The adsorption of α-amylase on barley proteins affects the in vitro digestion of starch in barley flour

Key structural factors that determine the in vitro enzymatic digestibility of amylose-complexes

The effects of complexing conditions on the formation of amylose-lipid-protein complexes and relationships between structure and digestion of amylose-lipid and amylose-lipid-protein complexes were poorly understood. The objective of this study was to investigate the effects of complexing time (0, 0.5, 2, 4 and 6 h) and temperature (60, 70, 80, 90 and 100 °C) on the structure and in vitro amylolysis of amylose-lauric acid (AM-LA) and amylose-lauric acid-β-lactoglobulin (AM-LA-βLG) complexes, and to understand the relationships between structure and in vitro digestiblity of these complexes. Longer complexing time and higher complexing temperature promoted the formation of greater amounts of the more stable type II crystallites than type I crystallites in both AM-LA and AM-LA-βLG complexes, which in turn decreased the rate and extent of the complexes digestion to a greater extent. Correlation analyses between parameters for structure and digestion kinetics showed that both the quantity of AM-LA and AM-LA-βLG complexes and the quality of their arrangement into V-type crystallites influenced their rate and extent of digestion. This study demonstrates that AM-LA and AM-LA-βLG complexes can be prepared with designed structural and functional properties tailored for various applications.

The particle sizes of milled wheat fractions affect the in vitro starch digestibility and quality parameters of wire-cut cookies made thereof

Slow digestion of starch is linked to various health benefits. The impact of wheat particle size on in vitro starch digestibility and quality of wire-cut cookies was here evaluated by including four soft wheat fractions [i.e. flour (average diameter, 83 μm), fine farina (643 μm), coarse farina (999 μm) and bran (1036 μm)] in the recipe. The susceptibility of starch in these fractions to in vitro digestion decreased with increasing particle size, resulting in a 76% lower digestion rate for coarse farina than for flour as found with the single first-order kinetic model. Starch was protected from hydrolysis likely due to delayed diffusion of pancreatic α-amylase through the intact farina cell walls. When 20-65% starch in flour for the control cookie recipe was substituted with the same percentages in fine and coarse farina, the starch digestion rate decreased when substitution levels increased. A 62% lower digestion rate was found at 65% substitution with coarse farina. Cell wall intactness was largely preserved in the cookies and most of the starch appeared as ungelatinised granules. Further, the cookie spread ratio during baking was 48% and 33% higher and the cookies were 63% and 57% less hard than control cookies when made with 65% fine farina and 65% coarse farina, respectively. The relatively low specific surface area of large wheat particles resulted in low water absorption and less dense packing. In conclusion, encapsulation of starch by intact cell walls in coarse wheat fractions makes them promising ingredients when developing starchy food products for controlled energy release.

Effects of adding proteins from different sources during heat-moisture treatment on corn starch structure, physicochemical and in vitro digestibility

Proteins impact starch digestion, but the specific mechanism under heat-moisture treatment remains unclear. This study examined how proteins from various sources-white kidney bean, soybean, casein, whey-altered corn starch's structure, physicochemical properties, and digestibility during heat-moisture treatment (HMT). HMT and protein addition could significantly reduce starch's digestibility. The kidney bean protein-starch complex under HMT had the highest resistant starch at 19.74 %. Most proteins effectively inhibit α-amylase, with kidney bean being the most significantly (IC50 = 1.712 ± 0.085 mg/mL). HMT makes starch obtain a more rigid structure, limits its swelling ability, and reduces paste viscosity and amylose leaching. At the same time, proteins also improve starch's short-range order, acting as a physical barrier to digestion. Rheological and low-field NMR analyses revealed that protein enhanced the complexes' shear stability and water-binding capacity. These findings enrich the understanding of how proteins from different sources affect starch digestion under HMT, aiding the creation of nutritious, hypoglycemic foods.

Effects of protein morphological structures on the cereal processing, sensorial property and starch digestion: a review

In cereals, the protein body and protein matrix are usually two morphological protein structures. However, processing treatments can affect protein structures, change protein bodies into the matrix, or induce a change in the matrix structure; therefore, the processing-induced matrix was listed as the third morphological structure of the protein. Previous research on the effect of proteins was mainly based on protein content and composition, but these studies arrived at different conclusions. Studying the effect of protein morphological structures on sensorial property and starch digestion can provide a theoretical basis for selecting cultivars with high sensorial property and help produce low-glycemic index foods for people with diabetes, controlling their postprandial blood sugar. This study aimed to review the distribution and structure of protein bodies, protein matrices, and processing-induced matrices, as well as their influence on cereal sensorial property and starch digestion. Therefore, we determined the protein morphological structures in different cereal cultivars and summarized its impact. Protein bodies mainly have steric stabilization effects on starch gelatinization, whereas the protein matrix serves as a physical barrier surrounding the starch to inhibit water absorption and α-amylase. Processing can change protein morphological structures, enabling protein bodies to act as a physical matrix barrier.

