Effects of the drying method on the oxidative stability of the free and encapsulated fractions of microencapsulated sunflower oil

Summary The influence of the drying method, freeze‐drying and spray‐drying, on the oxidative stability of microencapsulated sunflower oil depended on the type of encapsulation matrix. For a dairy‐type matrix, formed by sodium caseinate and lactose, greater losses of tocopherols were detected during spray‐drying, but both the free and encapsulated oil fractions were more stable against lipid oxidation than their freeze‐dried counterparts. Results suggested that the free oil was also constituted by droplets that preserved their interfacial membrane and were protected by the matrix. Therefore, the free oil was not necessarily the non‐encapsulated fraction. For a matrix constituted by gelatine, maltodextrin and sucrose, the emulsion showed low stability and a great destabilisation during spray‐drying. No significant effect of the drying method on the oxidative stability of the encapsulated fraction was found with this matrix, but the free oil of the spray‐dried sample oxidised faster, probably due to the emulsion destabilisation observed, which gave rise to a great amount of oil on the particle surface as a consequence of large droplets poorly stabilised. Schematic representation of the effects of the drying method on the oxidative stability of sunflower oil encapsulated in two food matrices