Properties of complexes of whey protein isolate fibrils (WPIF) and octenyl succinate starch (OSS) and their applications in emulsion stabilization and custard cream

Emulsifying properties of octenyl succinate starch (OSS), an emulsifier widely used in the food industry, need to be improved further. This work aimed to improve the emulsification properties of OSS based on its complexation with whey protein isolate fibrils (WPIF). The zeta-potential and turbidity results indicated that WPIF and OSS formed soluble electrostatic complexes at a low mixing ratio (r (WPIF/OSS) = 0.10–0.50) and pH 3.0–5.0. According to the FTIR and TEM results of WPIF/OSS complexes, molecular interactions existed between WPIF and OSS. The oil-in-water emulsion with WPIF/OSS complexes as emulsifiers were constructed, and the optimum condition was searched by controlling the pH value of 3.0–7.0, r of 0.10–10.00, and complexes concentration of 0.25–3.00 wt%. The emulsification properties of the WPIF, OSS and WPIF/OSS complexes were evaluated by comparing the particle size, zeta-potential and visual appearance of fresh and stored emulsions. WPIF/OSS complex at r = 0.10, pH = 3.0, and 1.00 wt% total concentration exhibited the best emulsification properties and the best resistance to high salt (200 mM) and high temperature (90 °C). The addition of WPIF/OSS significantly improved the quality of the custard cream. This work used the novel nano-material of WPIF to improve the emulsifying properties of OSS and expanded the application of OSS in food products.