Saponification producing 4 fatty acids

[663697]

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How would the reaction below produce 4 fatty acids upon saponification of the triacylglycerol? The answer says that a small percentage of one of the fatty acids isomerized for this to happen.

I'm only aware of hydration of alkenes (acid catalyzed) to produce an alcohol, so I'm not sure how the reaction conditions with NaOH would produce a 4th fatty acid tail.

(Chem QPack #66)

 

[aldol16]

You're just misunderstanding the question. They didn't say it produces a new fatty acid unit. Just four different fatty acids salts instead of the three you would expect. In other words, you would expect three different fatty acid salts: R1-COO, R2-COO, and R3-COO. But here, you see four different ones. You would see that if, say, R3 had isomerized and some of the triacylglycerols instead had R3' instead of R3. Then, after saponification, you would see R1-COO, R2-COO, R3-COO, and R3'-COO.