Slowly digestible starch: concept, mechanism, and proposed extended glycemic index

Investigation of the link between first-order kinetic models of the in vitro digestion of native starches and the accompanying changes in their crystallinity and structure

Starch is the main source of dietary energy for humans. In order to understand the mechanisms governing native starch in vitro digestion, digestion data for six starches [wheat, maize, (waxy) maize, rice, potato and pea] of different botanical sources were fitted with the most common first-order kinetic models, i.e. the single, sequential, parallel and combined models. Parallel and combined models provided the most accurate fits and showed that all starches studied except potato starch followed a biphasic in vitro digestion pattern. The biological relevance of the kinetic parameters was explored by determining changes in crystallinity and molecular structure of the undigested starch residues during in vitro digestion. While the crystallinity of the undigested potato starch residues did not change substantially, a respectively small and large decrease in their amylose content and chain length during in vitro digestion was observed, indicating that amylose was digested slightly preferentially over amylopectin in native starch. However, the molecular structure of the starch residues changed too slowly and/or only to an insufficient extent to relate it to the kinetic parameters of the digested fractions predicted by the models. Such parameters thus need to be interpreted with caution, as their biological relevance still needs to be proven.

Multi-scale structural insights on starch digestibility of instant rice

Multi-scale structures were investigated to understand starch digestibility of instant rice. A wide range of maximum starch digested ratio, up to about 20%, was observed among instant rice prepared from different rice varieties. Instant rice with a smooth and densely packed cross-section showed slower starch digestibility than those with a porous and loosely packed structure. All samples displayed B + V type crystallinity, with V-type crystallinity negatively correlating with maximum starch digested percentage. After digestion, starch chain-length distributions were significantly altered: rapidly digested starch comprised long amylose and short amylopectin chains, while slowly digested starch comprised chains with a peak degree of polymerization (DP) around 130. These results indicate that instant rice with a compact microstructure, high V-type crystallinity, and DP 130 fractions during digestion can reduce starch digestibility. This study provides insights for food industry to develop instant rice products with slow starch digestibility, potentially improving human health.

Slowly hydrolyzable property of microbial dextrans at the small intestinal α-glucosidase levels leads to the modulated glycemic responses in the mouse model

Dextran-type α-glucans have been known as non-digestible ingredients that can be considered prebiotics to promote colon health. However, recent studies have revealed that various α-linked glucosyl units are hydrolyzed to glucose by small intestinal α-glucosidases. This study analyzed the structural characteristics of exopolysaccharides (EPSs) from Weissella species, and the hydrolysis properties at both in vitro/in vivo levels were investigated. Compared with a previous in vitro digestion model using fungal α-hydrolytic enzymes, dextrans, which mainly consist of α-1,6 linkages with small amounts of α-1,3 linked glucose units, were slowly hydrolyzed to glucose by mammalian mucosal α-glucosidases, resulting in attenuation of the initial glycemic response following administration of EPS samples to mice via oral gavage. The results of this study demonstrate the concept of dextran-type α-glucans as glycemic carbohydrates rather than dietary fibers or prebiotics. Slowly digestible dextrans can be applied as a functional ingredient to regulate postprandial glucose delivery throughout the gastrointestinal tract.

Investigation of the effect of ultrasonication on starch-fatty acid complexes and the stabilization mechanism

The complexation of physically modified starch with fatty acids is favorable for the production of resistant starch. However, there is a lack of information on the effect of ultrasonication (UC) on the structure and properties of starch complexes and the molecular mechanism of the stabilization. Here, the multi-scale structure and in vitro digestive properties of starch-fatty acid complexes before and after UC were investigated, and the stabilization mechanisms of starch and fatty acids were explored. The results showed that the physicochemical properties and multi-scale structure of the starch-fatty acid complexes significantly changed with the type of fatty acids. The solubility and swelling power of the starch-fatty acid complexes were significantly decreased after UC (P < 0.05), which facilitated the binding of starch with fatty acids. The XRD results revealed that after the addition of fatty acids, the starch-fatty acid complexes showed typical V-shaped complexes. In addition, the starch-fatty acid complexes showed a significant increase in complexing index, improved short-range ordering and enhanced thermal stability. However, the differences in the structure and properties of the fatty acids themselves resulted in no significant improvement in the multi-scale structure of maize starch-palmitic acid by UC. In terms of digestibility, especially the complexes after UC were more compact in structure, which increased the difficulty of enzymatic digestion and thus slowed down the digestion process. DFT calculations and combined with FT-IR analysis showed that non-covalent interactions such as hydrogen bonding and hydrophobic interactions were the main driving force for the formation of the complexes, with binding energies (lauric acid, myristic acid and palmitic acid) of -30.50, -22.14 and -14.10 kcal/mol, respectively. Molecular dynamics simulations further confirmed the molecular mechanism of inclusion complex formation and stabilization. This study is important for the regulation of starchy foods by controlling processing conditions, and provides important information on the role of fatty acids in the regulation of starch complexes and the binding mechanism.

Effects of varied preparation processes on polyphenol-rice starch complexes, in vitro starch digestion, and polyphenols release

This study synthesized composite samples incorporating four representative polyphenolic structures, gallic acid (GA), quercetin (QC), resveratrol (RES), and magnolol (MN), with rice starch using various preparation processes, including the addition of polyphenols and alteration of temperature and pH, via co-gelatinization. Subsequently, the complexation rates, starch digestion properties, and polyphenol release during in vitro digestion were examined. The results indicated that both the preparation process and structural variations of polyphenols affected starch digestion and polyphenol release by modulating the complexation. All polyphenols displayed inhibitory effects on rice starch digestion, with GA being the most efficient polyphenol. Additionally, rice starch exhibited a protective effect against RES during in vitro digestion, as rice starch-coated RES reduced the damage from stomach acids. Overall, these findings may help optimize the processing conditions for the synthesis of polyphenol-rice starch-based food products.

New insights into starch, lipid, and protein interactions - Colon microbiota fermentation

Starch, lipids, and proteins are essential biological macromolecules that play a crucial role in providing energy and nutrition to our bodies. Interactions between these macromolecules have been shown to impact starch digestibility. Understanding and controlling starch digestibility is a key area of research. Investigating the mechanisms behind the interactions of these three components and their influence on starch digestibility is of significant practical importance. Moreover, these interactions can result in the formation of resistant starch, which can be fermented by gut microbiota in the colon, leading to various health benefits. While current research has predominantly focused on the digestive properties of starch in the small intestine, there is a notable gap in understanding the colonic microbial fermentation phase of resistant starch. The benefits of fermentation of resistant starch in the colon may outweigh its glucose-lowering effect in the small intestine. Thus, it is crucial to study the fermentation behavior of resistant starch in the colon. This paper investigates the impact of interactions among starch, lipids, and proteins on starch digestion, with a specific focus on the fermentation phase of indigestible carbohydrates in the colon. Furthermore, valuable insights are offered for guiding future research endeavors.

