Gastric Mixing During Food Digestion: Mechanisms and Applications

Abstract

Gastric mixing is a complex process that is governed by meal properties, such as food buffering capacity, physical properties, and the rate of breakdown as well as physiological factors, such as the rate of gastric secretions, gastric emptying, and gastric motility. Gastric mixing processes have been studied through the use of experimental and computational methods. Gastric mixing impacts the intragastric pH distribution and residence time in the stomach for ingested materials. Development of a fundamental understanding of the advective and diffusion processes and their roles in gastric mixing will be important in furthering our understanding of food breakdown, microbial survival, and drug dissolution during gastric digestion.

Structural breakdown of starch‐based foods during gastric digestion and its link to glycemic response: In vivo and in vitro considerations

“…The time required for the gastric contents to decrease in pH after a meal depends on the mixing between stomach regions, meal composition, meal buffering capacity, and amount of food eaten. This dynamically changing pH provides a suitable pH for the activity of pepsin (pH 2 to 5) and lipase (pH 4 to 6) (Bornhorst, 2017; Gargouri et al., 1989; Minekus et al., 2014; Smith & Morton, 2010a), as well as the remaining activity of salivary α‐amylase (pH 3.5 to 7) from saliva that is incorporated into the food bolus (Freitas et al., 2018; Mackie, 2019) or from the involuntary swallowing of saliva during and after the meal. The remaining salivary α‐amylase activity is important in the digestion of starch‐based foods, as it can prolong the contact time between starch granules in food bolus with the amylolytic enzyme (see Section 5.2 for further discussion on this topic).…”

“…When quantified in an in vitro system, moisture uptake behavior has been shown to influence the rate and mode of disintegration of the food particles during gastric digestion (Kong & Singh, 2009b). Gastric mixing affects intragastric pH distribution and residence time of the food particles in the stomach, and its quantification provides information on the local biochemical environment for food digestion (Bornhorst, 2017). For starch‐based foods, gastric mixing determines whether the chemical degradation within certain location in the stomach is due to remaining salivary α‐amylase activity or acid hydrolysis.…”

“…However, this binding is reversible and nonspecific, providing a chance for α‐amylase to bind with starch granules in the food bolus, depending on the extent of structural breakdown during mastication (Dhital, Gidley, & Warren, 2015). Therefore, with the weaker gastric contractile activity, higher pH, and slower inactivation of α‐amylase in the proximal stomach, it will most likely be the main site for continuing amylolysis during gastric digestion, which in turn causes further softening of food bolus (Bornhorst, 2017; Bornhorst, Hivert, et al., 2014).…”

Monitoring food digestion with magnetic resonance techniques

“…The second phase is gastric digestion, during which the food mass in the stomach is prepared for further digestion and absorption in the intestines. Gastric digestion involves mixing and addition of hydrochloric acid along with pepsin (a protease) and gastric lipase (6) . The third phase is intestinal digestion; from the stomach food passes through the pyloric valve into the small intestine where pancreatic proteases, lipases and amylase are added along with bile and the resulting chyme is mixed.…”

Mechanics of the stomach: A review of an emerging field of biomechanics

“… In general, one distinguishes between three types of gastric mixing processes, that is, solid‐solid, solid‐liquid, and liquid‐liquid mixing, depending on the consistency of the digesta. [] In the stomach, solid particles are disintegrated by fragmentation (cleavage into smaller pieces of roughly similar size) and erosion (abrasion of the surface by fluid shear stress). For tough small particles—like carrot or nut particles of a few millimeters in diameter—erosion dominates.…”