1072Effect of type of soy-based foods on their in vitro digestibility using a Gastric Digestion Simulator
1Institute of Food Research, National Food and Agriculture Research Organization, Tsukuba, Ibaraki, Japan
2School of Integrative and Global Majors, University of Tsukuba, Tsukuba, Ibaraki, Japan
3Faculty of Health and Medical Science, Teikyo Heisei University, Toshima, Tokyo, Japan
4Graduate School of Science and Technology, University of Tsukuba, Tsukuba, Ibaraki, Japan
5Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo,Tokyo, Japan
6Faculty of Human Life, Jumonji University, Niiza, Saitama, Japan
Various soy-based foods are being consumed in East Asia. Their texture, microstructure, and digestibility can be influenced by food processing methods. The gastric digestion simulator (GDS), which is equipped with a quantitatively simulated human gastric peristalsis, enables direct observation and analysis of the digestion behavior of food particles. The purpose of this study was to investigate the influence of processing methods on the in vitro gastric digestibility of soy-based foods using GDS.
Sliken tofu, koya-dofu, okara, and boiled soybeans were purchased from local markets. Silken tofu and koya-dofu were cut into 5 mm cubes. The okara was rolled into balls with diameters of 10 mm. Each boiled soybean sample was cut in half. Eighty grams of soy-based food samples were used for in vitro digestion experiments. Each food sample was placed in a beaker containing 30 mL of simulated salivary fluid (SSF, pH 7.0) for 2 min. Afterwards, the mixture was introduced into the GDS vessel containing 240 mL of simulated gastric fluid (SGF, pH 1.3). The GDS experiments with simulated gastric peristalsis (1.5 cycles/min) and 0.1 M HCl addition (45 mL in total) were performed at 37 °C for 3 h. Proteins in the gastric contents sampled during the GDS experiment were analyzed using HPLC.
During the 180 min of the GDS experiments, the silken tofu particles quickly disintegrated owing to their soft and fragile texture. Koya-dofu particles with a sponge-like texture did not disintegrate as quickly as silken tofu particles. SGF was considered to penetrate the Koya-dofu particles easily and cause sudden disintegration after 120 min. As okara has a very crumbly texture, the okara bolus quickly dispersed in the GDS vessel without the disintegration of okara particles. For boiled soybean particles, most of the cotyledons disintegrated during the first 30 min, whereas the outer shell remained undigested after 180 min. The HPLC results demonstrated that the protein digestibility of the gastric contents sampled during the GDS experiments was affected by the type of soy-based food.
The use of our GDS demonstrated how the type of soy-based food affects the physical and chemical gastric digestion.