This work was primarily aimed to evaluate the use of maltodextrin in combination with hydroxypropyl
methylcellulose as wall materials for microencapsulation of both walnut and chia oils by spray drying. The effect
of rosemary extract on the oxidative stability of the microencapsulated oils was examined under prolonged
storage conditions. After a 45-day storage, the microencapsulated chia oil with rosemary extract showed lower
formation of primary oxidation compounds than the control without additives, highlighting a protective effect
of the antioxidant. Nevertheless, during the entire storage period the unencapsulated chia oil reported lower
oxidative damage than their encapsulated counterparts, showing that the spray drying process affected its
stability negatively. Walnut oil microencapsulation protected the oil from oxidation in comparison with its
unencapsulated counterpart which was further apparent from the 30th day of storage. The addition of
1600 ppm of rosemary extract effectively protected microencapsulated walnut oil, showing – throughout the
storage period – lower oxidation values in comparison with its analogous unencapsulated oil. The microcapsule
surface oil and the images obtained by scanning electron microscopy at the beginning and at the end of the assay
showed that the wall material has not been altered during storage.