Effects of amphiphilic carbon nanotube constructed active cling film on blueberry shelf life quality

Multi-walled carbon nanotubes (MWCNTs) have restricted their application in food packaging, due mainly to the inherent hydrophobicity. In this study, a synergistic physical adsorption-chemical grafting modification was proposed to construct an amphiphilic HPMC/AO-MWCNTs (hydroxypropyl methylcellulose/hydropropropropyl methylcellulose) composite. Acid-Catalyzed Oxidation-MWCNTs composite system was obtained to realize the controlled loading of nanomaterials on the surface of a food-grade DTT (derivative ternary tissue) matrix. The amphiphilic HM-CSA-AP (hydroxypropyl methylcellulose-carbon nanotube-based self-assembled layer-active packaging film) was prepared after modification. The results show that the optimal performance was achieved when assembled in 3 layers. Among them, the tensile strength reached 68.44 MPa, which was 27.85% higher than that of the DTT layer; The oxygen barrier rate increased by 62%, whereas, the transmission rate of water vapor decreased by 64%, which was 55.10% higher than that of PE (polyethylene) film and 25.11% lower than that of PVDC (polyvinylidene chloride) film. Compared with the PVDC membrane, the oxygen barrier rate increased by 56.25%, whereas, the transmission rate of water vapor decreased by 22.83%. A dense barrier layer was formed with the labyrinth effect. The number of E. coli, S. aureus, yeast, and mold colonies decreased by 61.44%, 50.72%, 64.37%, and 52.90%, respectively, in the HM-CSA-AP at the number of the self-assembled layers of 3, compared with the DTT; The number of colonies decreased by 53% to 64%, and 54% to 65%, respectively, compared with the PE and PVDC film. The decrease was attributed to the synergistic effect of physical puncture from the HPMC/AO-MWCNTs release. The blueberry preservation experiment showed that the HM-CSA-AP shared excellent shelf quality: The weight loss rate of blueberries increased most slowly after 12 d of storage at 25℃, with the maximum weight loss rate of only 1.17%; The spoilage rate was 15.44%, which was significantly lower than that of the blank control group at the 8th day (22.17%, which had basically lost its edible value); The hardness of fruit was maintained at 3.86 N, which was 2.01 times higher than that of the blank control group; The malondialdehyde content (20.46 mmol/g) failed to reach 1/2 of the blank control group (51.34 mmol/g); The vitamin C content (47.47 mg/100 g) was about three times that of the blank control group; The titratable acid declined 13.35% on day 6 of storage, compared with day 0 of storage. The slowest decrease was observed, compared with the rest groups. The preservation mechanisms also included the inhibition of respiratory metabolism by the high oxygen barrier properties, the retardation of pectinase activity by the low moisture permeability, and synergistic bacterial inhibition by nanotube-loaded antioxidants. The HM-CSA-AP system was synergistically optimized, in terms of the oxygen-blocking and moisture-permeable properties. The dispersion stability of nanomaterials was obtained after optimization. The finding can also provide an innovative solution to the environmentally friendly active food packaging for freshness storage and transportation in the field of berries and fruits.