Spray freezing drying microencapsulation of krill oil enhances digestion and storage stability

This study explores microencapsulation of krill oil (KO) by Spray-Freezing-Drying (SFD) as an effective process to protect KO from degradation due to environmental factors. Gum arabic (GA) and whey protein concentrate (WPC) were employed as wall materials and the resulting KO microcapsules were characterized in terms of color, astaxanthin content, water activity, antioxidant activity, microencapsulation efficiency and morphology. The bioaccessibility of both types of KO microcapsules was evaluated (by in vitro digestion), thermodynamic parameters were calculated through a moisture adsorption study for the prediction of the maximum stability of the microcapsules, and the kinetic stability of the astaxanthin content during the storage of the microcapsules was analyzed. The encapsulation efficiency of KO was around 96% in both treatments; however, a less porous structure and a slightly higher astaxanthin content were found in the microcapsules made with WPC. A significant increase in the bioaccessibility values of the microencapsulated KO compared to the free KO was found, however, no significant differences were found between the bioaccessibility, and antioxidant activity values obtained for both types of KO microcapsules. The moisture content of the monolayer was relatively low for both samples. It was found that the maximum stability occurred in the zone of minimum integral entropy with water activity values of 0.26 and 0.14 for KO microencapsulated with WPC and GA, respectively; this is confirmed by studying the effect of water activity on the degradation of astaxanthin content in both types of microcapsules stored at 35 degrees C.