Slow Digestion Research Articles

Inhibition of the amylolytic hydrolysis of starch by ethanol

Gelatinized native corn starch dispersion (GSD, 5 g/100 mL water) was diluted with ethanol/water mixtures (EWM, 0.0, 1.0, 2.5, and 5.0 mL ethanol/100 mL) to a final concentration of 2.0 g GSD/100 mL EWM. The GSD were subjected to digestion by porcine pancreas α-amylase (0.33 and 0.66 IU/mL) at 37 °C for 90 min. The digested starch was reduced as an inverse function of ethanol concentration. The digested starch reduction can be as high as 15–30%, depending on the α-amylase concentration. Log-of-slope (LOS) method was used for analyzing the digestion kinetics curve, showing the presence of two (fast and slow) time scales. The fast and slow digestion kinetics were linked to rapidly (RDS) and slowly (SDS) starch fractions. It was found that ethanol reduced the RDS fraction, while increasing the resistant starch (RS) fraction. FTIR analysis suggested that modification of the enzyme secondary structure is behind the inhibition of the α-amylase activity by ethanol solvation.

The role of thermostable proteinaceous α-amylase inhibitors in slowing starch digestion in pasta

Starch in pasta is slowly digested, which is nutritionally advantageous because it reduces post-prandial glycemia, a risk factor for type 2 diabetes. We examine the role of proteinaceous amylase inhibitors, providing insights into how wheat proteins slow starch digestion. Gluten samples were extracted in the laboratory and also commercially obtained, and incubated in water at 37 °C and 100 °C. The centrifuged supernatant and gluten pellet were incubated with porcine α-amylase, and enzymatic activity measurement revealed that the supernatant from gluten heated to 100 °C retained the capacity to significantly reduce amylolytic activity. Confocal microscopy showed that the gluten pellet had become porous following heat treatment. These results are consistent with an increased concentration of soluble proteins after cooking. Proteins in the soluble fraction and gluten pellet were identified with mass spectrometry proteomics, which screened a limited number of endogenous double-headed α-amylase/trypsin inhibitors (α-AI(s)), found to be enriched in the supernatant after cooking. Endogenous α-AI(s) play a role in slowing starch digestion by interacting with α-amylase as it penetrates the gluten network that entraps the starch, resulting in an immobilization of the enzyme onto the gluten network, so that the digestion of starch entrapped by the gluten network is inhibited.

Physicochemical, functional properties and ATR‐FTIR digestion analysis of thermally treated starches isolated from black and bayo beans

Previous studies have related the slow digestion properties of isolated starches with their amylose to amylopectin ratio as well as their molecular structure, and in the case of flours, with their accompanying components such as proteins and fibers; which are known to restrict, to different extents the starch digestion by amylolytic enzymes. However, the botanical origin as well as the internal architecture of native starch granules plays a significant role in these characteristics. Moreover, these features can be improved by using hydrothermal treatments, such as heat moisture treatment (HMT) and annealing (ANN), that promote changes to granular architecture, increase internal crystallite order and decrease the amount of amorphous zones. In this study, HMT and ANN treated starches from two bean varieties and a normal maize starch are analyzed in terms of thermal stability, assessed by differential scanning calorimetry, viscosity by rapid visco analysis and in vitro amylolysis. The HMT and ANN treatments promote lower hydrolysis when compared to native granules, due to new and/or improved molecular interactions between starch molecules, assessed by attenuated total reflectance‐fourier transform infra red spectroscopy; such interactions increase the amount of crystalline residues after digestion, which is related with lower water absorption during cooking, and enhanced thermal stability, despite the lower enthalpies in thermal treated starches (≈3 J g−1 in Black bean with HMT). Furthermore, the hydrolysis residues after 120 min of amylolysis present a higher ratio of crystalline regions, that improve with thermal treatments, this demonstrates that these processes increase the order of existing crystallites due to new molecular interactions among starch molecules.

