CQ-VR, Chemistry Research Centre, Chemistry Department, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal.
J Agric Food Chem. 2012 Sep 5;60(35):8710-9. doi: 10.1021/jf301527e. Epub 2012 Aug 22.
To study the mechanism of coffee melanoidin formation, green coffee beans were prepared by (1) removal of the hot water extractable components (WECoffee); (2) direct incorporation of sucrose (SucCoffee); and (3) direct incorporation of type II arabinogalactan-proteins (AGPCoffee). As a control of sucrose and AGP incorporation, lyophilized green coffee beans were also immersed in water (control). The original coffee and the four modified "in bean" coffee models were roasted and their chemical characteristics compared. The formation of material not identified as carbohydrates or protein, usually referred to as "unknown material" and related to melanoidins, and the development of the brown color during coffee roasting have distinct origins. Therefore, a new parameter for coffee melanoidin evaluation, named the "melanoidin browning index" (MBI), was introduced to handle simultaneously the two concepts. Sucrose is important for the formation of colored structures but not to the formation of "unknown material". Type II AGPs also increase the brown color of the melanoidins, but did not increase the amount of "unknown material". The green coffee hot water extractable components are essential for coffee melanoidin formation during roasting. The cell wall material was able to generate a large amount of "unknown material". The galactomannans modified by the roasting and the melanoidin populations enriched in galactomannans accounted for 47% of the high molecular weight brown color material, showing that these polysaccharides are very relevant for coffee melanoidin formation.
为了研究咖啡类黑素形成的机制，采用以下三种方法制备绿咖啡豆：（1）去除热水可提取成分（WECoffee）；（2）直接添加蔗糖（SucCoffee）；（3）直接添加 II 型阿拉伯半乳聚糖-蛋白质（AGPCoffee）。作为蔗糖和 AGP 掺入的对照，冻干绿咖啡豆也被浸泡在水中（对照）。对原始咖啡和四种改良的“豆内”咖啡模型进行烘焙，并比较其化学特性。通常被称为“未知物质”并与类黑素相关的、未被鉴定为碳水化合物或蛋白质的物质的形成，以及咖啡烘焙过程中棕色的发展，具有明显的起源。因此，引入了一个新的咖啡类黑素评价参数，称为“类黑素褐变指数”（MBI），以同时处理这两个概念。蔗糖对于有色结构的形成很重要，但对于“未知物质”的形成不重要。II 型 AGP 也会增加类黑素的棕色，但不会增加“未知物质”的量。绿咖啡的热水可提取成分对于烘焙过程中咖啡类黑素的形成是必不可少的。细胞壁物质能够产生大量的“未知物质”。经过烘焙修饰的半乳甘露聚糖和富含半乳甘露聚糖的类黑素群体占高分子量棕色物质的 47%，表明这些多糖与咖啡类黑素的形成密切相关。
