Rheological Properties and Textural Attributes of Cooked Brown and White Rice During Gastric Digestion in Vivo

Physical properties of gastric chyme from cooked brown and white rice meals were determined over an 8 h postprandial period in the proximal and distal stomach regions of pigs. Rice gastric chyme behaved as a Herschel-Bulkely fluid; the shear stress values were significantly different as a result of rice type, stomach region, and digestion time (p < 0.001). Shear stress values were greater in brown rice compared to white rice, and consistently greater in the proximal region compared to the distal region. The gastric chyme behaved as a weak gel, with G' greater than G". Rice grain firmness and hardness showed significant differences as a result of rice type, stomach region, and digestion time (p < 0.001). Rice grains decreased in firmness and hardness over the 8 h postprandial period. The median particle diameter was significantly different between stomach regions; the distal region had a smaller median particle diameter compared to the proximal region for both rice types. Our results support the traditional functional description of the stomach, with the main location of breakdown being the distal region. However, our results also suggest that food is not only broken down and immediately emptied; there is a mixing that will occur between the proximal and distal regions, although the full extent of the meal mixing still needs to be quantified. These results help to better understand the physical breakdown processes that food undergoes during gastric digestion, allowing for future optimization of food properties to control their digestive characteristics.