Plant proteins mitigate in vitro wheat starch digestibility

Study on the Mechanism of Effect of Protein on Starch Digestibility in Fermented Barley

Previous studies have shown that fermented barley has a lower digestion rate. However, it remains unclear whether the antidigestibility of starch in fermented barley is affected by other nonstarch components. In this paper, the removal of protein, lipid, and β-glucan improved the hydrolysis rate of starch and the protein showed the greatest effect. Subsequently, the inhibitory mechanism of protein on starch digestion was elucidated from the perspective of starch physicochemical properties and structural changes. The removal of protein increased the swelling power of starch from 10.09 to 11.14%. The short-range molecular ordered structure and the helical structure content decreased. The removal of protein reduced the coating and particle size of the starch particles, making the Maltese cross more dispersed. In summary, protein in fermented barley enhanced the ordered structure of starch by forming a physical barrier around starch and prevented the expansion of starch, which inhibited the hydrolysis of starch.

Biological methane potentials of food waste of different components: Methane yields, production kinetics, and element balance

This study assessed the methane production from food waste (FW) with dominant components of Meat (MFW), Fruit &Veg (VFW), Grain (GFW), Dairy (DFW), and the mixed feed of these components (MixFW). The high protein and lipid content FW (HPLFW) of MFW, DFW, and MixFW showed the methane yields of 337.0 ± 3.0, 307.4 ± 0.8, and 297.1 ± 1.2 ml-CH4/gCOD, respectively, while those for the high carbohydrate content FW (HCFW) of VFW and GFW were 238.3 ± 1.2 and 171.2 ± 0.3 ml-CH4/gCOD, respectively. A modified two-component kinetic (MTK) model was demonstrated to be the best to describe the methane production kinetics of both HPLFW and HCFW types of feeds. The element balance analysis revealed the element formula of the FW feeds and the methane-conversion organic content. The results obtained from this study showed that the high lipid and animal protein content increased the methane yield and biogas methane composition.

Effects of soy protein isolate interaction with brown rice starch on the multiscale structure of brown rice bread

BACKGROUND

Gluten-free bread (GFB) has technical bottlenecks such as hard texture, rough taste and low nutrition in practical production. In order to solve these problems, this study used germinated brown rice starch as the main raw material, and investigated the effects of soybean isolate protein (SPI) on the multiscale structure of germinated brown rice starch and bread quality.

RESULTS

A gluten-free rice bread process simulation system was established, and the interaction between SPI and starch in the simulation system was characterized. The result shows that the interaction forces between SPI and germinated brown rice starch were mainly represented by hydrogen bonds, and with the addition of SPI, the crystallinity of starch showed a downward trend. At the same time, when the amount of SPI was 3%, the appearance quality was the best and the specific volume of bread was 1.08 mL g-1. When the amount of SPI was 6%, the texture quality was the best. Compared with the bread without SPI, the hardness of the bread with 6% SPI was reduced by 0.13 times, the springiness was increased by 0.03 times, the color was the most vibrant, the L* value being 1.02 times the original, and the baking loss was reduced to 0.98 times the original.

CONCLUSIONS

The interaction force between SPI and germinated brown rice starch and its effect on bread quality were clarified, and these results inform choices about providing a theoretical basis for the subsequent development of higher-quality GFB. © 2024 Society of Chemical Industry.

Role of pea protein isolate in modulating pea starch digestibility: insights from physicochemical and microstructural analysis

BACKGROUND

Understanding the interactions between protein and starch is crucial in revealing the mechanisms by which protein influences starch digestibility. The present study investigated the impact of different contents of pea protein isolate (PPI) on the physicochemical properties and digestibility of pea starch (PS).

RESULTS

The results demonstrated that as the content of PPI increased from 0% to 12%, and the digestion of PS decreased by 12.3%. Rheological analysis indicated that PPI primarily interacted with molecular chains of PS through hydrogen bonds. Increasing the content of PPI resulted in a 30.6% decrease in the hardness of the composite gels, accompanied by a 10% reduction in the short-ordered structure of PS. This hindered the formation of molecular aggregation and resulted in a loose and disordered gel network structure. The microstructure confirmed that the attachment of PPI to PS served as a physical barrier, impeding starch digestibility.

