A near real dynamic in vitro human stomach (new DIVHS) system has recently been advanced in this study, based on the previous rope-driven in vitro human stomach model (RD-IV-HSM).

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Previously, a dynamic in vitro rat stomach system (DIVRS-I) designed based on the principles of morphological bionics was reported. The digestibilities of casein powder and raw rice particles were found to be lower than those in vivo due to perhaps the less efficient compression performance and lower mixing efficiency. In this study, a 2nd version of the rat stomach system (DIVRS-II) with an additional rolling extrusion type motility on the wall of the soft-elastic silicone rat stomach model is introduced. The DIVRS-II was then tested by comparing the digestive behaviors of the casein powder suspensions and raw rice particles with those previously published data obtained from the in vivo test on living rats, the DIVRS-I, and the stirred tank reactor at its optimum stirring speed. The results have indicated that although the digestibilities of the casein powder and raw rice particles in the DIVRS-II are still lower than the average results obtained from in vivo, they are significantly improved by about 50% and 32% at the end of digestion compared with that in the DIVRS-I, respectively. The work has demonstrated that the powerful rolling extrusion is highly effective and has contributed to the significant improvement of digestibility as shown here. In addition, the digestibility presented in the DIVRS-II was found already higher than that tested in the STR at its optimum speed, indicating the high potential of the soft-elastic stomach under the influence of the "rolling and squeezing" for more realistic investigation of food digestion.

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Previously, we have prepared a version of the dynamic in vitro rat stomach system (DIVRS-II or Biomimic Rat II). It was constructed and tested by showing similar digestive behaviors with those occurred in vivo. In the present work, a 3D-printed plastic mold was employed to create highly repeatable silicone rat stomach model. It has been seen to have shortened the time to handcraft a model like that used in DIVRS-II. The maximum mechanical force of the current stomach model generated by rolling extrusion is found to be more stable probably due to the more uniform wall thickness of the new model. Then the effects of the simulated gastric secretion patterns and contraction frequency of the system on the in vitro digestibility of casein powder suspensions were investigated. The results have shown that the location of the gastric secretion injection has an impact on experimental digestibility. The position of rolling-extrusion area, established at the central part of glandular portion (stomach B), displayed the highest digestibility compared to that at the other locations. Furthermore, the extent of digestion was positively correlated with the contraction frequency of the model stomach system, with the maximum frequency of 12cpm giving the highest digestibility. This highest digestibility is almost the same as the average value found in vivo. The better digestive performance produced by optimizing the gastric secretion pattern and contraction frequency may be both resulted from the improved mixing efficiency of the food matrix with digestive juice. This study shows that it is possible to achieve what in vivo in a simulated digestion device, which may be used for future food and nutrition studies in vitro.