Why can mixed triglycerides have different isomeric forms?

Mixed triglycerides can exist in different isomeric forms because of the specific arrangement of their constituent fatty-acid radicals on the glycerol molecule.1

Because a glycerol molecule has three carbon positions where fatty acids can attach, the placement of different acid radicals creates structural variations:

• Three different fatty acids: If a mixed triglyceride contains three different acid radicals, it can exist in three distinct isomeric forms, depending on which of the three acids is linked to the central carbon of the glycerol backbone.1
• Two of the same fatty acid: If a triglyceride contains two radicals of the same acid and one radical of a different acid, it can exist in two isomeric forms.1

These structural differences occur because the fatty acids are not randomly distributed; their specific positioning on the glycerol carbons determines the isomer.1