CONCLUSION

In summary, the primary mechanism by which PPI inhibited PS digestion involved steric hindrance exerted by PPI and its interaction with PS via hydrogen bonds. These findings contribute to a better understanding of the interaction mechanisms between PS and PPI and offer insights for the optimal utilization of pea resources. © 2024 Society of Chemical Industry.

The role of fiber in modulating plant protein-induced metabolic responses

The rising consumption of plant protein foods and the emergence of meat alternatives have prompted interest in the health benefits of such products, which contain fiber in addition to protein. This review investigates the effect of fiber on plant-based protein metabolism and evaluates its contribution to gut-derived health impacts. Plant proteins, which often come with added fiber, can have varying health outcomes. Factors such as processing and the presence of fiber and starch influence the digestibility of plant proteins, potentially leading to increased proteolytic fermentation in the gut and the production of harmful metabolites. However, fermentable fiber can counteract this effect by serving as a primary substrate for gut microbes, decreasing proteolytic activity. The increased amount of fiber, rather than the protein source itself, plays a significant role in the observed health benefits of plant-based diets in human studies. Differences between extrinsic and intrinsic fiber in the food matrix further impact protein fermentation and digestibility. Thus, in novel protein products without naturally occurring fiber, the health impact may differ from conventional plant protein sources. The influence of various fibers on plant-based protein metabolism throughout the gastrointestinal tract is not fully understood, necessitating further research.

Strategic exploration of whole grain cereals in modulating the glycaemic response

In the current context, diabetes presents itself as a widespread and complex global health issue. This study explores the significant influence of food microstructure and food matrix components interaction (protein, lipid, polyphenols, etc.) on the starch digestibility and the glycaemic response of post-prandial glycemia, focusing on the potential effectiveness of incorporating bioactive components from whole grain cereals into dietary strategies for the management and potential prevention of diabetes. This study aims to integrate the regulation of postprandial glycaemic homeostasis, including the complexities of starch digestion, the significant potential of bioactive whole grain components and the impact of food processing, to develop a comprehensive framework that combines these elements into a strategic approach to diabetes nutrition. The convergence of these nutritional strategies is analyzed in the context of various prevalent dietary patterns, with the objective of creating an accessible approach to mitigate and prevent diabetes. The objective remains to coalesce these nutritional paradigms into a coherent strategy that not only addresses the current public health crisis but also threads a preventative approach to mitigate future prevalence and impact.

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.

Changing the ionic strength can regulate the resistant starch content of binary complex including starch and protein or its hydrolysates

Ionic strength condition is a crucial parameter for food processing, but it remains unclear how ionic strength alters the structure and digestibility of binary complexes containing starch and protein/protein hydrolysates. Here, the binary complex with varied ionic strength (0-0.40 M) was built by native corn starch (NS) and soy protein isolate (SPI)/hydrolysates (SPIH) through NaCl. The inclusion of SPI and SPIH allowed a compact network structure, especially the SPIH with reduced molecule size, which enriched the resistant starch (RS) of NS-SPIH. Particularly, the higher ionic strength caused the larger nonperiodic structures and induced loosener network structures, largely increasing the possibility of amylase for starch digestion and resulting in a decreased RS content from 19.07 % to 15.52 %. In other words, the SPIH hindered starch digestion while increasing ionic strength had the opposite effect, which should be considered in staple food production.