Endometrial Cancer: A Pilot Study of the Tissue Microbiota

BACKGROUND

The endometrium remains a difficult tissue for the analysis of microbiota, mainly due to the low bacterial presence and the sampling procedures. Among its pathologies, endometrial cancer has not yet been completely investigated for its relationship with microbiota composition. In this work, we report on possible correlations between endometrial microbiota dysbiosis and endometrial cancer.

METHODS

Women with endometrial cancer at various stages of tumor progression were enrolled together with women with a benign polymyomatous uterus as the control. Analyses were performed using biopsies collected at two specific endometrial sites during the surgery. This study adopted two approaches: the absolute quantification of the bacterial load, using droplet digital PCR (ddPCR), and the analysis of the bacterial composition, using a deep metabarcoding NGS procedure.

RESULTS

ddPCR provided the first-ever assessment of the absolute quantification of bacterial DNA in the endometrium, confirming a generally low microbial abundance. Metabarcoding analysis revealed a different microbiota distribution in the two endometrial sites, regardless of pathology, accompanied by an overall higher prevalence of pathogenic bacterial genera in cancerous tissues.

CONCLUSIONS

These results pave the way for future studies aimed at identifying potential biomarkers and gaining a deeper understanding of the role of bacteria associated with tumors.

α-Glucan-type exopolysaccharides with varied linkage patterns: Mitigating post-prandial glucose spike and prolonging the glycemic response

Microbial exopolysaccharides (EPSs) are traditionally known as prebiotics that foster colon health by serving as microbiota nutrients, while remaining undigested in the small intestine. However, recent findings suggest that α-glucan structures in EPS, with their varied α-linkage types, can be hydrolyzed by mammalian α-glucosidases at differing rates. This study explores α-glucan-type EPSs, including dextran, alternan, and reuteran, assessing their digestive properties both in vitro and in vivo. Notably, while fungal amyloglucosidase - a common in vitro tool for carbohydrate digestibility analysis - shows limited efficacy in breaking down these structures, mammalian intestinal α-glucosidases can partially degrade them into glucose, albeit slowly. In vivo experiments with mice revealed that various EPSs elicited a significantly lower glycemic response (p < 0.05) than glucose, indicating their nature as carbohydrates that are digested slowly. This leads to the conclusion that different α-glucan-type EPSs may serve as ingredients that attenuate post-prandial glycemic responses. Furthermore, rather than serving as mere dietary fibers, they hold the potential for blood glucose regulation, offering new avenues for managing obesity, Type 2 diabetes, and other related-chronic diseases.

The Construction of Sodium Alginate/Carboxymethyl Chitosan Microcapsules as the Physical Barrier to Reduce Corn Starch Digestion

To enhance the resistant starch (RS) content of corn starch, in this work, carboxymethyl chitosan/corn starch/sodium alginate microcapsules (CMCS/CS/SA) with varying concentrations of SA in a citric acid (CA) solution were designed. As the SA concentration increased from 0.5% to 2%, the swelling of the CMCS/CS/SA microcapsule decreased from 15.28 ± 0.21 g/g to 3.76 ± 0.66 g/g at 95 °C. Comparatively, the onset, peak, and conclusion temperatures (To, Tp, and Tc) of CMCS/CS/SA microcapsules were higher than those of unencapsulated CS, indicating that the dense network structure of microcapsules reduced the contact area between starch granules and water, thereby improving thermal stability. With increasing SA concentration, the intact and dense network of CMCS/CS/SA microcapsules remained less damaged after 120 min of digestion, suggesting that the microcapsules with a high SA concentration provided better protection to starch, thereby reducing amylase digestibility. Moreover, as the SA concentration increased from 0.5% to 2%, the RS content of the microcapsules during in vitro digestion rose from 42.37 ± 0.07% to 57.65 ± 0.45%, attributed to the blocking effect of the microcapsule shell on amylase activity. This study offers innovative insights and strategies to develop functional starch with glycemic control properties, holding significant scientific and practical value in preventing diseases associated with abnormal glucose metabolism.

Resistant starch and type 2 diabetes mellitus: Clinical perspective

The immediate and well-documented benefits of carbohydrate restriction include improved glycemic control in individuals with diabetes mellitus. Starch, a significant source of carbohydrates, is categorized as rapidly digestible, slowly digestible, or resistant starch (RS). RS, which is a non-viscous fermentable fiber, has shown promise in animal studies for antidiabetic effects by improving glucose metabolism. Although the exact mechanism by which RS affects glucose metabolism remains unclear, it is expected to positively impact glucose tolerance and insulin sensitivity. The fermentation of RS by colonic microbiota in the large bowel produces short-chain fatty acids, which exert multiple metabolic effects on glucose regulation and homeostasis. Moreover, RS may influence glucose metabolism via bile acid modulation, independent of its fermentation. Diets rich in RS could aid in blood glucose homeostasis. However, it is uncertain whether they can alter the metabolic pathology associated with glucose regulation. In essence, RS has the potential to lower postprandial glucose levels similarly to a low-glycemic index diet. Yet, its efficacy as a medical nutrition therapy for type 2 diabetes needs further investigation. To confirm the role of RS in glycemic control and to possibly recommend it as an additional dietary approach for people with type 2 diabetes mellitus, a well-designed, large-scale intervention is required.

Variations in the effects of extrusion treatments and ferulic acid addition on starch digestibility with different botanical backgrounds

In the current study, the effects of extrusion using a haake rheometer with a twin-roll mixer, with and without FA addition, on the structures and in vitro digestibility of starches from different sources were investigated. After extruding for 15 min at 90 °C with a moisture content of 40 %, no matter FA was added or not, lager Ap molecules were preferentially debranched, while Am with longer CL were depolymerized simultaneously, resulting to reduced averaged molecular size of Ap and shortened Am chains. Of all starches, regardless of their botanical backgrounds, although synergic effects were found between extrusion and FA addition on reducing their relative crystallinity and the ordered structures, distinctly different effects on the in vitro digestibility of these starches have also been observed especially regarding the digestion of starch branches with DP > 10 Particularly, the Am chains with DP 10-1000 was remaining undigested when FA was added. This study provides important information concerning how to adjust starch digestibility into a healthy range through altering the starch structures using extrusion technique with the addition of phytochemicals or not.

