A citrus pericarp-inspired ternary bio-mimetic film with slow-release functional units and its application in preserving grape.

Abstract

Inspired by the hierarchical protective structure of citrus pericarp, a biomimetic ternary film is fabricated for high-performance grape preservation. The system comprises an outer gellan gum (GG) layer mimicking hydrophobic epicuticular wax and an inner chitosan (CH) matrix reproducing the cushioning albedo tissue. Eugenol-loaded alginate microcapsules (MCs), analogous to citrus oil glands, enable sustained release. Optimized MCs (Alginate:eugenol = 3:1) achieve 91.0% encapsulation efficiency and biphasic release over 60 h. When integrated into GG/CH films, MCs enhance mechanical strength to over 50 MPa, increase opacity to over 0.83, and increase hydrophilicity (contact angle ∼85°). During 15-day storage, coated grapes exhibit reduced weight loss (∼25.2% vs. 31.9% control), maintained firmness (∼4 N), suppressed microbial growth (1.5-log reduction), and alleviated oxidative damage, along with inhibited changes in soluble solids, titratable acidity, and total phenolics. This biomimetic strategy integrates structural design with active delivery, offering a sustainable approach for prolonging the fruit shelf life.