美拉德反应Maillard reaction

初期：糖的羰基与氨基缩合生成 N-糖基胺（席夫碱），再经阿马多利重排生成 1-氨基-1-脱氧-2-酮糖。中期：阿马多利产物脱水、裂解生成糠醛、还原酮和二羰基化合物；二羰基与氨基酸发生斯特雷克降解，生成醛（风味的重要来源）和氨基酮，后者缩合成吡嗪类香气物质。后期：各种中间体聚合成棕黑色的类黑精。

Early stage: the sugar carbonyl condenses with an amino group to give an N-glycosylamine (Schiff base), which undergoes Amadori rearrangement to a 1-amino-1-deoxy-2-ketose. Intermediate stage: Amadori products dehydrate and fragment into furfurals, reductones and dicarbonyls; dicarbonyls react with amino acids in Strecker degradation, giving aldehydes (key flavours) and aminoketones that condense into aroma-rich pyrazines. Final stage: intermediates polymerise into brown melanoidins.

1912 年法国化学家路易-卡米耶·美拉德在研究蛋白质生物合成时，加热葡萄糖与甘氨酸溶液，发现溶液变棕并放出 CO₂，首次系统描述了这一反应。1953 年美国农业部的霍奇提出了至今仍在使用的反应机理框架。

In 1912 the French chemist Louis-Camille Maillard, studying protein biosynthesis, heated glucose with glycine and saw the solution turn brown and release CO₂, giving the first systematic description of the reaction. In 1953 John Hodge of the US Department of Agriculture proposed the mechanistic scheme still used today.

温度越高、水分活度适中（约 0.6–0.8）、pH 偏碱时反应越快；面包表皮刷碱水的椒盐卷饼因此颜色更深。美拉德反应会降低赖氨酸等必需氨基酸的营养价值，高温下天冬酰胺与还原糖还会生成可能致癌的丙烯酰胺。在体内，葡萄糖与蛋白质的类似反应生成糖化血红蛋白（HbA1c）和晚期糖基化终产物，与糖尿病并发症相关。

It runs faster at higher temperature, at intermediate water activity (about 0.6–0.8) and at alkaline pH, which is why lye-dipped pretzels brown so deeply. It lowers the nutritional value of essential amino acids such as lysine, and at high temperature asparagine and reducing sugars form acrylamide, a probable carcinogen. In the body similar reactions of glucose with proteins form glycated haemoglobin (HbA1c) and advanced glycation end products linked to diabetic complications.