Sviluppo di bioaerogels come ingredienti chiave nello sviluppo di alimenti funzionali per promuovere la salute attraverso la dieta

Developing new ingredients is a topic of great interest in the agri-food sector, as they can offer new solutions to the growing challenges that this sector is facing, such as the need to guarantee the well-being of the global population and environmental sustainability. Aerogels, materials with unique physical properties characterised by high porosity, low density and high internal surface area, have the potential to meet these needs. However, studies concerning the development of such materials are mainly focused on applications in sectors far from the food one, using precursors and processes that make aerogels unsuitable for human consumption. The aim of this PhD thesis was thus to develop aerogels using food-grade precursors and processes, studying their potential applicability as innovative food ingredients. To this aim, the PhD project was divided into four parts. In the first part, the potentialities of aerogels as ingredients for the development of analogues of protein-rich tissues (e.g., meat) were studied. To this aim, monolithic aerogels based on cellulose and whey proteins were produced and characterised. Whey protein aerogels were then exploited for the physical entrapment of spirulin cells. The latter were effectively incorporated within the aerogels, begetting a protein-based cellular solid; at the same time, the aerogelation process allowed for the significant removal of the typical flavour and colour of spirulina, which undermine its use in foods. The second part was focused on the evaluation of whey protein aerogels as ingredients able to load and steer the release of bioactive molecules. To this end, during a short-term scientific mission at Hamburg University of Technology, aerogels in the form of beads were loaded with vanillin, selected as a representative molecule with aroma and health properties. While vanillin is easily lost during food processing, its impregnation into aerogels allowed for a controlled release in aqueous media, which was found to be further modulated by the application of a hydrophobic surface layer based on ethylcellulose onto the aerogel particles. In the third part, aerogels were exploited to absorb and structure liquid oil to obtain innovative fat replacers. Powders of aerogel particles smaller than 50 μm were produced from both proteins and plant tissues. Upon interaction with oil, these powders resulted in fat replacers with rheological properties comparable to those of hard fats. In vitro digestibility tests showed that this approach is able to modulate both protein and oil digestibility. The aerogel oil-structuring capacity was also validated in the preparation of low-saturated fat cocoa spreads. Given the complex behaviour of aerogels in the presence of oil, the fourth part of the thesis, carried out as a visiting PhD student at Toronto Metropolitan University, was dedicated to a fundamental understanding of the interactions of aerogel powders with food solvents. This approach revealed the chemical-physical mechanisms driving the capacity of aerogels to interact with oil and/or water. By the aware management of these mechanisms, the oil-structuring capacity of aerogels was further improved by adding an adequate amount of water, which resulted in the formation of capillary suspensions. The fifth and final part of this PhD thesis was dedicated to the evaluation of the upscaling potential of aerogel production, to determine the readiness of this technology for entering the food ingredient market. This activity, partly carried out at Keey Aerogel Company during a short-term scientific mission, demonstrated that the production of aerogels is scalable and that the selling price of aerogel-based ingredients would be in line with that of functional ingredients currently available on the market.

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