A novel technique to obtain polysaccharide gels that emulate encapsulation beads with size and shape suitable for rheological, mechanical and other measurements

Abstract

In this work we built up and tested diffusion cells designed to obtain polysaccharide hydrogels by ionotropic gelation. The objective was to obtain gel samples that emulated the wall material of encapsulation beads but, unlike them, have appropriate size and shape for measurement of their structural properties, since these are of paramount importance for the protection, carry and delivery of bioactive compounds. Three polysaccharides widely used for encapsulation and with different gelation mechanisms were tested: kappa/iota-carrageenan (which gels mainly in the presence of K+ ions), and sodium alginate and low methoxyl pectin (which both gel in the presence of Ca2+ ions). The diffusion cells consisted of two nitrocellulose membrane filters supported between three rings made by 3D printing. They were filled with the polysaccharide solution, hermetically tightened with screws and nuts, and submerged into the saline solution. The membrane filters effectively avoided the loss of the polysaccharide solution but allowed the diffusion of the ions (either Ca2+ or K+) into the polysaccharide solutions to promote their gelation. Firm, self-standing gels were obtained, and their rheological and mechanical properties were successfully measured. Samples of different shapes and sizes could be obtained with this technique, for other types of measurement.