Resistant starch and the gut microbiome: Exploring beneficial interactions and dietary impacts

The intricate relationship between resistant starch (RS) and the gut microbiome presents a dynamic frontier in nutrition science. This review synthesizes current understandings of how RS, an indigestible form of starch found naturally in certain foods and also enhanced through various modification methods, interacts with the gut microbiome. We particularly focus on how RS fermentation in the colon contributes to the production of beneficial volatile fatty acids (VFAs) such as butyrate, acetate, and propionate. These VFAs have been recognized for their vital roles in maintaining gut barrier integrity, modulating inflammation, and potentially influencing systemic health. Additionally, we discuss the dietary implications of consuming foods rich in RS, both in terms of gut health and broader metabolic outcomes. By consolidating these insights, we emphasize the significance of RS in the context of dietary strategies aimed at harnessing the gut microbiome's potential to impact human health.

Understanding the gut microbiota by considering human evolution: a story of fire, cereals, cooking, molecular ingenuity, and functional cooperation

SUMMARYThe microbial community inhabiting the human colon, referred to as the gut microbiota, is mostly composed of bacterial species that, through extensive metabolic networking, degrade and ferment components of food and human secretions. The taxonomic composition of the microbiota has been extensively investigated in metagenomic studies that have also revealed details of molecular processes by which common components of the human diet are metabolized by specific members of the microbiota. Most studies of the gut microbiota aim to detect deviations in microbiota composition in patients relative to controls in the hope of showing that some diseases and conditions are due to or exacerbated by alterations to the gut microbiota. The aim of this review is to consider the gut microbiota in relation to the evolution of Homo sapiens which was heavily influenced by the consumption of a nutrient-dense non-arboreal diet, limited gut storage capacity, and acquisition of skills relating to mastering fire, cooking, and cultivation of cereal crops. The review delves into the past to gain an appreciation of what is important in the present. A holistic view of "healthy" microbiota function is proposed based on the evolutionary pathway shared by humans and gut microbes.

Effects of the kinetic pattern of dietary glucose release on nitrogen utilization, the portal amino acid profile, and nutrient transporter expression in intestinal enterocytes in piglets

BACKGROUND

Promoting the synchronization of glucose and amino acid release in the digestive tract of pigs could effectively improve dietary nitrogen utilization. The rational allocation of dietary starch sources and the exploration of appropriate dietary glucose release kinetics may promote the dynamic balance of dietary glucose and amino acid supplies. However, research on the effects of diets with different glucose release kinetic profiles on amino acid absorption and portal amino acid appearance in piglets is limited. This study aimed to investigate the effects of the kinetic pattern of dietary glucose release on nitrogen utilization, the portal amino acid profile, and nutrient transporter expression in intestinal enterocytes in piglets.

METHODS

Sixty-four barrows (15.00 ± 1.12 kg) were randomly allotted to 4 groups and fed diets formulated with starch from corn, corn/barley, corn/sorghum, or corn/cassava combinations (diets were coded A, B, C, or D respectively). Protein retention, the concentrations of portal amino acid and glucose, and the relative expression of amino acid and glucose transporter mRNAs were investigated. In vitro digestion was used to compare the dietary glucose release profiles.

RESULTS

Four piglet diets with different glucose release kinetics were constructed by adjusting starch sources. The in vivo appearance dynamics of portal glucose were consistent with those of in vitro dietary glucose release kinetics. Total nitrogen excretion was reduced in the piglets in group B, while apparent nitrogen digestibility and nitrogen retention increased (P < 0.05). Regardless of the time (2 h or 4 h after morning feeding), the portal total free amino acids content and contents of some individual amino acids (Thr, Glu, Gly, Ala, and Ile) of the piglets in group B were significantly higher than those in groups A, C, and D (P < 0.05). Cluster analysis showed that different glucose release kinetic patterns resulted in different portal amino acid patterns in piglets, which decreased gradually with the extension of feeding time. The portal His/Phe, Pro/Glu, Leu/Val, Lys/Met, Tyr/Ile and Ala/Gly appeared higher similarity among the diet treatments. In the anterior jejunum, the glucose transporter SGLT1 was significantly positively correlated with the amino acid transporters B0AT1, EAAC1, and CAT1.

CONCLUSIONS

Rational allocation of starch resources could regulate dietary glucose release kinetics. In the present study, group B (corn/barley) diet exhibited a better glucose release kinetic pattern than the other groups, which could affect the portal amino acid contents and patterns by regulating the expression of amino acid transporters in the small intestine, thereby promoting nitrogen deposition in the body, and improving the utilization efficiency of dietary nitrogen.

New Insight into the Effects of Endogenous Protein and Lipids on the Enzymatic Digestion of Starch in Sorghum Flour

The effects of endogenous lipids and protein in sorghum flour on starch digestion were studied following the depletion of lipids and/or protein and after the reconstitution of separated fractions. The removal of protein or lipids moderately increases the digestibility of starch in raw (uncooked) sorghum flour to values close to those for purified starch. Rapid Visco Analyzer data (as a model for the cooking process) show that cooked sorghum flours with lipids have a lower starch digestibility than those without lipids after RVA processing, due to the formation of starch-lipid complexes as evidenced by their higher final viscosity and larger enthalpy changes. Additionally, the formation of a starch-lipid-protein ternary complex was identified in cooked sorghum flour, rather than in a reconstituted ternary mixture, according to the unique cooling stage viscosity peak and a greater enthalpy of lipid complexes. After heating, the sorghum flour showed a lower digestibility than the depleted flours and the reconstituted flours. The results indicate that the natural organization of components in sorghum flour is an important factor in facilitating the interactions between starch, lipids, and protein during RVA processing and, in turn, reducing the starch digestion.

Optimization of 4,6-α and 4,3-α-Glucanotransferase Production in Lactococcus lactis and Determination of Their Effects on Some Quality Characteristics of Bakery Products

In this study, the production of 4,6-α (4,6-α-GTase) and 4,3-α-glucanotransferase (4,3-α-GTase), expressed previously in Lactococcus lactis, was optimized and these enzymes were used to investigate glycemic index reduction and staling delay in bakery products. HP-SEC analysis showed that the relevant enzymes were able to produce oligosaccharides from potato starch or malto-oligosaccharides. Response Surface Methodology (RSM) was used to optimize enzyme synthesis and the highest enzyme activities of 15.63 ± 1.65 and 19.01 ± 1.75 U/mL were obtained at 1% glucose, pH 6, and 30 °C for 4,6-α-GTase and 4,3-α-GTase enzymes, respectively. SEM analysis showed that both enzymes reduced the size of the starch granules. These enzymes were purified by ultrafiltration and used to produce bread and bun at an enzyme activity of 4 U/g, resulting in a decrease in the specific volume of the bread. It was found that the estimated glycemic index (eGI) of bread formulated with 4,6-α-GTase decreased by 18.01%, and the eGI of bread prepared with 4,3-α-GTase decreased by 13.61%, indicating a potential delay in staling. No significant differences were observed in the sensory properties of the bakery products. This is the first study showing that 4,6-α-GTase and 4,3-α-GTase enzymes have potential in increasing health benefits and improving technological aspects regarding bakery products.

