Enzymatic esterification reactions for the production of steryl esters were conducted using different sources of sterols and free fatty acids from mixtures of vegetable oil deodorizer distillates and refined oil. This work discusses the possibility of using free fatty acids from alternative and less expensive sources, determining their influence on the yield of steryl ester production as well as on the validity of a kinetic model previously developed for defined reaction medium composition. The extrapolation capacity of such a model was investigated, identifying the cases where a lack of model fitting was observed and establishing the range of conditions for model applicability. Based on a sensitivity analysis, guidelines to obtain acceptable yields (>80%) were established. This paper shows that the use of alternative sources of sterols and free fatty acids for the production of steryl esters is possible; however, there are constraints and guidelines that have to be taken into account.