The impact of different soluble endogenous proteins and their combinations with β-glucan on the in vitro digestibility, microstructure, and physicochemical properties of highland barley starch

The impacts of protein types and its interaction with β-glucan on the in vitro digestibility of highland barley starch were investigated through analyzing physicochemical and microstructural properties of highland barley flour (HBF) after sequentially removing water- (WP), salt- (SP), alcohol- (AP) and alkali-soluble (AlkP) proteins. Resistant starch (RS) increased significantly in HBF after removing WP and SP, and RS of HBF was lower than that of without β-glucan. After removing WP, SP and AP, swelling powers of HBF without β-glucan (9.33-9.77) were higher than those of HBF (12.09-15.95). Trends of peak viscosity and peak temperature (thermal degradation temperature) were similar as swelling power, and HBF without AP showed the highest peak temperature (310.33 °C). Removals of different proteins improved the crystalline structure and short-range order of starch. There was a blue shift in T2 values and an opposite change in free water proportion. The matrix on starch surface was mainly formed by AP and AlkP, which could be aggregated by β-glucan. But, the inhibitory effect of AP or AlkP was stronger than that of proteins combined with β-glucan. These results help in the development of starch-based foods with different digestive properties by combining different protein types with β-glucan.

Tailoring the formulation of sugar-snap cookies to lower in vitro starch digestibility: A response surface modelling approach

An I-optimal response surface experimental design revealed impacts of dough moisture content (DMC, 14-22%) and level of wheat flour substitution (10-50%) by wheat gluten and one of six different native starches [wheat, (waxy) maize, rice, potato, pea] on sugar-snap cookie starch thermal properties, in vitro starch digestion, dough and cookie hardness and spread ratio. Increasing DMCs from 14 to 22% increased the cookie starch digestion rate constants of each starch source used. A linear increase of the constant by 25-30% across the 14 to 22% DMC range for all starches was predicted and validated. That cookie spread and hardness were related to the water retention capacity of the native starches used suggested that they underwent limited changes during baking. For each starch examined, formulations were optimized to lower in vitro starch digestion rate and extent, and cookie hardness, while maximizing dough spread ratio.

Including protein hydrolysates during thermal processing mitigates the starch digestion of resulted starch-based binary matrix

Staple foods with starch and protein components are usually consumed after thermal processing. To date, how including protein hydrolysates (with varied hydrolysis degrees) tailors the structure and digestion features of starch-based matrix with thermal processing has not yet been sufficiently understood. Here, corn starch (CS), soy protein isolate (SPI), and soy protein isolate hydrolysates (SPIH) with different hydrolysis time (5-60 min) were used to prepare starch-based binary matrices. With the addition of SPI or SPIH during thermal processing, the resultant binary systems exhibited higher thermal stability (breakdown visibility was increased by 1.9-10.8 times), denser networks, and fewer short-range orders (R995/1022 was decreased by up to 15.3 %). These structural changes allowed an inhibited starch digestion within the binary system, especially with increased SPI or SPIH content. Compared with CS, the content of resistant starch (RS) for CS-SPI binary complex (10:3 w/w) increased from 9.89 % to 16.69 %. Compared to SPI, SPIH inclusion displayed a stronger inhibitory effect on starch digestion since the reduced molecule size of SPIH probably enhanced its interplays with starch or amylase. For instance, the 10:3 w/w starch-SPIH 60 binary matrix possessed the highest RS content (19.07 %).

Impact of Cooking Methods on Phenolic Acid Composition, Antioxidant Activity, and Starch Digestibility of Chinese Triticale Porridges: A Comparative Study between Atmospheric Pressure and High Pressure Boiling

Water boiling under atmospheric pressure (CAP) and water boiling under high pressure (CHP) are two popular domestic cooking methods for Chinese porridge making. In this study, we aimed to evaluate the effects of these two methods on the phenolic acid composition, antioxidant activity, and starch digestibility of triticale porridges. The contents of total free and total bound phenolic acids in the CHP sample were 1.3 and 1.6 times higher than those in the CAP counterpart, respectively, although the DPPH and ABTS values of these two samples were comparable. CAP induced more small pieces of starch than CHP, and the gelatinization enthalpy was 19% higher in the CHP sample than that in the CAP. Both cooking methods increased the starch digestibility, while the CHP sample (58.84) showed a lower GI than the CAP (61.52). These results may promote the application of triticale in health-promoting staple foods.

