A multiscale kinetics model for the analysis of starch amylolysis

Extrusion of decoction residues of Roselle (Hibiscus sabdariffa L.) with different starchy wall materials retaining the polyphenol content after in vitro digestion

Decoction residues (DR) of Roselle are a waste with high polyphenol content. The remaining polyphenols are resistant to thermal treatments and have antioxidant properties. An alternative for the use of the DR is the extrusion with wall material that can preserve the antioxidant capacity of the polyphenols. The present study aimed to produce a functional ingredient with the Roselle DR by extrusion with different commercial starchy wall materials (Capsul, N-Lok, and Globe). The extrudates were analyzed for morphology, bioaccessibility of polyphenols, antioxidant capacity (AC), and starch digestion rate. The confocal microscopy showed the presence of fiber with polyphenols. The extruded with Capsul and Globe showed the highest slowly digestible starch (SDS) and resistant starch (RS) content. The bioaccessibility of polyphenols was higher in the Capsul and Globe extrudates indicating gradual release during the intestinal digestion. Capsul and Globe showed the best results in protecting the polyphenols.

How Digestive Processes Can Affect the Bioavailability of PCBs Associated with Microplastics: A Modeling Study Supported by Empirical Data

The transfer kinetics of plastic-associated chemicals during intestinal digestive processes is unknown. Here, we assessed whether digestive processes affect chemical exchange kinetics on microplastics, using an in vitro gut fluid digestive model mimicking the human upper intestinal tract. Chemical exchange kinetics of microplastics were measured for 10 polychlorinated biphenyls (PCBs) as proxies for the broad class of hydrophobic organic chemicals. Following earlier studies, olive oil was used as a proxy for digestible food, under high and low digestive enzyme activities. The micelle-water and oil-water partition coefficients of the 10 PCBs were also determined to evaluate the relative contribution of each gut component to sorb PCBs. A new biphasic and reversible chemical exchange model, which included the digestion process, fitted well to the empirical data. We demonstrate that the digestive processes that break down contaminated food can lead to a substantial increase in chemical concentration in microplastics by a factor of 10-20, thereby reducing the overall chemical bioavailability in the gastrointestinal tract when compared to a scenario without microplastics. Higher enzyme activities result in more chemicals being released by the digested food, thereby resulting in higher chemical concentrations in the microplastics. While the model-calibrated kinetic parameters are specific to the studied scenario, we argue that the mechanism of the reduced bioavailability of chemicals and the modeling tool developed have generic relevance. These digestive processes should be considered when assessing the risks of microplastics to humans and also biomagnification in aquatic food webs.

A procedure for determining the number and pattern of digestible starch fractions in multiphasic food digestograms

BACKGROUND

Plant-based foods are frequently heterogenous systems, containing multiple starch fractions with distinct digestion rate constants. An unbiased determination of the number and digestion pattern of these fractions is a prerequisite for understanding the digestive characteristics of food.

RESULTS

A non-linear least-squares procedure based on a conditional selection of simple first-order kinetics or a combination of parallel and sequential kinetics models was developed. The procedure gave robust results fitting manually generated data, and was applied to in vitro experimental digestion data of retrograded rice starches. By correlating fitting parameters with starch structural parameters, it showed that rice starches with a lower amylose content, longer amylose chains, and amylopectin intermediate chains had more digestible starch fractions after long-term retrogradation.

CONCLUSION

This procedure enables the structural basis of starch digestibility and the development of food products with slow starch digestibility to be better understood. © 2022 Society of Chemical Industry.

