## 3 Plastics Used for Food Packaging
### Selected Plant-derived Polymers
#### 3.3.3 Polysaccharides
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Permeability**} & \multicolumn{3}{c}{**Mechanical Properties**} \\ \cline{2-5}
**Film Composition** & \multicolumn{1}{c}{\(\mathbf{O_{2}}\)} & \multicolumn{1}{c}{\(\mathbf{H_{2}O Vapor}\)} & \multicolumn{1}{c}{\(\mathbf{Tensile}\)} & \multicolumn{1}{c}{\(\mathbf{Elongation}\)} & \multicolumn{1}{c}{\(\mathbf{References}\)} \\ \cline{2-5}  & \multicolumn{3}{c}{**[g\(\cdot\)mm/(m\({}^{2}\cdot\)d\(\cdot\)at\(\cdot\)at\()\)] *} & \multicolumn{1}{c}{**[MPa]**} & \multicolumn{1}{c}{**[\%]**} & \\ \hline High amylose cornstarch films & & 1260 & & & \\ without plasticizer & NR & (20 \({}^{\circ}\)C; 52.9\% RH) & 34.32 & 1.41 & [189] \\ (amylose:amylopectin ratio 80:20) & & & & & \\ Low amylose cornstarch films & & 1430 & & & \\ without plasticizer & NR & (20 \({}^{\circ}\)C; 52.9\% RH) & 44.38 & 2.40 & [189] \\ (amylose:amylopectin ratio 25:75) & & 0.182 & & & \\ Thermoplastic (cassava) & (Ambient temp., & 36.8 & 5.8 & 78 & [190; 191] \\ starch (extrusion) & 0\% RH) & & & & \\ Methylcellulose mixtures & & 446–945 & & & \\ in ethanol & NR & (25 \({}^{\circ}\)C; 52\% RH) & 25–33 & 29–14 & [192] \\ Hydroxypropyl methylcellulose & & 974,000 & & & \\ without plasticizer & & (23 \({}^{\circ}\)C; 50\% RH) & 61.04 & 29.51 & [193] \\ Carboxymethyl cellulose film & & 683 & & & \\ with glycerol (casting method) & & (25 \({}^{\circ}\)C, 52.8\% RH) & 6.10 & 201.73 & [194] \\ CMC-film with 50 wt\% ethanol & & & 2570 & & \\ organosyl lignin with glycerol & NR & (20 \({}^{\circ}\)C, 0\% RH) & 20 & 5.92 & [149] \\ (casting method) & & & & & \\ Agar/10\% lignin composite film & & 13,400 & & & \\ with glycerol & & (25 \({}^{\circ}\)C, 50\% RH) & 51.8 & 22.1 & [195] \\ (Sodium) alginate film with & & 13,600 & & & \\ glycerol (casting method) & & NR & (25 \({}^{\circ}\)C, 50\% RH) & 41.1 & 8.5 & [196] \\ Chitosan film with glycerol & 0.188 \(\times\) 10\({}^{-2}\) & 210–3020 & & & \\ (25 \({}^{\circ}\)C, \(<\)50\% RH) & (25 \({}^{\circ}\)C, 0–100\% RH) & 8.9 & 38.5 & [197] \\ \hline \hline \end{tabular}  
* In some data, the units were normalized. NR: Data not reported.  
\end{table} 
Table 4: Barrier and mechanical properties of polysaccharide-based polymers. Figure 5: Overview of several polysaccharides used for food packaging (edible) films: (**a**) starch, (**b**) cellulose, (**c**) alginate, and (**d**) chitosan [188]. Starch  
Starch is a natural polysaccharide easily available on an industrial scale. Many plant-based polysaccharides and cost-effective starch-based materials have been extensively investigated as an alternative material for fossil-based food packaging applications due to their environmental compatibility and biodegradability [198]. Although starch-based packaging, which has good film-forming properties and excellent oxygen barrier, is already in wide use, this material still has some disadvantages such as the poor vapor and oxygen moisture barrier and poor mechanical properties compared to conventional non-biodegradable plastics used in food packaging industry (Tables 1 and 4) [198; 199; 200]. The oxygen barrier properties are correlated to a high-ordered hydrogen-bonded network structure. The barrier properties can be improved by increasing the crystallinity or a higher content of amylopectin [199]. The poor moisture barrier is caused by a strong hydrophilic behavior [200]. A higher crystalline structure in starch-based films leads to less sensitivity of moisture and to environmental relative humidity. Considering the poor mechanical properties, starch-based films show a relatively high tensile strength while the elongation percentage is low [199]. The high tensile strength is attributed to the extensive intra-molecular hydrogen bonds between amylose, amylopectin, and amylose-amylopectin molecules. Amorphous regions in starch-based films formed by amylose cause brittleness and thereby influence the poor mechanical properties [189].