Development and characterisation of fibre-based dual-network raft system for gastro-oesophageal reflux disease : A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Abstract

Gastro-oesophageal reflux disease (GERD) is a highly prevalent chronic gastrointestinal disorder in which post-prandial reflux is increasingly recognised as being driven by physical and geometric factors within the stomach rather than acid secretion alone. Raft-forming systems offer a non-systemic therapeutic strategy by forming a buoyant, cohesive gel that caps the post-prandial acid pocket and limits oesophageal exposure. However, commercially available raft formulations are dominated by alginate-based systems, which are prone to heterogeneous gelation, brittleness, and erosion under strongly acidic gastric conditions. This study aimed to develop and characterise a fibre-based composite dual-network raft-forming system using psyllium husk and low-methoxy (LM) pectin, and to evaluate the role of calcium caseinate (CaCN) and microcrystalline cellulose (MCC) as structural reinforcement agents under simulated gastric conditions. Raft formulations were prepared at a fixed total polymer concentration of 4% (w/w) and evaluated using a combination of qualitative screening and quantitative physicochemical characterisation, including visual observation, texture profile analysis, oscillatory rheology, ATR-FTIR spectroscopy and particle size distribution. A sodium alginate formulation was used as the control system. All fibre-based formulations formed floating rafts rapidly in simulated gastric fluid (pH 1.2, 37 °C) and demonstrated improved macroscopic cohesion and persistence compared to the alginate control. Texture analysis indicated that rafts prepared from alginate possessed higher values of firmness and consistency, implying rigid gel formation, while mechanically weaker but coherent systems were generated from fibre formulations. Oscillatory rheological measurements showed elastic-dominant behaviour (G′ > G″) across all formulations, confirming gel-like network formation, while revealing formulation-dependent differences in viscoelastic strength and resistance to strain-induced structural breakdown. FTIR spectroscopy confirmed that raft stabilisation occurred through physical interactions, such as hydrogen bonding and calcium-mediated ionic association, without evidence of covalent chemical modification. Particle size distribution analysis of the formed raft systems demonstrated differences in dispersed structural domains, reflecting formulation-dependent hydration, network development, and structural organisation under simulated gastric conditions. Compared to psyllium-LM pectin systems alone, the inclusion of calcium caseinate contributed to improved raft cohesion and viscoelastic stability, indicating a reinforcing effect of protein–polysaccharide interactions on raft formation and structural integrity under simulated gastric conditions. Overall, this work evidences that psyllium husk-LM pectin composite systems can develop stable, elastic-dominant gastric rafts with mechanical properties fundamentally different from those provided by traditional alginate systems. The combination of hydration-driven fibre networks with calcium-responsive polysaccharides and selected reinforcement agents represents a very promising design approach for next-generation, food-grade raft-forming systems. These results extend current structure-function knowledge of gastric raft materials and provide a sound basis for subsequent translational development of fibre-based, non-systemic methods for the management of post-prandial reflux.