Digestion properties of corn starch modified by α-D-glucan branching enzyme and cyclodextrin glycosyltransferase

Corn starch was modified using α-D-glucan branching enzyme (GBE) and cyclodextrin glucosyltransferase (CGTase), and their in vitro digestibility were investigated. Compared to native corn starch and single-enzyme treated starch, dual-enzyme modified starch had higher amount of slowly digestible starch (SDS) and resistant starch (RS) contents. The chain length distributions and the ratio of α-1,6 linkages of the dual-enzyme modified starch indicated an increase in short side-chains (DP < 13) as well as branching degree, compared with control starch (corn starch treated without enzyme). Cyclodextrins formed in starch modified reaction was found to complex with branched amylopectin clusters by hydrogen bonding and other intermolecular forces, showing V-type X-ray diffraction pattern. The presence of the crystalline regions of dual-enzyme modified starch favored digestion rate reduction, which may give some useful reference for the development of modified starch with slow digestion property.

In vitro digestibility and quality attributes of white salted noodles supplemented with pullulanase-treated flour

This study aimed to develop a noodle with slow digestibility by adding pullulanase-treated wheat flour (PF). PF was prepared from normal wheat flour (NF) by pullulanase treatment, then its characteristics were compared with NF. Varying proportions (0%, 3%, 6%, 9%, 12% and 15%) of PF were substituted for NF to produce white salted noodles (WSN). The rheological, digestive, cooking, color and textural properties of WSN were evaluated. This showed that the amylose content of PF (83 wt%, total starch) was 62% higher than that of NF. After pullulanase treatment, the pasting temperature increased from 62.7 to 75.0 °C and the crystal structure of the starch changed from a mixture of A- and V-types to one of B- and V-types. Microstructure graphs showed that the structure of PF was more compact than that of NF. PF substitution produced noodles of acceptable quality with increased water absorption, cooking loss, L* value, hardness, and resilience and decreased cooking yield compared with the control (100% NF). In vitro digestibility tests showed that k (the kinetic constant) for cooked WSN decreased from 0.405 to 0.168 as substitution levels of PF increased from 0% to 15%, indicating that PF still exhibited slow digestibility after cooking.

A multiscale kinetics model for the analysis of starch amylolysis

Simple exponential decaying functions are commonly used for fitting the kinetics of starch digested by amylolytic enzymes. A common assumption is that a sole exponential function can account for the kinetics of the whole digestible starch. Recent studies using logarithm-of-slope (LOS) plots showed that digestion kinetics can exhibit multi-scale behavior, an effect reflecting starch fractions with different digestion characteristics. This work proposed an extension of the widely used Goñi et al.'s model to account for two starch fractions; one fraction linked with fast digestion rate and other with slow digestion rates. The fitting of experimental data was carried out by solving numerically a nonlinear least-squares problem. The estimated parameters have a straightforward interpretation in terms of reaction rates and digestible/resistant starch fractions. Two experimental examples were used for illustrating the performance of the multi-exponential function.

Productions and Functional Properties of Palm Sugars

Sugar profile, antioxidant properties, DNA damages, and in vitro predicted glycaemic index (pGI) of palm sugars (syrup and powder) were investigated in comparison with refined cane sugar. It was found that palm sugars exhibited better nutritional qualities than refined cane sugars. Palm sugars in both syrup and powder forms showed similar results, except in some properties. They contained a high content of fructose and glucose. They also exhibited better antioxidant properties, as evidenced by the high content of phenolic compounds and flavonoids. This contributed to their great antioxidant activities when assessed by DPPH radical scavenging activity and FRAP assay. The addition of palm sugar extracts to the reaction mixture effectively protected against DNA damage. For pGI, the mixture of corn starch and palm sugars showed slow digestion rate and, consequently, lower pGI values than those of refined cane sugars. Nutritional and functional properties of palm sugars were thought to be influenced by their retained phytonutrients, as they were processed under mild conditions.