A review of endogenous non-starch components in cereal matrix: spatial distribution and mechanisms for inhibiting starch digestion

As compared with exogenous components, non-starch components (NSCS), such as proteins, lipids, non-starch polysaccharides (NSPs), and polyphenols, inherently present in cereals, are more effective at inhibiting starch digestibility. Existing research has mostly focused on complex systems but overlooked the analysis of the in-situ role of the NSCS. This study reviews the crucial mechanisms by which endogenous NSCS inhibit starch digestion, emphasizing the spatial distribution-function relationship. Starch granules are filled with pores/channels-associated proteins and lipids, embedding in the protein matrix, and maintained by endosperm cell walls. The potential starch digestion inhibition of endogenous NSCS is achieved by altering starch gelatinization, molecular structure, digestive enzyme activity, and accessibility. Starch gelatinization is constrained by endogenous NSCS, particularly cell wall NSPs and matrix proteins. The stability of the starch crystal structure is enhanced by the proteins and lipids distributed in the starch granule pores and channels. Endogenous polyphenols greatly inhibit digestive enzymes and participate in the cross-linking of NSPs in the cell wall space, which together constitute a physical barrier that hinders amylase diffusion. Additionally, the spatial entanglement of NSCS and starch under heat and non-heat processing conditions reduces starch accessibility. This review provides novel evidence for the health benefits of whole cereals.

Pretreatments and Particle Size on the Glycemic Index and Rheological and Functional Food Properties of Bean Flours

The beans' protein and slow-digesting carbohydrate content make it an appealing choice for healthy food development. However, its properties are influenced by the flour extraction processes. This study is aimed at evaluating the effect of particle size and three pretreatments-drying (D), soaking + cooking + dehydrating 3 h (SCD3), and soaking + cooking + dehydrating 24 h (SCD24)-on the estimated glycemic index (eGI) compared with raw bean flour (R). The methodology covered water absorption (WAI), water solubility (WSI), amylose content, starch digestibility, eGI, phenolic quantification, and rheology. The results showed that WAI correlated negatively with WSI and amylose, varying among pretreatments and sizes. WAI increased as D < SCD24 < SCD3 < R. Glucose release (HI) differed between fine (125 μm) and coarse fractions (242 μm), with SCD24 and R showing the lowest eGI (22.8-24.2). SCD3 had the highest flavonoid concentration, while R and D had more quercetin-3-glucoside. SCD24 displayed higher elastic/viscous moduli than R. Bean flours from all treatments had low GI and contained bioactive polyphenols (catechin, epicatechin, ferulic acid, quercetin). The optimal treatment was SCD24, particularly in the coarse fraction, showing potential for functional food development and novel applications such as precision nutrition.

Impact of red kidney bean protein on starch digestion and exploring its underlying mechanism

This study aimed to investigate the effect of different proportions of red kidney bean protein (RKP) on the digestibility of co-gelatinized wheat starch (WS) and corn starch (CS), as well as explore the potential underlying mechanisms. The results showed a significant reduction in both the rate and extent of digestion for WS and CS after adding the RKP during co-gelatinization. Furthermore, incorporating RKP at 0 % to 20 % levels increased the content of resistant starch (RS) by 34.89 % and 14.43 % in the digested systems of wheat starch and maize starch, respectively, while decreasing the concentration of rapidly digestible starch (RDS) by 12.24 % and 20.39 %, respectively. Furthermore, RKP was found to inhibit α-amylase in a dose-dependent and non-competitive manner. Its interaction with starch occurred through hydrogen bonds and hydrophobic interactions, resulting in a modification of the short-range ordered structure of starch and ultimately leading to inhibition of starch digestion. The physical barrier effect of RKP on starch digestion also contributed to its inhibitory action. Considering the health-related delay in the rate and extent of postprandial starch digestion, Our findings have important inspirational value for the use of red kidney bean protein in hypoglycemic foods.

Mechanisms of rice protein hydrolysate regulating the in vitro digestibility of rice starch under extrusion treatment in terms of structure, physicochemical properties and interactions

The effect of protein hydrolysates on starch digestibility has been observed in other heat treatments but has yet to be extensively researched under extrusion. This study aimed to analyze the physicochemical properties, structure, and starch digestibility of extruded rice starch-protein hydrolysate (ERS-RPH) complexes prepared by extrusion treatment. The resistant starch contents of ERS-RPH (12.30 %-19.36 %) were higher than those of extruded starch alone (6.33 %). The interaction forces, physical barrier effects, and enzyme inhibition indicated that RPHs at varying hydrolysis degrees hindered starch digestibility by reducing its contact with enzyme and via adhesion and hydrogen bonding with starch. RPHs with higher hydrolysis exhibited greater inhibition of starch digestibility, limiting the swelling power of starch and the leaching of amylose, thereby improving the thermal stability of starch. Fourier transform infrared spectroscopy results revealed the presence of hydrogen bonding interactions between RPHs and starch in complexes, intensifying the ordered structure of starch. Extrusion caused an increase of 6.8 %-10.8 % in the relative crystallinity of ERS-RPH compared to extruded starch alone. Moreover, the strength of V-type structure was reinforced after extrusion. These results enhanced comprehension of how PRHs regulate starch digestibility under extrusion, and offer direction for producing slow-digesting foods.

