Fabrication of ultrafine Himalayan walnut oil Pickering emulsions by ultrasonic emulsification: Techno-functional properties of emulsions and microcapsules

Abstract

In present scenario, much of the attention has been put on the production and utilization of Pickering emulsions deciphering enhanced stability and applicability over wide environmental conditions. In this context the present study was carried out to elaborate effect of different wall materials and pH systems on the physicochemical, structural and morphological properties of Himalayan walnut oil Pickering emulsions by ultrasonic emulsification. In this study, concentrated Pickering emulsion of Himalayan walnut oil (HWO) was prepared utilizing soy protein isolate (SPI), maltodextrin (MD) stabilized by pectin at varying concentrations and pH systems (4.0, 7.0). With increase in pectin and SPI concentration and lowering MD, stable emulsions were obtained as deciphered by an Emulsion stability index (ESI) of 100 for 7 days at ambient storage. HWO Pickering emulsions were analysed for particle size measurements (2.13–13.64 µm) and depicted negative zeta potential values (−3.70 to −18.58). Lyophilized HWO microcapsules depicted moderate encapsulation efficiency (44.69–57.63 %) whereas the hygroscopicity values of the microcapsule ranged from (0.21–12.10 %). Thermogravimetric analysis (TGA) of the samples depicted the temperature of maximum degradation rate up to 550 °C whereas XRD spectra depicted amorphous nature of oil microcapsules. FTIR spectra revealed a close association between the SPI-MD-Pectin matrix. SEM analysis revealed stable oil globules entrapped in protein-polysaccharide matrix with no visible cracks and fissures.