Properties of Encapsulated Fish Oil in Electrospun Zein Fibres under Simulated in Vitro Conditions

In this study, omega-3-rich fish oil was encapsulated in electrosprayed zein beads and electrospun zein fibres using 10 or 20 % (w/w) zein protein solutions, respectively. The zein solutions were prepared in either 70 % (w/w) aqueous ethanol or isopropanol solvents dispersed with 30 % (w/w) fish oil. Scanning electron microscopy revealed that the ethanolic zein protein solutions generated smooth fibres while isopropanol-based solutions resulted in beads with an average size of 1 μm. The release of encapsulated fish oil from the zein encapsulant subjected to in vitro gastrointestinal conditions was evaluated using simulated gastric and intestinal fluids with and without the presence of digestive enzymes. The electrospun/electrosprayed matrices exhibited a combination of swelling and erosion. The extent of matrix swelling, erosion and diffusion of fish oil determined the kinetics of fish oil release from zein protein carriers. Fourier transform infrared spectroscopy analyses were conducted to study the changes of the secondary structure of zein as functions of protein concentration, solvent types and digestive treatments. An increased percentage of α-helical was detected under ethanolic formulation and at higher concentration of zein protein. Enzymatic treatment further disrupted the formation of α-helical and produced higher percentage of random coil structures.