Dry fractionation of coconut oil for food and cosmetic applications: Routes to manage its atypical crystallization properties

Abstract: Besides the culinary use of virgin or refined oil, coconut is also known as CBS (cocoa butter substitute) and as MCT (medium chain triglyceride) oil after processing. Like palm kernel oil, coconut oil belongs to the class of lauric fats and is made up of saturated short and medium chain triglycerides (C6-C14). CBS are obtained by dry fractionation followed by full hydrogenation; they are used for confectionary applications. Although often called fractionated coconut oils, MCT oils are produced by successive high pressure splitting, full hydrogenation, fractional distillation and re-esterification steps.
The particular composition of coconut oil is responsible for its crystal morphology (small spherulites made of needle-like crystals) and its crystallization behavior which greatly differ from those of other oils. For this reason, crystallization in static mode is required due to viscosity issues under shear. This work shows the potential of coconut oil in static crystallization for obtaining CBS; it also shows how a crystallization in specific static mode makes it possible to obtain, after separation on membrane press-filters, MCT-like liquid fractions (olein) with improved cold stability. An alternative crystallization route operating in dynamic mode was also explored, which consists of seeding with fully hydrogenated soybean oil (FHSO - stearic acid enriched) or with palm super stearin (POSS - palmitic acid enriched). The influence of long-chain triglycerides on the crystallization properties during cooling was investigated by monitoring crystallization kinetics (by p-NMR), crystal morphologies (by optical microscopy) and polymorphic forms (by powder X-Ray diffraction). The physicochemical properties of the so-obtained olein were compared to those of MCT-like obtained in static crystallization mode and those of real MCT coconut oils. It was shown that the most efficient effect was with POSS, however the cold stability of the so-obtained olein was lower compared to static crystallization.