Evaluation of time-dependent behaviour of pectin-based raft formulation for gastroesophageal reflux disease (GERD): A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of science in Food Innovation at Lincoln University

Abstract

Gastroesophageal reflux disease (GERD) is a frequent gastrointestinal disease which normally leads to the heartburn and chest pain. This condition is primarily caused by the malfunction of the lower oesophagus sphincter through which the acidic stomach contents are expelled into the oesophagus. Traditional medications like proton pump inhibitors and H₂-receptor antagonists reduce stomach acid but fail to prevent reflux. The raft-forming antacids work differently: they produce a floating gel barrier (raft) which rests on the stomach contents and prevents the acid to come in contact with the oesophagus. The sodium alginate is used by most clinical raft systems, which limits the creation of new polymers capable of providing superior raft structure and stability. This paper has considered pectin hybrid raft formulations as possible alternatives to sodium alginate with particular emphasis on the role of composition on raft integrity and mechanical performance under simulated gastric environments. Sodium alginate (C) was compared with four pectin formulation (T1-T4). These were prepared taking calcium carbonate as the source of calcium and the sodium bicarbonate to produce gas. Formulation was strengthened by addition of Calcium caseinate and microcrystalline cellulose (MCC) in some formulations. The formation of the rafts was tested in the presence of simulated gastric fluid (pH 1.2, 37°C) for the duration of 3 hours and measured the Raft surface coverage, the raft thickness, porosity, cohesiveness and persistence. Chemical compatibility and interactions were studied by using ATR-FTIR spectroscopy. Back-extrusion texture analysis was used to determine mechanical properties; firmness, consistency, cohesiveness, and work of cohesion after 30 minutes and 2 hours at 37°C. Oscillatory rheology was used, where the amplitude sweep was performed to identify the linear viscoelastic region, which was followed by frequency sweep to identify the viscoelasticity and deformation resistance, respectively. Overall, pectin formulations formed thinner and yet far more homogeneous and cohesive rafts when compared with the control of alginate. The raft of control thicker, but it was porous, uneven, and had higher bubble content. T4 (pectin + calcium caseinate + MCC) was the best among the pectin formulation. It formed a thick, fine, spread raft containing practically minimum foam and stood integrated and floating for entire 3 hrs. ATR-FTIR results gave a confirmation of a connected polymer network with the calcium interactions having pectin cross-linking and higher interactions between the hybrid blends. The visual observations were consistent with texture and rheology measurements, which showed more elastic and strain-tolerant structure, and less time-dependent relaxation, in particular, of T4. Altogether, pectin-based hybrid rafts, especially of MCC, have high potential as strong, gastro-boundary barriers and have the potential to replace alginate-based antacid rafts.