Enrichment of resistant starch in starch-protein hydrolysate binary matrix by modulating pH during thermal processing

Controlling the digestion features of starch-based food matrices following thermal processing plays vital roles in reducing risks of metabolic diseases such as obesity and type II diabetes. To date, it remains largely unclear how regulating the pH during thermal processing alters the microstructure and digestion features of starch-based matrix including protein hydrolysates. Considering this, corn starch (CS) and soybean protein isolate (SPI) (or its hydrolysates (SPIH)) were used to prepare thermally-processed CS-SPI and CS-SPIH binary matrices under different pH values (3 to 9), followed by inspection of changes in the structures and digestibility using combined methods. It was found that including SPI (especially SPIH) caused structural changes of those binary systems, such as reduced network sizes, increased V-crystals and reduced nanoscale structures, which could allow more resistant starch (RS). This phenomenon was especially true when including SPIH with regulated pH value. For instance, SPIH inclusion at pH 5 caused the highest RS content (about 20.30%), presumably linked to the reduced molecule size of SPIH with strengthened aggregation at pH 5. In contrast, the acidic (pH 3) and alkaline (pH 9) conditions allowed reduced short-range orders and tailored porous networks and thus less RS (ca. 17.46% at pH 3 and 16.74% at pH 9).

Investigation of Foreign Amylase Adulteration in Honey Distributed in Japan by Rapid and Improved Native PAGE Activity Staining Method

Foreign amylase addition to honey in an effort to disguise diastase activity has become a widespread form of food fraud. However, since there is no report on the investigation in Japan, we investigated foreign amylases in 67 commercial honeys in Japan. First, the α-glucosidase and diastase activities of honeys were measured, which revealed that only α-glucosidase activity was significantly low in several samples. As both enzymes are secreted from honeybee glands, it is unlikely that only one enzyme was inactivated during processing. Therefore, we suspected the presence of foreign amylase. α-Amylase in honey were assigned using protein analysis software based on LC-QTOF-MS. As a result, α-amylases from Aspergillus and Geobacillus were detected in 13 and 6 out of 67 honeys, respectively. To detect foreign amylases easily, we developed a cost-effective method using native PAGE. Conventional native PAGE failed to separate the α-amylase derived from honeybee and Geobacillus. However, when native PAGE was performed using a gel containing 1 % maltodextrin, the α-amylase from honeybee did not migrated in the gel and the α-amylase could be separated from the other two α-amylases. The results from this method were consistent with those of LC-QTOF-MS method, suggesting that the novel native PAGE method can be used to detect foreign amylases.

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.

Effect of protein on the gelatinization behavior and digestibility of corn flour with different amylose contents

The effects of endogenous proteins on the gelatinization behavior and digestibility of waxy corn flour (WCF), normal corn flour (NCF) and high amylose corn flour (HCF) were systematically investigated. Microscopic characteristics showed that the proteins surrounded multiple starch granules, which led to an increase in the particle size of the corn flour, but no significant change in the relative crystallinity. Small angle x-ray scattering experiments during pasting revealed that the starch granules of NCF remained compact, while WCF and HCF were relatively loose. Carbon-13 nuclear magnetic resonance spectroscopy (13C NMR) showed that the proteins retained the helical structure of starch allowing NCF to have a higher Resistant starch(RS) content. The presence of protein led to a decrease in swelling power, viscosity, and in vitro digestibility of starch, and a noticeable increase in gelatinization temperature and thermal stability. RS increased most significantly in NCF from 3.86 % to 15.27 %. The effect of protein on the water activity of starch with different amylose contents after pasting was also inconsistent. This study will contribute to the understanding of the interaction between starch and protein in corn flours with different amylose contents and contribute to the development of corn flours.

Synthesis and Functions of Resistant Starch

Resistant starch (RS) has become a popular topic of research in recent years. Most scholars believe that there are 5 types of RS. However, accumulating evidence indicates that in addition to starch-lipid complexes, which are the fifth type of RS, complexes containing starch and other substances can also be generated. The physicochemical properties and physiologic functions of these complexes are worth exploring. New physiologic functions of several original RSs are constantly being discovered. Research shows that RS can provide health improvements in many patients with chronic diseases, including diabetes and obesity, and even has potential benefits for kidney disease and colorectal cancer. Moreover, RS can alter the short-chain fatty acids and microorganisms in the gut, positively regulating the body's internal environment. Despite the increase in its market demand, RS production remains limited. Upscaling RS production is thus an urgent requirement. This paper provides detailed insights into the classification, synthesis, and efficacy of RS, serving as a starting point for the future development and applications of RS based on the current status quo.

Salt adopted in soaking solution controls the yield and starch digestion kinetics of intact pulse cotyledon cells

Intact cellular powders have gained attention as a functional ingredient due to their lower glycemic response and potential benefits in colon. The isolation of intact cells in the laboratory and pilot plant settings is mainly achieved through thermal treatment with or without the use of limited salts. However, the effects of salt type and concentration on cell porosity, and their impact on the enzymic hydrolysis of encapsulated macro-nutrients such as starch, have been overlooked. In this study, different salt-soaking solutions were used to isolate intact cotyledon cells from white kidney beans. The use of Na₂CO₃ and Na₃PO₄ soaking treatments, with high pH (11.5-12.7) and high amount of Na ion (0.1, 0.5 M), greatly improved the yield of cellular powder (49.6-55.5 %), due to the solubilization of pectin through β-elimination and ion exchange. Intact cell walls serve as a physical barrier, significantly reducing the susceptibility of cell to amylolysis when compared to white kidney bean flour and starch counterparts. However, the solubilization of pectin may facilitate enzyme access into the cells by enlarging cell wall permeability. These findings provide new insights into the processing optimization to improve the yield and nutritional value of intact pulse cotyledon cells as a functional food ingredient.