Effects of Heating Temperatures and Acid Concentrations on Physicochemical Properties and Starch Digestibility of Citric Acid Esterified Tapioca Starches

Physicochemical properties and starch digestibility of modified tapioca starch using various citric acid concentrations (10, 30, and 50 g/100 g dry starch) and heating temperatures (100, 120, and 140 °C for 5 h) are investigated. It is found that the degree of esterification increases with increasing dose of citric acid and heating temperature. Differential scanning calorimetry shows that citrate starch samples exposed to high acid dose (30 g/100 g citric acid) and temperature (120 °C) are resistant to gelatinization. In addition, transitional enthalpy also decreases with increasing concentration and temperature. The microstructure of esterified starch is observed to have agglomerated granules, with corrosions/fissures and small overlapping layers on the surfaces, which are observed in all modified samples. Citric acid esterification of tapioca starch provided advantages in terms of the increase resistant starch content and slow digestion rate when compared to native starch.

Controlling lipid digestion profiles using mixtures of different types of microgel: Alginate beads and carrageenan beads

For certain applications, it is useful to control the rate and extent of lipid digestion in different regions of the gastrointestinal tract (GIT) e.g., to control bioavailability, satiety, or blood lipid levels. In the current study, lipid digestion was modulated by mixing two kinds of lipid-loaded biopolymer microgels (alginate beads and carrageenan beads) with different GIT responses. The microgels were formed by mixing lipid droplets with anionic polysaccharide solutions, and then injecting them into a calcium ion solution to cross-link the polysaccharides. Alginate beads remained intact throughout the GIT, leading to a relatively slow digestion rate, whereas carrageenan beads became deformed and dissociated, leading to faster digestion. Experiments using an in vitro GIT model indicated that the rate of lipid digestion could be controlled by mixing alginate microgels with carrageenan microgels. The rate of lipid digestion of the mixed system (1:1) was between that of the two individual systems. These mixed microgel systems may be useful in developing functional foods that modulate lipid blood levels, hormone release, and energy intake.

Making Kafirin, the Sorghum Prolamin, into a Viable Alternative Protein Source

AbstractKafirin, the sorghum prolamin, is the most hydrophobic of the prolamins, and forms disulfide cross‐links because of its high cysteine content. It is noted for its slow digestibility but does not trigger any adverse response when consumed by celiacs. These properties make kafirin potentially valuable in both food and nonfood applications, especially as a bioplastic and encapsulating agent. Despite these valuable properties, to date there is no commercial production of kafirin and consequently no commercial products. Extraction technologies that could be upscaled for industrial use are described. Also, genetic and physicochemical techniques that have been applied to improve the functional and nutritional properties of kafirin as a functional food ingredient and as a bioplastic are reviewed. It is proposed that kafirin extraction and bioplastic manufacture should be located at the site of grain bioethanol production. This would enable the use of a consistent supply of inexpensive, high‐protein feedstock from sorghum distillers dried grains with solubles, as well as a ready supply of inexpensive ethanol for extraction. In addition, equipment would be available for solvent recovery, and transportation costs could be minimized. These factors would contribute to making kafirin economically viable as an alternative protein source.

A Systematic Study of RNAi Effects and dsRNA Stability in Tribolium castaneum and Acyrthosiphon pisum, Following Injection and Ingestion of Analogous dsRNAs.

