α-Amylase action on starch in chickpea flour following hydrothermal processing and different drying, cooling and storage conditions

Inhibition mechanism of different structural polyphenols against α-amylase studied by solid-state NMR and molecular docking

Polyphenol has the considerable effects for inhibition of digestive enzymes, however, inhibition mechanism of molecular size-dependent polyphenols on enzyme activity is still lacking. Herein, inhibition effect and binding interactions of three different structural polyphenols (catechol, quercetin and hesperidin) on α-amylase were studied. Inhibition assays proved that polyphenols significantly inhibited α-amylase and their effects were increased with their molecular sizes. Hesperidin showed the highest inhibition ability of α-amylase, which was determined as IC50 = 0.43 mg/mL. Fluorescence and FT-IR spectroscopy proved that inter-molecular interactions between polyphenols and α-amylase occurred through non-covalent bonds. Besides, the secondary structure of α-amylase was obviously changed after binding with polyphenols. Inter-molecular interactions were investigated using solid-state NMR and molecular docking. Findings proved that hydrogen bonds and π-π stacking interactions were the mainly inter-molecular interactions. We hope this contribution could provide a theoretical basis for developing some digestive enzyme inhibitors from natural polyphenols.

Impact of chickpea hummus on postprandial blood glucose, insulin and gut hormones in healthy humans combined with mechanistic studies of food structure, rheology and digestion kinetics

Slowing the rate of carbohydrate digestion leads to low postprandial glucose and insulin responses, which are associated with reduced risk of type 2 diabetes. There is increasing evidence that food structure plays a crucial role in influencing the bioaccessibility and digestion kinetics of macronutrients. The aims of this study were to compare the effects of two hummus meals, with different degrees of cell wall integrity, on postprandial metabolic responses in relation to the microstructural and rheological characteristics of the meals. A randomised crossover trial in 15 healthy participants was designed to compare the acute effect of 27 g of starch, provided as hummus made from either intact chickpea cells (ICC) or ruptured chickpea cells (RCC), on postprandial metabolic responses. In vitro starch digestibility, microstructural and rheological experiments were also conducted to evaluate differences between the two chickpea hummus meals. Blood insulin and GIP concentrations were significantly lower (P < 0.02, P < 0.03) after the consumption of the ICC meal than the meal containing RCC. In vitro starch digestion for 90 min was slower in ICC than in RCC. Microscopic examination of hummus samples digested in vitro for 90 min revealed more intact chickpea cells in ICC compared to the RCC sample. Rheological experiments showed that fracture for ICC hummus samples occurred at smaller strains compared to RCC samples. However, the storage modulus for ICC was higher than RCC, which may be explained by the presence of intact cells in ICC. Food structure can affect the rate and extent of starch bioaccessibility and digestion and may explain the difference in the time course of metabolic responses between meals. The rheological properties were measured on the two types of meals before ingestion, showing significant differences that may point to different breakdown mechanisms during subsequent digestion. This trial was registered at clinicaltrial.gov as NCT03424187.

In vitro gastrointestinal digestion methods of carbohydrate-rich foods

The trend toward healthier food products has led to an increase in the research of in vitro gastrointestinal digestion methods. Among the most used models, static models are the simplest. Most static models have three stages: oral, gastric, and intestinal, simulating the enzymatic, electrolyte, pH, temperature, and bile salt conditions. The studies that have taken the most notice are those related to antioxidant activity, followed by those dealing with proteins and carbohydrates using most of them static in vitro digestion models. The number of these studies has increased over the years, passing from 45 to 415 in a 10-year period (2012-2023) and showing an interest in knowing the impact of food on human health. Nevertheless, published papers report different methodologies and analytical approaches. This review discusses the similarities and differences between the published static in vitro gastrointestinal digestion methods, with a focus on carbohydrates, finding that the most used protocol is Infogest, but with differences, mainly in the type of enzymes and their activity. Regarding in vitro gastrointestinal digestion of carbohydrates, many of the published studies are related to food and biomacromolecules, being the oral phase the most omitted, while the intestinal phase in the most diverse. Other methodologies to study the intestinal phase have been recommended, but the number of in vitro digestion studies using these methodologies (RSIE and BBMV) is still scarce but could represent a good alternative to analyze carbohydrates foods when combining with Infogest. More studies are required in this area.

Quantitative saccharide release of hydrothermally treated flours by validated salivary/pancreatic on-surface amylolysis (nanoGIT) and high-performance thin-layer chromatography

The susceptibility of hydrothermally treated flour products to amylolysis was studied. The human salivary α-amylase and porcine pancreatin enzyme mixture containing α-amylase were used on-surface to investigate the release of glucose, maltose, and maltotriose. On the same adsorbent surface (all-in-one), their high-performance thin-layer chromatography separation and detection via selective chemical derivatization was performed. For the first time, the all-in-one nanoGIT system was studied quantitatively and validated for the simulated static oral and intestinal on-surface amylolysis of ten different hydrothermally treated flours and soluble starch. Differences were detected in the digestibility of refined and whole flours from wheat, spelt, and rye as well as from einkorn, amaranth, emmer, and oat. Amaranth released the lowest amount of saccharides and spelt the highest in both oral and intestinal digestion systems. The results suggest that consumption of whole grain products may be beneficial because of their lower saccharide release, with particular attention to rye.