Heat-moisture treatment to modify structure and functionality and reduce digestibility of wrinkled and round pea starches

Heat-moisture treatment (HMT) was employed to modify wrinkled pea (74.2 % and 76.5 % amylose) and round pea starches (35.9 % and 34.8 % amylose) at 35.0 % moisture, 110 or 130 °C, and 6 h. HMT increased the gelatinization temperatures and decreased the gelatinization enthalpy changes, reduced the pasting viscosities and gel hardness, and enhanced the enzymatic resistance of the pea starches in comparison with the native counterparts, with greater extents of changes observed for HMT at 130 °C overall. Although HMT decreased the relative crystallinity and elevated the proportion of amorphous conformation, the remaining double-helical crystallites in the modified samples showed improved thermal stability as revealed by differential scanning calorimetry (DSC). More importantly, the HMT-modified pea starches required a higher heating temperature of 120 °C, rather than 95 °C, in Rapid Visco Analyser to provide greater pasting viscosities and develop firmer gels, suggesting that the modified samples had stronger molecular entanglement than the native counterparts. Such molecular entanglement could also reduce enzymatic digestion of HMT-modified starches after boiling in water. With more diverse functional profiles and increased resistant starch (RS) contents (particularly for the HMT-modified wrinkled pea starches having 22.7-29.9 % RS), the HMT-modified pea starches could be promising new ingredients for food applications.

Enhancing physicochemical, rheological properties, and in vitro rumen fermentation of starch with Melastoma candidum D. Don fruit extract

The utilization of polyphenol-modified starch in ruminants has not undergone extensive exploration. This study aimed to investigate the impact of the complex formed between starch and Melastoma candidum D. Don fruit extract on physicochemical properties, phenol release kinetics in various buffers simulating the gastrointestinal tract, methane production, and post-rumen digestibility. The interaction between starch and M. candidum D. Don fruit extract significantly (p < 0.001) increased resistant starch and particle size diameter. The maximum phenolic release from complex between starch and M. candidum D. Don fruit extract, due to gastrointestinal tract-simulated buffers, ranged from 22.96 to 34.60 mg/100 mg tannic acid equivalent. However, rumen and abomasum-simulated buffers released more phenolic content, whereas the intestine-simulated buffer showed higher antioxidant activity (ferric ion-reducing antioxidant power). Furthermore, complex between starch and M. candidum D. Don fruit extract significantly decreased dry matter rumen digestibility (p < 0.001) and maximum methane gas production (p < 0.001).

Starch ordered structures control starch reassembly behaviors during heat-moisture treatment for modulating its digestibility

This study investigated the effect of starch crystallinity on starch reassembly behaviors during the heat-moisture treatment (HMT) using starches with A-type crystal content of 0.00%-19.03%. The results showed that HMT reduced the native starch crystal content from 19.03% to 15.02% and increased starch thermostability, leading to a decrease in rapidly digestible starch (RDS) content from 86.91% to 76.71%. Moreover, starches containing a crystal content of 2.51%-8.11% exhibited significant reassembly during the HMT, and the resulting modified starches had more crystals and less RDS of 63.43%-69.31%. Interestingly, starches lacked A-type crystals but had some helical structures exhibiting A-type crystalline structures and lower digestibility after HMT. These findings verified that starch could significantly reassemble to form crystalline structures during the HMT. Controlling the crystal content of starch granules, particularly between 2.51% and 8.11%, was a promising approach for promoting starch reassembly during HMT and reducing starch digestibility.

A Comprehensive Review of the Effects of Glycemic Carbohydrates on the Neurocognitive Functions Based on Gut Microenvironment Regulation and Glycemic Fluctuation Control

Improper glycemic carbohydrates (GCs) consumption can be a potential risk factor for metabolic diseases such as obesity and diabetes, which may lead to cognitive impairment. Although several potential mechanisms have been studied, the biological relationship between carbohydrate consumption and neurocognitive impairment is still uncertain. In this review, the main effects and mechanisms of GCs' digestive characteristics on cognitive functions are comprehensively elucidated. Additionally, healthier carbohydrate selection, a reliable research model, and future directions are discussed. Individuals in their early and late lives and patients with metabolic diseases are highly susceptible to dietary-induced cognitive impairment. It is well known that gut function is closely related to dietary patterns. Unhealthy carbohydrate diet-induced gut microenvironment disorders negatively impact cognitive functions through the gut-brain axis. Moreover, severe glycemic fluctuations, due to rapidly digestible carbohydrate consumption or metabolic diseases, can impair neurocognitive functions by disrupting glucose metabolism, dysregulating calcium homeostasis, oxidative stress, inflammatory responses, and accumulating advanced glycation end products. Unstable glycemic status can lead to more severe neurological impairment than persistent hyperglycemia. Slow-digested or resistant carbohydrates might contribute to better neurocognitive functions due to stable glycemic response and healthier gut functions than fully gelatinized starch and nutritive sugars.

Recent progress in regulating starch digestibility using natural additives and sustainable processing operations

The development of a healthier and more sustainable food supply is a main concern of consumers, industry, governments, and international institutions. Foods containing high levels of rapidly digestible starches have been linked to a rise in the number of people suffering from diet-related chronic diseases. Consequently, there is interest in reducing the digestibility of starch to improve their healthiness. The ability of natural additives including proteins, dietary fibers, and polyphenols, and sustainable processing technologies such as high-intensity ultrasonic, pulsed electric field, non-thermal plasma, γ-ray irradiation that regulate reduce starch digestibility in foods are reviewed. The potential mechanisms of action, advantages, and disadvantages of each approach at inhibiting starch digestibility is highlighted. The potential for commercializing these technologies is discussed, and areas where further research are required are emphasized. Natural additives and sustainable processing operations can effectively reduce the digestibility of starch and inhibit postprandial sugar "spikes" in the bloodstream by adjusting the structural changes, which can be used to create healthier and more sustainable foods and have broad application prospects.