RNA interference (RNAi) effects in insects are highly variable and may be largely dependent upon the stability of introduced double-stranded RNAs to digestion by nucleases. Here, we report a systematic comparison of RNAi effects in susceptible red flour beetle (Tribolium castaneum) and recalcitrant pea aphid (Acyrthosiphon pisum) following delivery of dsRNAs of identical length targeting expression of V-type ATPase subunit E (VTE) and inhibitor of apoptosis (IAP) genes. Injection and ingestion of VTE and IAP dsRNAs resulted in up to 100% mortality of T. castaneum larvae and sustained suppression (>80%) of transcript levels. In A. pisum, injection of VTE but not IAP dsRNA resulted in up to 65% mortality and transient suppression (ca. 40%) of VTE transcript levels. Feeding aphids on VTE dsRNA reduced growth and fecundity although no evidence for gene suppression was obtained. Rapid degradation of dsRNAs by aphid salivary, haemolymph and gut nucleases contrasted with stability in T. castaneum larvae where it appears that exo-nuclease activity is responsible for relatively slow digestion of dsRNAs. This is the first study to directly compare RNAi effects and dsRNA stability in receptive and refractory insect species and provides further evidence that dsRNA susceptibility to nucleases is a key factor in determining RNAi efficiency.

Pharmacologic Glycemic Management of Type 2 Diabetes in Adults.

Pharmacologic Glycemic Management of Type 2 Diabetes in Adults.

In vitro digestion properties of native isolated starches from Mexican blue maize (Zea mays L.) landrace

Mexican blue maize (Zea mays L.) grains have been scantily appraised concerning their impact on human health, as dietary carbohydrates. The purpose of this study was to investigate the in-vitro digestion properties of wet-milled blue native maize starches obtained from an array of fifteen Mexican genotypes Elotero Sinaloa landrace. The total starch, amylose content and resistant starch in the blue raw maize starches varied from 99.32 to 99.60%, 16.49–26.50% and 0.44–2.85%, respectively. The modified first-order model adequately predicted the kinetics of starch digestion. Although native starches from blue maize were digested almost entirely (>97%), considerable variability was observed in the rates of hydrolysis (K), which ranged from 0.0020 to 0.0047 min−1. The blue raw maize starches had low hydrolysis index (HI) and average glycemic index (GHAVG), which varied from 13.84 to 20.29% and 48.00–52.36%, respectively. Overall, the results suggest that native starches of the collection of Mexican blue maize could be valuable information for the development of functional food, particularly when slow or minimum starch digestion is highly desired.

Slowly digestible properties of lotus seed starch-glycerine monostearin complexes formed by high pressure homogenization

Starch-lipid complexes were prepared using lotus seed starch (LS) and glycerin monostearate (GMS) via a high-pressure homogenization process, and the effect of high pressure homogenization (HPH) on the slow digestion properties of LS-GMS was investigated. The digestion profiles showed HPH treatment reduced the digestive rate of LS-GMS, and the extent of this change was dependent on homogenized pressure. Scanning electron microscopy displayed HPH treatment change the morphology of LS-GMS, with high pressure producing more compact block-shape structure to resist enzyme digestion. The results of Gel-permeation chromatography and Small-angle X-ray scattering revealed high homogenization pressure impacted molecular weight distribution and semi-crystalline region of complexes, resulting in the formation of new semi-crystalline with repeat unit distance of 16–18 nm and molecular weight distribution of 2.50–2.80 × 105 Da, which displayed strong enzymatic resistance. Differential scanning calorimeter results revealed new semi-crystalline lamellar may originate from type-II complexes that exhibited a high transition temperature.

Biofunctionality of native and nano-structured blue corn starch in prediabetic Wistar rats

ABSTRACTThe biofunctionality of native and nanostructured starch obtained from blue corn was evaluated on prediabetic Wistar rats. The surface of both types of starch was analyzed by atomic force microscopy (AFM). Total polyphenols content, antioxidant activity and digestibility were also evaluated. Prediabetes was induced by feeding a diet high in fat, carbohydrates and the administration of streptozotocin. Experimental design included a control group, prediabetic group and two prediabetic groups, one supplemented with native starch and the other with nanostructured starch. AFM analysis showed nano-cavities <5 nm in nanostructured starch. Nanostructured starch also had a higher content of total polyphenols, higher antioxidant activity and higher percentage of slow digestibility starch compared to native starch. Glucose, triglycerides 34 and insulin in the plasma increased significantly in the prediabetic group. Nanostructured starch administration decreased the levels of glucose and insulin in the plasma and therefore has potential as functional ingredient.

