Preparation and characterization of soy protein isolate/SiO2 nanocomposite films and their walnut oil microcapsules

In this study, nano-SiO₂/soy protein isolate composite film was prepared by casting method. The effects of (adding 0%, 1%, 3%, 5%, 7%, and 9% w/w) nano-SiO₂ on the properties of the resulting blend films were investigated. Results showed that the addition of 5% nano-SiO₂ exhibited good barrier properties. The mechanical properties including tensile strength and elongation at break of the film with 7% nano-SiO₂ is increased by 82.6% and 31.49% correspondingly. Differential scanning calorimetry indicated that the melting temperature of the composite film is increased by 56.6°C compared with the pure film. The wall material modified by nano-SiO₂ (adding 1%, 3%, 5%, 7%, and 9% w/w) was used for encapsulating walnut oil by spray drying. After accelerating oxidation test at 63°C for 12 days, we found that the encapsulation efficiency value of walnut oil microcapsules with 0%, 1%, 3%, 5%, 7%, and 9% nano-SiO₂ decreased by 64.23%, 48%, 21%, 22%, 21.00%, and 31% respectively. The results suggested that the stability of the core material was improved by adding nano-SiO₂ to the wall material.