From vegetable waste to value-added natural flavourings and flavoured products: bioactive and volatile compound characterization through sustainable approaches

The need for sustainable food systems is growing nowadays. Thisis in line with the increasing interest in valorising the vegetable waste (fruits and vegetables account for 45% of global food waste in 2026), including the one which does not meet high aesthetic marketing standards, as well as the growing demand for natural products (e.g., natural flavours) over artificial ones. This thesis therefore explores innovative approaches to increase the value of discarded plant-derived materials through green extraction techniques, vegetable oil aromatisation and enrichment, and fungal biotransformation processes. Indeed, this wide project emerged from the collaboration between the University of Camerino and New Flavours, a company specialising in the production of natural flavours. The first part of the presented results (Project 1) focuses on the comprehensive characterization of extracts obtained from discarded chili peppers through different extraction technologies, including Soxhlet extraction, Ultrasound-Assisted Extraction (UAE), and Supercritical CO2 Extraction (SFE), combined with green ethanolic and hydroalcoholic solvents. The added value of natural flavourings was significant: UAE was the fastest technique for obtaining extracts rich in vitamin C (up to 1.27 mg/g of dry extract) and antioxidant compounds. Conversely, SFE was the most effective technique for obtaining carotenoid – rich extracts, with the highest pungency, total polyphenolic and alpha- tocopherol contents, while also retaining most of the fragrances of the original chili matrix. The second part of the wide project reported in this thesis (Project 2) investigates the valorization of discarded Calabrian chili peppers and PDO Genoese basil leaves as flavouring matrices for commercial olive oil and grape seed oil, which were used as green solvents for UAE-based aromatisation. The resulting oils were evaluated in terms of quality parameters and the composition of their bioactive and volatile compounds. Subsequently, providing information about this beneficial enrichment process significantly improved consumer responses, with flavour liking and purchase intention increasing to 20.37% for grape seed oil-based samples, even if 77.14% of participants were unfamiliar with this vegetable oil, for instance. The third part of the reported results (Project 3) focuses on the optimization of lemon peel aromatization in refined olive or grape seed oil, using wasted Sorrento lemon peels, a Box–Behnken experimental design towards optimized extraction conditions in terms of oxidative stability, bioactive and volatile compounds. This approach provides a sustainable and scalable method to convert multiple low-value by-products into highest-value flavoured oils. Finally, an exploratory study (Project 4) investigates the potential of mango peels or discarded basil leaves as substrates for the generation of novel aromas through fermentation with a basidiomycete (i.e., Laetiporus montanus). The produced volatile compounds were analyzed through GC-MS-O, identifying promising and more pleasant odorous compounds with new fresh-minty, floral, sweetish, fruity nuances, differently from the unfermented original material. Besides, production could be scalable. In conclusion, natural flavouring extracts from discarded matrices or flavoured products were obtained through sustainable approaches, towards enhanced sensorial profiles and relevant bioactive compound enrichments, in line with the original aims of the wide project.