Pickering emulsions stabilized by soybean protein isolate/cellulose nanofibrils: Influence of pH

Abstract

Emulsions including Pickering emulsions and nanoemulsions have enormous application potential for inhibiting lipid oxidation. Polysaccharides like κ-carrageenan can improve the gel-like behavior of protein-stabilized Pickering emulsions. Tea water-insoluble proteins and κ-carrageenan can be used for preparing fish oil-in-water Pickering emulsions and fish oil gels. The characteristics of Pickering emulsions and fish oil gels at different proportion of tea water-insoluble proteins and κ-carrageenan were analyzed by high-speed homogenization assisted with ultrasonic treatment. The physicochemical analysis and secondary structure of mixtures showed that the turbidity reduced, particle size unchanged except that of mixtures at 80:20 and zeta potential was unaltered with the addition of κ-carrageenan; meanwhile, the secondary structure of mixtures changed due to the addition of κ-carrageenan. The viscoelastic behavior enhanced compared with that stabilized by tea water-insoluble proteins only. Fish oil gels using mixture-stabilized PEs as a template had a solid-like behavior with a storage modulus of approximately 200 kPa. Besides, the effects of tocopherol nanoemulsions on lipid oxidation of fish sausages were assessed during 16-day storage at 4 °C. Nanoemulsions including 250 and 500 mg/kg tocopherol improved fish sausages’ quality during cold storage and effectively inhibited lipid oxidation due to low peroxide value and high polyunsaturated fatty acid content. The droplet diameter of nanoemulsions including tocopherol stored at 4 °C for 16 days was below 500 nm. The small droplets with even distribution, and high stability of tocopherol nanoemulsions might explain the potential mechanism of inhibiting lipid oxidation in fish sausages. Interestingly, nanoemulsions encapsulated with 250 mg/kg tocopherol were effective to delay the lipid oxidation and improve fish sausages quality during cold storage. These findings will be useful for developing new edible hydrocolloid systems such as Pickering emulsions and nanoemulsions to inhibit lipid oxidation in aquatic products and broaden the application of emulsions in food industry.