## 3 Plastics Used for Food Packaging
### Selected Biodegradable Synthetically Manufactured Polymers  
#### 3.2.1 Biomass-derived Chemically Manufactured Polymers  
One commercially manufactured example should be discussed here: poly (lactic acid) (PLA) and related products. PLA is a thermoplastic and biodegradable aliphatic polyester (Figure 2). As it has its roots in the aliphatic class of polyesters, PLA can be created either by chemical processing of lactic acid monomer or by fermentation of a carbohydrate [102]. PLA is the first polymer synthesized from bio-based monomers commercialized on a large scale and can be shaped into injection molded objects, films, coatings, and 3D printed materials [103]. Next to PHAs, starch, and PCL, PLA is the primary biodegradable polymer used for monolayer and some multilayer applications [83; 104]. So, PLA films are applied as thermoformed trays, cups, bowls, bags, or jars for packaging of fresh salads, ready-to-eat meals, deli products, beverages, potato chips, and yoghurt among other uses [105; 106]. Renewability, biodegradability, and biocompatibility are attribu  
Figure 1: Classification of plastics used for packaging applications. Adapted from [95]. Poly(amide) (PA), poly(butylene adipateerephthalate) (PBAT), poly(butylene succinate) (PBS), poly(butylene succinate) (PBS), poly(caprolactone) (PCL), poly(ethylene) (PE), poly(ethylene terephthalate) (PET), poly(hydroxyalkanoate) (PHA), poly(lactic acid) (PLA), poly(propylene) (PP), poly(trimethylene terephthalate) (PTT). Figure 2: PLA structure. the best polymeric substitutes for various fossil-based polymers [83]. However, the PLA synthesis--and in turn the corresponding products--are still rather expensive [39]. So far, PLA and corresponding copolymers are used to substitute polyolefins as high-density poly(ethylene) (HDPE), low-density poly(ethylene) (LDPE), poly(propylene) (PP), PET, and poly(styrene) (PS) as packaging materials [37, 83] due to comparable mechanical properties like stiffness and tensile strength, gas permeability, and transparency (Table 1) [107, 108, 109]. The production of composites by adding nanof fillers is a way to extend and improve the properties of PLA [83, 104, 109]. The addition of many nanofillers (three-dimensional spherical and polyhedral, two-dimensional nanofibers or one-dimensional sheet-like nanoparticles) has been studied and lead to satisfactory achievements in the design of PLA nanocomposites [116]. [PERSON] et al. studied the effectiveness of PLA-based packaging solutions compared to a conventional reference package consisting of APET/PET trays wrapped in plastic films of poly(vinyl chloride) (PVC) to store red fresh meat during its refrigerated shelf life. By using PLA packaging in combination with a gas mixture of 66% O\({}_{2}\), 25% CO\({}_{2}\), and 9% N\({}_{2}\), it was possible to maintain an optimum red color together with a reduced content of volatile compounds associated to off-flavors of meat samples [117]. [PERSON] et al. investigated biocomposite films of PLA with zinc oxide regarding mechanical, barrier, and antimicrobial properties. The results showed that PLA films with 5 wt% of zinc oxide exhibit good mechanical properties related to a high modulus and stress at yielding, decrease of permeability to CO\({}_{2}\) and O\({}_{2}\) carbon dioxide and oxygen, and a slight increase of water vapor permeability. Furthermore, the incorporation of 5% zinc oxide leads to an antimicrobial activity against _E. coli_ after 24 h with a reduction value of 99.99% [37]. [PERSON] and [PERSON] incorporated cellulose natural fibers from palm sprouts in a PLA matrix. The results showed that the mechanical resistance increased, and the water absorption rate decreased significantly with the optimum concentration of palm