葡萄糖-果糖-甘氨酸褐变反应的动力学模型。

A kinetic model for the glucose-fructose-glycine browning reaction.

作者信息

Mundt Sandra, Wedzicha Bronislaw L

机构信息

Procter Department of Food Science, University of Leeds, United Kingdom.

出版信息

J Agric Food Chem. 2003 Jun 4;51(12):3651-5. doi: 10.1021/jf026027e.

DOI:10.1021/jf026027e

PMID:12769540

Abstract

The browning of glucose-fructose-glycine mixtures involves parallel glucose-glycine and fructose-glycine reactions, which share a common intermediate, the immediate precursor of melanoidins in the kinetic model. At pH 5.5, 55 degrees C glucose is converted into this intermediate in a two step process where k(1) = (7.8 +/- 1.1) x 10(-)(4) mol L(-)(1) h(-)(1) and k(2) = (1.84 +/- 0.31) x 10(-)(3) h(-)(1) according to established kinetics, whereas fructose is converted into this intermediate in a single step where k(4) = 5.32 x 10(-)(5)()()mol L(-)(1) h(-)(1). The intermediate is converted to melanoidins in a single rate limiting process where k(mix) = 0.0177 h(-)(1) and the molar extinction coefficient (based on the concentration of sugar converted) of the melanoidins so formed is 1073 +/- 4 mol(-)(1) L cm(-)(1). Whereas the value of k(mix) is the same when the individual sugars undergo browning, the value of the molar extinction coefficient is similar to that for melanoidins from the glucose-glycine reaction (955 +/- 45 mol(-)(1) L cm(-)(1)) but it is approximately double the value for melanoidins from the fructose-glycine reaction (478 +/- 18 mol(-)(1) L cm(-)(1)). This is the reason that the effects of glucose and fructose on the rate of browning are synergistic.

摘要

葡萄糖-果糖-甘氨酸混合物的褐变涉及平行的葡萄糖-甘氨酸反应和果糖-甘氨酸反应，这两个反应有一个共同的中间体，即动力学模型中类黑素的直接前体。在pH 5.5、55℃条件下，葡萄糖通过两步过程转化为该中间体，根据既定动力学，其中k(1) = (7.8 ± 1.1) × 10⁻⁴ mol·L⁻¹·h⁻¹，k(2) = (1.84 ± 0.31) × 10⁻³ h⁻¹，而果糖通过一步反应转化为该中间体，其中k(4) = 5.32 × 10⁻⁵ mol·L⁻¹·h⁻¹。该中间体通过一个单一的限速过程转化为类黑素，其中k(mix) = 0.0177 h⁻¹，如此形成的类黑素的摩尔消光系数（基于转化的糖浓度）为1073 ± 4 mol⁻¹·L·cm⁻¹。虽然当单个糖发生褐变时k(mix)的值相同，但摩尔消光系数的值与葡萄糖-甘氨酸反应生成的类黑素的值相似（955 ± 45 mol⁻¹·L·cm⁻¹），但大约是果糖-甘氨酸反应生成的类黑素值的两倍（478 ± 18 mol⁻¹·L·cm⁻¹）。这就是葡萄糖和果糖对褐变速率的影响具有协同作用的原因。