Moccia, Federica (2022) Sustainable production of functional materials from agri-food by-products. [Tesi di dottorato]

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This PhD research project was aimed at the exploitation of phenolic compounds from agri-food by-products for applications in human health or as additives for functional materials. Agri-food industry is responsible for the generation of high volumes of organic by-products along the entire supply chain, whose disposal represents a cost to the food processor and has a negative impact on the environment. On the other hand, these waste products are becoming increasingly attractive as easily available, low cost and sustainable sources of functional compounds, first of all phenolic compounds, which are finding increasing applications not only as food supplements but also as additives for the implementation of functional materials. In this context, specific aims of the PhD project were: a) Characterization of the antioxidant and functional properties and of the main phenolic constituents of selected agri-food by-products; b) Improvement of the antioxidant properties of agri-food by-products by hydrolytic activation treatments or bioprocessing (e.g. fermentation) and characterization of the main structural modifications induced on the phenolic constituents; c) Exploitation of agri-food by-products derived phenolic compounds as additives for the implementation of functional materials. Main outcomes can be summarized as follows: • Hydrolytic treatments induced specific boosting effects on the antioxidant properties of agri-food by-products as a consequence of the removal of non-active components (mainly polysaccharides) and of structural modifications induced on lignin and hydrolyzable tannins, whereas fermentation processes led, in the case of pomegranate wastes, to a material with a very high content of the bioactive ellagic acid, likely as a result of hydrolytic phenomena. • Incorporation of extracts from pecan nut shell, an agri-food by-product endowed with very potent antioxidant properties in poly(lactic acid) and whey protein films, provided materials with enhanced antioxidant and antimicrobial properties for use in food-related applications, such as active packaging, whereas functionalization of chitosan films with hydrolyzed spent coffee ground/silver nanoparticles led to materials with antioxidant and antibacterial activities for use in the biomedical sector. In the frame of the collaboration with the industrial partner of the PhD project “Centro di Ricerche per la Chimica Fine”, particular attention was devoted to tannins and by-products of the tannin industry. In particular, the research activity was directed to: d) Improvement of the antioxidant and antipollutant properties of exhausted woods and chestnut wood fiber, that is the residual materials after industrial tannin extraction, by hydrolytic activation. e) Comparative evaluation of the antioxidant properties of wood tannin-based coated substrates, which showed the superior ability of condensed tannins to form a functional and robust antioxidant coating for material functionalization. f) Development of a rational and tunable deep eutectic solvent-based processing for valorization of chestnut wood fiber as a source of ellagic acid and lignin. Finally, as part of the project carried out in collaboration with the foreign partner of the project, Prof. Andreas Schieber (Institute of Nutritional and Food Science, Molecular Food Technology, University of Bonn), new facile and low-cost protocols for the synthesis of anthocyanin metabolites of biological interest were developed. Research work on related topics concerning food pigments resulted in the preparation and characterization of a new cyanine from oxidative coupling of chlorogenic acid with tryptophan with potential properties for use as a red dye for food coloring.

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