Enhancement of Digestibility of Casein Powder and Raw Rice Particles in an Improved Dynamic Rat Stomach Model Through an Additional Rolling Mechanism.

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.