In vitro digestion of bread: How is it influenced by the bolus characteristics?

Abstract

This study aimed to understand the impact of in vitro oral processing methods on bolus formation and the kinetics of starch hydrolysis of refined white bread during in vitro gastrointestinal digestion. Four in vitro oral processing methods (i.e., cut, cut‐and‐pestle, blend, and grind) were performed at two levels of disintegration (less and more intensive) and compared with human mastication. Boluses prepared using the in vitro methods had a larger particle size (20–69 mm2 vs. 14 mm2), a higher moisture content (64–68% vs. 47%), a softer texture (1.3–2.3 N vs. 6.3 N) and a less adhesive surface (0.3–1.0 vs. 1.6 N•s) as compared to the in vivo masticated ones. Moreover, in vitro prepared blouses were digested more rapidly than in vivo masticated ones during the stimulated intestinal digestion from 150 min onward, with a higher hydrolysis rate (0.011–0.012 mg/mL • min vs. 0.010 mg/mL • min) and a higher equilibrium concentration of reducing sugar (5.5–6.3 mg/mL vs. 4.9 mg/mL). Among all the in vitro methods, the blending and grinding methods produced boluses that most closely resemble the in vivo masticated ones in terms of their physical characteristics. The blending method also produced boluses having the highest amount of reducing sugar released (6.32 mg/mL). The amount of reducing sugar present in the PBS buffer outside the dialysis tube might be controlled by the diffusion efficiency at the beginning of the digestion (≤120 min) and then be largely influenced by the particle size of the bolus in the latter stage of the digestion. Practical application Studying the in vitro starch amyloysis is valuable for predicting the postprandial glycemic potential of starchy food. This work provides novel insights on the role of in vitro oral processing in the prediction of the glycemic potential of carbohydrate‐rich staple food. Blending method is recommended because of its ability to produce boluses with similar physical characteristics as the in vivo masticated boluses. But the excessive structural breakdown occurred during blending also resulted in a higher enzymatic accessibility and a higher rate of starch digestion. Further study is needed to propose a new in vitro method that stimulates multiple actions occurred during mastication (cutting, grinding, and shearing), in order to match both physical properties and digestion profiles. Moreover, the amount of artificial saliva added should be adjusted according to the specific type of food.

Effect of Bread Structure and In Vitro Oral Processing Methods in Bolus Disintegration and Glycemic Index

“…However, there is not a direct relationship between food chemical composition and these effects on health because alterations in food matrix structures lead to differences in nutrient bioavailability, rates of absorption and post-prandial outcomes that might modify their potential health risks [4]. Additionally, the breakdown of the food matrix during the digestion process affects the rate at which foods are digested [5]. Therefore, clear attention should be given to the food matrix structure as well as to the food digestive process in order to understand how to control the glycemic index of carbohydrate-rich foods.…”

Role of the bolus degree of structure on the protein digestibility during in vitro digestion of a pea protein‐fortified sponge cake chewed by elderly

“…Finally, it can be seen that the DH of bolus pools reached at the end of digestion are not significantly different between them, but they are slightly superior ( p = .04) to the DH obtained by the FSC and PP samples (Figure d and Table D in Appendix section). This could be attributed to the differences in the median particle size ( D 50 ) between the real (≈0.30 mm) versus artificial (≈0.45 mm) boli, as it is hypothesized a smaller particle size could enhance enzymatic hydrolysis analogous to what is seen for starch hydrolysis (Gao et al, ). However, in the same study, the starch digestion level was higher for the artificial as compared to the real boli, being attributed to their differences in hydration level, which were ≈20% higher in artificial boli.…”

“…To this extent, an international consensus for a harmonized static protocol based on physiologically relevant conditions in humans has been recently achieved during the INFOGEST cost action (Minekus et al, ). Recently, Gao et al () used this protocol to study the influence of the degree of breakdown of artificial and real bread boli produced ex vivo from human mastication. They found that more disintegrated boli had a higher starch hydrolysis rate.…”

Potential Impact of Oat Ingredient Type on Oral Fragmentation of Biscuits and Oro-Digestibility of Starch—An In Vitro Approach

“…Some research has been conducted on in vitro methods for studying the degree of in-mouth breakdown in relation to its impact on subsequent digestion. For example, a very recent study [27] using white bread compared four different in vitro oral processing methods (cutting with a knife, cutting and grinding with a pestle, blending, and grinding) to investigate the effect of fragmentation on bolus formation and on in vitro digestion. Another study [10] subjected pastas with different compositions to four different breakdown procedures (chewing by one volunteer, grinding / maceration, cutting with a knife, and cutting with a knife and grinding with a pestle) followed by in vitro gastric digestion.…”

“…One study of bread and spaghetti boluses obtained in vivo determined and compared the level of particle degradation and digestion before swallowing for each food [8]; the results highlighted the influence of oral digestion on the entire digestion process. In another recent study using white bread [27], different in vitro oral processing methods were applied to obtain boluses and their characteristics were compared with those of in vivo boluses; the kinetics of starch hydrolysis in the different boluses were also compared by performing in vitro gastrointestinal digestions.…”