Raman Multi-Omic Snapshots of Koshihikari Rice Kernels Reveal Important Molecular Diversities with Potential Benefits in Healthcare

This study exploits quantitative algorithms of Raman spectroscopy to assess, at the molecular scale, the nutritional quality of individual kernels of the Japanese short-grain rice cultivar Koshihikari in terms of amylose-to-amylopectin ratio, fractions of phenylalanine and tryptophan aromatic amino acid residues, protein-to-carbohydrate ratio, and fractions of protein secondary structures. Statistical assessments on a large number of rice kernels reveal wide distributions of the above nutritional parameters over nominally homogeneous kernel batches. This demonstrates that genetic classifications cannot catch omic fluctuations, which are strongly influenced by a number of extrinsic factors, including the location of individual grass plants within the same rice field and the level of kernel maturation. The possibility of collecting nearly real-time Raman "multi-omic snapshots" of individual rice kernels allows for the automatic (low-cost) differentiation of groups of kernels with restricted nutritional characteristics that could be used in the formulation of functional foods for specific diseases and in positively modulating the intestinal microbiota for protection against bacterial infection and cancer prevention.

Interaction between starch and dietary compounds: New findings and perspectives to produce functional foods

Due to the increased prevalence of overweight, obesity, diabetes, colon cancer, cardiovascular diseases, and metabolic syndrome, dietary approaches to reduce starch digestion and regulate glucose homeostasis have gained attention. Starch is a polysaccharide in most daily food consumed as bakery products, snacks, breakfast cereals, and pasta, which are often vilified. However, it is also present in beans, lentils, and oatmeal, which are considered healthy food products. The difference relays on the food matrix and the thermal process that can produce interactions between starch and dietary compounds (protein, lipid, non-starch polysaccharide, and bioactive compounds) or among starch chains (retrogradation). Such interactions produce structural changes so the digestive enzymes cannot hydrolyze them; additionally, the physical barrier of some macromolecules (proteins, hydrocolloids) restricts starch gelatinization and accessibility of the digestive enzymes to hydrolyze the starch. The interactions mentioned above and the use of some macromolecules as physical barriers could be explored as a pathway to develop functional foods. This review analyzes the interactions between starch and dietary compounds influenced by the processing of some food matrices to better understand their potential for developing functional foods.

Slow Digestible Starch in Native Pea Starch (Pisum sativum L.) Lowers Glycemic Response with No Adverse Effects on Gastrointestinal Symptoms in Healthy Adults

Diabetes prevalence achieved 470B in 2021. Diabetics are looking for foods that allow them to better manage the postprandial glycemia. Owing to its large amylose fraction, pea starch may contribute to formulate recipes with a lower glycemic index (GI). This study measured the rapidly, slowly digested and resistant fractions in pea starch and in a powder mix recipe. Starch fractions were determined according to the Englyst methodology. A nonblind repeat measure crossover design trial in healthy humans was used to study the GI of pea starch and maltodextrin powder mix recipes against glucose. Gastrointestinal symptoms were measured. Thirteen healthy volunteers aged 18-60 years with body mass index <30 kg/m2 and fasting blood glucose <6.1 mmol/L participated in the study. They consumed 25 g available carbohydrate portions of the test products. Blood glucose was measured at -5 and 0 min before consumption till 180 min after starting to eat. The slow digestible starch (SDS) content of native pea starch was 30% of the total starch content. The pea-based powder mix recipe contained 25% SDS in comparison with 9% for the maltodextrin-based recipe. The glucose response after pea starch was significantly lower compared with maltodextrin. The glucose response after pea starch recipe was significantly lower compared with maltodextrin recipe. There was no significant difference in mean scores for well-being and gastrointestinal symptoms after consumption of pea starch and maltodextrin or between the two recipes. In conclusion, this study has demonstrated the presence of high SDS content in pea starch, which reduced postprandial glycemic response compared with maltodextrin. The pea starch recipe did not induce any negative gastrointestinal symptoms. Pea starch may, therefore, prove to be a beneficial ingredient in developing food products for improving glycemic control without undesirable side effects.

Genotype specific starch characteristics in relation to resistant starch formation in table potatoes

Table potatoes are important staple foods with a higher satiety index than rice or pasta, but also reach a higher glycemic index (GI), leading to contradictory dietary recommendations. Previous studies identified resistant starch (RS) content as primary criterium for the GI. Hence, the relevance of starch molecular properties for genotype specific RS formation was investigated. Six common table potato varieties were used to investigate the starch pasting and digestibility in whole tubers and their isolated starches. A Micro-Visco Amylograph was used to simulate the cooking process for isolated starches and determine their pasting curves. In vitro starch digestibility was determined for raw freeze-dried cooked tubers kept at 4 °C for up to 72 h and for isolated starches. Moreover, important molecular starch properties, including granule size distribution, molar mass distribution, amylose content and inter- and intra-molecular structures were determined. The results show substantial differences in starch digestibility and pasting characteristics among genotypes. Soraya starch showed small and low-branched amylopectin and small granule size as characteristics for rapid RS formation in isolated starch, which was not evident in the whole tuber. In contrast, Huckleberry Gold formed RS in the tuber already shortly after cooking, whereas slow RS formation was evident in the isolated starch. The results suggest, that starch structural characteristics play a role in RS formation, but non-starch constituents of the tuber have to be considered as well. The results help to identify breeding goals for varieties with low GI and high nutritional value.

Structural characterization of different starch-fatty acid complexes and their effects on human intestinal microflora

Resistant starch type 5 (RS5), a starch-lipid complex, exhibited potential health benefits in blood glucose and insulin control due to the low digestibility. The effects of the crystalline structure of starch and chain length of fatty acid on the structure, in vitro digestibility, and fermentation ability in RS5 were investigated by compounding (maize, rice, wheat, potato, cassava, lotus, and ginkgo) of different debranched starches with 12-18C fatty acid (lauric, myristic, palmitic, and stearic acids), respectively. The complex showed a V-type structure, formed by lotus and ginkgo debranched starches, and fatty acid exhibited a higher short-range order and crystallinity, and lower in vitro digestibility than others due to the neat interior structure of more linear glucan chains. Furthermore, a fatty acid with 12C (lauric acid)-debranched starches complexes had the highest complex index among all complexes, which might be attributed to the activation energy required for complex formation increased with the lengthening of the lipid carbon chain. Therefore, the lotus starch-lauric acid complex (LS12) exhibited remarkable ability in intestinal flora fermentation to produce short-chain fatty acid (SCFAs), reducing intestinal pH, and creating a favorable environment for beneficial bacteria.

