Effect of carvacrol in the properties of films based on poly (vinyl alcohol) with different molecular characteristics

[EN] Poly (vinyl alcohol) (PVA) is a hydrophilic linear polymer obtained from the controlled hydrolysis of poly (vinyl acetate) (PVAc). The molecular weight (Mw) and degree of hydrolysis (DH) of PVA are considered relevant in both the functionality of the polymer and its capacity for film formation. This study analysed the influence of the Mw and DH of PVA on both the film's ability to incorporate carvacrol (CA), for the purposes of obtaining active films for food packaging application, as well as on the film microstructure, thermal behaviour and its functional properties as packaging material. CA was incorporated at 5 and 10 g/100 g polymer by emulsification in the polymer-water solutions, while the films were obtained by casting. The higher Mw polymer provided films with a better mechanical performance but less CA retention and a more heterogeneous structure. In contrast, low Mw, partially acetylated PVA gave rise to homogenous films with a higher CA content that increased the mechanical resistance and stretchability of the films. The melting temperature of this polymer with acetyl groups was lower than the degradation temperature, which makes thermoprocessing feasible.The authors would like to thank the financial support from the Ministerio de Economia y Competitividad (MINECO) of Spain, through the project AGL2016-76699-R. Author Johana Andrade thanks the Departamento de Narino-Colombia y la Fundacion CEIBA for the doctoral grant. The authors also thank the services rendered by the Electron Microscopy Service of the UPV.Andrade, J.; González Martínez, MC.; Chiralt Boix, MA. (2020). Effect of carvacrol in the properties of films based on poly (vinyl alcohol) with different molecular characteristics. 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Applications of Chitosan as Food Packaging Materials

The interest in biopolymers has increased due to the depletion of the fossil fuel reserve and the environmental impact caused by the accumulation of non-biodegradable plastic-based packaging materials. Many biopolymers have been developed from food waste products to reduce this waste and, at the same time, to obtain new food packaging materials. Chitosan is thus an alternative to synthetic polymers, and a raw material for new materials. To assess the suitability of a material as a food packaging material, it is necessary to study their mechanical and permeability properties. Mechanical properties allow to predict the behaviour of films during transportation, handling and storage of packaged foods. Barrier properties play a key role in maintaining the food product quality. Properties values depend on the type of chitosan used. Mechanical and barrier properties of pure chitosan films are suitable for food packaging and active packaging. These properties can be modified by combining chitosan with other components such as plasticizers, other polysaccharides, proteins and lipids. These combinations adapt the properties of the final polymer to the needs of the food to extend its useful life, while maintaining quality properties of the food and the biodegradability of the polymer. Chitosan displays antimicrobial activity against a wide range of foodborne filamentous fungi, yeast, and gram-negative and gram-positive bacteria. This antimicrobial property and film-forming capacity has made chitosan the reference polymer to develop active packaging with the ability to inhibit the growth of microorganisms and improve food safety. Regarding the optical properties, pure chitosan films in the visible range show high transmittance values, being optically transparent films. This is an important parameter related to the acceptability of the films by the consumer. In addition, chitosan-based films exhibit remarkable UV absorbance, which allows to protect food from lipid oxidations induced by UV radiation