Refined oils from plant seeds are mixtures of triacylglycerols (TAGs), up to 99%, but they still contain some amount of other lipids and small molecules.
In general, edible plant oils contain 98% triglycerides, 2% phospholipids, and a variety of hydrocarbons [Article Heating effect on quality characteristics of mixed canola cooking oils
].For example, as can be seen on the photograph, these impurities lead to a formation of a middle layer when you mix various vegetable oils (corn, canola, walnut oils in this case) with water, mix them into an emulsion and then separate them into 2 phases by centrifugation.
What are the common methods to further purify plant oils into essentially pure triglyceride liquids, which would then form a plain oil/water interface?
I can only think of using a solvent that can be added to the oil mixture to separate all the unwanted components based on polarity. However, the solvent must be harmless.
But more importantly, do you know what those impurities might be? Could they be other glycerides? Proteins? Carbohydrates? I recommend analyzing all the possible components present in those oils. That way, different techniques can be tested to rule them out.
It may be purified through the following process: saponification reaction - hydrolysis reaction - separation and preliminary purification - distillation to remove water - ion exchange - vacuum distillation - decolorization and purification
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