|BORNHORST, GAIL - University Of California|
|RUTHERFURD, SHANE - Massey University|
|ROMAN, MAXINE - University Of California|
|MOUGHAN, PAUL - Massey University|
|SINGH, R. PAUL - University Of California|
Submitted to: Food Biophysics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2014
Publication Date: 9/1/2014
Citation: Bornhorst, G., Rutherfurd, S.M., Roman, M., Burri, B.J., Moughan, P.J., Singh, R. 2014. Gastric pH distribution and mixing of soft and rigid food particles in the stomach using a dual-marker technique. Food Biophysics. 9:292-300. DOI 10.1007/s11483-014-9354-3.
Interpretive Summary: Food matrices are important modifiers of nutrient intake. The type of matrix—whether it is solid or liquid, firm or soft, can influence nutrient absorption. Gastric mixing plays a key role in the overall digestion process. It determines the availability of acid and enzymes to individual solid food particles. It controls the length of time these particles are subject to mechanical breakdown from stomach contraction waves. However, little is known about the how food composition impacts nutrient digestion. Mixing of a particle-laden material during peristaltic flow in the stomach has not been measured. We measured the mixing of solid particles of food using two indigestible markers. These markers were imbedded in soft (cooked brown and white rice) and rigid (raw and roasted almonds) particle meals fed to growing pigs. Gastric pH was not uniform throughout the stomach and it varied over time. Furthermore, there were differences between soft and rigid meals. We used this information to calculate the total percentage of each meal that was mixed. White rice had the greatest amount of mixing, becoming 94% mixed after 480 minutes. Almonds underwent a much slower mixing process. Food matrix plays a role in overall meal mixing during gastric digestion.
Technical Abstract: Mixing of a particle-laden material during peristaltic flow in the stomach has not been quantified in vivo. Gastric mixing plays a key role in the overall gastric digestion process; it determines the availability of acid and enzymes to individual solid food particles and controls the length of time particles will spend in the antral region, where they are subject to mechanical breakdown from antral contraction waves. The mixing of solid particles has been quantified using a dual-indigestible marker technique (TiO2 and Cr2O3) in soft (cooked brown and white rice) and rigid (raw and roasted almonds) particle meals fed to growing pigs. Each meal consisted of two portions, separately marked by one of the two indigestible markers and given to the pigs consecutively. At time periods varying from 20 to 720 min after completion of the meal, ten intragastric chyme samples were taken from each pig to determine the marker concentration and pH value. Gastric pH was not homogeneous throughout the stomach and varied over time, with differences observed between soft and rigid meals (p < 0.0001). Using a statistically-based mixing index M, the total percentage of each meal that was mixed could be calculated. White rice had the greatest amount of mixing, becoming 94% mixed after 480 min of digestion compared to 72% mixing for brown rice. Rigid particles underwent a slower mixing process and only arrived at 65 and 71% mixing after 720 min for raw and roasted almonds, respectively. Meal composition plays a role in overall meal mixing during gastric digestion.