Effect of various physical modifications of pea protein isolate (PPI) on 3D printing behavior and dysphagia properties of strawberry-PPI gels

With an increase in elder population, the need for dysphagia diets has increased because older adults develop chewing and swallowing disorders due to reduced physiological functioning. 3D printing can design safe dysphagia diets with desirable textures and attractive appearances through various modifications of the printing ink ingredients. In this study, various physical modifications including heating, microwave and ultrasound were used to improve the gelation of pea protein isolate (PPI), which was then mixed with strawberry powder at different ratios (18, 20 and 22%) for the formulation of 3D printing inks to develop a dysphagia diet. Results showed that physical modifications improved the 3D printing accuracy and self-supporting ability of strawberry-PPI gels, especially for the microwave and heating modifications. Further studies revealed that the physical modifications improved the rheological and textural properties of strawberry-PPI gels through the alteration in the secondary and tertiary structure of PPI. The microstructural results of the strawberry-PPI gels showed that the physical modifications resulted in the formation of large protein aggregates, which disrupted the smooth globular structure of the PPI and facilitated the formation of a denser structure, allowing the 3D printed product to exhibit good structural stability and sharper line resolution. According to the test results of the International Dysphagia Diet Standardization Initiative (IDDSI), strawberry-PPI gels with a modified PPI content of 20% can be classified as a level 4 pureed/extremely thick dysphagia diet. This study provides recommendations for developing 3D printing dysphagia diets with high content of protein using physical modifications.