PLA is one of the biodegradable materials that have received the most attention from domestic and foreign research. Medical, packaging and fiber are its three popular application areas. PLA uses natural lactic acid as the main raw material, which has good biodegradability and biocompatibility. Its life cycle load on the environment is significantly lower than that of petroleum-based materials, and is considered to be the most promising green packaging material.
Polylactic acid (PLA) can be completely decomposed into carbon dioxide and water under natural conditions after being discarded. It has good water resistance, mechanical properties and biocompatibility. It can be absorbed by organisms and has no pollution to the environment. At the same time, PLA also has good mechanical properties. It has high impact strength, good flexibility and thermal stability. It has good permeability to oxygen and water vapor, and at the same time has good transparency, anti-mildew, antibacterial, and its service life is 2 to 3 years.
PLA has good transparency and gloss, and its excellent performance is comparable to cellophane and PET, which is a performance that other degradable plastics do not have. The transparency and gloss of PLA is 2 to 3 times that of ordinary PP film and 10 times that of LDPE. Its high transparency makes PLA as a packaging material beautiful in appearance. For example, it can be used for candy packaging. At present, many candy packaging on the market use PLA packaging film.
PLA can be made into film products with high transparency, good barrier properties, excellent processability and mechanical properties, and can be used for flexible packaging of fruits and vegetables. It can create a suitable storage environment for fruits and vegetables, maintain the life of fruits and vegetables, delay aging, and maintain the color, fragrance, taste and appearance of fruits and vegetables. However, when applied to actual food packaging materials, some modifications are needed to adapt to the characteristics of the food itself, so as to achieve a better packaging effect.
PLA can form a weakly acidic environment on the surface of the product, which has the basis of antibacterial and mildew resistance. If other antibacterial agents are used supplementally, an antibacterial rate of more than 90% can be achieved, which can be used for antibacterial packaging of products. Some researchers took Agaricus bisporus and Golden Ears as examples to study the fresh-keeping effect of the new PLA nano antibacterial composite film on edible fungi, thereby prolonging the shelf life of edible fungi and maintaining good quality status. The results show that: PLA/rosemary essential oil (REO)/AgO composite film can effectively delay the decrease of vitamin C content in golden ears. Compared with LDPE film, PLA film and PLA/REO/TiO2 film, the water permeability of PLA/REO/Ag composite film is significantly higher than that of other films. It is concluded that the PLA film can effectively prevent the formation of condensed water and achieve the effect of inhibiting the growth of microorganisms. At the same time, it also has an excellent antibacterial effect, can effectively inhibit the reproduction of microorganisms during storage of golden ears, and can significantly extend the shelf life to 16 days.