甘油三酯Triglyceride

三个脂肪酸可以相同（简单甘油酯）或不同（混合甘油酯）。脂肪酸越饱和、碳链越长，熔点越高：牛油富含饱和脂肪酸呈固态，橄榄油富含油酸呈液态。甘油三酯是非极性分子，密度小于水，不溶于水。碘值反映不饱和度，皂化值反映平均分子量。

The three fatty acids may be the same (a simple triglyceride) or different (a mixed one). The more saturated and longer the chains, the higher the melting point: beef tallow, rich in saturated acids, is solid, while olive oil, rich in oleic acid, is liquid. Triglycerides are nonpolar, less dense than water and insoluble in it. The iodine value measures unsaturation and the saponification value average molecular mass.

1779 年舍勒在皂化橄榄油时发现了甘油；1813 年起谢弗勒尔证明油脂是脂肪酸与甘油的化合物。1902 年诺尔曼获得用镍催化剂氢化液态油的专利，由此诞生了人造黄油和起酥油工业。后来人们认识到部分氢化产生的反式脂肪有害健康，许多国家已限制使用。

Scheele discovered glycerol in 1779 while saponifying olive oil, and from 1813 Chevreul showed that fats are compounds of fatty acids and glycerol. In 1902 Normann patented the nickel-catalysed hydrogenation of liquid oils, founding the margarine and shortening industries. When the trans fats from partial hydrogenation were later found to harm health, many countries restricted them.

食物中的甘油三酯在小肠中被胰脂肪酶水解为脂肪酸和单酰甘油，吸收后重新合成并以乳糜微粒运输。多余的能量以甘油三酯形式储存在脂肪组织中，需要时由激素敏感脂肪酶动员。血清甘油三酯正常值一般低于 1.7 mmol/L，过高与胰腺炎和心血管疾病风险相关。生物柴油是甘油三酯与甲醇酯交换得到的脂肪酸甲酯。

Dietary triglycerides are hydrolysed in the small intestine by pancreatic lipase to fatty acids and monoacylglycerols, absorbed, reassembled and carried in chylomicrons. Surplus energy is stored as triglyceride in adipose tissue and released when needed by hormone-sensitive lipase. Serum triglycerides are normally below about 1.7 mmol/L; higher levels are linked to pancreatitis and cardiovascular risk. Biodiesel is the fatty acid methyl ester made by transesterifying triglycerides with methanol.