KINETICS OF MAILLARD REACTIONS BETWEEN THE MAJOR SUGARS AND AMINO-ACIDS OF BOILED GRAPE JUICE

Model systems were employed to determine the reactivities of major sug ars, fructose and glucose, and amino acids, glutamine and arginine, fo und in the accumulation of 5-hydroxymethyl furfural (HMF) in grape jui ce, and brown pigment formation (BPF) at 55, 65, and 75 degrees C over ten days at pH 3.5. Fructose was found to be more reactive than gluco se in both HMF accumulation and BPF at all temperatures. With fructose as substrate, glutamine was more reactive than arginine, but with glu cose, arginine was found to be more reactive than glutamine under the same conditions. Reaction order was 0.5 for both HMF accumulation and BPF. Rate constants for HMF accumulation and BPF were determined by us ing a non-linear equation with an n value of 0.5. Analysis of variance (ANOVA) was performed to determine any significant difference between the rate constants of amino acid and sugar determined at varying temp erature. Results of ANOVA indicated that the temperature is the most i mportant parameter.