Study of unripe and inferior banana flours pre-gelatinized by four different physical methods

This study aimed to prepare the pre-gelatinized banana flours and compare the effects of four physical treatment methods (autoclaving, microwave, ultrasound, and heat-moisture) on the digestive and structural characteristics of unripe and inferior banana flours. After the four physical treatments, the resistant starch (RS) content values of unripe and inferior banana flours were decreased from 96.85% (RS2) to 28.99-48.37% (RS2 + RS3), while C∞ and k values were increased from 5.90% and 0.039 min^-1 to 56.22-74.58% and 0.040-0.059 min^-1, respectively. The gelatinization enthalpy (ΔHg) and I_1047/1022 ratio (short-range ordered crystalline structures) were decreased from 15.19 J/g and 1.0139 to 12.01-13.72 J/g, 0.9275-0.9811, respectively. The relative crystallinity decreased from 36.25% to 21.69-26.30%, and the XRD patterns of ultrasound (UT) and heat-moisture (HMT) treatment flours maintained the C-type, but those samples pre-gelatinized by autoclave (AT) and microwave (MT) treatment were changed to C + V-type, and heat-moisture (HMT) treatment was changed to A-type. The surface of pre-gelatinized samples was rough, and MT and HMT showed large amorphous holes. The above changes in structure further confirmed the results of digestibility. According to the experimental results, UT was more suitable for processing unripe and inferior banana flours as UT had a higher RS content and thermal gelatinization temperatures, a lower degree and rate of hydrolysis, and a more crystalline structure. The study can provide a theoretical basis for developing and utilizing unripe and inferior banana flours.

Insoluble dietary fiber from wheat bran retards starch digestion by reducing the activity of alpha-amylase

This study investigated effects of insoluble dietary fiber (IDF) from wheat bran on starch digestion in vitro, analyzed the inhibition kinetics of IDF toward α-amylase and discussed the underlying mechanisms. Digestion results showed IDF significantly retarded starch digestion with reduced digestion rate and digestible starch content. Enzyme inhibition kinetics indicated IDF was a mixed-type inhibitor to α-amylase, because IDF could bind α-amylase, as evidenced by confocal laser scanning microscopy. Fluorescence quenching and UV-vis absorption experiments conformed this, found IDF led to static fluorescence quenching of α-amylase, mainly through van der Waals and/or hydrogen bonding forces. This interaction induced alternations in α-amylase secondary structure, showing more loosening and misfolding structures. This may prevent the active site of enzyme from capturing substrates, contributing to reduced α-amylase activity. These results would shed light on the utilization of IDF in functional foods for the management of postprandial blood glucose.

Effect of protein-starch interactions on starch retrogradation and implications for food product quality

Starch retrogradation is a consequential part of food processing that greatly impacts the texture and acceptability of products containing both starch and proteins, but the effect of proteins on starch retrogradation has only recently been explored. With the increased popularity of plant-based proteins in recent years, incorporation of proteins into starch-based products is more commonplace. These formulation changes may have unforeseen effects on ingredient functionality and sensory outcomes of starch-containing products during storage, which makes the investigation of protein-starch interactions and subsequent impact on starch retrogradation and product quality essential. Protein can inhibit or promote starch retrogradation based on its exposed residues. Charged residues promote charge-dipole interactions between starch-bound phosphate and protein, hydrophobic groups restrict amylose release and reassociation, while hydrophilic groups impact water/molecular mobility. Covalent bonds (disulfide linkages) formed between proteins may enhance starch retrogradation, while glycosidic bonds formed between starch and protein during high-temperature processing may limit starch retrogradation. With these protein-starch interactions in mind, products can be formulated with proteins that enhance or delay textural changes in starch-containing products. Future work to understand the impact of starch-protein interactions on retrogradation should focus on integrating the fields of proteomics and carbohydrate chemistry. This interdisciplinary approach should result in better methods to characterize mechanisms of interaction between starch and proteins to optimize their food applications. This review provides useful interpretations of current literature characterizing the mechanistic effect of protein on starch retrogradation.

