It has been found that esterification of a hydroxy-fatty acid by a lipase can be coupled with oleate hydratase (OHase) generation of that hydroxy-FA from an unsaturated FA with a cis C9-C10 double bond, e.g. oleic acid, in a single aqueous buffered reaction medium at low temperature, e.g. 30° C. A simple one-pot enzymatic method to produce fatty acid estolides from one or more triglycerides, e.g. starting from a natural plant oil, is thereby enabled in which the same lipase catalyses both the initial hydrolysis of triglyceride and the final esterification step.