Fabricating an anti-shrinking κ-carrageenan/sodium carboxymethyl starch film by incorporating carboxylated cellulose nanofibrils for fruit preservation

A stronger and dimension-stabilized film was obtained using κ-carrageenan and sodium carboxymethyl starch (CMS) with carboxylated cellulose nanocrystals (C-CNC) as a reinforcing agent and anti-shrinkage agent. C-CNC endowed the films with better mechanical properties as well as excellent dimensional stability. The film solutions showed shear thinning and acted as a pseudoplastic fluid. When C-CNC content was increased from 0% to 12%, the tensile strength and elongation at break of the films improved from 23.89 MPa to 38.37 MPa and 21.00% to 27.31%, respectively. The films maintained good thermal stability and barrier performance. The Zeta potential of the film suspension can reach below -30 mV, indicating C-CNC enhanced the electrostatic repulsion in the film-forming system, which favored the network structure more continuous and stable. By virtue of the excellent mechanical properties and dimensional stability, strawberries can be tightly wrapped without cracks by the coatings to delay the deterioration greatly. By comparing the weight loss rate, Vc, total soluble solid, hardness, titratable acid and pH, CCC12-coated strawberries were closer to fresh ones. Therefore, this study has developed a feasible, low-cost and green fruit coating that can be potentially utilized on a large-scale.