Abstract
Three-dimensional (3D) printing enables the precise control of food structure, but its impact on human chewing behaviour and subsequent digestion is not well understood. This study investigated how 3D printing infill density affects textural properties, in vivo chewing time, and in vitro digestibility of protein and starch using a clean-label (additive-free) food model based on a single formulation consisting of wheat flour (WF) and pea protein isolate (PPI) at a 3:1 mass ratio. Increasing the infill densities from 20% to 100% reduced sample porosity, resulting in a significant increase in hardness, cohesiveness, and chewiness as measured by texture profile analysis (TPA). When chewing duration was standardised, no significant differences were observed in the digestion rate constants or the total amounts of protein and starch hydrolysed across different infill densities. However, when chewing duration was not controlled, prolonged chewing of high-infill-density samples enhanced oral breakdown, accelerating the hydrolysis of protein and starch at the early stage of in vitro digestion. Notably, the final bioaccessibility of these macronutrients remained unchanged at the end of digestion, regardless of the infill density or the varying chewing duration. These findings demonstrate the potential of 3D printing to design functional foods with tailored structural and textural properties, thereby modulating digestion kinetics. The preservation of final nutrient bioaccessibility supports the development of texture-modified foods where nutritional adequacy must be maintained, such as for individuals with age-related chewing difficulties. This study extends beyond established structure-texture relationships to directly link 3D-printed food design with human oral processing and macronutrient digestion outcomes.