Physicochemical characteristics, ATR-FTIR molecular interactions and in vitro starch and protein digestion of thermally-treated whole pulse flours

Hydrothermal treatments, annealing (ANN) and heat moisture treatment (HMT) were applied to four whole pulse flours (black bean, broad bean, chickpea and lentil) with the aim to increase their slow digestible (SDS) and resistant starch (RS) fractions. In order to assess differences in their molecular interactions, they were analyzed and compared by ATR-FTIR before and after in vitro digestion. Both hydrothermal treatments promoted changes on starch granular architecture, being reflected on their thermal and pasting properties, that where positively correlated with their amylose and protein contents (R=0.96, P<0.01). Overall, the proposed hydrothermal treatments increased their SDS and RS fractions, but they had different effect on their in vitro protein digestion. The ATR-FTIR analysis of cooked flours before and after digestion showed that thermal treatments promoted new physical interactions at molecular scale between starch and proteins, that were correlated with the amount of RS fraction. The outcomes of this study could help to understand the slow digestion properties and possible interactions of the flour components in these four pulses.

Effects of palm oil on structural and in vitro digestion properties of cooked rice starches

The glycemic potency of rice depends upon the rate and extent of starch hydrolysis by pancreatic amylase and intestinal alpha-glucosidases. However, complexation of starch molecules with lipids is known to reduce the enzymic hydrolysis. In this study, we elucidated the varietal effect of rice starches on the formation of amylose-lipid complex, after cooking with palm oil, a common cooking oil. The amount of complexed lipid followed the order of black (2.5%), brown (2.5%), white (1.5%) and waxy (0.5%) rice starches. After heating with palm oil, the relative crystallinity of all the rice starches were destroyed whilst a V-type peak at 20° 2θ was increased, indicating the formation of amylose-lipid complex. This is also suggested from the DSC data where the melting enthalpy increased significantly after cooking in palm oil for all rice samples. The formation of amylose-lipid complex reduced the in vitro starch digestibility, enhancing the resistance starch content whilst decreasing the rapid and slow digestion fractions of non-waxy varieties. The rate and extent of in vitro starch hydrolysis seems to be dependent on the presence or absence of amylose fraction. With the mechanistic details, the present study suggests the applicability of palm oil addition during the rice cooking to enhance its nutritional functionality.

Nutritional property of starch in a whole-grain-like structural form

Starch is the main constituent of cereal grains, but less attention has been paid for its contribution to the health benefits of whole-grain foods. In the current investigation, the slow digestion property of corn starch in a whole-grain-like structural form (WGLSF), which mimicked the whole grain microstructure, was studied to better understand the nutritional property of whole grain starch. The WGLSF-starch prepared through Ca2+-induced alginate gelation in the presence of starch and β-glucan showed a reduced content of rapidly digestible starch (RDS) (∼40.4–23.6%) and increased content of resistant starch (RS) (∼20.7–30.9%) and slowly digestible starch (SDS) (∼38.9–47.8%) along the alginate concentrations (0.1–0.4%, w/v). Consistently, the postprandial glycaemic response of the cooked WGLSF-starch (0.3% alginate) exhibited a significant reduction (35.5%) of glucose peak compared to their physical mixture. Scanning electron microscope (SEM) observation demonstrated that the starch granules were embedded in the β-glucan-alginate co-formed gel matrix with a cell wall-like structure, which might cause a decrease of enzyme accessibility to the substrate, and ultimately a slow digestion profile of starch and reduced glycaemic response. Thus, maximization of the slow digestion property of starch in whole-grain food processing might be essential to further improve the nutritional property of whole-grain foods.