Effects of rice protein, soy isolate protein, and whey concentrate protein on the digestibility and physicochemical properties of extruded rice starch

Protein, as the second major component in starchy foods, is crucial for its influence on the physicochemical properties and digestibility of starch. However, the effect of different sources of protein on starch digestibility is still unclear. In this paper, the effects of different sources of proteins (rice protein: RP, soybean isolate protein: SPI, and whey concentrate protein: WPC) on structural features, digestibility, and enzyme activity of extruded rice starch were investigated. The addition of all three proteins reduced the starch digestibility of extrudates. Native SPI and WPC suppressed amyloglucosidase activity, and all three proteins exhibited stronger amyloglucosidase inhibition when hydrolyzed. The rheological properties and Fourier transform infrared spectroscopy results revealed the exogenous proteins and starch interacted through non-covalent bonds and improved the ordered structures in the extrudates. The extrusion process also facilitated the formation of a V-type structure. The sum of SDS and RS content of extrudates was negatively correlated with the content of leached amylose and positively correlated with the ratio of 1047/1022 cm^-1 . These findings suggest that the inclusion of exogenous proteins during extrusion can affect starch digestibility through mechanisms such as the interaction with starch molecules, as well as the inhibition of amylase activity. PRACTICAL APPLICATION: This result indicated that the addition of protein during extrusion not only increased the nutritional value of the extrudate, but also decreased the starch digestibility. Extrusion technology can efficiently produce extruded products with protein, expanding further applications of protein in food and providing new healthy staple food options for special populations, such as diabetic and overweight people.

Effect of pearling on nutritional value of highland barley flour and processing characteristics of noodles

Highland barley is increasingly recognized as its nutritional benefits but its structure restricts the development and utilization in the food industry. The quality of highland barley products may be impacted by pearling, an essential step before the hull bran is consumed or further processed. The nutrition, function and edible qualities of three highland barley flour (HBF) with different pearling rates were assessed in this study. The content of resistant starch was the highest when the pearling rate of QB27 and BHB was 4%, while 8% of QB13. Un-pearled HBF showed higher DPPH, ABTS and superoxide radicals inhibition rates. The break rates of QB13, QB27 and BHB obviously decreased from 51.7%, 53.3% and 38.3% to 35.0%, 15.0% and 6.7% respectively at 12% pearling rate. PLS-DA model further attributed the improvement of pearling on noodles quality to the alteration of resilience, hardness, tension distance, breaking rate and water absorption of noodles.

Predicting the Glycemic Index of Biscuits Using Static In Vitro Digestion Protocols

In vitro digestion methods that can accurately predict the estimated GI (eGI) values of complex carbohydrate foods, including biscuits, are worth exploring. In the current study, standard commercial biscuits with varied clinical GI values between 9~30 were digested using both the INFOGEST and single-enzyme digestion protocols. The digestion kinetic parameters were acquired through mathematical fitting by mathematical kinetics models. The results showed that compared with the INFOGEST protocol, the AUR180 deduced from digesting using either porcine pancreatin or α-amylase showed the best potential in predicting the eGI values. Accordingly, mathematical equations were established based on the relations between the AUR180 and the GI values. When digesting using porcine pancreatin, GI= 1.834 + 0.009 ×AUCR180 (R2= 0.952), and when digesting using only α-amylase, GI= 6.101 + 0.009 ×AUCR180 (R2=0.902). The AUR180 represents the area under the curve of the reducing-sugar content normalized to the total carbohydrates versus the digestion time in 180 min. The in vitro method presented enabled the rapid and accurate prediction of the eGI values of biscuits, and the validity of the formula was verified by another batch of biscuits with a known GI, and the error rate of most samples was less than 30%.

Inconsistency between polyphenol-enzyme binding interactions and enzyme inhibition: Galloyl moiety decreases amyloglucosidase inhibition of catechins

Inhibiting carbohydrate-hydrolyzing enzymes has been considered as an effective approach for controlling starch digestion and postprandial blood glucose level. α-Amylase and amyloglucosidase (AMG) are commonly applied in analysis of starch digestion behaviour. Catechins have been shown with the inhibiting effects on α-amylase. However, the inhibitory activity of catechins against AMG needs to be further studied. Therefore, AMG inhibition of 8 catechins and the mechanisms were studied in this work through substrate depletion, inhibition kinetics, molecular docking, fluorescence quenching, differential scanning calorimetry, and isothermal titration calorimetry. The inhibitory activity of catechins with galloyl moiety (CGMs) was found to be lower than the corresponding catechins without the moiety (Cs). All catechins were anti-competitive inhibitors, indicating that they tended to bind with AMG-starch complex in the digestion system, rather than with AMG directly. Interestingly, CGMs had higher quenching effects on AMG fluorescence than Cs, due to the additional π-stacking between aromatic rings of GM and AMG fluorophores. Also, CGMs had a higher binding affinity to AMG, due to the tendency of GM to AMG active site, although the affinity was much weaker than that of starch to AMG. Besides, catechins did not affect AMG thermostability. Therefore, there was an inconsistency between catechins-AMG binding interactions and the enzyme inhibition because the predominant sites for catechins binding were the non-active sites on AMG-starch complex, rather than the enzyme active ones. Conclusively, inhibition mode should also be considered when evaluating the inhibitory activity of a polyphenol based on the polyphenol-enzyme binding affinity.

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.