Tapioca Starch Improves the Quality of Virgatus nemipterus Surimi Gel by Enhancing Molecular Interaction in the Gel System

The gel prepared using Nemipterus virgatus (N. virgatus) surimi alone still has some defects in texture and taste. Complexing with polysaccharides is an efficient strategy to enhance its gel properties. The main objective of this study was to analyze the relationship between the gel quality and molecular interaction of N. virgatus surimi gel after complexing with tapioca starch. The results make clear that the gel strength, hardness, and chewiness of surimi gel were increased by molecular interaction with tapioca starch. At the appropriate addition amount (12%, w/w), the surimi gel had an excellent gel strength (17.48 N), water-holding capacity (WHC) (89.01%), lower cooking loss rate (CLR) (0.95%), and shortened T2 relaxation time. Microstructure analysis indicated that the addition of tapioca starch facilitated even distribution in the gel network structure, resulting in a significant reduction in cavity diameter, with the minimum diameter reduced to 20.33 μm. In addition, tapioca starch enhanced the hydrogen bonding and hydrophobic interaction in the gel system and promoted the transformation of α-helix to β-sheet (p < 0.05). Correlation analysis showed that the increased physicochemical properties of surimi gel were closely related to the enhanced noncovalent interactions. In conclusion, noncovalent complexation with tapioca starch is an efficient strategy to enhance the quality of surimi gel.

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.

A review of starch swelling behavior: Its mechanism, determination methods, influencing factors, and influence on food quality

Swelling behavior involves the process of starch granules absorbing enough water to swell and increase the viscosity of starch suspension under hydrothermal conditions, making it one of the important aspects in starch research. The changes that starch granules undergo during the swelling process are important factors in predicting their functional properties in food processing. However, the factors that affect starch swelling and how swelling, in turn, affects the texture and digestion characteristics of starch-based foods have not been systematically summarized. Compared to its long chains, the short chains of amylose easily interact with amylopectin chains to inhibit starch swelling. Generally, reducing the swelling of starch could increase the strength of the gel while limiting the accessibility of digestive enzymes to starch chains, resulting in a reduction in starch digestibility. This article aims to conduct a comprehensive review of the mechanism of starch swelling, its influencing factors, and the relationship between swelling and the pasting, gelling, and digestion characteristics of starch. The role of starch swelling in the edible quality and nutritional characteristics of starch-based foods is also discussed, and future research directions for starch swelling are proposed.

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).

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.

Study on the mechanism of various exogenous proteins with different inhibitions on wheat starch digestion: From the distribution behaviors of protein in the starch matrix

This study aimed to compare the effect of various exogenous proteins on wheat starch (WS) digestion and assess the relevant mechanisms based on the distribution behaviors of exogenous proteins in the starch matrix. Rice protein (RP), soy protein isolate (SPI), and whey protein isolate (WPI) all effectively suppressed the rapid digestion of WS but with different modes. RP increased the slowly digestible starch content, while SPI and WPI increased the resistant starch content. Fluorescence images showed that RP aggregated and competed for effective space with starch granules, while SPI and WPI formed continuous network structures among the starch matrix. These distribution behaviors endowed different reductions in starch digestion by influencing the gelatinization and ordered structure of starch. Pasting and water mobility results suggested all exogenous proteins inhibited the water migration and swelling of starch. Simultaneously, X-ray diffraction and Fourier transform infrared spectroscopy analysis showed that exogenous proteins improved the ordered structures of starch. RP had a more significant effect on the long-term ordered structure, while SPI and WPI had a more effective effect on the short-term ordered structure. These findings will enrich the theory of exogenous protein inhibiting starch digestion and inspire the applications in low-glycemic index food.

