Strategies for Enhancing Expansion in Starch-Based Microcellular Foams Produced by Supercritical Fluid Extrusion

Supercritical fluid extrusion is usually a recent mixer extruder technical development for production of extended starch-based foams where formation of a microcellular structure is simply achieved by injection of supercritical CO2 in to the melt. The excessive successful diffusivity of CO2 in the porous matrix favors get away of the gas to the environment, reducing the amount available for diffusion in to the bubbles, posing a significant challenge thus. This review utilized two approaches to address this issue: increasing the nucleation rate and thus the final bubble density in the foam, and reducing the melt heat range. The former was achieved by decreasing the nozzle diameter to be able to achieve an increased pressure drop rate as the starch-CO2 melt flows through the nozzle. The next methodology was evaluated by presenting a cooling zone before the access of the melt into the nozzle. Bubble density increased more than when the nozzle radius was decreased from 3 fourfold.00 to 1 1.50 mm. An increased bubble density resulted in a greater resistance or barrier to diffusion of CO2 to the surroundings, and increased expansion ratio by as very much as 160%. Cooling of the melt led to a decrease in diffusion coefficient of CO2 in the starch melt, and thus reduced CO2 reduction to the environment. The expansion ratio increased by 34% because the melt temp reduced from 60 to 40°C. The above-mentioned strategies can be useful in controlling and improving expansion, which determines the textural attributes of the expanded food product ultimately.

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