Mechanical and gas permeability properties of poly(L-lactic acid)–based films and their application in fresh produce preservation—Review

Abstract

Plastics have remained the best choice for fruit and vegetable packaging due to their exceptional transparency, flexibility, optional good barrier and cost-effectiveness. However, a large number of plastics end up in the environment after serving their intended purpose and persist there for centuries. Since worldwide attention to environmental issues has become an irreversible historical trend, cost-effective renewable biodegradable packaging material is highly desirable for the packaging industry to satisfy both industrial demands as well as consumer expectations. Poly (L-lactic acid) (PLLA), a renewable biodegradable polymer derived from biomass, has been widely studied as a very attractive polymer for food packaging applications. However, its brittle nature and medium CO₂/O₂ permeability are not friendly for its utilisation in the aspect of fresh agricultural products packaging. In such a context, great efforts have been devoted to improvements in the mechanical and permeability of PLLA to meet the requirements of food packaging. The main purpose of the review is to summarise the mechanical and permeability properties of composite films developed by the incorporation of toughness reinforcing agents into the PLLA matrix. The elongation at break of PLA can be increased up to 250 times by modification, and the CO₂ permeability of PLA can be increased by 2–3 times by modification. We also elaborate on studies of the preservation effect of PLLA composite films on fresh fruits and vegetables.