Unlocking the potential of faba bean blanching water: From waste to ingredient - Insights into composition, cholesterol-lowering property, and bakery application : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Abstract

The rising demand for sustainable food systems has driven interest in upcycling byproducts from legume processing. This thesis examines the potential of faba bean blanching water (FBBW), a byproduct commonly wasted in faba bean processing, as a source of bioactive compounds and its use in food production. The aims were to investigate the nutritional and bioactive composition of FBBW, evaluate its cholesterol-lowering properties, and assess its efficacy as an ingredient in baked goods. The research involved a compositional analysis of FBBW, including the quantification of carbohydrates, proteins, peptides, amino acids, phytochemicals, and minerals. In vitro assays were performed to test the inhibitory effects of FBBW on HMG-CoA reductase, as well as its impact on cholesterol micellization. Finally, FBBW was incorporated into sponge cakes to evaluate its effects on texture, sensory attributes, and consumer acceptance. The results indicated that bioactive compounds are abundant in FBBW dry matter, including peptides, saponins, and phenolic compounds, all of which contribute to its specific health-promoting attributes. Notably, the peptides in FBBW significantly inhibited HMG-CoA reductase, a key enzyme in cholesterol production, with the inhibitory activity at 64 – 70%. This enzyme inhibition is important for lowering cholesterol levels because it reduces the rate of cholesterol synthesis in the liver. Saponins, which were the predominant component of FBBW, also reduced cholesterol by decreasing cholesterol micellization, a mechanism required for cholesterol absorption in the gut, with the inhibition at 48 – 53%. Saponins significantly reduced cholesterol’s bioavailability, restricting its absorption and contributing to a decrease in overall cholesterol levels. This dual-action mechanism of FBBW shows that it has the potential to effectively manage cholesterol levels while also improving cardiovascular health. Furthermore, FBBW was investigated for its potential as a functional element in food applications, particularly baking products like sponge cakes. When FBBW was added to sponge cake formulations, it improved physicochemical aspects, including texture and adhesiveness. Textural improvements were observed as enhanced softness and cohesion, resulting in a more pleasant mouthfeel. Textural study utilizing instrumental analysis supported these findings, demonstrating that cakes containing FBBW had better adhesiveness (P < 0.05) and moisture retention (P < 0.05). Importantly, consumer sensory evaluations confirmed these instrumental findings, with desirable acceptance ratings for overall satisfaction (P > 0.05) and similar flavour and textural acceptance. Thus FBBW not only has potential for better health outcomes but also provides useful functional qualitites as a food ingredient. These findings highlight the adaptability of FBBW as a sustainable, functional ingredient that may promote health and reduces food waste.