The Separation oleic acid from olive oil by double fractionation.how to explane this?

I don't know the details of this particular process but when separating out a middle boiling point component of a mixture by distillation it is necessary to separate out the heavy and lighter boiling point components in two stages of distillation. Does the oleic acid have to have water stripped from it? (If so this might account for the second distillation)

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