Effects of Heat-Moisture Treatment Whole Tartary Buckwheat Flour on Processing Characteristics, Organoleptic Quality, and Flavor of Noodles

The effects of heat-moisture treatment whole tartary buckwheat flour (HTBF) with different contents on the pasting properties and hydration characteristics of tartary buckwheat noodle mix flour (TBMF), dough moisture distribution, cooking properties, texture properties, and flavor of noodles were studied. The results showed that the optimal additional amount of HTBF is determined to be 40%. The peak viscosity, trough viscosity, breakdown value, and final viscosity decreased significantly, and the optimal cooking time of the noodles decreased with increasing HTBF. Compared with the sample without HTBF, HTBF addition increased the water absorption of the sample and decreased its water solubility. When the amount of HTBF >30%, the content of strongly bound water in dough increased significantly; at HTBF >40%, the water absorption and cooking loss of noodles increased rapidly, and the hardness of noodles was decreased; and with HMBF addition at 60%, the chewiness, resilience, and elasticity decreased. Moreover, HMBF addition reduced the relative content of volatile alkanes, while increasing the amount of volatile alcohols. HTBF addition also elevated the content of slow-digesting starch (SDS) and resistant starch (RS) in noodles, providing noodles with better health benefits in preventing chronic diseases. These results proved the possibility of applying heat-moisture treatment grains to noodles, and they provide a theoretical basis for the research and development of staple foods with a hypoglycemic index.

The solution properties of galactomannan after simulated digestion of guar fortified bread predict the extent of postprandial insulin reduction in healthy adult overweight subjects

Coil overlap occurs when random coil polysaccharides such as cereal beta-glucan or galactomannan in solution are abundant enough and large enough to entangle with one another to form networks. It was recently shown that this concept applied to in vitro digested cereal-based foods could predict the efficacy of the food to reduce postprandial glycaemia. In the current study we further investigate the role of coil overlap for prediction of glycaemic and insulinaemic responses using four guar fortified breads (10-15% wheat flour replacement level) with galactomannans of different weight-average molecular weight (M_w). The breads, including a wheat flour control, were tested in a randomised crossover study in 12 overweight adults. Addition of guar reduced postprandial serum insulin, but not glucose responses. The extent of postprandial insulin reduction correlated with the solution properties of galactomannan after in vitro digestion. A significantly greater reduction in insulin response was observed for two of the breads where the galactomannan M_w and concentration in solution after in vitro digestion was above coil overlap, in contrast to two other breads, which resulted in digests containing galactomannan below coil overlap and a significantly lower reduction of postprandial insulin. Further in vitro digestion experiments focusing on amylolysis of starch with kinetic modelling showed a greater proportion of slowly digested starch in breads with galactomannan above coil overlap than below. A combination of the molecular weight of dietary fibre in a food and its soluble concentration are key parameters explaining its physiological efficiency in the upper gastrointestinal tract.

Dietary compounds slow starch enzymatic digestion: A review

Dietary compounds significantly affected starch enzymatic digestion. However, effects of dietary compounds on starch digestion and their underlying mechanisms have been not systematically discussed yet. This review summarized the effects of dietary compounds including cell walls, proteins, lipids, non-starchy polysaccharides, and polyphenols on starch enzymatic digestion. Cell walls, proteins, and non-starchy polysaccharides restricted starch disruption during hydrothermal treatment and the retained ordered structures limited enzymatic binding. Moreover, they encapsulated starch granules and formed physical barriers for enzyme accessibility. Proteins, non-starchy polysaccharides along with lipids and polyphenols interacted with starch and formed ordered assemblies. Furthermore, non-starchy polysaccharides and polyphenols showed robust abilities to reduce activities of α-amylase and α-glucosidase. Accordingly, it can be concluded that dietary compounds lowered starch digestion mainly by three modes: (i) prevented ordered structures from disruption and formed ordered assemblies chaperoned with these dietary compounds; (ii) formed physical barriers and prevented enzymes from accessing/binding to starch; (iii) reduced enzymes activities. Dietary compounds showed great potentials in lowering starch enzymatic digestion, thereby modulating postprandial glucose response to food and preventing or treating type II diabetes disease.

Isothermal Mashing of Barley Malt: New Insights into Wort Composition and Enzyme Temperature Ranges

The basic step in beer production is mashing, during which insoluble starch chains, and to a lesser extent cell walls and proteins are broken down by enzymatic hydrolysis. Since the beginning of the modern brewing process there have been empirical studies into the optimum effective temperatures of the corresponding enzymes, and mashing has been carried out accordingly. The resulting resting temperatures of proteolysis, cytolysis and amylolysis with the maltose and saccharification rest, are now rarely changed, only being adapted to the properties of the raw materials used to a limited extent. New varieties of barley and other raw materials used in breweries, as well as modern processes in malting plants, ensure better enzyme potential and optimized malt gelatinization temperatures. The aim of this paper is to determine enzyme activity in barley malt during mashing. For this purpose, isothermal mashing was used, i.e., a mashing process with a constant resting temperature over the entire mashing period. The obtained worts were analyzed for the attributes of extract, final attenuation, β-glucan, total nitrogen, free amino nitrogen, viscosity, and pH as well as sugar composition and individual amino acids. The change in these attributes indicates the enzyme activity of the malt.

