The effect of polylactic acid-based blend films modified with various biodegradable polymers on the preservation of strawberries

Polylactic acid (PLA) has garnered much attention in the field of fruit and vegetable packaging. Despite its poor flexibility and water resistance, PLA film faces challenges in being used for strawberry storage and freshness preservation due to its inability to maintain flavor quality. In this study, a series of PLA-based modified films was produced by melt blending and extrusion cast processing with PLA as the main component, along with flexible biodegradable polyesters or polycarbonate as the secondary component. First, five different biodegradable polymers were used to investigate the effect of the flexibility and barrier properties of different dispersed phases on the morphology, mechanical properties, and water vapor barrier of PLA-based blend films. Next, the impact on the freshness of strawberries was assessed through examination of fruit color and weight, as well as the levels of O2 and CO2 in the packaging bags. The results showed that the size of the dispersed phase and interfacial bonding with PLA were the key factors determining the mechanical and barrier properties of the blend films. The PLA-polycaprolactone (PCL) blend showed the best compatibility among them, with PCL having the smallest dispersion size (D=0.58 µm), higher toughness than the other four PLA blends, and greater enhancement of PLA. Additionally, it exhibited a similar rate of quality loss in strawberry preservation compared to commercial PE. As a result, the color and luster were more completely preserved. The results of this study may help the future development of degradable plastics, to reduce environmental pollution.