Department of Food and Nutrition, Kyung-Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul 130-701, Republic of Korea.
Department of Food and Nutrition, Kyung-Hee University, 1 Hoegi-dong, Dongdaemun-gu, Seoul 130-701, Republic of Korea.
Food Chem. 2008 May 15;108(2):582-92. doi: 10.1016/j.foodchem.2007.11.014. Epub 2007 Nov 17.
This study investigates the effect of reaction pH on enolization and racemization reactions of glucose and fructose on heating with amino acid enantiomers, can influence the formation of melanoidins as result of the Maillard reaction. Remarkable enolization reaction of sugars was observed in the course of the Maillard reaction. Especially, the degree of sugar enolization was increased as the pH levels increased, which was higher in fructose than glucose systems. Otherwise, enolization of sugars on heating with amino acid was higher in glucose than fructose systems. Formation of isomer in Glc/d-Lys, Fru/d-Asn and Fru/d-Lys were increased upon increase of pH levels. The relative amounts of isomers in Glc/l-Asn and Glc/d-Asn were decreased upon increase of pH levels. Browning development was dependent on the pH levels, being more significant for model systems apart from heated glucose solution alone. Browning development of fructose systems was higher than glucose-amino acid systems. The l- and d-isomers both showed different absorption in the UV-vis spectra and that these occur at similar shape. Every peak has a stable absorbance appeared in the range between 260 and 320nm, characteristic of melanoidins.
本研究考察了反应 pH 值对加热时葡萄糖和果糖与氨基酸对映体的烯醇化和外消旋反应的影响，这种影响会影响美拉德反应中类黑精的形成。在美拉德反应过程中观察到了显著的糖烯醇化反应。特别是，随着 pH 值的升高，糖的烯醇化程度增加，果糖体系中的烯醇化程度高于葡萄糖体系。另一方面，在加热条件下，与氨基酸的糖烯醇化反应在葡萄糖体系中高于果糖体系。在 Glc/d-Lys、Fru/d-Asn 和 Fru/d-Lys 中，随着 pH 值的升高，异构物的形成增加。在 Glc/l-Asn 和 Glc/d-Asn 中，异构物的相对量随着 pH 值的升高而降低。褐变发展取决于 pH 值，除了单独加热葡萄糖溶液之外，模型体系中的褐变发展更为显著。果糖体系的褐变发展高于葡萄糖-氨基酸体系。l-和 d-异构体在 UV-vis 光谱中均显示出不同的吸收，且这些吸收具有相似的形状。每个峰在 260nm 到 320nm 之间都有一个稳定的吸光度，这是类黑精的特征。
