What is the chemical structure of butter?

Butter is a mixture of triglycerides* of several different fatty acids*, so no single chemical structure can be drawn. A list of the more common fatty acids in butter is given below. The glycerides break down after some time, releasing the free fatty acids. The butyric acid released is responsible for the nauseating smell of rancid butter. (The caproic acid also smells wretched).

The color of butter comes from the presence of small amounts of carotene*.

Fatty acids in butter. Percentage composition from Practical Physiological Chemistry, P. B. Hawk, O. Bergeim, Blakiston:Philadelphia, 1943.

Fatty acid Structure % total fatty acid in butter
oleic acid CH3(CH2)7CH=CH(CH2)7COOH 31.9
myristic acid CH3(CH2)12COOH 19.8
palmitic acid CH3(CH2)14COOH 15.2
stearic acid CH3(CH2)16COOH 14.9
lauric acid CH3(CH2)10COOH 5.8
butyric acid CH3CH2CH2COOH 2.9
caproic acid CH3(CH2)4COOH 1.9
capric acid CH3(CH2)8COOH 1.6
caprylic acid CH3(CH2)6COOH 0.8
linoleic acid CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH 0.2
linolenic acid CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH 0.1

Author: Fred Senese senese@antoine.frostburg.edu

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