## 3 Impact of Cold Plasma on Packaging Properties
### Thermal Properties  
Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are the two most important approaches in understanding the thermal properties of biopolymers and their films. Thermal studies not only provide information on the changes in heating/cooling behaviors but also scrutinize the thermodynamic and thermophysical properties [52]. TGA shows the thermal stability of the samples and the DSC techniques determine the melting temperature (T\({}_{\rm m}\)), glass transition temperature (T\({}_{\rm g}\)), denaturation temperature (T\({}_{\rm d}\)), and enthalpy (\(\Delta\)H). The T\({}_{\rm g}\) is the temperature at which the polymer chains become more mobile, meaning that they have more freedom of movement, whereas the melting temperature is the temperature at which crystalline structures are lost and the polymer chains become a disordered liquid [107]. Thermal parameters are important in determining the processing conditions of the biopolymers and their applications in packaging, as heat sealing is a critical point in the packaging [58; 108]. Table 2 summarizes the thermal properties of biopolymer films exposed to plasma treatment. [PERSON], [PERSON] [87] scrutinized the impact of high voltage (80 kV) atmospheric cold plasma treatment (HVACP) on thermal properties of (com, potato, rice, and tapicoca) starch films. It was reported that HVACP treatment created a highly ordered structure in the films and thus showed higher T\({}_{\rm g}\) and \(\Delta\)H\({}_{\rm m}\) as compared to control films. It was also observed that the T\({}_{\rm g}\) and \(\Delta\)H\({}_{\rm m}\) values were highest for com starch with high amylose content whereas it was found to be lowest for the rice starch with the lowest amylose content [87]. In another study, [PERSON], [PERSON] [80] studied the thermal properties of zein films and DSC results showed that atmospheric cold plasma treatment for 60 s enhanced the denaturation temperature (T\({}_{\rm den}\)), which could be attributed to the crosslinking of the polar compounds generated at the film surface. A similar result was reported for zein-polylactic acid film, where plasma treatment for the 60 s and 120 s led to the formation of more thermally stable films and was attributed to the enhancement of intermolecular hydrogen bonding interactions between zein and PLA molecules with the increase in plasma treatment [46]. They also reported that the TGA of the zein films reflected that the thermal degradation temperature (T\({}_{\rm deg}\)) increased for plasma-treated film and was found to be highest for the film treated for 45 s. Similarly, TGA of the zein-polylactic acid composite film showed that plasma-treated film (for the 60 s and 120 s) demonstrated a lower thermal degradation (73.66%) as compared to untreated composite film (77.31%). This increase in thermal stability may be attributed to the enhancement of compatibility between two different phases upon the application of cold plasma [46]. Apart from the plasma treatment time and voltage, types of plasma forming gases are also important factors that control the thermal stability of the biopolymer-based films. [PERSON], [PERSON] [78] carried out DSC of gelatin-corn oil emulsion-based films treated with O\({}_{2}\), N\({}_{2}\), air, Ar, and ethanol-argon (EtOH-Ar) plasma. The DSC analysis of these films showed that plasm treatment using different plasma forming gases had a different impact on the thermal properties like melting temperature (T\({}_{\rm m}\)) and melting enthalpy (\(\Delta\)H\({}_{\rm m}\)). On the application of air, T\({}_{\rm m}\) and \(\Delta\)H\({}_{\rm m}\) increased significantly from 51.9 \(\pm\) 0.1 to 58.9 \(\pm\) 0.1 (\({}^{\circ}\)C),and 65.5 \(\pm\) 0.04 to 123.8 \(\pm\) 0.1(J/g), respectively, and this can be attributed to changes in the chain mobility of the films.