淀粉Starch

α-1,4 连接使直链淀粉卷曲成每圈约 6 个葡萄糖的左手螺旋，碘分子进入螺旋腔形成蓝色包合物，这是检验淀粉的灵敏方法；支链淀粉与碘呈紫红色。淀粉以颗粒形式存在，在热水中吸水膨胀、颗粒破裂形成黏稠糊液，称为糊化（玉米淀粉约 62–72 °C）；冷却后分子重新有序排列称为回生，面包变硬就是回生所致。

α-1,4 linkage coils amylose into a left-handed helix of about six glucoses per turn; iodine slips into the helix to form a blue complex, a sensitive test for starch, while amylopectin gives a red-violet colour. Starch occurs as granules that swell and burst in hot water to form a viscous paste, gelatinisation (about 62–72 °C for corn starch); on cooling the molecules re-order, retrogradation, which is why bread goes stale.

古埃及已用小麦淀粉制作纸莎草纸的黏合剂。1811 年基希霍夫发现淀粉在稀酸中加热可转化为葡萄糖，开创了淀粉糖工业。1833 年佩扬和佩索兹从麦芽中提取出能分解淀粉的物质，称为“淀粉酶（diastase）”，这是最早发现的酶之一。1940 年代人们区分了直链淀粉和支链淀粉。

Ancient Egyptians used wheat starch as an adhesive for papyrus. In 1811 Kirchhoff found that warming starch with dilute acid turns it into glucose, founding the starch-sugar industry. In 1833 Payen and Persoz extracted from malt a substance that breaks down starch, diastase, one of the first enzymes discovered. Amylose and amylopectin were distinguished in the 1940s.

唾液和胰液中的 α-淀粉酶把淀粉水解为麦芽糖和糊精，再由小肠麦芽糖酶分解为葡萄糖。抗性淀粉不被小肠消化，作用类似膳食纤维。工业上淀粉用于生产葡萄糖、果葡糖浆、乙醇、柠檬酸，也用作食品增稠剂、造纸施胶剂、纺织浆料和生物降解塑料（热塑性淀粉）。

α-Amylase in saliva and pancreatic juice hydrolyses starch to maltose and dextrins, which intestinal maltase splits to glucose. Resistant starch escapes small-intestine digestion and acts like dietary fibre. Industry turns starch into glucose, high-fructose syrup, ethanol and citric acid, and uses it as a food thickener, paper size, textile size and biodegradable plastic (thermoplastic starch).