Stale bread waste recycling as ingredient for fresh oven-baked white bread: effects on dough viscoelasticity, bread molecular organization, texture, and starch digestibility

BACKGROUND

Wasted food produced for human consumption is estimated at 33% globally, and bread is the food product with the highest percentage. There is an ongoing drive to reincorporate food waste still useful and safe into the production chain of food for human consumption. This work aims to contribute to the study of the feasibility of recycling stale bread waste flour (BWF) into fresh oven-baked white bread, by replacing 0, 20, 40, 60, 80, and 100 g/100 g of the wheat flour with BWF.

RESULTS

Storage and loss moduli increased as the BWF content increased. The baked loaf exhibited decreased lightness and yellowness but increased redness. Increasing BWF contents produced decreased loaf volume and hardness but increased moisture content. Fourier-transform infrared analysis showed that the BWF addition induced important changes in the water, protein, and starch molecular organization. Therefore, starch digestibility showed reductions in both rapidly and slowly digestible starch fractions. Principal component analysis revealed that replacements of up 20 g/100 g can produce white bread with textural, colour, and starch digestibility characteristics like that of the control bread.

CONCLUSION

The fresh oven-baked white bread variation produced by replacing 20 g/100 g of the wheat flour with BWF exhibited comparable colour, volume, texture, and starch digestibility features as a control bread did made with 0 g/100 BWF. Higher replacement percentages of wheat flour by stale BWF produced unsuitable drawbacks in the white bread characteristics, but those might be deemed as convenient in other types of bakery products. © 2023 Society of Chemical Industry.

Effect of high-amylose starch branching enzyme II wheat mutants on starch digestibility in bread, product quality, postprandial satiety and glycaemic response

High-amylose starch branching enzyme II (sbeII) mutant wheat has potential to be low-glycaemic compared to conventional wheat; however, the effects of bread made from sbeII wheat flour on glycaemic response and product quality require investigation. We report the impact of white bread made from sbeII wheat flour on in vitro starch digestibility and product quality, and on postprandial glycaemia in vivo, compared to an isoglucidic wild-type (WT) control white bread. Starch in sbeII bread was ∼20% less susceptible to in vitro amylolysis leading to ∼15% lower glycaemic response measured in vivo, compared to the WT control bread, without major effects on bread appearance or texture, measured instrumentally. Despite the early termination of the in vivo intervention study due to the COVID-19 outbreak (n = 8 out of 19), results from this study indicate that sbeII wheat produces bread with lower starch digestibility than conventional white bread.

Impact of white bread made from sbeII wheat flour on postprandial glycaemic response.

Enzyme kinetic approach for mechanistic insight and predictions of in vivo starch digestibility and the glycaemic index of foods

BACKGROUND

Starch is a principal dietary source of digestible carbohydrate and energy. Glycaemic and insulinaemic responses to foods containing starch vary considerably and glucose responses to starchy foods are often described by the glycaemic index (GI) and/or glycaemic load (GL). Low GI/GL foods are beneficial in the management of cardiometabolic disorders (e.g., type 2 diabetes, cardiovascular disease). Differences in rates and extents of digestion of starch-containing foods will affect postprandial glycaemia.

SCOPE AND APPROACH

Amylolysis kinetics are influenced by structural properties of the food matrix and of starch itself. Native (raw) semi-crystalline starch is digested slowly but hydrothermal processing (cooking) gelatinises the starch and greatly increases its digestibility. In plants, starch granules are contained within cells and intact cell walls can limit accessibility of water and digestive enzymes hindering gelatinisation and digestibility. In vitro studies of starch digestion by α-amylase model early stages in digestion and can suggest likely rates of digestion in vivo and expected glycaemic responses. Reports that metabolic responses to dietary starch are influenced by α-amylase gene copy number, heightens interest in amylolysis.

KEY FINDINGS AND CONCLUSIONS

This review shows how enzyme kinetic strategies can provide explanations for differences in digestion rate of different starchy foods. Michaelis-Menten and Log of Slope analyses provide kinetic parameters (e.g., K m and k cat /K m ) for evaluating catalytic efficiency and ease of digestibility of starch by α-amylase. Suitable kinetic methods maximise the information that can be obtained from in vitro work for predictions of starch digestion and glycaemic responses in vivo.

Modelling multiphasic starch digestograms with multiterm exponential and non-exponential equations

The first-order kinetic and the Peleg models were respectively expanded to yield three-term exponential and non-exponential models for triphasic starch digestograms. Ten typical samples are presented, and the models suitably (r² > 0.95; p < 0.05) described their digestograms. Nonlinear regression constraints or conditions to ensure the stability, convergence, and practicability of the models are discussed. These were extended to existing two-term exponential models and an adapted two-term non-exponential model. The two-term models adequately (r² > 0.88; p < 0.05) described biphasic digestograms with practical digestion parameters, as exemplified by 10 presented digestograms. These multiterm models will add to models for describing multiphasic starch digestograms, ensuring such are properly modelled with objective predictability indices to assist researchers and for inter-laboratory comparisons. The integrals of the multiterm exponential and non-exponential models are presented to estimate or predict in vitro glycaemic indices.