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Background: How starch-based food structure can affect the rate and extent of digestion in the small intestine and resulting glycemic response is not properly understood. One possible explanation is that food structure influences gastric digestion, which subsequently determines digestion kinetics in the small intestine and glucose absorption. However, this possibility has not been investigated in detail., Objectives: Using growing pigs as a digestion model for adult humans, this study aimed to investigate how physical structure of starch-rich foods affects small intestinal digestion and glycemic response., Methods: Male growing pigs (21.7 ± 1.8 kg, Large White × Landrace) were fed one of the 6 cooked diets (250-g starch equivalent) with varying initial structures (rice grain, semolina porridge, wheat or rice couscous, or wheat or rice noodle). The glycemic response, small intestinal content particle size and hydrolyzed starch content, ileal starch digestibility, and portal vein plasma glucose were measured. Glycemic response was measured as plasma glucose concentration collected from an in-dwelling jugular vein catheter for up to 390 min postprandial. Portal vein blood samples and small intestinal content were measured after sedation and euthanasia of the pigs at 30, 60, 120, or 240 min postprandial. Data were analyzed with a mixed-model ANOVA., Results: The plasma glucose Δmax overall and iAUC overall for couscous and porridge diets (smaller-sized diets) were higher than that of intact grain and noodle diets (larger-sized diets): 29.0 ± 3.2 compared with 21.7 ± 2.6 mg/dL and 5659 ± 727 compared with 2704 ± 521 mg/dL⋅min, for the smaller-sized and larger-sized diets, respectively (P < 0.05). Ileal starch digestibility was not significantly different between the diets (P ≥ 0.05). The iAUC overall was inversely related to the starch gastric emptying half-time of the diets (r = -0.90, P = 0.015)., Conclusions: Starch-based food structure affected the glycemic response and starch digestion kinetics in the small intestine of growing pigs., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

How the stomach can serve as a biochemical environment for starch digestion and the implications on starch emptying are not well-understood. Biochemical changes during gastric digestion of cooked wheat- and rice-based diets of varying particle size and microstructure were investigated using a growing pig model. In larger-particle size diets (rice grain, rice noodle, pasta), pH >3 was maintained in the proximal stomach digesta even until 240 min digestion, resulting in extended remaining amylase activity and accumulation of maltose from starch hydrolysis in the stomach. In smaller-particle size diets (couscous, rice couscous, semolina porridge), gastric acidification occurred faster to produce homogeneous intragastric pH and deactivated amylase. The hypothesis of the study was that food macrostructure would impact gastric acidification kinetics, and the resulting biochemical environment for starch hydrolysis in the stomach may further affect the mechanisms of food breakdown in the stomach and gastric emptying of starch., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

There is currently a limited understanding of the effect of food structure on physical breakdown and gastric emptying of solid starch-based foods during gastric digestion. Moisture uptake, pH, particle size, rheological, and textural properties of six solid starch-based diets from different sources (Durum wheat and high amylose white rice) and of different macrostructures (porridge, native grain, agglomerate/couscous, and noodle) were monitored during 240 min of gastric digestion in a growing pig model. Changes in the physical properties of the gastric digesta were attributed to the influence of gastric secretions and gastric emptying, which were both dependent on the buffering capacity and initial macrostructure of the diets. Differences between the proximal and distal stomach regions were found in the intragastric pH and texture of the gastric digesta. For example, rice couscous, which had the smallest particle size and highest buffering capacity among the rice-based diets, had the shortest gastric emptying half-time and no significant differences between proximal and distal stomach digesta physical properties. Additionally, a relationship between gastric breakdown rate, expressed as gastric softening half-time from texture analysis, and gastric emptying half-time of dry matter was also observed. These findings provide new insights into the breakdown processes of starch-based solid foods in the stomach, which can be beneficial for the development of food structures with controlled rates of breakdown and gastric emptying during digestion.