Ultraviolet shielding and antibacterial dialdehyde cellulose-polyvinyl alcohol (PVA) composite packaging film for strawberry preservation.

With the aim of improving capacity of food packaging films, active composite films are fabricated by cross-linking of dialdehyde cellulose (DAC) and polyvinyl alcohol (PVA) with polyethyleneimine (PEI). Comparing with pure PVA film, the composite film containing 15 % DAC shows excellent properties. The multi network formed between PVA, DAC and PEI improve elongation of film from 88.7 % to 117.0 %, and UV shielding from 13 % to 94 %. The aldehyde groups of DAC enable film the ability of 54.4 % 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 92 % 2,2'-zino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radicals scavenging, respectively. It also can effectively inhibit the growth of E. coli and S. aureus. In addition, DAC alters the density structure of PVA and reduces water vapor permeability of films from 981 to 737 g/m2·day. Based on the optical, transport, anti-oxidization and anti-microbial properties, the composite film has charming packaging capacity and prolongs shelf life of strawberries from 4 to 10 days. During storage, the weight and hardness loss of strawberries wrapped in composite film are 21.5 % and 28.9 %, respectively. The retention rates of total soluble solids, anthocyanins and flavonoids of strawberries wrapped with composite film containing 15 % DAC are 74.0 %, 93.0 % and 86.2 %, respectively. Which are 20 %, 70 % and 230 % times higher than that in strawberries wrapped with pure PVA, respectively. Furthermore, the composite film also effectively reduces the accumulation of malondialdehyde (MDA). Therefore, the composite film based on cross-linking is promising to control the postharvest quality of perishable berries.