Encapsulated starch characteristics and its shell matrix mechanisms controlling starch digestion

Encapsulated starch can be classified as physically inaccessible starch or type 1 resistant starch (RS1), which is produced by encapsulating starch granules within food matrices using various encapsulation techniques. Encapsulated starch has the potential to be used as a functional ingredient in low-/medium-glycemic index (GI) foods as it can help control glycemic and insulin responses. Despite its remarkable benefits, the relevant information related to entrapped starch and its application is still insufficient and needs further elucidation. The objective of this work is to present a comprehensive overview of the current techniques utilized for the preparation of encapsulated starch and its characteristics, thereby extending the fundamental knowledge. Furthermore, this review delves into the mechanisms governing starch hydrolysis regulated by shell matrices and provides the prospective utilization of encapsulated starch in food production.

The impact of the soluble protein fraction and kernel hardness on wheat flour starch digestibility

Wheat is the staple crop for 35% of the world's population, providing a major source of calories, mainly in the form of starch. The digestibility of wheat starch varies between different flours and products. Wheat products that are rapidly digested elicit large post-prandial glucose peaks associated with metabolic disorders. We investigated the impact of protein on starch digestion in three commercial flours with different grain hardness. A soluble extract of wheat proteins reduced starch digestion, even following gastric proteolysis. This extract was enriched in proteinaceous α-amylase inhibitors which were partially degraded during gastric proteolysis. Starch digestion kinetic analysis was carried out for flour samples pre-treated with different pepsin activities. The rate of starch digestion was altered following pepsin pre-digestion, and the extent of starch digestion increased in response to pepsin pre-digestion. We conclude that soluble proteinaceous alpha-amylase inhibitors present in wheat can escape gastric digestion and significantly contribute to reducing starch digestion in the small intestine.

Effect of starch-protein interaction on regulating the digestibility of waxy rice starch under radio frequency treatment with added CaCl2

This study investigated the effect of starch-protein interaction on regulating the digestibility of waxy rice starch under radio frequency (RF) treatment with added salts. The results showed that starch-protein interactions could significantly reduce the digestibility of waxy rice starch (WRS) under synergetic Ca²⁺-RF treatment. With the increase of Ca²⁺ content (0-2 %), the resistant starch content of WRS-WPI, WRS-SPI and WRS-PPI increased from 35.53 %, 36.12 % and 38.78 % to 51.05 %, 52.82 % and 55.93 %, respectively. The addition of appropriate Ca²⁺ content could increase the short-range ordered structure and lamella structure and form a more compact and uniform microstructure. In addition, the interaction between WRS and protein was mainly through hydrogen bonding and hydrophobic interactions during RF treatment. Furthermore, the presence of Ca²⁺ could improve the distribution and mobility of water molecules and regulate the rheological properties of WRS-protein complexes. This study offers theoretical guidance for the design and production of rice starch-based products with lower digestibility.

The Mechanism Underlying the Amylose-Zein Complexation Process and the Stability of the Molecular Conformation of Amylose-Zein Complexes in Water Based on Molecular Dynamics Simulation

The aim of this study was to employ molecular dynamics simulations to elucidate the mechanism involved in amylose–zein complexation and the stability of the molecular conformation of amylose–zein complexes in water at the atomic and molecular levels. The average root mean square deviation and radius of gyration were lower for amylose–zein complexes (1.11 nm and 1 nm, respectively) than for amylose (2.13 nm and 1.2 nm, respectively), suggesting a significantly higher conformational stability for amylose–zein complexes than for amylose in water. The results of radial distribution function, solvent-accessible surface area, and intramolecular and intermolecular hydrogen bonds revealed that the amylose–zein interaction inhibited water permeation into the amylose cavity, leading to enhanced conformational stabilities of the V-type helical structure of amylose and the amylose–zein complexes. Furthermore, the amylose in amylose–zein complexes displayed the thermodynamically stable 4C1 conformation. These findings can provide theoretical guidance in terms of the application of protein on starch processing aiming to improve the physicochemical and functional properties of starch (such as swelling capacity, pasting properties, and digestibility) for developing novel low-digestibility starch–protein products.