How Does Starch Structure Impact Amylolysis? Review of Current Strategies for Starch Digestibility Study

In vitro digestibility of starch is a common analysis in human nutrition research, and generally consists of performing the hydrolysis of starch by α-amylase in specific conditions. Similar in vitro assays are also used in other research fields, where different methods can be used. Overall, the in vitro hydrolysis of native starch is a bridge between all of these methods. In this literature review, we examine the use of amylolysis assays in recent publications investigating the complex starch structure-amylolysis relation. This review is divided in two parts: (1) a brief review of the factors influencing the hydrolysis of starch and (2) a systematic review of the experimental designs and methods used in publications for the period 2016–2020. The latter reports on starch materials, factors investigated, characterization of the starch hydrolysis kinetics and data analysis techniques. This review shows that the dominant research strategy favors the comparison between a few starch samples most frequently described through crystallinity, granule type, amylose and chain length distribution with marked characteristics. This strategy aims at circumventing the multifactorial aspect of the starch digestion mechanism by focusing on specific features. An alternative strategy relies on computational approaches such as multivariate statistical analysis and machine learning techniques to decipher the role of each factor on amylolysis. While promising to address complexity, the limited use of a computational approach can be explained by the small size of the experimental datasets in most publications. This review shows that key steps towards the production of larger datasets are already available, in particular the generalization of rapid hydrolysis assays and the development of quantification approaches for most analytical results.

Understanding how different modification processes affect the physiochemical, functional, thermal, morphological structures and digestibility of cardaba banana starch

In this study, starch was isolated from cardaba banana starch and was subjected to modification by heat-moisture treatment, citric acid, octenyl succinic anhydride, and sodium hexametaphosphate. Both the native and modified cardaba banana starches were examined for chemical, functional, pasting, thermal, morphological, structural, and antioxidant properties, as well as in vitro starch digestibility. Modification significantly influenced the properties of the cardaba banana starch. Cross-linking treatment improved the water, oil absorption, alkaline hydration capacity, swelling power, solubility and paste clarity of the starch. The final viscosity of the banana starch paste was increased alongside succinic anhydride modification which in turn enhanced the suitability of the starch in the production of high viscous products. Both FTIR spectra and X-ray diffractograms confirmed the starch had a C-type starch which was not affected by modification. Modification led to a decrease in relative crystallinity of the starch with succinylation having the maximum effect. The starch fractions; both SDS and RS significantly increased due to modification while the hydrolysis and glycemic index of the starch were significantly decreased by chemical modification. In conclusion, both physical and chemical modification of cardaba banana starch produced a starch that can serve as functional food or functional food ingredients.

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.

Elucidation of the low resistant starch phenotype in Phaseolus vulgaris exhibited in the yellow bean Cebo Cela

Dry beans(Phaseolus vulgaris) are rich in complex carbohydrates including resistant starch (RS). RS, the starch fraction that escapes digestion, typically ranges from 35% in raw beans to 4% in cooked beans. A low RS bean genotype, Cebo Cela, was identified with 96% less RS (1.5% RS) than normal raw beans. The goal of this research was to elucidate the factors responsible for this low RS phenotype. The low RS phenotype was evaluated in whole bean flour and starch in Cebo Cela (yellow), Canario (yellow), Alpena (navy) and Samurai (otebo). α-Amylase activation was found to be a major contributor of the low RS content phenotype of the whole bean flour for Cebo Cela (-21.9% inhibition). Total starch (43.6%-40.2%), amylose (31.0%-31.5%), molecular weight and chain length distributions of amylose and amylopectin did not contribute to the low RS phenotype. Yellow bean starches were digested nearly 1.5 times (95%-94%) faster than starch granules from otebo and navy beans (65%-73%) due to lower proportions of amylopectin chains. PRACTICAL APPLICATION: This study is of value to the food industry because the yellow bean, Cebo Cela, is easily hydrolyzed by α-amylase and also has α-amylase promotion properties. Therefore, Cebo Cela can be used as an alternate starch source for ethanol fermentation and for the production of maltodextrins and fructose/glucose syrups which are used as food thickeners and sweeteners.

