There has been a great deal of interest in adequately controlling digestibility of the ingested foods in the human digestive tract. Gastric digestion plays an important role in the process of food digestion, being strongly affected by both physical and chemical digestion processes. Over the last decade, the importance of in vitro gastric digestion models has been increasing, which is mainly attributed to superior applicability to various conditions as well as better reproducibility of experimental data. The authors developed a human gastric digestion simulator (GDS) that simplifies the antrum geometry and function. The major advantages of the GDS include quantitatively simulated gastric peristalsis and direct observation of the digestion behaviors of food particles in the gastric contents. In this review, we provide a brief overview of the findings obtained through a series of studies using the GDS. First, the current progress of in vitro gastric digestion studies is described. We next introduce the history and development of the GDS and findings on the digestion characteristics of representative foods and food models using the GDS. Further improvement of the GDS could potentially make it a useful tool for designing novel functional foods for which digestibility and release of nutrients and bioactives are well controlled.

The aim of this study was to evaluate the anti-diabetic potential of acetic acid-free red vinegar (RV) containing a candidate, 6-O-caffeoylsophorose (CS), in spontaneously diabetic Torii (SDT) rats. In accordance with administration protocols, ingestion by SDT began between the ages of 11 and 16 weeks which corresponded to normal and pre-diabetic stages, respectively. Daily intake of RV (4.3mg/kg/day) led to a significant reduction in fasting blood glucose level (BGL) in 28-wk SDT (fasting BGL: control, 133.8±12.8mg/mL; RV, 98.5±19.8mg/mL), while no anti-diabetic effect was obtained in SDT fed from 27 weeks of age. These results demonstrated that RV has physiological potential to suppress promotion of diabetes, but not to improve the developed of onset.

To elucidate the mechanism of flavor release from water-in-oil (W/O) emulsions containing a semi-solid fat, we analyzed the release of aroma components using a model emulsion with 57 volatiles. This methodology utilized headspace solid-phase microextraction-gas chromatography/mass spectrometry and evaluation of water droplet distribution, solid fat contents, and interface elastic modulus. The ratio of release of unsaturated aldehydes and esters from an unsaturated monoglyceride emulsion to that from a saturated monoglyceride emulsion increased with the increasing value of LogP_ow. For volatile fatty acids, the rate was relatively lower and did not depend on the value of LogP_ow. Furthermore, the release of lactones from the unsaturated monoglyceride emulsion was greater than that from the saturated monoglyceride emulsion. We conclude that lactone release was influenced by the interaction of carbon chains between lactones and the monoglyceride emulsions. Additionally, the carbon chain of saturated fatty acids on the interface inhibited volatile fatty acid access to the interface as a result of steric hindrance. Finally, the release of alcohols and esters was assumed to be affected by a combination of these effects.

The kuchidoke of rice crackers refers to their “melt-in-the-mouth” sensation, which includes the “absorption of saliva” and the feeling of a “bolus residue in the mouth”. The saliva absorption rate of the bolus and the mass fraction of bolus particles (≤53µm) were positively correlated with the kuchidoke score. The viscosities of an artificial bolus were reduced by the addition of α-amylase, and the time required for reducing the initial viscosity by half was negatively correlated with the kuchidoke score. Additionally, the thickness of the rice cracker’s cellular structure was negatively correlated with the kuchidoke score, while the size of the cellular structure was positively correlated with the kuchidoke score. Therefore, rice crackers with a high kuchidoke score tend to be thinner with a larger cellular structure. This leads to a higher saliva absorption rate and a finer bolus residue, resulting in more rapid enzymatic digestion during mastication.

To ensure food safety, tests for detecting foodborne pathogens at various stages of the food manufacturing process, including production; storage; and distribution, need to be shorter and more sensitive. To that end, an automated device was developed for concentrating E.coli in food suspension samples using dead-end hollow fiber microfiltration, which reliably produced retentates that contained added E. coli at high concentrations in the hollow fiber. We used the device for a variety of food suspension samples that were conventionally prepared. Food used included cabbage leaves, Japanese pickles, seafood, meat, seeds and other processed foods. We applied suspension samples spiked with E. coli to the prototype concentrator. E.coli concentrated in the hollow fiber was recovered by backflush and measured by the plate method. Using the device, we could easily concentrate E. coli that was added to 20-100mL suspension samples of sterilized cabbage by 9.55 to 47 times and recover approximately 90% of it as viable cell counts. For these spikes between 0.5 and 2.6×10⁴CFU/mL in 100mL samples, excellent recovery rates were obtained. For other food samples, the concentration factor was 4.23 to 9.98 and the recovery rate was over 82.3%. The variability in recovery was also small.