The chemical composition of the walnut pellicle and its benefits to health

Abstract

Walnut pellicle is a layer of film wrapped around the surface of the walnut kernel. The walnut pellicle is rich in tannin compounds, which can react with salivary proteins to produce a bitter and astringent taste, affecting the taste of walnuts. Consequently, the walnut pellicle is typically discarded as waste during food processing. The paper reviews the composition of polyphenolic compounds in the walnut pellicle, mainly including more than 110 kinds of phenolic compounds such as tannins, flavonoids, and phenolic acids; as well as the progress of research on the functional activities in various fields, including inflammation protection, hypolipidemic, antimicrobial, antitumor, and anti-aging, and other five aspects of bioactivity; and finally, elaborates on the interaction between the polyphenolic compounds of the walnut pellicle and walnut proteins, and the possibility that de-phenolization might reduce the structural properties of walnut proteins during processing.