Structure, thermal stability, and in vitro digestibility of rice starch-protein hydrolysate complexes prepared using different hydrothermal treatments

In this study, rice starch-protein hydrolysate (WPH-S) complexes with high resistant starch (RS) content were prepared by heat-moisture treatment (HMT) and annealing (ANN). The effects of different hydrothermal treatments on the structure and thermal stability of the WPH-S complexes and their relationship with starch digestibility were further discussed. The results showed that RS contents of ANN-WPH-S complexes (35.09-40.26 g/100 g) were higher than that of HMT-WPH-S complexes (24.15-38.74 g/100 g). Under hydrothermal treatments, WPH decreased the hydrolysis kinetic constant (k) of starch form 4.07 × 10^-2-4.63 × 10^-2 min^-1 to 3.29 × 10^-2-3.67 × 10^-2 min^-1. HMT and ANN promoted hydrogen bonding between WPH and starch molecules, thus increasing the molecular size of starch. In addition, the shear stability of WPH-S mixture was improved with the hysteresis loop area decreased after HMT/ANN treatments, resulting in a more stable structure. Most importantly, the hydrothermal treatment made the scatterers of WPH-S complexes denser and the surface smoother. Especially after ANN treatment, the WPH₆₀-S complex formed a denser aggregate structure, which hindered the in vitro digestion of starch to a certain extent. These results enrich our understanding of the regulation of starch digestion by protein hydrolysates under different hydrothermal treatments and have guiding significance for the development of foods with a low glycemic index.

Mining the A.E. Watkins Wheat Landrace Collection for Variation in Starch Digestibility Using a New High-Throughput Assay

Breeding for less digestible starch in wheat can improve the health impact of bread and other wheat foods. The application of forward genetic approaches has lately opened opportunities for the discovery of new genes that influence the digestibility of starch, without the burden of detrimental effects on yield or on pasta and bread-making quality. In this study we developed a high-throughput in vitro starch digestibility assay (HTA) for use in forward genetic approaches to screen wheat germplasm. The HTA was validated using standard maize and wheat starches. Using the HTA we measured starch digestibility in hydrothermally processed flour samples and found wide variation among 118 wheat landraces from the A. E. Watkins collection and among eight elite UK varieties (23.5 to 39.9% and 31.2 to 43.5% starch digested after 90 min, respectively). We further investigated starch digestibility in fractions of sieved wholemeal flour and purified starch in a subset of the Watkins lines and elite varieties and found that the matrix properties of flour rather than the intrinsic properties of starch granules conferred lower starch digestibility.

Substituting Whole Wheat Flour with Pigeon Pea (Cajanus cajan) Flour in Chapati: Effect on Nutritional Characteristics, Color Profiles, and In Vitro Starch and Protein Digestion

Pigeon pea (Cajanus cajan (L.) Millsp.), a potential legume as an economical source of protein, is commonly cultivated in tropical and subtropical regions of the world. Therefore, pigeon pea may be potentially used as a substitute to improve the nutritional profile of foods. In the present study, the effect of substitution of whole wheat flour (WWF) with 20% and 40% pigeon pea flour (PPF) on the nutritional properties, color profiles, and starch and protein digestibility of chapati was investigated. The results showed that PPF had higher protein content but less carbohydrate than WWF. The protein content of chapati substituted with 20% and 40% PPF increased by 1.18 and 1.34 times, respectively, compared to WWF chapati, along with a marked decrease in carbohydrate content. Analyses further revealed an increase in the lightness and yellowness and a decrease in the redness of the chapati. Furthermore, glucose release from chapati with 20% and 40% PPF under simulated digestion was attenuated, corresponding to decreased hydrolysis and a predicted glycemic index. In the 40% PPF chapati, a significant reduction in slowly digestible starch (SDS) with increased resistant starch (RS) proportions was achieved without altering the effect on rapidly digestible starch (RDS). In addition, the level of amino-group residues was markedly elevated in 20% and 40% PPF substituted chapati compared to WWF chapati. These findings suggest that PPF can serve as a promising plant-based alternative ingredient to improve the nutrient value of chapati by reducing starch and increasing protein digestibility.

