Comparison of four digestion protocols on the physical characteristics of gastric digesta from cooked couscous using the Human Gastric Simulator.

In vitro digestion is widely employed in food, nutraceutical and pharmaceutical research, and numerous in vitro gastric digestion protocols have been proposed, with a wide range of experimental conditions. Differences in the simulated gastric fluids (pH, mineral content, enzyme type and enzyme activity) of different digestion protocols may alter the results for the digestion of the same meal. This study aimed to investigate how variations in the gastric secretion rate and composition in four in vitro digestion protocols (Infogest Riddet, Infogest Semi-dynamic, UC Davis and United States Pharmacopeia) impacted the physical properties of the emptied gastric digesta. Cooked couscous was used as a model meal and subjected to simulated gastric digestion using a dynamic gastric model, the Human Gastric Simulator (HGS). The digesta were collected from the outlet of the HGS after 15, 30, 60, 90, 120, 150, or 180 min. The gastric emptying of dry matter, pH, rheological properties, and particle size were evaluated. The digestion protocol significantly influenced the solid content and moisture content of the digesta (p < 0.001), particles per gram of dry matter (p < 0.0001), gastric emptying of dry matter (p < 0.003), shear stress at 0.45 s-1 and consistency coefficient (p < 0.0001). The presence of NaHCO3 in the Infogest Riddet and Infogest Semi-dynamic gastric secretions provided an additional buffering effect and increased the digesta pH during gastric digestion. Similarly, the inclusion of mucin in the UC Davis protocol resulted in a higher flow and viscoelastic properties of the emptied digesta. The highest dilution of gastric content in the United States Pharmacopeia (USP) protocol resulted in larger particles emptied from the HGS and the longest gastric emptying half-time of all digestion protocols. These findings provide new insights into the impact of digestion protocols on the digesta properties, which can be beneficial for the design and standardization of in vitro digestion models.

Egg white gel structure determines biochemical digestion with consequences on softening and mechanical disintegration during in vitro gastric digestion.

The aim of this work was to investigate the role of biochemical digestion on softening and disintegration kinetics of pH 5 and pH 9 egg white gel (EWGs) during in vitro gastric digestion. EWG samples (5 mm length cubes) underwent in vitro digestion by incubation in simulated gastric fluid at different time intervals for up to 240 min. The hardness was measured using a Texture Analyser; softening kinetics was fit to the Weibull model. Results revealed that pH 9 EWG had the highest softening halftime (458 ± 86 min), indicating the slowest softening, whereas pH 5 EWG had the lowest softening halftime (197 ± 12 min), indicating the quickest softening. The digested samples were immediately exposed to mechanical forces generated by the human gastric simulator (HGS) for 10 min to investigate the influence of gastric juice on the breakdown behaviour of EWG cubes. The breakdown behaviour of the disintegrated samples was characterized by fitting the cumulative distributions of particle surface areas to a mixed Weibull function (R2 > 0.99). The weight of fine particles (α) showed that regardless of gastric juice diffusion, the pH 5 EWG (α = 0.22 ± 0.03) disintegrated into more fine particles than those resulting from pH 9 EWG disintegration (α = 0.07 ± 0.02). As expected, the diffusion of gastric juice enhanced erosion of the EWG particles into fine particles. Result obtained from the particle surface area distribution is in good agreement with the softening kinetics of EWGs during simulated in vitro gastric phase.

Role of biochemical and mechanical disintegration on ß-carotene release from steamed and fried sweet potatoes during in vitro gastric digestion.

The role of biochemical and mechanical disintegration on ß-carotene release from steamed sweet potatoes (SSP) and fried sweet potatoes (FSP) during in vitro gastric digestion was investigated. Results revealed that, in the absence of mechanical forces generated by the stomach, biochemical digestion did not have a great effect on the breakdown of cell walls within the sweet potato food matrix and the release of ß-carotene was similar in both SSP and FSP. Cell wall in the plant-food may act as a physical 'barrier' towards the action of gastric juice and to the release of nutrients into the gastric digesta. However, FSP underwent quicker softening and collapse during in vitro gastric digestion compared to the compact and denser structure of SSP. This may explain the faster cell wall breakdown and subsequent ß-carotene release from FSP cellular matrix than SSP when mechanical forces are applied as in the human gastric simulator (HGS).

Gastric digestion in vivo and in vitro: how the structural aspects of food influence the digestion process.

Food digestion is crucial for sustaining life. Although it has been examined for more than 300 years, the basic principles are not entirely understood. Antral motility is well characterized, and current research is seeking to determine flow patterns generated by the stomach's peristaltic contractions. The rate of gastric emptying for solid and liquid meals has been determined according to variations in meal composition, energy content, and subject characteristics. The glycemic response has been measured for many carbohydrate foods and is altered by factors such as amount of processing, particle size, and starch structure. Similarly, ileal starch digestibility is altered by food and starch properties. Even though many foods have been studied according to their glycemic response, starch digestibility, and in vitro digestion kinetics, the rate-determining processes and underlying mechanisms remain to be established. The link between food properties, digestion processes, and final health outcomes must be strengthened for functional food optimization.