Development of sustainable antimicrobial nanomaterials for innovation in the food industry

Food waste, from post-harvesting to households, is assuming dramatic proportions posing several economic, environmental, and social concerns. Among reasons for losses there is spoilage/microbial contamination due to bad conservation/incorrect packaging. Therefore, the development of innovative solutions, e.g. active packaging (AP), to counteract excessive food loss represent a trend topic in research applied to food industry. AP could act in the monitoring of food conservation over time or by releasing substances that ensure prolonged food preservation. To this aim, some Industry 4.0 components (such as 3D printing, the Internet of Things and nanotechnology) can play a crucial role. The present research work focuses on the green synthesis of antimicrobial inorganic nanomaterials and their implementation in biopolymeric matrices for the fabrication of novel bio nanocomposites as sustainable innovative food packaging to reduce environmental impact and improve food safety and quality. The thesis is divided in four chapters dedicated to the research activities carried out during the PhD course preceded by a brief introduction discussing some general aspects of the research topic. In Chapter 1, the results relevant to the synthesis and analytical characterization of the inorganic nanomaterials are presented. Specifically, silver nanoparticles and ZnO nanostructures are reported. In Chapter 2, the development and analytical characterization of self-standing films of zein or zein/casein (proteinaceous matrices) for the entrapment of silver nanoparticles are described. Additionally, their antifungal activity proving their final properties as active materials for food preservation are also discussed. Chapter 3 deals with a polysaccharidic polymer (alginate) for the development of robust cross-linked coatings by adding cations and for implementing ZnO elongated nanostructures. Morphological and spectroscopic characterization of the films is presented together with water uptake and ion release tests. Such films were further characterised in risk assessment studies to evaluate zinc oral bioaccessibility, as described in the last Chapter. Chapter 4 presents the findings obtained prevalently during the research period at the University of the Balearic Islands regarding the setup of a fully automatic Sequential Injection (SIA) Analysis system for the simulated gastric digestion of Alginate/ZnO films and the following zinc ion release with spectrophotometric detection. This study contributes to the evaluation of potential risks associated to novel packaging being an early example of risk assessment. The main results of the research about the successful preparation of two classes of nanomaterial/biopolymer films as well as innovative analytical platforms for the evaluation of packaging safety are summarized in the concluding remarks.