Modeling of in vitro digestion behavior of corn starches of different digestibility using modified log of slope (LOS) method

This study aimed to further improve the previously described first-order equation representing in vitro digestion of starch by extensively explaining modified log of slope (LOS) plot method. Hydrolysis curves of various starches were analyzed using original and/or modified LOS plot methods. Some starches showed significant differences in the results from the two methods; specifically, the modified method better described the digestive behavior of starch with various digestion properties, supported by higher determination coefficient values and better estimation of the digestibility data over digestive phase. The digestion parameters obtained from the modified method provided multiple types of information, including amount and digestion rate of each starch fraction (rapidly digestible, slowly digestible, and resistant starch), supporting the concept of digestible fraction classification. Therefore, the modified LOS plot method described here can be applied as an effective tool for analyzing and describing the multi-scale in vitro digestion behavior of starch.

Addition of chickpea markedly increases the indigestible carbohydrate content in semolina pasta as eaten

BACKGROUND

There is a growing interest in increasing dietary fiber (DF) consumption because of the health benefits associated with this nutrient. Pulses are considered a good source of non-digestible carbohydrates. The aim of this study was to investigate the possibility of substituting semolina with chickpea flour to increase indigestible carbohydrate content without altering the texture of the pasta.

RESULTS

Pasta was prepared by extruding semolina-chickpea blends. The protein and DF content in the cooked pasta increased with the chickpea level, with an important contribution of resistant starch (RS) to the DF values. The optimum cooking time decreased as the chickpea content increased, which was related to the degree of starch gelatinization of the raw pasta. The in vitro digestible starch content decreased with the chickpea substitution level, concomitant with the increase in RS content. In general, the texture of the chickpea-containing pasta was similar to that of semolina pasta.

CONCLUSIONS

Pending acceptability studies on these pastas may grant their promotion as good fiber sources, probably helpful in the fight against obesity and diet-related non-communicable diseases. © 2020 Society of Chemical Industry.

Valorisation of rejected unripe plantain fruits of Musa AAB Simmonds: from nutritional characterisation to the conceptual process design for prebiotic production

The increasing consumption of plantain fruits with specific quality standards generates high agricultural waste. This work aimed at valorising the rejected unripe pulp of Dominico-Hartón plantain fruits (Musa AAB Simmonds). The pulp was characterised physico-chemically, thermally and functionally. The data gathered experimentally and collected from different databases were used to design a production process of isomalto-oligosaccharides (IMO) syrup. The plantain flour contains high levels of starch (87 ± 2%) and amylose (31.2 ± 0.8%). The flour showed stability at high temperatures (pasting temperature of 79.26 ± 0.02 °C), allowing its use in high temperature processes. In vitro gastrointestinal digestion of the plantain flour showed that when cooked, the glycemic index of the flour increased from 47.7 ± 2.2 to 84.2 ± 1.8, while its resistant starch content only slightly decreased from 71.7 ± 1% to 52.6 ± 2%, suggesting that this type of flour preserves high content of dietary fibre after digestion. The conceptual process design showed that 24.48 g of IMO are theoretically obtained from 53.24 g of plantain flour maltose. These results suggest that the rejected plantain pulp holds high potential as an ingredient for the production of prebiotic compounds such as IMO.

Catalytic liquefaction of sewage sludge to small molecular weight chemicals

The catalytic hydrotreatment of sewage sludge, the wet solid byproducts from wastewater treatment plants, using supported Ir, Pt, Pd, Ru catalysts had been investigated with different solvent conditions. Reactions were carried out in a batch set-up at elevated temperatures (400 °C) using a hydrogen donor (formic acid (FA) in isopropanol (IPA) or hydrogen gas), with sewage sludge obtained from different sampling places. Sewage sludge conversions of up to 83.72% were achieved using Pt/C, whereas the performance for the others catalysts is different and solvent had a strong effect on the conversion rate and product constitution. The sewage sludge oils were characterised using a range of analytical techniques (GC, GC-MS, GCxGC, GPC) and were shown to consist of monomers, mainly alkanes and higher oligomers.

