Reducing cherry rain-cracking: Development and characterization of cold-water fish gelatin films reinforced by dual rod-spherical nanoscale structures formed under magnetic fields

Abstract

In order to solve the problem of cherry rain-cracking, cold-water fish gelatin (CFG)-based edible films (CFG, CFG-CNC [cellulose nanocrystals], CFG-CA [chitosan hydrochloride-sodium alginate nanoparticles], CFG–CNC–CA, and their magnetic field [MF] films) were prepared with reinforcement by rod-spherical dual-nanoscale structures. Here, the spherical nanoparticles CA were formed based on static electricity interaction between chitosan hydrochloride and sodium alginate according to pre-gel method, whereas the rods consisted of CNC extracted from sugarcane bagasse. Studies were conducted in laboratory to determine the coating-ductility, hydrophobic, water-vapor barrier, mechanical, and retention properties, and in the field to determine cracking index (CI) and cracking ratio (CR). MF treatment was found to induce the rod-spherical dual-nanoparticles to arrange into C–O–C linkages. Compared to the other films, the CFG–CNC–CA (MF) film showed superior coating-ductility properties (surface tension: 61.8 mN m−1), hydrophobicity (water contact angle: 111.6°), and water-vapor barrier (water-vapor permeability: 7.43 × 10−10 gm−1Pa−1s−1), as well as superior mechanical (Young's modulus: 351 MPa; tensile strength: 30.1 MPa) and retention properties on cherry (water solubility: 38.4%; swelling degree: 876%). Compared with the experimental control, the total CI of cherries treated with CFG–CNC–CA (MF) was reduced from 43.3% to 11.8%, and the total CR was reduced from 34.8% to 11.1%, type Ⅰ’ cracking in particular experienced a greater reduction (from 26.7% to 9.16%) than did type Ⅱ’ (13.7%–4.96%) or Ⅲ’ (8.90%–3.48%). Thus, this study successfully provided a reference for edible CFG–CNC–CA (MF) coatings that prevent and control cherry rain-cracking disasters worldwide in a timely, safe, and efficient manner.