Microencapsulation of Olive Oils from Nizip and Kilis Yağlik Varieties by Freeze-Drying: Effects of Wall Materials on Physicochemical Properties and Bioactive Compounds

This study investigated the characteristics and bioactive properties of olive oils obtained from regional Nizip Yaglik (NY) and Kilis Yaglik (KY) olive varieties, encapsulated using maltodextrin (MD) and whey protein isolate (WPI) as wall materials. Olive oils were first emulsified with different WPI-MD ratios (1:1, 1:4, 1:10) and subsequently freeze-dried to produce microcapsule powders. A comprehensive evaluation was conducted, including physicochemical properties (encapsulation efficiency, moisture content, water activity, bulk density, flowability, wettability, particle size, and color), FTIR spectral profiles, morphological features, total phenolic content, and antioxidant activity. The results demonstrated that combining WPI with MD yielded high encapsulation efficiency and favorable reconstitution characteristics, effectively protecting sensitive bioactive constituents from oxidative degradation during processing and storage. Increasing the proportion of MD in the wall matrix improved emulsion stability and microencapsulation yield, while also slightly enhancing powder brightness. FTIR analyses confirmed that the fundamental chemical structure of olive oil was preserved across all formulations. The freeze-dried microcapsules displayed superior stability relative to non-encapsulated oils, retaining higher levels of phenolic compounds and antioxidant capacity. Among the formulations, elevated MD ratios enhanced powder flowability, whereas WPI played a crucial role in emulsification performance and capsule surface integrity. Overall, these findings underscore the effectiveness of MD-WPI blends as promising wall materials for the freeze-drying encapsulation of regional olive oils, offering a viable strategy to preserve their distinctive qualities and bioactive potential for functional food applications.