Studio dell'impatto delle tecnologie sostenibili sui composti bioattivi alimentari naturali e valorizzazione dei sottoprodotti alimentari come ingredienti funzionali

This PhD thesis focuses on designing novel and environmentally friendly extraction processes to recover natural antioxidants (i.e., polyphenols) from food by-products to enhance the oxidative stability of oils and emulsions. Lipid oxidation causes undesirable changes in the chemical and sensory properties of edible oils, turning them into food waste. This research promotes sustainability first by transforming by-products into valuable compounds and second by reducing waste generation through the inhibition of lipid oxidation. Following a comprehensive literature review (Chapter 2) to identify the most promising sustainable extraction processes, the gained knowledge was applied to improve the quality of phenolic extracts, with a focus on the effect of the extraction process on the type and content of phenolic compounds, antioxidant activity, chlorophyll content, and color. As the presence of chlorophylls can limit the use of phenolic extracts in food products due to undesirable coloration, in Chapter 3, the co-extraction of chlorophylls during the recovery of polyphenols from sugar beet leaves (SBLs) was minimized by adjusting the extraction conditions. In Chapter 4, a UV-A post-treatment was utilized to decolorize the chlorophyll-containing phenolic extracts with a maintained antioxidant activity in oil systems. This treatment converted bound polyphenols to their free form. The obtained extracts were proven to be suitable substitutes for butylated hydroxytoluene (BHT), a synthetic antioxidant, as supported by their comparable antioxidant activity in the oil systems. Chapters 5 and 6 explored the impact of an acid hydrolysis post-treatment on the antioxidant activity of phenolic extracts. This post-treatment converted glycosidic polyphenols to their aglycone form, enhancing the antioxidant activity of the extract. At high concentrations, acid-hydrolyzed extracts of SBLs exhibited prooxidant behavior in soybean oil-in-water emulsion with a shorter lag phase, while the extracts of parsley acid hydrolyzed under the same condition improved the oxidative stability of the emulsion significantly even at higher concentrations. This finding shows the robust impact of phenolic compound type, instead of content, on the antioxidant activity. Overall, this research successfully developed effective natural antioxidants from plant sources, contributing to sustainable food systems. However, it is essential for future research to apply these extraction processes on an industrial scale and to confirm the safety of these extracts for human consumption.