Influence of instant rice characteristics and processing conditions on starch digestibility-A review

Instant rice is increasingly popular around the world due to its convenience, but it commonly has a high glycemic index, and a frequent consumption might contribute to the occurrence of many chronic diseases. In this review, the main factors determining starch digestibility of instant rice were comprehensively evaluated, aiming to help the rice industry develop instant rice with slow starch digestibility. Starch digestibility in instant rice can be reduced by manipulating its intrinsic and extrinsic nutrients. Processing conditions, including pre-gelatinization, storage, and reheating are also important for the starch digestibility of instant rice. Individual differences in terms of glycemic response to the same carbohydrate-based diet should be considered when knowledge is transformed from in vitro method to human conditions. This review contains important information that has the potential to reduce the starch digestibility of instant rice and improve public health.

The effect of psyllium fiber on the in vitro starch digestion of steamed and roasted wheat based dough

This study aimed to determine how the addition of psyllium fiber to steamed and roasted wheat-based flat dough pieces affected the in vitro starch digestibility. Wheat flour was replaced with 10% psyllium fiber in the preparation of fiber-enriched dough samples. Two distinct methods of heating were utilised: steaming (100 °C, 2 min & 10 min) and roasting (100 °C, 2 min & 250 °C, 2 min). Rapidly digestible starch (RDS) fractions reduced significantly in both steamed and roasted samples, whereas slowly digestible starch (SDS) fractions increased significantly only in samples roasted at 100 °C and steamed for 2 min. The roasted samples had a lower RDS fraction than the steamed samples only when fiber was added. This study demonstrated the effect of processing method, duration, temperature, formed structure, matrix and the addition of psyllium fiber on in vitro starch digestion by altering starch gelatinization, gluten network, and consequently enzyme access to substrates.

Structural basis for rice starch multi-digestible fractions revealed by consecutive reaction kinetics model

BACKGROUND

Starch-based foods (e.g. rice) usually contain multiple starch fractions with distinct digestion rate constants, although their nature is currently unknown. The present study applied the recently developed consecutive reaction kinetics model to fit the in vitro digestion curves for starch fractions deconvoluted from the overall digestograms to differentiate their binding and catalysis rates to starch digestive enzymes. The fitting parameters were then correlated with starch molecular structures obtained from published data to understand starch structural features determining the binding and catalytic rate constants.

RESULTS

Binding and catalysis rates for the rapidly (RDF) and slowly digestible starch fraction (SDF) were controlled by distinct starch structural features. Typically, (i) the binding rate constant for RDF was negatively correlated with the amount of amylose short to intermediate chains, whereas it was positively correlated with the relative length of amylopectin intermediate chains; (ii) the catalysis rate constant for RDF was negatively correlated with the amount of amylose short to intermediate chains, relative length of amylose intermediate chains and amount of amylopectin long chains, whereas it was positively correlated with starch molecular size as well as relative length of amylopectin intermediate chains; (iii) and the catalysis rate constant for SDF was negatively correlated with the amount of amylopectin long chains, whereas it was positively correlated with starch molecular size.

CONCLUSION

These results provide a better understanding of the nature of different starch digestible fractions and the development of foods such as rice with slow starch digestibility. © 2023 Society of Chemical Industry.

Functional Food Based on Potato

Potato (Solanum tuberosum L.) has gradually become a stable food worldwide since it can be a practical nutritional supplement and antioxidant as well as an energy provider for human beings. Financially and nutritionally, the cultivation and utility of potatoes is worthy of attention from the world. Exploring the functionality and maximizing the utilization of its component parts as well as developing new products based on the potato is still an ongoing issue. To maximize the benefits of potato and induce new high-value products while avoiding unfavorable properties of the crop has been a growing trend in food and medical areas. This review intends to summarize the factors that influence changes in the key functional components of potatoes and to discuss the focus of referenced literature which may require further research efforts. Next, it summarizes the application of the latest commercial products and potential value of components existing in potato. In particular, there are several main tasks for future potato research: preparing starchy foods for special groups of people and developing fiber-rich products to supply dietary fiber intake, manufacturing bio-friendly and specific design films/coatings in the packaging industry, extracting bioactive proteins and potato protease inhibitors with high biological activity, and continuing to build and examine the health benefits of new commercial products based on potato protein. Notably, preservation methods play a key role in the phytochemical content left in foods, and potato performs superiorly to many common vegetables when meeting the demands of daily mineral intake and alleviating mineral deficiencies.

Macromolecular α-glucans with α-1,3/α-1,4 branching structures produced using dual glycosyltransferases: Elucidation of physicochemical and slowly digestible properties

Amylosucrase from Neisseria polysaccharea (NpAS) produces the linear amylose-like α-glucans by the elongation property from sucrose, and 4,3-α-glucanotransferase from Lactobacillus fermentum NCC 2970 (4,3-αGT) newly synthesizes the α-1,3 linkages after cleaving the α-1,4 linkages by the glycosyltransferring property. This study focused on the synthesis of high molecular α-1,3/α-1,4-linked glucans by combining NpAS and 4,3-αGT and analyzed their structural and digestive properties. The enzymatically synthesized α-glucans have a molecular weight of >1.6 × 10⁷ g mol^-1, and the α-4,3 branching ratios on the structures increased as the amount of 4,3-αGT increased. The synthesized α-glucans were hydrolyzed to linear maltooligosaccharides and α-4,3 branched α-limit dextrins (α-LDx) by human pancreatic α-amylase, and the amounts of produced α-LDx were increased depending on the ratio of synthesized α-1,3 linkages. In addition, approximately 80 % of the synthesized products were partially hydrolyzed by mammalian α-glucosidases, and the glucose generation rates decelerated as the amounts of α-1,3 linkages increased. In conclusion, new types of α-glucans with α-1,4 and α-1,3 linkages were successfully synthesized by a dual enzyme reaction. These can be utilized as slowly digestible and prebiotic ingredients in the gastrointestinal tract due to their novel linkage patterns and high molecular weights.

Dragon Fruit Peel Waste (Hylocereus undatus) as a Potential Ingredient for Reducing Lipid Peroxidation, Dietary Advanced Glycation End Products, and Starch Digestibility in Cookies

Excessive consumption of cookies has been linked to harmful health outcomes owing to the presence of refined carbohydrates and heat-induced toxicants including end products of lipid peroxidation and dietary advanced glycation end products (dAGEs). To address this issue, this study explores the addition of dragon fruit peel powder (DFP), which is rich in phytochemicals and dietary fibers, to cookies as a potential solution to mitigate their adverse effects. The results indicate that adding DFP at 1%, 2%, and 5% w/w of raw cookie dough significantly improves the total phenolic and betacyanin contents and antioxidant activity, as evidenced by increased ferric-reducing antioxidant power. DFP incorporation also led to reductions in malondialdehyde and dAGEs (p < 0.05). Furthermore, the starch digestibility, hydrolysis index, and predicted glycemic index were all reduced in the presence of DFP, with the latter estimate being due to the higher content of undigested starch. Incorporating DFP in cookies resulted in significant changes in their physical properties, including texture and color. However, sensory evaluation indicates that the overall acceptability of the cookies was not negatively impacted by the addition of up to 2% DFP, suggesting that it is a viable option for enhancing the nutritional value of cookies without compromising their palatability. These findings suggest that DFP is a sustainable and healthier ingredient that can improve the antioxidant capacity of cookies while also mitigating the harmful effects of heat-induced toxins.

