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The article discusses research which examines the contribution of low-molecular-weight pigment 2,4-dihydroxy-2,5-dimethyl-3 (2H) to the color of soy sauce. It showed that the color of soy sauce was due to the high-molecular-weight and hydrophilic compounds melanoidins and is considered to be attributable to melanoidins formed by the Millard reaction. It revealed that the chemical structure of meloidins cannot be clarified since they are identified as high-molecular-weight heterogeneous polymers.

The article discusses a study which examines the browning reaction between lysine and furfural by heating. The study found that a novel yellow compound named furpipate was formed during the reaction as the major low-molecular-weight colored compound in the solution. It is described that the furpipate was the major colored compound of the heated solution containing lysine and furfural.

The article discusses the result of the study regarding the factors that affect the formation of decomposition products, in Japan. The factors that affect browning and formation of decomposition products of a model orange juice solution were examined. Ascorbic acid stimulated by amino acids and citric acid was essential for browning. There is no observed presence of decomposition products that show equal formation pattern as the browning, aside from the furfural solution with added amino acids.

Furfural is an important intermediate compound of the Maillard reaction of pentose or ascorbic acid. We examined the browning of furfural and lysine by heating these compounds in solution and found two yellow compounds. The first, furpipate, is a novel pipecolic acid derivative and was ( Z)-3-(2-furylmethylidene)-3 H, 4 H, 5 H, 6 H-pyridine-2-carboxylic acid. The second was decarboxylated-furpipate. Furpipate shows absorption maxima at 370 nm and 310 nm under acidic and alkaline conditions, respectively. This compound was the major colored compound of the heated solution containing lysine and furfural. [ABSTRACT FROM AUTHOR]