3D printed protein/polysaccharide food simulant for dysphagia diet: Impact of cellulose nanocrystals

With the intensified aging population, the demand for dysphagia diet is growing rapidly. The food texture in a dysphagia diet needs to be adjusted to be easy-to-swallow. Thus, most food is transformed in mashed form, which is not visually appealing and reduces patients' appetite, resulting in a malnutrition risk. Three-dimensional (3D) food printing is an efficient technique to fabricate food designs with an attractive appearance and tailored nutritional content. In this work, we developed cellulose nanocrystal (CNC)-based protein/polysaccharide aqueous food inks using two commonly used proteins, namely gelatin B (GB) and whey protein isolate (WPI) for 3D printing, in combination with a polysaccharide frequently found in dysphagia diet, i.e. xanthan gum (XG). To ensure proper printability and shape retention, 2 wt% GB, 8 wt% XG and 8 wt% WPI were selected. Adding 1.0 wt% CNC in GB/XG and 1.5 wt% in WPI/XG improved the viscosity, yield stress and self-supporting ability of the inks, leading to higher shape fidelity right after printing and better shape retention for at least 96 h when stored at 4 °C. Additionally, the thermal stability of GB/XG mixed gels was also largely enhanced by CNC addition, resulting in a high shape retention with ∼90% of its original side area even at 50 °C. As a demonstration, some complex 3D shapes fabricated using both GB/XG/1.0CNC and WPI/XG/1.5CNC inks by single and multi-material DIW printing could also well retain their structures after heating at 50 °C for 5 min. Texture profile can also be tailored by both CNC concentrations and post-processing temperatures. Holding the temperature at 4 °C on the GB/XG/1.5CNC sample turned it from a non-approved classification into a level 5-minced and moist dysphagia diet formulation, according to the International Dysphagia Diet Standardization Initiative (IDDSI) test framework. This work provides rheological and processing guidelines for designing attractive food creations for dysphagic patients using 3D printing.