Properties and Stability of Spray-Dried and Freeze-Dried Microcapsules Co-Encapsulated with Fish Oil, Phytosterol Esters, and Limonene

The objectives of this study were to investigate the properties and stability of microcapsules containing fish oil co-encapsulated with phytosterol ester and limonene, prepared by spray-drying and freeze-drying methods. Whey protein isolate and soluble corn fiber were used as wall materials in the encapsulation process. The properties of microcapsules, including structure, glass transition, volatile/non-volatiles retention, microencapsulation efficiency, oxidation stability, color measurement, and sensory profiles, were evaluated after drying and during a seven-day accelerated storage trial. The finding reveals that drying methods have an effect on the retention of volatile fraction and the physical structure of the wall matrix consisted of WPI and SCF, consequently influencing the storage stability of the powders. Significantly higher retention of volatile fraction (p < 0.05) and lower surface oil were found in the spray-dried samples, resulting in the higher microencapsulation efficiency. However, samples dehydrated by both methods have good redispersion properties, showing no statistical significance (p > 0.05). The oxidation of the encapsulated oils was comparable for both spray- and freeze-dried samples during the seven-day accelerated storage trial but the loss of limonene flavor was significantly higher in the freeze-dried samples (p < 0.05). Sensory evaluation indicated that the addition of limonene could mask the unpleasant fishy odor in the co-encapsulated microcapsules. Overall, freeze drying did not produce powders with superior properties and did not show better protection towards the core materials than spray drying.