Functionalizing asparagus dietary fibres via mechanical processing

Samenvatting

This thesis reports on the potential of agro-food by-products, specifically dietary fibre-rich materials, to be processed into dietary fibre concentrates (DFC) with enhanced techno-functional properties. Dietary fibre, abundant in various plant by-products, offers significant health benefits, including lowering the glycemic index, improving gastrointestinal motility, and reducing the risks of obesity, cardiovascular diseases, and diabetes. Despite these benefits, fibre intake worldwide remains below recommended levels. This study focused on mechanical processing techniques to produce DFC from asparagus pomace, enhancing their techno-functional properties while maintaining environmental sustainability.---The first chapter evaluated colloid milling as a wet milling process to enhance the techno-functional properties of asparagus DFC compared to conventional pin milling. The results showed significant improvements in swelling capacity, water holding capacity, and emulsifying activity of asparagus DFC after intensive colloid milling, attributed to the formation of a three-dimensional network of highly branched micro-fibres in suspension. Extending this investigation to DFCs derived from six different plant sources, the second chapter showed that the techno-functional potential of DFCs varies significantly depending on the raw material, with asparagus and orange peel showing notable improvements after colloid milling. These enhanced properties were linked to changes in particle morphology, particularly particle elongation.---In another more application-focused study in Chapter 3, the use of asparagus DFC in high internal phase O/W emulsions for 3D food printing was assessed. Increasing the concentration of asparagus fibre improved the 3D printing performance of the emulsions due to enhanced rheological properties, demonstrating that DFC could be used as a functional ingredient to fortify the printability of edible 3D-printed inks. Furthermore, the influence of dietary fibres from asparagus and citrus on lipid digestion in high internal phase emulsions was examined using an in vitro digestion model. It was found that the type of emulsifier (whey protein vs. Tween 20) significantly influenced the effect of fibres on lipid digestion, with citrus fibre having a more pronounced effect in enhancing the initial lipid digestion rate and total lipid digestibility in whey protein-stabilized emulsions.---The final chapter provides a comprehensive discussion of the findings, comparing various mechanical techniques for processing DFCs and assessing their feasibility for industrial production. It emphasizes the importance of the role of water during fibre processing and the challenges for more sustainable processing of DFCs. Additionally, potential applications of DFCs for food manufacturing are discussed, along with future research directions, such as exploring bioactive compounds in DFCs, the colour changes during processing, and the further use of DFCs in non-food materials.---This work supports the increasing demand for sustainable food systems by exploring ways to reduce food waste and repurpose by-products. The application of DFCs in functional foods and materials demonstrates potential benefits for both health and environmental sustainability, aligning with current societal efforts to promote circular economies and healthier lifestyles. Overall, the outcome of this research supports innovation in food production, while also addressing pressing global challenges related to sustainability and resource utilization.