Impact of wheat bran micronization on dough properties and bread quality: Part II - Quality, antioxidant and nutritional properties of bread

To investigate the impact of superfine grinding of wheat bran on bread quality, antioxidant and nutritional properties, bran with different particle sizes (coarse, D₅₀ of 362.3 μm; medium, 60.4 μm; superfine, 11.3 μm) were produced and fortified to white bread at three levels (10, 20 and 30%). At 20% fortification, compared to coarse bran, superfine bran increased the hardness and reduced the brightness of bread crumb by 56.3 and 3.30%, respectively, while it decreased bread's cell size by 10.7% and insignificantly impacted on bread's specific volume and porosity. Superfine bran retarded bread staling by 8.3% than coarse bran. It resulted in significantly better sensory attributes of bread in taste, texture and general palatability, and the fortified bread was overall acceptable (score > 6). Moreover, faster release of antioxidants (285-353% higher k), slower release of glucose (10.8% lower k), 3.76% less rapidly digestible starch, 5.65% more slowly digestible starch and 13.2% more resistant starch were found in the superfine group than the coarse one. Results demonstrated the potential of 20% fortification of superfine bran in developing fibre-enriched bread with satisfactory quality, increased antioxidant property and improved glycaemic modulation.

Structure Characterization and Potential Probiotic Effects of Sorghum and Oat Resistant Dextrins

Resistant dextrins (RDs) were prepared from sorghum and oat starches to determine their molecular structure, physicochemical properties, digestibility and prebiotics effect in vitro. The results showed that the particle size of sorghum resistant dextrin (SRD) and oat resistant dextrin (ORD) was significantly smaller than their respective starches. They formed a block structure, and lost the original A-type structure. In addition, SRD and ORD had good thermal stability, solubility (>90%) and enzymatic hydrolysis resistance (digestibility < 5%). The potential probiotic effects of ORD and SRD were studied by measurement of their promoting effects on the growth of Lactiplantibacillus plantarum, Lactobacillus acidophilus and Lactobacillus delbrueckii. For Lactiplantibacillus plantarum and Lactobacillus acidophilus, the promoting effect of ORD was the best (p < 0.05), and the counts increased by 8.89 and 8.74 log CFU/mL, respectively, compared with the control. For Lactobacillus delbrueckii, SRD was most effective, increasing the counts by 8.72 log CFU/mL compared with the control. These characteristics make SRD and ORD suitable for use as soluble dietary fiber and prebiotics in beverages and the excipients of low-glycemic-index products.

α-Amylase Changed the Catalytic Behaviors of Amyloglucosidase Regarding Starch Digestion Both in the Absence and Presence of Tannic Acid

The courses of starch digestion with individual α-amylase (AA), amyloglucosidase (AMG), and AA/AMG bi-enzyme system were performed and analyzed by first-order-reaction equations in the absence and presence of tannic acid (TA). An antagonistic effect between AA and AMG occurred at the digestion phase of readily-digestible starch due to the higher catalytic efficiency of AMG for starchy-substrates with more complex structures. This effect caused a faster rate of glucose production with AMG than with AA/AMG bi-enzyme system at this phase both in the absence and presence of TA. TA had a higher binding affinity to AA than to AMG as accessed by several methods, such as inhibition kinetics, fluorescence quenching, isothermal titration calorimetry (ITC), and molecular docking. Besides, differential scanning calorimetry (DSC) indicated that the change in the thermal and structural stabilities of enzymes in the presence of TA was related to the enzyme residues involved in binding with TA, rather than the inhibitory effects of TA. The binding characters of TA to both enzymes resulted in more “free” AMG without TA binding in AA/AMG bi-enzyme system than that in individual AMG. This binding property caused more and faster rate of glucose production at the digestion phase of slowly digestible starch (SDS) in the bi-enzyme system.

Identification of Key Gene Networks and Deciphering Transcriptional Regulators Associated With Peanut Embryo Abortion Mediated by Calcium Deficiency

Peanut embryo development is easily affected by a variety of nutrient elements in the soil, especially the calcium level. Peanut produces abortive embryos in calcium-deficient soil, but underlying mechanism remains unclear. Thus, identifying key transcriptional regulators and their associated regulatory networks promises to contribute to a better understanding of this process. In this study, cellular biology and gene expression analyses were performed to investigate peanut embryo development with the aim to discern the global architecture of gene regulatory networks underlying peanut embryo abortion under calcium deficiency conditions. The endomembrane systems tended to disintegrate, impairing cell growth and starch, protein and lipid body accumulation, resulting in aborted seeds. RNA-seq analysis showed that the gene expression profile in peanut embryos was significantly changed under calcium deficiency. Further analysis indicated that multiple signal pathways were involved in the peanut embryo abortion. Differential expressed genes (DEGs) related to cytoplasmic free Ca²⁺ were significantly altered. DEGs in plant hormone signaling pathways tended to be associated with increased IAA and ethylene but with decreased ABA, gibberellin, cytokinin, and brassinosteroid levels. Certain vital genes, including apoptosis-inducing factor, WRKYs and ethylene-responsive transcription factors, were up-regulated, while key regulators of embryo development, such as TCP4, WRI1, FUS3, ABI3, and GLK1 were down-regulated. Weighted gene co-expression network analysis (WGCNA) identified 16 significant modules associated with the plant hormone signaling, MAPK signaling, ubiquitin mediated proteolysis, reserve substance biosynthesis and metabolism pathways to decipher regulatory network. The most significant module was darkolivegreen2 and FUS3 (AH06G23930) had the highest connectivity among this module. Importantly, key transcription factors involved in embryogenesis or ovule development including TCP4, GLK1, ABI3, bHLH115, MYC2, etc., were also present in this module and down regulated under calcium deficiency. This study presents the first global view of the gene regulatory network involved in peanut embryo abortion under calcium deficiency conditions and lays foundation for improving peanut tolerances to calcium deficiency by a targeted manipulation of molecular breeding.

