Optimization of microencapsulation of pumpkin seed oil

In this study, cold–pressed pumpkin seed oil was encapsulated with wall material combination consisting of different ratios of whey protein, maltodextrin and gum arabic by freeze–drying. The oxidative stability of microcapsules was investigated at 20°C during 12 weeks. By using D–optimal mixture design to maximize encapsulation efficiency, solubility and total content of polyunsaturated fatty acids, optimum wall material combination was found. The stabilities of all emulsions were quite high. In the first 24 hours, no phase separation was detected. After 48 hours, the heights of cream separated from emulsions ranged between 13.65–35.28%. All of the emulsions were characterized by non–Newtonian type (pseudoplastic, shear–thinning) flow characteristics. The droplet sizes of oil globules ranged between 1.11–1.84 μm and showed bimodal distribution. Microcapsules had irregular shapes and extremely porous and rough surfaces. The size of reconstituted microcapsules ranged between 25.65–70.50 μm and showed bimodal distribution. Moreover, the flowability properties of microcapsules were considerably poor. The solubilities in water of microcapsules ranged between 25.44–36.09%. Microencapsulation led to decrease in monounsaturated, polyunsaturated fatty acids, α– and γ–tocopherols and total phenolic contents of cold–pressed pumpkin seed oil. The moisture contents of microcapsules increased from 2.65–3.72% to 3.22–4.66% throughout the storage. The water activity values also increased similarly. Oxidation of surface and encapsulated oils extracted from trials with higher encapsulation efficiency such as Run–6, Run–10 and Run–17 progressed slowly. The optimum combination of wall material consisted of 13.5757% whey protein, 4.24381% maltodextrin and 2.18044% gum arabic.