Media milling derived starch-polyphenol particles: structural and antioxidant effects on Pickering emulsion stability

This study investigated how media milling affects complexing between corn starch and representative polyphenols, namely epigallocatechin gallate, gallic acid, ferulic acid and curcumin, emulsifying and antioxidant behavior of these complexes. Media milling promoted the formation of starch-polyphenol complexes and preserved over 80% free radical scavenging capacities of polyphenols except curcumin. Encapsulation efficiency of curcumin and epigallocatechin gallate in the complexes was over 80%, while that of ferulic acid and gallic acid was below 50%. Multi-level structural analysis indicated that epigallocatechin gallate disrupted lamellar structure of starch with multiple hydroxyl groups interacting with starch molecules while hydrophobic interactions between curcumin, ferulic acid, and starch reduced degree of starch chain depolymerization. XRD analysis confirmed no existing of "V" type complex, suggesting these complexes were formed through intermolecular interactions instead of intramolecular single helical inclusions. Epigallocatechin gallate-starch complex had high contact angle of 70.23 ± 2.74° and lowest interfacial tension, which resulted in the best emulsifying ability, forming emulsions with the smallest emulsion droplets (14.61 ± 4.24 μm), and high interfacial modulus. All Pickering emulsions exhibited high oxidative stability, among which epigallocatechin gallate stabilized emulsion showed the lowest lipid oxidation products during storage due to high encapsulation efficiency and anchoring of complex at the oil-water interface. This study provides valuable guidance for developing functional starch-based Pickering emulsions food product with long-storage performance and high antioxidant activities by altering interactions between starch and polyphenols.