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.

Mechanism of peptides from rice hydrolyzed proteins hindering starch digestion subjected to hydrothermal treatment

Clarifying the interactions between food components is critical in designing carbohydrate-based foods with low digestibility. To date, the hindering effect of starch-protein interactions on starch digestion has attracted extensive attention. In this study, rice proteins were further hydrolyzed, and rice peptides (RP) with different molecular weights were obtained by ultrafiltration. The effects and possible mechanisms of RP with different molecular weights on the structure, thermal properties, and in vitro digestibility of cooked rice starch were investigated. All peptides slowed the digestion of rice starch in a concentration-dependent manner. A concentration of 10% RP_>10 decreased the rapidly digestible starch content from 68.02 to 45.90 g/100 g, and increased the resistant starch content from 17.54 to 36.54 g/100 g. The addition of RP improved the thermal stability of the starch and reduced the amount of leached amylose. Infrared analysis shows that strong hydrogen bonds formed between RP (especially RP_>10) and starch during co-gelatinization. In addition, RP improved the compactness of aggregated structure and played an important role in hindering the enzymatic hydrolysis of starch. These results enrich the theory of starch-protein interactions and have important implications for the development of carbohydrate-based foods with low digestibility and protein functional foods.

Effects of exogenous proteins on enzyme desizing of starch and its mechanism

Added protein to starch has abundantly applied to size the yarns. However, scarce information is available about the impact of proteins on the enzyme desizing of starch. Thus, the objective of this study was to explore the effect of corn gluten, soybean protein and bone glue on enzyme desizing and reveal the interference mechanism. The desizing efficiency of starch was detected after added proteins. The contact angle, swelling ability, protein content and structure of starch adhesion on desized yarn were measured to analyze the effect of protein on desizing. In addition, the binding forces between protein and starch were detected, and the inhibition mechanism was analyzed. Experimental results showed that desizing efficiencies of starch were decreased after adding the protein. Corn gluten had the strongest influence in hindering desizing due to the weakest promotion in the swelling of film and the stronger binding force between protein and starch, mainly through hydrophobic interaction and hydrogen bond. Improving the swelling ability of film and inhibiting the binding between starch and protein may be feasible ways to reduce the inhibition of protein on desizing.

Structural evolution, digestibility and inhibition on starch digestion of rice glutelin fibril aggregates as affected by incubation

Structural evolution, digestibility and inhibition on starch digestion of rice glutelin fibril aggregates (RGFAs) as affected by incubation were investigated. Thioflavin T fluorescence intensity of the RGFAs, incubated for 4-day, reached the maximum values, which ranged from 845.00 ± 23.52 to 873.67 ± 50.30. Transmission electron microscopy (TEM) observed that the samples heated for 2 h (2 h fibril) were self-assembled from small glutelin aggregates and a few protofibrils into mature fibrils, the samples heated for 4-10 h (4-10 h fibril) were elongated into long, branched fibrils, and the longer fibrils of 15 h fibril sample dissociated into short fibrils after 4-day of incubation. Compared to rice glutelin, the RGFAs showed thermal stability and resistance to proteolysis. The fluorescence retention rate of 6 h fibril, after incubation for 4-day, was 8.62 ± 0.61 % after in vitro stomach and pancreas digestion, which was the highest among all of the samples. The RGFAs incubated for 1-day displayed much better inhibition effects on starch digestion. This was the first study to clarify the relationship between incubation and physicochemical/functional properties of protein fibrils, which could help understand the preservation of food protein fibrils and their application.