Nutritional Management of Cats and Dogs with Diabetes Mellitus

This article reviews the nutritional assessment and management of diabetic dogs and cats. It discusses how to determine appropriate nutritional goals for individual patients, including comorbid patients with diabetes. Considerations for macronutrient and micronutrient modifications will be reviewed.

Bread Products from Blends of African Climate Resilient Crops: Baking Quality, Sensory Profile and Consumers' Perception

With food insecurity rising dramatically in Sub-Saharan Africa, promoting the use of sorghum, cowpea and cassava flours in staple food such as bread may reduce wheat imports and stimulate the local economy through new value chains. However, studies addressing the technological functionality of blends of these crops and the sensory properties of the obtained breads are scarce. In this study, cowpea varieties (i.e., Glenda and Bechuana), dry-heating of cowpea flour and cowpea to sorghum ratio were studied for their effects on the physical and sensory properties of breads made from flour blends. Increasing cowpea Glenda flour addition from 9 to 27% (in place of sorghum) significantly improved bread specific volume and crumb texture in terms of instrumental hardness and cohesiveness. These improvements were explained by higher water binding, starch gelatinization temperatures and starch granule integrity during pasting of cowpea compared to sorghum and cassava. Differences in physicochemical properties among cowpea flours did not significantly affect bread properties and texture sensory attributes. However, cowpea variety and dry-heating significantly affected flavour attributes (i.e., beany, yeasty and ryebread). Consumer tests indicated that composite breads could be significantly distinguished for most of the sensory attributes compared to commercial wholemeal wheat bread. Nevertheless, the majority of consumers scored the composite breads from neutral to positive with regard to liking. Using these composite doughs, chapati were produced in Uganda by street vendors and tin breads by local bakeries, demonstrating the practical relevance of the study and the potential impact for the local situation. Overall, this study shows that sorghum, cowpea and cassava flour blends can be used for commercial bread-type applications instead of wheat in Sub-Saharan Africa.

A novel very small granular starch from Chlorella sp. MBFJNU-17

Novel resources of very small granular starch are of great interests to food scientists. We previously found Chlorella sp. MBFJNU-17 contained small granular starch but whether the MBFJNU-17 was a novel resource of very small granular starch remained unresolved. This study isolated and characterized the starch from MBFJNU-17 in comparison with quinoa starch (a typical very small granular starch), and discussed whether the MBFJNU-17 could be a resource of very small granular starch. Results showed that chlorella starch displayed a smaller size (1024 nm) than quinoa starch did (1107 nm), suggesting MBFJNU-17 was a good resource of very small granular starch. Additionally, chlorella starch had less amylose, higher proportion of long amylopectin branches, more ordered structures, thinner amorphous lamellae, better paste thermostability, and slower enzymatic digestion than quinoa starch did. These findings indicated that Chlorella sp. MBFJNU-17 was a novel resource of very small granular starch with desirable thermostability and nutritional attributes.

Resistant starch from sweet potatoes: Recent advancements and applications in the food sector

In tropical and subtropical areas, tuber and root crops are staple foods and a key source of energy. Sweet potato (SP) is currently regarded as one of the world's top ten foods because of its diverse sizes, shapes, color, and health benefits. The resistant starch (RS) content of SP is substantial. It is predicted to become the cheapest item in the food industry due to its extensive variety, food stability, emulsifier and fat substitution capabilities, and as filler. As a result, interest in SP-sourced RS has recently increased. Due to their unique nutritional and functional qualities, novelty has become a popular research focus in recent years. This review will summarize the current understanding of SP starch components and their impact on the technological and physicochemical properties of produced starch for commercial viability. The importance of sweet potato RS in addressing future RS demand sustainability is emphasized. SPs are a viable alternative to tubers as a sustainable raw material for RS production. It has an advantage over tubers because of its intrinsic nutritional value and climatic endurance. Thermal, chemical, and enzymatic treatments are effective RS manufacturing procedures. The adaptability of sweet potato RS allows for a wide range of food applications.

Effect of autoclave-cooling cycles combined pullulanase on the physicochemical and structural properties of resistant starch from black Tartary buckwheat

A starch-rich portion is produced as a by-product of black Tartary buckwheat processing. The effect of enzymatic combined with autoclaving-cooling cycles (one, two, or three times) on the physicochemical and structural properties of black Tartary buckwheat type 3 resistant starch (BRS) was evaluated. The autoclaving-cooling cycles enhanced solubility and reduced swelling, with the BRS content increasing from 14.12% to 25.18%. The high crystallinity of the BRS reflected a high molecular order. However, increasing the number of autoclaving-cooling cycles did not result in higher BRS content. The highest BRS yield in the autoclaved starch samples was 25.18% after double-autoclaving-cooling cycles. Furthermore, the autoclaving-cooling cycles altered the crystalline structure of black Tartary buckwheat, and the subsequent crystallinity changed from 36.33% to 42.05% to 38.27%. Fourier-transform infrared spectroscopy shows that the number of cycles results in more efficient double-helical packing within the crystalline lamella. Principal component analysis showed that the autoclaving-cooling cycle treatment leads to significant changes in the molecular structure of resistant starch (RS). These results indicated that autoclaving-cooling cycles might be a feasible way for producing RS from black Tartary buckwheat starch with better structural stability to expand their application range.

Starch fine molecular structures: The basis for designer rice with slower digestibility and desirable texture properties

Development of whole rice with low glycaemic index has been achieved, however, these rices are frequently associated with a poor texture property. Recent advances in terms of understanding the importance of starch fine molecular structures on the starch digestibility/texture of cooked whole rice have shed new insights on mechanisms of starch digestibility and texture from molecular levels. With an extensive discussion on the correlative and causal relationships among starch molecular structure, texture and starch digestibility of cooked whole rice, this review identified desirable starch fine molecular structures contributing to both slow starch digestibility and preferable textures. For instance, the selection of rice variety having more amylopectin intermediate chains while less amylopectin long chains might help develop cooked whole rice with both slower starch digestibility and softer texture. The information could help rice industry transform cooked whole rice into a healthier food product with slow starch digestibility and desirable texture.

