Effects of Chitosan/EGCG@MNPs Nanocomposite Packaging on Preservation of Blueberries Stored at Low Temperature and Normal Temperature

In this study, EGCG loaded melanin-like nanoparticles (EGCG@MNPs) were incorporated into chitosan matrix for preparing an active nanocomposite food packaging film to extend shelf-life of post-harvest blueberries. First, the chitosan/EGCG@MNPs nanocomposite film was successfully prepared using a solution casting method. Then, the films were manufactured as individual heat-sealing packaging bags in which fresh blueberries were packed in, and the packaged blueberries were stored at 4 and 25 ℃, respectively. During storage, the sensory and physicochemical indexes such as weight loss, decay rate, hardness, respiration intensity, microorganisms, and apparent quality of blueberries were analyzed to explore the preservation effect of the nanocomposite packaging films. The results showed that the weight loss, decay rate and hardness of blueberry was significantly delayed (P<0.05) when packed in nanocomposite packaging. It was presumed that the respiration intensity of blueberries was effectively inhibited, thus reducing the consumption of active substances and the browning degree of fruit surface. At the end of storage, the blueberries packaged with nanocomposite films maintained a high anthocyanin content, with retention rates of 90.1% and 99.0% at 4 and 25 ℃, respectively. And the DPPH· scavenging rate of the packed blueberries was 6.2%, 6.3% higher than that of control group, indicated a higher level of antioxidant capacity maintaining. What's more, the activity of polyphenol oxidase (PPO) and the growth of microorganisms were significantly inhibited (P<0.05), which effectively improved the sensory quality and delayed the senescence of blueberry fruits. Therefore, the chitosan/EGCG@MNPs nanocomposite packaging combined with low temperature has been proved as an effect way to preserve the postharvest blueberries.