Effects of Endogenous Non-Starch Nutrients in Acorn (Quercus wutaishanica Blume) Kernels on the Physicochemical Properties and In Vitro Digestibility of Starch

The present study investigated the multi-scale structure of starch derived from acorn kernels and the effects of the non-starch nutrients on the physicochemical properties and in vitro digestibility of starch. The average polymerization degree of acorn starch was 27.3, and the apparent amylose content was 31.4%. The crystal structure remained as C-type but the relative crystallinity of acorn flour decreased from 26.55% to 25.13%, 25.86% and 26.29% after the treatments of degreasing, deproteinization, and the removal of β-glucan, respectively. After the above treatments, the conclusion temperature of acorn flour decreased and had a significant positive correlation with the decrease in the crystallinity. The aggregation between starch granules, and the interactions between starch granules and both proteins and lipids, reduced significantly after degreasing and deproteinization treatments. The endogenous protein, fat, and β-glucan played key roles in reducing the digestibility of acorn starch relative to other compounds, which was dictated by the ability for these compounds to form complexes with starch and inhibit hydrolysis.

Mutual interactions between α‑amylase and amyloglucosidase on the digestion of starch with distinct chain-length distributions at fully gelatinized state

Amyloglucosidase (AMG) and α-amylase (AMY) are involved in the human small intestine for starch digestion, whereas their mutual interactions with starch molecules of distinct structures are still unknown. In current...

Mashing performance as a function of malt particle size in beer production

Significant innovations have occurred over the past 50 years in the malting and brewing industries, focused on optimization of the beer mashing, boiling and fermentation processes. One of the challenges faced in beer brewing has been in the malting process to obtain the desired malt and wort quality to produce high-quality beer products. The hydrolytic enzymes produced during grain germination are mostly entrapped inside the cellular matrices of the grain. The intra-grain diffusion of enzymes for in-situ hydrolysis, as well as diffusion of enzymes to wort, depends upon the malt size and malt size fractions obtained after milling. This review investigates the relationship between varying barley grain particle size distribution and the efficiency of the malting and mashing processes. Recommended ideal particle size of barley grain before and after milling are proposed based on the review of existing literature. Each brewing batch of grains with a proportion of >80% plump grains (>2.5 mm in size) is suggested to be the optimal size before milling, whereas the optimum grain particle size after milling ranged between 0.25 and 0.5 mm. The current review will summarize the theoretical aspects for malt milling and the particle size characteristics for optimizing the brewing process.

Effects of whey protein on the in vitro digestibility and physicochemical properties of potato starch

The aim of this study was to examine the effect of whey protein isolate (WPI) on the digestibility and physicochemical properties of potato starch (PS) after heat treatment. WPI reduced the digestibility of PS and increased the order and aggregation structure of gelatinized PS. Examination of the rheological properties of the PS-WPI mixed system before and after adding different chemicals (sodium chloride, urea, and sodium dodecyl sulfate) indicated an involvement of hydrogen bonds and hydrophobic interactions in the PS-WPI gelatinization system. The pasting properties, swelling power, and thermal properties indicated that WPI suppressed the swelling and gelatinization of PS. The addition of WPI reduced the amylose leaching rate from the starch granules, indicating that the presence of exogenous protein could prevent amylose diffusion from the starch granules. Native WPI and its hydrolysate also inhibited amyloglucosidase activity. These findings indicated that the mechanism by which WPI reduces PS digestion involves hydrophobic interactions and hydrogen bonding between WPI and PS, as well as enzyme activity inhibition.

Effect of Heat-Moisture Treatments on Digestibility and Physicochemical Property of Whole Quinoa Flour

The starch digestion processing of whole grain foods is associated with its health benefits in improving insulin resistance. This study modified the digestibility of whole quinoa flour (WQ) via heat-moisture treatment (HMT), HMT combined with pullulanase (HMT+P), HMT combined with microwave (HMT+M), and HMT combined with citric acids (HMT+A), respectively. Results showed that all the treatments significantly increased (p < 0.05) the total dietary fiber (TDF) content, amylose content, and resistant starch (RS) content, however, significantly decreased (p < 0.05) the amylopectin content and rapidly digestible starch (RDS) content of WQ. HMT+P brought the highest TDF content (15.3%), amylose content (31.24%), and RS content (15.71%), and the lowest amylopecyin content (30.02%) and RDS content (23.65%). HMT+M brought the highest slowly digestible starch (SDS) content (25.09%). The estimated glycemic index (eGI) was respectively reduced from 74.36 to 70.59, 65.87, 69.79, and 69.12 by HMT, HMT+P, HMT+M, and HMT+A. Moreover, a significant and consistent reduction in the heat enthalpy (ΔH) of WQ was observed (p < 0.05), after four treatments. All these effects were caused by changes in the starch structure, as evidenced by the observed conjunction of protein and starch by a confocal laser scanning microscope (CLSM), the decrease in relative crystallinity, and transformation of starch crystal.