Development and characterization of soy protein-based custard-like soft foods for elderly individuals with swallowing difficulties

There is growing interest in developing protein-rich foods for the elderly using plant proteins. The application of soy protein isolate (SPI) as a model protein to create protein-rich, custard-like soft foods presents a unique opportunity for innovative formulations tailored to those within the aging population suffering from swallowing difficulties. This study investigated the physicochemical and textural properties of custard-type soft food formulations developed using SPI for dysphagic elderly individuals, with the goal of achieving characteristics similar to those of optimal milk protein-based counterparts. The protein content in the SPI-based custards varied from 8.9 % to 13.9 % and the milk-protein based custards had 8.9 % protein content. There was a substantial difference in textural, rheological and creep resistance and other properties between SPI and milk protein-based formulations. The SPI-based custards also had lower water-holding capacity, looser structure, and higher level of insoluble protein aggregates. The SPI-based custards imparted a more spreadable mouthfeel suitable for the aging population. The custards containing 13.9 % SPI had higher gel strength, viscosity, texture, and product stability. All of these custards were classified as Level 6 - Soft & Bite-sized dysphagia diet, based on International Dysphagia Diet Standardisation Initiative (IDDSI) tests. Instrumental IDDSI tests for Level 6 foods corroborated these observations, yielding reliable and consistent data. This research provides insights for developing protein-rich plant-based soft foods intended for the elderly population that have characteristics close to milk protein-based custards and comply with IDSSI criteria.