Nutritional and Nutraceutical Properties of Triticum dicoccum Wheat and Its Health Benefits: An Overview.

Triticum dicoccum wheat is one of the ancient wheat species and is gaining popularity due to its suggested health benefits as well as its suitability for organic farming. In some parts of the world, certain traditional foods prepared with dicoccum wheat are preferred due to their better taste, texture, and flavor. It is rich in bioactive compounds and its starch has been reported to have slow digestibility. However, content and composition of bioactive compounds is reported to vary depending on the geographical location, seasonal variations, varieties used, and the analytical methods followed. Therefore, in the present study, we report the food uses, digestibility of starch, nutritional and nutraceutical compositions of dicoccum wheat grown in different parts of the world, and also its health benefits in ameliorating diabetes and celiac disease.

Gut contents, digestive half-lives and feeding state prediction in the soil predatory mite Pergamasus longicornis (Mesostigmata: Parasitidae)

Mid- and hind-gut lumenal changes are described in the free-living predatory soil mite Pergamasus longicornis (Berlese) from a time series of histological sections scored during and after feeding on fly larval prey. Three distinct types of tangible material are found in the lumen. Bayesian estimation of the change points in the states of the gut lumenal contents over time is made using a time-homogenous first order Markov model. Exponential processes within the gut exhibit ‘stiff’ dynamics. A lumen is present throughout the midgut from 5 min after the start of feeding as the gut rapidly expands. It peaks at about 21.5 h–1.5 days and persists post-feeding (even when the gut is contracted) up until fasting/starvation commences 10 days post start of feeding. The disappearance of the lumen commences 144 h after the start of feeding. Complete disappearance of the gut lumen may take 5–9 weeks from feeding commencing. Clear watery prey material arrives up to 10 min from the start of feeding, driving gut lumen expansion. Intracellular digestion triggered by maximum gut expansion is indicated. Detectable granular prey material appears in the lumen during the concentrative phase of coxal droplet production and, despite a noticeable collapse around 12 h, lasts in part for 52.5 h. Posterior midgut regions differ slightly from anterior regions in their main prey food dynamics being somewhat faster in processing yet being slightly delayed. Posterior regions are confirmed as Last-In-Last-Out depots, anterior regions confirmed as First-In-First-Out conveyor belt processes. Evidence for differential lability of prey fractions is found. A scheme is presented of granular imbibed prey material being first initially rapidly absorbed (t_{frac{1}{2}} = 23 min), and also being quickly partly converted to globular material extra-corporeally/extracellularly (t_{frac{1}{2}} = 36 min)—which then rapidly disappears (t_{frac{1}{2}} = 1.1 h, from a peak around 4 h). This is then followed by slow intracellular digestion (t_{frac{1}{2}} = 6.9 h) of the resultant resistant prey residue matching the slow rate of appearance of opaque pre-excretory egestive refractive grains (overall t_{frac{1}{2}} = 4.5 days). The latter confirmed latent ‘catabolic fraction’ (along with Malpighian tubule produced guanine crystals) drives rectal vesicle expansion as ‘faeces’ during the later phases of gut emptying/contraction. Catabolic half-lives are of the order of 6.3–7.8 h. Membraneous material is only present in the lumen of the gut in starving mites. No obvious peritrophic membrane was observed. The total feeding cycle time may be slightly over 52.5 h. Full clearance in the gut system of a single meal including egestive and excretory products may take up to 3 weeks. Independent corroborative photographs are included and with posterior predictive densities confirm the physiological sequence of ingestion/digestion, egestion, excretion, defecation, together with their timings. Visually dark midguts almost certainly indicate egestive refractive grains (xanthine?) production. Nomograms to diagnose the feeding state of P. longicornis in field samples are presented and show that the timing of these four phases in the wild could be inferred by scoring 10–12 mites out of a sample of 20. Suggestions to critically confirm or refute the conclusions are included.