## 3 Plastics Used for Food Packaging
### Selected Plant-derived Polymers
#### 3.3.3 Polysaccharides
As starch-based films are odorless, colorless, and tasteless, starch is used in either pure or blended form as a biodegradable coating or packaging film. The coatings of edible starch are also applied for other kinds of foods to maintain quality and to extend the shelf life of products [200; 201; 202; 203; 204]. However, as starch blends may contain additives like compatibilizers and plasticizers that can migrate out of the matrix, only some starch blends are suitable for food packaging applications [106]. Starch has already been combined with lignin to improve its poor thermo-mechanical properties while simultaneously decreasing its water vapor permeability significantly [205]. [PERSON] et al. confirmed these findings in their studies, showing that the presence of lignin in combination with CNC increased maximum stress and modulus of elasticity, barrier properties, and the thermal stability of the material [206; 207]. [PERSON] et al. published a study concerning starch-based coatings for paper packaging materials with lignin, investigating the self-supporting films regarding their mechanical properties and chemical stability in water as well as their barrier properties when used as coating on paper board. When lignin is added, the dissolution of starch from the composites could be significantly decreased. The addition of ammonium zirconium carbonate (AZC) leads to further improvement of the storage modulus, indicating that crosslinking had occurred [208]. Cellulose and Derivatives  
Cellulose represents the most abundant renewable polymer source available in nature. Biodegradable films made out of this raw material are characterized by renewability, low cost, non-toxicity, biocompatibility, biodegradability, and chemical stability [209]. For example, cellulose films (known as Cellophane(r)) are used for wrapping fruits in bio-based trays [105]. Films made of cellulose exhibit good toughness, tensile strength, high surface gloss, and good transparency [210]. Whereas hemicellulose-based films are brittle, the flexibility, toughness, and oxygen permeability can be improved by addition of plasticizers [211; 212]. A disadvantage of cellulose films is their poor water vapor barrier. This is caused by the underlying hydrophilic nature of polysaccharides [83]. Soaking cellulose with alkali to swell the structure followed by different derivatization reactions, CMC, methylcellulose (MC), hydroxypropyl cellulose (HPC), and hydroxypropylmethyl cellulose (HPMC) are available. They are used as raw materials to prepare biodegradable films, which are transparent, water soluble, odorless, tasteless, and flexible and have moderate strength and resistance to lipid compounds (Table 4) [213]. CMC is most often used for biodegradable film production. It is highly soluble (in water) and crystalline and can build solid and flexible films [214; 215]. Beneficial characteristics include film-forming properties, good mechanical and gas barrier properties, transparency, ease of processing, and low price [216]. Next to its good film-forming properties, CMC has been studied as antibacterial food packaging in composites with chitosan [217; 218] and pectin [219]. [PERSON] et al. investigated the incorporation of organosolv lignin from corncob in CMC-based films, which leads to an improved water resistance of approx. 60% and reduction in the water vapor permeability of 20%, while also enhancing the thermal stability and antioxidant activity [149]. As mentioned before, mechanical and barrier properties of cellulose-based films can be improved by the production of nanocomposites. [PERSON] et al. proposed nanocomposites using chitosan as nanofiller in HPMC to enhance mechanical and film barrier attributes. HPMC films containing different concentrations of chitosan as nanoparticles were analyzed for mechanical properties, water vapor permeability, and oxygen permeability. They realized that chitosan nanoparticles tended to fill up poriferous spaces in the HPMC-matrix.