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English Corner | 用化学学霸的角度看咖啡生豆

2015-04-29

【小编提示】由于本篇文章过长，为了大家能够更好地消化文中出现的新单词，我们将分为两篇文章与大家分享。

*Data on green-coffee composition refers to the genus Coffea species Arabica only. The chemical compositions of Coffea robusta and other species of coffee differ, sometimes significantly, from that of arabica.

注：文内有关咖啡生豆的成分组成数据仅基于该属物种阿拉比卡。而罗布斯塔或其他咖啡品种的化学组成则与之有所差异，有时差异显著。

Raw coffee beans are dense, green seeds consisting of about one-half carbohydrate on various forms and one-half a mixture of water, proteins, lipids, acids, and alkaloids. Roasters do not need to know much about green coffee’s chemistry to roast delicious coffee, but I offer the following summary to familiarize readers with the primary components of green coffee.

咖啡生豆质地紧密，这些绿色的种子，一半由各类碳水化合物组成，而另一半则为水、蛋白质、脂质、氨基酸和生物碱。对于咖啡烘焙师来说，烘焙出优质风味的咖啡豆并不需要了解过多有关咖啡生豆的化学组成。但我还是向读者提供了以下内容，帮助读者了解咖啡生豆的主要化学成分。

Structure(细胞)结构

A raw coffee bean’s structure is a three-dimensional cellulose, or polysaccharide, matrix containing approximately a million cells. Coating the cellulose strands within that matrix are hundreds of chemicals that roasting process will transform into the oils and soluble material that determine brewed coffee’s flavor. Green coffee’s cellulose structure contributes half of its dry weight. The cellulose contributes little to coffee flavor but does trap some volatile compounds, which are responsible for aroma, and adds to brewed coffee’s viscosity, increasing its perceived body.

一颗咖啡生豆的细胞结构是一个立体纤维素或多糖“矩阵”，约含有一百万个细胞。在“矩阵”中包裹着纤维素链的是数百种的化学物质，这些物质在烘焙过程中将转化为油脂和可溶性物质，决定了咖啡萃取后的风味。咖啡生豆的纤维素结构占到净重的一半。虽然纤维素本身对于咖啡风味的建树有限，但其固定住的一些挥发性化合物则决定着香气，增加了咖啡萃取后的粘稠度，并增加了咖啡的醇厚度。【求真正生物大牛指正本段内容！！！】

English Corner | 用化学学霸的角度看咖啡生豆

Sugars糖类

Sugars, dominated by sucrose, make up 6%-9% of a green bean’s dry weight and provide sweetness in the cup. Sucrose also contributes to development of acidity, as the caramelization of sucrose during roasting yields acetic acid.

糖类，最主要为蔗糖，占咖啡生豆净重的6%至9%，杯中咖啡甜味的来源。蔗糖同样有助于发展酸度，在烘焙过程中蔗糖的焦糖化反应将产生乙酸。

Lipids脂质

Lipids, primarily triglycerides, make up approximately 16% of green coffee’s dry weight. Although lipids are not water soluble, brewed coffee contains some, especially when the brewing method uses either no filtration (e.g., cupping) or a very porous filter (e.g., espresso, French press, or metal- or cloth-filter drip). Lipids in brewed coffee help retain aroma and contribute to coffee’s mouthfeel. Higher lipid content is generally associated with better green-coffee quality. Unfortunately, lipids also present challenges to quality, as they are vulnerable to oxidation and rancidity during storage of roasted beans.

脂质，主要为甘油三酯，约占咖啡生豆净重的16%。虽然脂质不溶于水，但萃取出的咖啡中仍会含有一些脂质，特别是采用无过滤方式（如杯测时采用的浸泡萃取法）或采用多孔过滤器具（如意式浓缩咖啡机、法压壶，或采用金属或滤布的滴滤器具）。脂质能够留住杯中咖啡的香气，并有助于提升咖啡的口感。脂质含量高通常意味着咖啡生豆的高品质。但脂质也同样挑战着咖啡的品质，在咖啡熟豆的储藏过程中，其易造成咖啡豆的氧化和腐烂。

English Corner | 用化学学霸的角度看咖啡生豆