Valorization of unpopped Foxnut starch in stabilizing Pickering emulsion using OSA modification

Starch was isolated from unpopped fox nut (Euryale ferox) and the effect of octenyl succinic anhydride (OSA) concentration (1, 2 and 3%) on physiochemical, functional, pasting, rheological and structural properties of was examined. The amylose content of native starch (22.9%) was higher than the modified starch (13.7%) for 3% OSA treatment. The water absorption capacity (1.29-0.9 g/g) significantly reduced, while oil absorption capacity (0.15-0.61 g/g), solubility (5-48%) and swelling power (2.77-13.60 g/g) increased after modification. The modification also altered the pasting properties by increasing the peak viscosity and reducing the pasting temperature. The cooked gel of all starch showed shear-thinning flow behavior and dynamic rheology confirmed reduction in storage and loss modulus after modification. Modified starch became rougher and irregular in shape and showed type A pattern as confirmed by SEM and XRD. Soybean oil-in-water Pickering emulsions were prepared by ultrasonication (US, 30 and 40% amplitude for 2 and 4 min) using starch as particle stabilizer and major factors influencing emulsion stability were investigated. Pickering emulsions prepared at 30 and 40% amplitude for 4 min US, produced the smaller droplet size, stable up to 15 days. However, all OSA modified starches were able to separate the oil and water even after the size of droplets increased with storage. The microstructure of the Pickering emulsions confirmed that starch particles aggregated in a tightly packed layer at the oil-water interface.

Automated summary

The research investigated the impact of octenyl succinic anhydride (OSA) concentration on the physicochemical, functional, pasting, rheological, and structural properties of starch isolated from unpopped fox nut. The modification significantly affected attributes such as water absorption capacity, oil absorption capacity, solubility, swelling power, and pasting properties. In addition, Pickering emulsions prepared using starch as a particle stabilizer exhibited stability and smaller droplet sizes, showing potential for use in food applications.