objective determination of damage due to unsuitable drying (overheating); also with higher concentrations of Amadori compounds a relationship with sensory changes was established. In summary it can be stated that by the use of Amadori compounds which are formed by thermal action or during storage a very sensitive indicator is available for incipient quality changes of dry produce of plant origin. © 1979 J. F. Bergmann Verlag.
