Functional and antioxidant bio-based polymer composites with potential applications in food packaging

The inadequate management of plastic wastes, along with the low biodegradability of conventional petroleum-based polymers, has led to a global climatic crisis. A potential solution is the substitution of these ordinary polymers by bioplastics, which production or management present a low impact on the environment. Moreover, revalue agro-food wastes to create new biocomposites is a good strategy to improve waste disposal with economic benefits. Adding agro-food wastes into a polymer matrix can also provide several enhancements to the final biocomposite, such as the reduction of the percentage of oil derivatives and higher biodegradation rate. In addition, the final biocomposites can develop additional and innovative features such as antioxidant activity, better barrier properties against gases, or UV-light protection. These properties can be useful to prevent the damaging biochemical reactions occurring during food storage, like oxidation, loss of firmness, browning, off-odors, etc, increasing the shelf life of foods. In this PhD-thesis, the development of eco-friendly materials with promising properties for food-packaging applications has been performed using a low-environmental impact approach. All projects were based on the use of food by-products or naturally derived molecules, and different processing techniques, like casting, extrusion, and hot-pressing, were employed. In the first part of the thesis, caffeic acid, as a natural derivative, was used to provide antioxidant and UV-blocking responses to a transparent polymer blend form by poly(ethyl-cyanoacrylate) (PECA) and polypropylene carbonate (PPC). The morphological and barrier properties have been characterized and discussed. Secondly, two food by-products, tealeaves extract and discarded balsamic vinegar, were used to modify the physicochemical properties of polyvinyl alcohol (PVA) films using one-pot method. Films showed tunable antioxidant and mechanical behaviors, varying respect to the concentration and the type of natural additive. The chemical composition of tea and tea waste extracts was analyzed, resulting in a wide variety of active polyphenols. Besides, films exhibited excellent oxygen barrier properties. 2 In the third project, versatile biocomposites (40 wt.% of cellulose and 60 wt.% of petroleum-based bioplastic) were fabricated using free-solvent and industry-scalable methods, like extrusion and hot-press. The content of the petroleum-based polymer, polycaprolactone (PCL), was reduced by incorporating an inorganic filler at high concentrations (10 and 25 wt.%). In addition, biocomposites were functionalized with two different natural derivatives: aqueous extract of pomegranate peel and curcumin, separately. Pomegranate peel extract provided a strong antioxidant response, while curcumin-composites displayed colorimetric-changes with pH. Finally, the pH-sensing properties of the curcumin biocomposites were tested during the storage of commercial shrimps. The last part of the thesis describes the development of edible and bio-based materials using the orange peel and orange essential oil. The gelation conditions of the orange peel pectin were modified to create bioactive and edible materials with different functional characteristics. The properties of three sets of samples were evaluated in the view of acting as a suitable edible packaging as coating/film, such as the transparency, solubility, and water barrier properties. In the end, the revalorization of edible vegetable waste through the fabrication of valuable and bioactive packaging using a facile sustainable water-based process was performed with success.