Editing Triglyceride (section)

== Chemical structure ==
[[File:Unsaturated Triglyceride Structural Formula V1.svg|thumb|upright=1.35|Example of a natural mixed triglyceride with residues of three different fatty acids. The first fatty acid residue is saturated (<span style="color:blue;">'''blue'''</span> highlighted), the second fatty acid residue contains one [[double bond]] within the carbon chain (<span style="color:green;">'''green'''</span> highlighted). The third fatty acid residue (a polyunsaturated fatty acid residue, highlighted in <span style="color:red;">'''red'''</span>) contains three [[double bond]]s within the carbon chain. All carbon-carbon double bonds shown are ''cis'' isomers.]]

The three fatty acids [[substituents]] can be the same, but they are usually different. The positions of the three fatty acids are specified using [[stereospecific numbering]] as sn-1, sn-2, and sn-3. The compositions of many fats and oils have been determined.<ref name=Alfieri>{{cite journal |display-authors=etal|last1=Andreina Alfieri |title=Effects of Plant Oil Interesterified Triacylglycerols on Lipemia and Human Health |journal=Int J Mol Sci |date=Dec 2017 |volume=19 |issue=1 |page=104 |doi=10.3390/ijms19010104 |doi-access=free |pmid=29301208 |pmc=5796054 }}</ref> Many triglycerides are known because many [[fatty acid]]s are known. The chain lengths of the fatty acid groups vary in naturally occurring triglycerides,  Those containing 16, 18, or 20 [[carbon]] atoms are defined as '''long-chain triglycerides''', while [[medium-chain triglycerides]] contain shorter fatty acids. Animals [[fatty acid synthesis|synthesize]] even-numbered fatty acids, but bacteria possess the ability to synthesise odd- and branched-chain fatty acids. As a result, [[ruminant]] animal fat contains odd-numbered fatty acids, such as 15, due to the action of [[bacteria]] in the [[rumen]].  Many fatty acids are unsaturated; some are polyunsaturated (e.g., those derived from [[linoleic acid]]).<ref name=Ullmann/>

Most natural fats contain a complex mixture of individual triglycerides. Because of their heterogeneity, they melt over a broad range of temperatures. Cocoa butter is unusual in that it is composed of only a few triglycerides, derived from [[Palmitic acid|palmitic]], [[Oleic acid|oleic]], and [[stearic acid]]s in the 1-, 2-, and 3-positions of glycerol, respectively.<ref name=Ullmann/>

The simplest triglycerides are those where the three fatty acids are identical. Their names indicate the fatty acid: [[stearin]] derived from stearic acid, [[triolein]] derived from [[oleic acid]], [[palmitin]] derived from [[palmitic acid]], etc.  These compounds can be obtained in three crystalline forms ([[Polymorphism (materials science)|polymorphs]]): α, β, and β′, the three forms differing in their melting points.<ref name=Ullmann>
{{cite encyclopedia
  |author=Alfred Thomas
  |encyclopedia=[[Ullmann's Encyclopedia of Industrial Chemistry]]
  |publisher=[[Wiley-VCH]]
  |place=Weinheim
  |year=2002
  |doi=10.1002/14356007.a10_173
  |chapter=Fats and Fatty Oils
  |isbn=3527306730
}}</ref><ref name=spring>
{{Cite journal
  |doi = 10.1007/BF02643296
  |title = Thermal properties of fats and oils
  |journal = [[J. Am. Oil Chem. Soc.]]
  |volume = 24
  |issue = 5
  |pages = 140
  |year = 1947
  |last1 = Charbonnet
  |first1 = G. H.
  |last2 = Singleton
  |first2 = W. S.
|s2cid = 101805872
 }}</ref>

A triglyceride containing different fatty acids is known as a ''mixed triglyceride''.<ref>{{Cite web |title=Mixed triglyceride {{!}} chemical compound {{!}} Britannica |url=https://www.britannica.com/science/mixed-triglyceride |access-date=2023-02-13 |website=www.britannica.com |language=en}}</ref> These are more common in nature.

If all three fatty acids on the glycerol differ, then the mixed triglyceride is [[Chirality (chemistry)|chiral]].