Pulp and peel of unripe stenospermocarpic mango (Mangifera indica L. cv Ataulfo) as an alternative source of starch, polyphenols and dietary fibre

As a result of climate change, the production of stenospermocarpic mangoes has increased dramatically. The stenospermocarpic mango, a fruit with reduced size and no seed, is considered to be a by-product that is both underutilised and wasted. Here, we studied the colour, chemical composition, polyphenol content, antioxidant capacity and starch in vitro digestibility of unripe stenospermocarpic mango flours (pulp and peel). The stenospermocarpic mango pulp flour had 11.7 g/100 g of dietary fibre with a balance of soluble and insoluble fractions; additionally, the total starch content of 41 g/100 g in its uncooked flour (resistant starch) can contribute to an increase in the indigestible carbohydrates. The mango peel flour had higher dietary fibre (40.5 g/100 g) and lower total starch content (21 g/100 g) compared with mango pulp flour. The mango pulp flour had higher phenolic compounds content (99.71 mg/g) and antioxidant capacity (248.5 mg/g, DPPH) compared with the peel flour (16.51 mg/g and 92.08 mg/g, DPPH), respectively. The rapidly digestible starch fraction was approximately 50%, with a balance in the content of slowly and resistant starch fractions in the mango pulp flour (approximately 20% per fraction). The flours of the pulp and peel of unripe stenospermocarpic mangoes can be used as alternative ingredients for preparing functional foods with high dietary fibre content and polyphenol compounds with antioxidant capacities.

Digestion kinetics of native and modified cardaba banana starch: A biphasic approach

To understand the mechanism through which cardaba banana starch is hydrolysed, the starch digestion kinetics of native and modified cardaba banana starch samples of Nigeria origin were investigated using an in vitro procedure. The digestion kinetics of the starch samples revealed the samples exhibited a biphasic digestogram. A second-order polynomial with an average coefficient of determinant (r²) of 0.7732 (p < 0.005) was used to segment the biphasic digestogram into two monophasic digestograms. The digestion kinetics parameters (average) obtained using a modified first-order model suggested the accuracy of the model in describing the digestogram. The values obtained for the initial and final digestion rate constant (initial, k_i = 3-4 × 10^-2 min^-1; final k_f = 6-8.3 × 10^-2 min^-1) revealed that the final monophasic segment had a faster rate of digestion after the initial resistant to digestion had been overcome. The logistic model approach in which the digestogram was carried out in a single process also accurately predicted the biphasic behaviours of the cardaba banana (average r² = 0.9736, p < 0.05; root mean square of error, RMSE = 1.588). Weibull model was used for the first time to describe the biphasic approach of cardaba banana starch and according to the digestogram parameters obtained (average r² = 0.9954, p < 0.05; root mean square of error, RMSE = 0.578), the model accurately predicts the biphasic digestogram. In comparison among the models, the Weibull model best described the biphasic digestogram of the cardaba banana starch. The maximum starch digestion obtained in each of the digestion approaches was less than 100% which is an indication of the presence of resistant starch.

Morphological, molecular evolution an in vitro digestibility of filamentous granules of banana starch during fruit development

The development of starch granules of a banana cultivar (morado variety - Musa AAA subgroup Red dacca) from filamentous shape to semi-spherical and finally to oval shape, was studied. The purity of the extracted starch changed from 83.5% (6 weeks) to 95.4% (16 weeks). Impurities were ascribed to cellulosic and latex fractions responsible for the integrity of the pristine fruit. The amylose content was stabilized at about 29.6% after the 12th week. The thermal analysis showed that the gelatinization enthalpy increased from 5.0 to 11.2 J/g from the 6th to the 12th week, indicating an increased degree of internal molecular organization. The analysis of chain-length distribution and gel permeation chromatography, showing that the content of long chains (B1, B2, and B3+) increased with the development of the starch granule. Also, XRD analysis indicated that C- type X-ray diffraction pattern from early to later phases of development, although the relative crystallinity content increased from 19.3 to 23.5% after 16 weeks of development. FTIR revealed the formation of more ordered structures with the development time. In vitro digestion tests showed that the resistant starch fraction increased from 37.5% for week 6 to 55.5% for week 16.