(659d) Development of a CFD Model for Investigating the Protein Digestion in Human Stomach

The human digestive system can be thought as a series of miniature chemical reactors, where different unit operations occur. Knowledge of the protein digestion in the human stomach is important for evaluating the nutrients bio-accessibility in foods. This research is carried out based on our previous studies of the mixing and emptying of liquid foods^[1] and the physics of “Magenstrasse”^[2]. The purpose is to develop a CFD (computational fluid dynamics) model that can be used to investigate the meat-protein digestion, emptying and dynamics of liquid and solid foods in the human stomach.

We first proposed a 0-D (0-dimensinal) model which can describe the gastric emptying for different types of food. The 0-D model has been validated with experimental data in published papers. Using the 0-D model to determine the emptying rate, the CFD studies by using OpenFOAM were performed. The movements of gastric wall and digestive environment inside the stomach (e.g. acidic effects and enzymatic functions) are taken into account in the CFD model. We characterized cooking effects on the digestion, showing that the digestibility increases with a higher temperature of heating on the meat. The numerical results show that the size of boluses and pH distribution have an important effect on the digestion of protein. Protein digestibility is highly dependent on the transportation of hydrogen ions, which is enhanced by ACWs (antral contraction waves) and TACs (terminal antral contractions). TACs force the gastric contents to flow back into the proximal antrum, enhancing the mixing of gastric contents, see Fig. 1. This study indicates, when masticatory capacity, hydrogen ions secretion, and gastric motions are weakened with advancing age, human’s capability of digesting meat-protein might be reduced considerably. In addition, the study captured a lag phase (period of minimal or absent emptying) with the solid meal emptying, which reflects the milling function of the stomach.

Figure 1: Vortical structures identified by Q=0.01 s^-1 coloured with vertical velocity component at time of 57 s (a) and 58 s (b).

References:

1. Li CY, Jin Y. A CFD model for investigating the dynamics of liquid gastric contents in human-stomach induced by gastric motility. Journal of Food Engineering 2021, 296, 110461.
2. Li CY, Xiao J, Chen XD, Jin Y. Mixing and emptying of gastric contents in human-stomach: A numerical study. Journal of Biomechanics 2021,118, 110293.