Formulation and characterisation of protein-rich custard-like soft food intended for the elderly with swallowing difficulties

Swallowing problem is prevalent in the elderly which requires high intake of protein through soft foods. This study developed protein-rich custard-type soft foods for elderly with dysphagia and evaluated the impact of milk protein content (3.9 % to 8.9 %) on the physicochemical properties of the formulations. Kappa-carrageenan and inulin were incorporated as a thickener and dietary fibre. Textural and rheological characteristics including viscosity, hardness, and deformation resistance, were measured using texture analyser and rheometer to compare with international standards for swallowing-friendly foods. The microstructure was visualised by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), which influenced custard's ease of swallowing. Results showed that the increasing kappa-carrageenan, inulin, and milk protein content increased the gel strength, viscosity, resistance to deformation and storage stability. The swallowability of the formulations was tested using the International Dysphagia Diet Standardization Initiative's (IDDSI) fork pressure and spoon tilt tests, classifying the products as Level 6 – Soft & Bite-Sized Foods. The instrumental IDDSI fork pressure test generated reliable data to optimise formulations. The custard formulation containing 0.7 % kappa-carrageenan, 2.4 % inulin, and 8.9 % milk protein was found to be optimal. This work provides insights for developing high-protein soft foods for the elderly with swallowing difficulties.