The effects of conjugation of walnut protein isolate with polyphenols on protein solubility, antioxidant activity, and emulsifying properties. (November 2022)

• Record Type: Journal Article
• Authors: Huang, Xuan; Yan, Chunjun; Lin, Ming; He, Changwei; Xu, Yanfei; Huang, Yukun; Zhou, Zheng
• Is Part Of: Food research international. Volume 161(2022)
• Publication Date: 2022-11
• Subjects: Walnut protein isolate -- Polyphenol conjugation -- Emulsifying properties -- Solubility -- Antioxidant capacity; Food -- Analysis -- Periodicals; Food industry and trade -- Periodicals; Food industry and trade -- Canada -- Periodicals; Food Technology -- Periodicals; Food -- Periodicals; Food-Processing Industry -- Periodicals; Aliments -- Industrie et commerce -- Périodiques; Aliments -- Industrie et commerce -- Canada -- Périodiques; Aliments -- Recherche -- Périodiques; Food industry and trade; Canada; Periodicals; Electronic journals; 664.005
• DOI: 10.1016/j.foodres.2022.111910
• Languages: English
• ISSNs: 0963-9969

Abstract

Graphical abstract: Highlights: Polyphenol conjugation affected the surface hydrophobicity and charge of AWPI. Polyphenol conjugation altered the secondary structure of AWPI. AWPI-polyphenol conjugates exhibited greatly improved solubility. AWPI-polyphenol conjugates showed enhanced emulsifying and antioxidant ability. Abstract: Alkaline-extracted walnut protein isolate (AWPI) shows poor solubility in aqueous solutions, resulting in relatively low emulsion capacity. This work investigated the influence of ellagic acid (EA) or epigallocatechin-3-gallate (EGCG) conjugation on the solubility and emulsifying properties of AWPI. The increase in polyphenol content and decrease in free amino and thiol groups of walnut proteins confirmed successful conjugation. AWPI polyphenol conjugates showed significantly reduced surface hydrophobicity, greatly enhanced surface charge, and consequently improved solubility. Circular dichroism (CD) results indicated that the polyphenol-conjugated AWPI contained relatively higher α-helical and lower β-sheet contents than AWPI. The antioxidant capacity of the polyphenol-conjugated AWPI was significantly enhanced. Additionally, polyphenol conjugation resulted in decreased mean particle sizes and increased surface charges of the walnut protein-covered oil droplets. The emulsions stabilized by AWPI-polyphenol conjugates were relatively more stable over a range of pH values (7.0–11.0) and thermal treatments (25 °C–90 °C). Moreover, they exhibited greater storage stability than those stabilized by unmodified AWPI.