Nonenzymatic Browning in Synthetic Systems Containing Ascorbic Acid, Amino Acids, Organic Acids, and Inorganic Salts

Abstract

The browning reactions between ascorbic acid and the 20 amino acids except tyrosine were studied at 44° and 72°C in model systems and the colour formation was followed by measurement of the absorbance at 400 nm. The progress and the extent of the colour development in unbuffered systems were dependent on temperature, incubation period, individual amino acids, and other additives. All amino acids except cysteine interacted with ascorbic acid, resulting in more pronounced colour formation than when ascorbic acid was present alone. Cysteine protected ascorbic acid against the formation of the brown pigment. Tryptophan exceeded all the other amino acids in enhancing the browning of ascorbic acid. At 72°C colour development caused by ascoibic acid and tryptophan was further enhanced by the presence of malic acid, citric acid, Feso4, Cuso4, and Na2Hpo4, but colour formation was reduced by fumaric acid, tartaric acid, succinic acid, Cacl2, Nahso3, tetrasodium pyrophosphate, sodium tripolyphosphate, sodium tetraphosphate, sodium metaphosphate, and sodium polyphosphate.