Title : Casein whey Pickering microcapsules for improved thermal stability and controlled release of curcumin in heat processed foods
Abstract:
Background: Curcumin is a bioactive polyphenol with remarkable antioxidant and anti-inflammatory potential, yet its poor water solubility and thermal instability limit its application in processed foods. Protein-based Pickering systems represent a promising clean-label route to stabilize such compounds without synthetic surfactants.
bjective: We aimed to design hybrid microgels composed of sodium caseinate (NaCas) and whey protein isolate (WPI) as food-grade Pickering stabilizers for curcumin-loaded oil-in-water emulsions and to evaluate their performance in heat-processed matrices (e.g. baked rolls).
Methods: NaCas/WPI complexes were produced via pH-induced aggregation (pH 5.8–6.2) followed by enzymatic crosslinking and Ca²⁺ bridging to form soft colloidal microgels (300–800 nm). These microgels served as solid stabilizers for curcumin-dispersed oil droplets (medium-chain triglycerides) in O/W emulsions. Interfacial activity, particle wettability, and droplet stability were assessed by ζ-potential, contact angle, and confocal microscopy. Oxidative and thermal stability of curcumin was examined during simulated baking (180–200 °C, 15 min), and in-vitro digestion was modelled.
Results: The NaCas/WPI Pickering emulsions exhibited excellent resistance to creaming and coalescence, maintaining particle size <2 µm after thermal treatment. Curcumin degradation during baking decreased by 55–65% compared with non-encapsulated curcumin oil dispersions. Spectroscopic and HPLC analyses revealed that the protein–curcumin binding and reduced oxygen permeability of the Pickering systems interface were responsible for the enhanced protection. Controlled release in the intestinal phase followed Weibull kinetics (b ≈ 0.7), indicating diffusion-controlled release linked to proteolytic breakdown of the wall.
Conclusions: Casein–whey Pickering microgels enable efficient encapsulation and thermal stabilization of curcumin in food matrices, providing a viable strategy for functional bakery applications. The system combines natural biopolymers, high process tolerance, and controlled bioaccessibility—making it attractive for commercial and academic development in clean-label functional foods.
