Exploring the synergistic effects of Grape seed tannin and psyllium husk fiber on the nutritional profile of starch : A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Starch is super versatile complex carbohydrate and a vital macronutrient providing energy to human body by breaking down into sugars. Starch structure and physicochemical properties vary from one source to another due to its interaction in food matrix. Interaction of starch with bioactive compounds such as tannins and fibre alter its textural and physicochemical properties by enhancing the overall nutritional profile. These interactions lead to production of functional foods having low glycaemic index. This study aimed to develop starch-fibre and starch-fibre-tannin complexes using corn starch (5%), grape seed tannins (0.5% by starch weight) and psyllium husk fibre (5% and 10%). The gels were prepared using Rapid Visco Analyser (RVA). Various analyses were conducted to capture the effect of fibre alone and fibre-tannin complex on starch properties. RVA studies showed an increase in the pasting viscosity of starch upon complexation with both fibres alone and the fibre-tannin complex. Starch-iodine binding studies were further conducted to unravel the mechanism of interaction between starch-fibre and starch-fibre-tannin with varied fibre concentrations. Decline in absorbance near 500-540 nm and 540-660 nm was observed in fibre only complex signifying that starch amylose helix was not available for iodine binding. Particle size distribution also showed variation in particle sizes of starch-fibre and starch-fibre-tannin complex in contrast to the control corn starch. Starch textural properties, including firmness, consistency, cohesiveness, and index of viscosity, were significantly affected by the addition of fibre alone and the fibre-tannin complex. Addition of fibre at both 5% and 10 % concentrations increased the firmness and consistency in all treatments compared to corn starch sample. The 5% fibre-tannin complex exhibited the highest antioxidant activity, indicating that tannins had greater ability to reduce Fe3+ ions in the presence of 5% fibre compared to 10% fibre concentrations, both before and after incubation in the FRAP assay. A similar trend was observed in the ABTS assay. Therefore, highlighting the contribution of fibre-tannin complexes in improving the antioxidant ability of starch-based foods. A significant decrease in RDS content and an increase SDS and RS content was observed in all samples compared to control starch during in-vitro starch digestibility, which could be a contributing factor in improving overall nutritional properties of starchy foods.