The suitability of psyllium husk mucilage as an alternate fibre-based substitute of sodium alginate in raft-forming antacids: A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Abstract

GERD (gastroesophageal reflux disease) is a disorder that affects a significant portion of the world’s population. The most common commercial medication used to relieve symptoms is Gaviscon, a sodium alginate-based raft-forming antacid. Gaviscon and similar medications help to reduce GERD symptoms by creating a physical barrier made from a gel raft, which sits atop the stomach's contents, blocking the backflow of stomach contents into the oesophagus. Market research shows an increased interest in creating more sustainable, natural, and functional alternatives in the pharmaceutical industry. Psyllium husk mucilage is one of these potential alternatives, a natural, soluble fibre with gel-forming and prebiotic properties. This study aimed to assess the suitability of psyllium husk mucilage as a natural fibre/polysaccharide to replace sodium alginate in raft-forming antacids. The combined effect of psyllium husk mucilage with additives, such as microcrystalline cellulose and calcium caseinate, was explored to understand the most effective combination for meeting standards of raft stability and efficacy for medicinal use. The investigation included raft formation assays and analytical techniques such as rheology, texture profile analysis, FTIR analysis, and particle size distribution. The control sample was a recreation of the well-known Gaviscon, a combination of sodium alginate, calcium carbonate and sodium bicarbonate. The raft-forming pre-trial found 2% psyllium husk to be the ideal concentration. The observational raft-forming analysis found psyllium rafts containing calcium caseinate to be less turbid and more cohesive than other psyllium samples, most similar to the control. FTIR analysis found evidence of calcium-mediated crosslinking in the control, but not in psyllium-based samples, which instead demonstrated greater hydration. Rheological analysis found the control to be superior in its ability to resist deformation under both increasing shear strain and constant shear over time, indicating frequency-independent elasticity. Psyllium samples, in comparison, all demonstrated the be significantly superior (p < 0.05) to all psyllium samples in all categories of firmness, consistency, cohesiveness and work of cohesion. Particle size distribution result indicated a large, monomodal particle population in the control due to homogeneous crosslinking structures, whereas psyllium samples presented bimodal distributions with heterogeneous particle sizes. Findings are expected to inform and support the development of novel functional antacid products using natural fibres. Future research should focus on incorporating controlled ionic crosslinking strategies or alternative crosslinking agents to enhance the mechanical strength and durability of psyllium-based raft systems for gastric applications.