Assembly of zein–polyphenol conjugates via carbodiimide method: Evaluation of physicochemical and functional properties

Recently, the carbodiimide-mediated coupling method has attracted the attention of some scholars in the food field for its safety and high efficiency. In this study, the carbodiimide method was utilized to assemble zein–polyphenol conjugates innovatively. The covalent insertion of polyphenols to zein was confirmed by the increase of molecular weight and the reduction of nucleophilic groups. Chlorogenic acid (CGA) as well as Gallic acid (GA) were selected as polyphenol models, and the total phenolic content of zein–CGA conjugate and zein–GA conjugate reached 71 mg/g and 43 mg/g, individually. Afterwards, the structural and chemical characteristics between zein–polyphenol conjugates and physical mixtures were compared. Scanning electron microscopy (SEM) indicated that zein–polyphenol conjugates formed regularly shaped spheres with small particle sizes. Compared with control zein and physical mixtures, zein–polyphenol conjugates demonstrated better solubility and dispersibility, higher thermal stability as well as lower surface hydrophobicity. In terms of antioxidant capacity, zein–GA conjugate showed higher scavenging abilities of ABTS and DPPH free radicals than zein–CGA conjugate. The present research developed a new approach to fabricating zein–polyphenol conjugates that can be applied in the food industry as functional additives or materials for delivery systems.