Drying of sodium alginate using Pressurized Gas eXpanded (PGX) liquid technology

Abstract

Pressurized Gas eXpanded (PGX) liquid technology is a scalable platform technology that simultaneously purifies, micronizes and dries aqueous solutions of biopolymers into fine structured open porous materials with unique morphologies using carbon dioxide (CO2) and ethanol at mild temperatures. The objective of this study was to investigate the effect of several PGX processing parameters on the physicochemical properties of sodium alginate (SA), a water-soluble polysaccharide from brown algae. PGX-processed SA (PGX-SA) had an open porous structure with a delicate network of fibrils, compared to the irregular shaped crystal-like non-porous particles of the raw SA dried using a conventional process. Upon PGX processing, the specific surface area was increased by more than 90 times compared to the raw SA. The use of low concentration (1.0% w/w) of the SA aqueous solution as the feed material and low ethanol flow rate (15 g/min), together with the mass flow rate ratio of 1:3.75:1.25 of aqueous solution:ethanol:CO2 resulted in a specific surface area of 164.5 m2/g of the PGX-SA. The PGX process shows great potential for simultaneously purifying and drying high molecular weight biopolymers into porous morphologies with large specific surface area for bioactive delivery systems in food, cosmetic and pharmaceutical applications.