Sorghum in foods: Functionality and potential in innovative products

Sorghum grain is a staple food for about 500 million people in 30 countries in Africa and Asia. Despite this contribution to global food production, most of the world's sorghum grain, and nearly all in Western countries, is used as animal feed. A combination of the increasingly important ability of sorghum crops to resist heat and drought, the limited history of the use of sorghum in Western foods, and the excellent functional properties of sorghum grain in healthy diets, suggests a greater focus on the development of new sorghum-based foods. An understanding of the structural and functional properties of sorghum grain to develop processes for production of new sorghum-based foods is required. In this review, we discuss the potential of sorghum in new food products, including sorghum grain composition, the functional properties of sorghum in foods, processing of sorghum-based products, the digestibility of sorghum protein and starch compared to other grains, and the health benefits of sorghum. In the potential for sorghum as a major ingredient in new foods, we suggest that the gluten-free status of sorghum is of relatively minor importance compared to the functionality of the slowly digested starch and the health benefits of the phenolic compounds present.

Starch, gallic acid, their inclusion complex and their effects in diabetes and other diseases—A review

Starch is the most important energy-providing component of food. It is useful for maintaining the structural and rheological consistency of food, ad thus, in turn, is responsible for maintaining the freshness of food. Polyphenols are present in plant products in huge amounts as secondary metabolites. Gallic acid, one of the potent plant polyphenols, has been reported to have excellent anti-inflammatory, antioxidative, anticarcinogenic, microbicidal, and antidiabetic properties. Till date, very few articles on the starch-polyphenol inclusion complex are present. Quite a few hypotheses have been proposed as to how the formation of an inclusion complex of starch with polyphenol can slower the digestion or the hydrolysis of starch. The efficient qualities of starch-polyphenol systems, such as reduced starch digestion, lower blood glucose and preserving food freshness, have formed a necessity for investigation in this area. The focus of this review centers on the recent research on starch-polyphenol interactions and starch-gallic acid inclusion complexes in native and extruded food systems, as well as how the production of these complexes can aid in the treatment of diseases, particularly diabetes mellitus.

Enrichment of Wholemeal Rye Bread with Plant Sterols: Rheological Analysis, Optimization of the Production, Nutritional Profile and Starch Digestibility

Bread is one of the staple foods of many countries, and its enrichment with bioactive compounds is trending. This phenomenon is focused on breads with a good nutritional profile, such as wholemeal rye bread (WRB), in which enrichment with plant sterols (PSs) is allowed in accordance with European regulations. The objective of the present study was to optimize the production of a WRB enriched with PS (PS-WRB) and to evaluate the proximate composition and starch digestibility as an indicator of nutritional quality. The rheological analysis showed that the bread dough presents satisfactory farinographic properties (dough development time 6 min; stability 4 min; degree of softening 100 Brabender units) but high water absorption (67%). The PS-WRB is high in dietary fiber and low in protein (20.4 and 7.7% w/w, dry basis, respectively) compared with other cereals reported in the scientific literature. In turn, a low starch proportion was hydrolyzed during the simulated digestion (59.9% of total starch), being also slowly hydrolyzed, as deduced from the rapidly digestible starch value (56.5% of total starch). In conclusion, WRB is a suitable matrix for PS enrichment, which allows for obtaining a product with a good nutritional profile and potential health benefits.

The Effects of Starch Molecular Fine Structure on Thermal and Digestion Properties of Rice Starch

Whole white rice is a major staple food for human consumption, with its starch digestion rate and location in the gastrointestinal tract having a critical role for human health. Starch has a multi-scale structure, which undergoes order-disorder transitions during rice cooking, and this structure is a major determinant of its digestibility. The length distributions of amylose and amylopectin chains are important determinants of rice starch gelatinization properties. Starch chain-length and molecular-size distributions are important determinants of nucleation and crystal growth rates, as well as of intra- and intermolecular interactions during retrogradation. A number of first-order kinetics models have been developed to fit starch digestograms, producing new information on the structural basis for starch digestive characteristics of cooked whole rice. Different starch digestible fractions with distinct digestion patterns have been found for the digestion of rice starch in fully gelatinized and retrograded states, the digestion kinetics of which are largely determined by starch fine molecular structures. Current insights and future directions to better understand digestibility of starch in whole cooked rice are summarized, pointing to ways of developing whole rice into a healthier food by way of having slower starch digestibility.

Relations between in vitro starch digestibility of commercial baked products and their macronutrients

BACKGROUND

Baked products such as biscuits and breads are the staple foods for a large population, with the starch digestion rate having a crucial effect on human health. Currently, there is a lack of information on general starch digestibility in commercial baked products and its correlation with macronutrient content.

RESULTS

The present study investigated the starch digestibility of 35 commercial baked products, ranging from low to high moisture contents. Biscuits generally had a slower starch digestion rate than mini-breads, whereas breads including whole wheat bread had the fastest digestion rate. Additionally, starch digestibility was negatively correlated with the calorie (R²  = 0.71) and fat content (R²  = 0.56) in per serving size, possibly because of the formation of amylose-lipid complex.

CONCLUSION

The present study provides a database for the in vitro starch digestibility of a large number of food items, which gives general indications on the performance of starch components of commercial products in the human gastrointestinal tract. © 2022 Society of Chemical Industry.

Butyrate-producing colonic clostridia: picky glycan utilization specialists

Butyrate-producing human gut microbiota members are recognized for their strong association with a healthy immune-homeostasis and protection from inflammatory disorders and colorectal cancer. These effects are attributed to butyrate, the terminal electron sink of glycan fermentation by prevalent and abundant colonic Firmicutes from the Lachnospiraceae and Oscillospiraceae families. Remarkably, our insight into the glycan utilization mechanisms and preferences of butyrogenic Firmicutes remains very limited as compared with other gut symbionts, especially from the Bacteroides, Bifidobacterium, and Lactobacillus genera. Here, we summarize recent findings on the strategies that colonic butyrate producers have evolved to harvest energy from major dietary fibres, especially plant structural and storage glycans, such as resistant starch, xylans, and mannans. Besides dietary fibre, we also present the unexpected discovery of a conserved protein apparatus that confers the growth of butyrate producers on human milk oligosaccharides (HMOs), which are unique to mother’s milk. The dual dietary fibre/HMO utilization machinery attests the adaptation of this group to both the infant and adult guts. These finding are discussed in relation to the early colonization of butyrogenic bacteria and the maturation of the microbiota during the transition from mother’s milk to solid food. To date, the described butyrogenic Firmicutes are glycan utilization specialists that target only a few glycans in a highly competitive manner relying on co-regulated glycan utilization loci. We describe the common pillars of this machinery, highlighting butyrate producers as a source for discovery of biochemically and structurally novel carbohydrate active enzymes.