Formulation and Stability Screening of Walnut Protein Concentrate-Whey Protein Isolate Stabilized Pickering Emulsions with Different Compounding Ratios: Capsanthin Loading, Multi-Condition Stability, and Application as a Butter Replacer in Spreadable

This study developed a dual-protein Pickering emulsion stabilized by walnut protein concentrate (WalPC) and whey protein isolate (WPI) for capsanthin delivery and functional fat replacement. Pickering emulsions with different WPI-WalPC ratios were prepared, and their functional properties and stability were systematically evaluated. The results showed that the WPI-WalPC ratio of 1:9 exhibited the optimal performance, with the highest emulsifying activity index (EAI, 48.55 m2/g) and emulsifying stability index (ESI, 240.91 min), as well as superior stability under different environmental conditions. The enhanced stability was closely related to the formation of a robust protein-stabilized interface, which improved the protection and delivery efficiency of capsanthin. Compared with capsanthin directly incorporated into walnut oil, the optimized Pickering emulsion exhibited higher capsanthin retention under storage, light, thermal, and high-pressure treatments. Furthermore, replacing 30% of butter with the capsanthin-loaded Pickering emulsion in spreadable paste improved sensory acceptability and oxidative stability, accompanied by reduced acid and peroxide values. Overall, this study provides a promising strategy for constructing dual-protein Pickering emulsions as multifunctional carriers for lipophilic compounds and functional ingredients for developing nutritious spreadable foods.