Preparation of Natural Food-Grade Core-Shell Starch/Zein Microparticles by Antisolvent Exchange and Transglutaminase Crosslinking for Reduced Digestion of Starch

The purpose of this study was to slow down the digestibility of starch granules by encapsulating it in zein shells. Drop of the preformed swollen corn starch (CS) granule suspension into thermal-treated zein ethanolic solution enables antisolvent precipitation of thermal-treated zein on the surface of the preformed swollen CS granules, leading to the formation of core-shell starch/zein microparticles. Confocal laser scanning microscopy images showed that the preformed swollen CS granules were coated by thermal-treated zein shells with a thickness of 0.48–0.95 μm. The volume average particle diameter of core-shell starch/zein microparticles was 14.70 μm and reached 18.59–30.98 μm after crosslinking by transglutaminase. The results of X-ray diffraction and Fourier transform infrared spectroscopy demonstrated that an interaction occurred between the preformed swollen CS granules and the thermal-treated zein. The results for thermodynamic characteristics, pasting properties, and swelling power indicated that the compact network structure of core-shell starch/zein microparticles crosslinked by transglutaminase could improve starch granule thermal stability and resistance to shearing forces. Compared to native CS, the peak gelatinization temperatures of core-shell starch/zein microparticles increased significantly (p < 0.05), with a maximum value of 76.64°C. The breakdown values and the swelling power at 95°C of core-shell starch/zein microparticles significantly (p < 0.05) decreased by 52.83–85.66% and 0.11–0.28%, respectively. The in vitro digestibility test showed that the contents of slowly digestible starch and resistant starch in the core-shell starch/zein microparticles increased to ∼42.66 and ∼34.75%, respectively, compared to those of native CS (9.56 and 2.48%, respectively). Our research supports the application of food-grade core-shell starch/zein microparticles to formulate low-digestibility food products.

In vitro gastro-small intestinal digestion of conventional and mildly processed pea protein ingredients

We report on the effect of processing, particularly heating, on the digestion dynamics of pea proteins using the standardised semi-dynamic in vitro digestion method. Fractions with native proteins were obtained by mild aqueous fractionation of pea flour. A commercial pea protein isolate was chosen as a benchmark. Heating dispersions of pea flour and mild protein fractions reduced the trypsin inhibitory activity to levels similar to that of the protein isolate. Protein-rich and non-soluble protein fractions were up to 18% better hydrolysed after being thermally denatured, particularly for proteins emptied later in the gastric phase. The degree of hydrolysis throughout the digestion was similar for these heated fractions and the conventional isolate. Further heating of the protein isolate reduced its digestibility as much as 9%. Protein solubility enhances the digestibility of native proteins, while heating aggregates the proteins, which ultimately reduces the achieved extent of hydrolysis from gastro-small intestinal enzymes.

Impacts, Tolerance, Adaptation, and Mitigation of Heat Stress on Wheat under Changing Climates

Heat stress (HS) is one of the major abiotic stresses affecting the production and quality of wheat. Rising temperatures are particularly threatening to wheat production. A detailed overview of morpho-physio-biochemical responses of wheat to HS is critical to identify various tolerance mechanisms and their use in identifying strategies to safeguard wheat production under changing climates. The development of thermotolerant wheat cultivars using conventional or molecular breeding and transgenic approaches is promising. Over the last decade, different omics approaches have revolutionized the way plant breeders and biotechnologists investigate underlying stress tolerance mechanisms and cellular homeostasis. Therefore, developing genomics, transcriptomics, proteomics, and metabolomics data sets and a deeper understanding of HS tolerance mechanisms of different wheat cultivars are needed. The most reliable method to improve plant resilience to HS must include agronomic management strategies, such as the adoption of climate-smart cultivation practices and use of osmoprotectants and cultured soil microbes. However, looking at the complex nature of HS, the adoption of a holistic approach integrating outcomes of breeding, physiological, agronomical, and biotechnological options is required. Our review aims to provide insights concerning morpho-physiological and molecular impacts, tolerance mechanisms, and adaptation strategies of HS in wheat. This review will help scientific communities in the identification, development, and promotion of thermotolerant wheat cultivars and management strategies to minimize negative impacts of HS.

Dual-frequency power ultrasound effects on the complexing index, physicochemical properties, and digestion mechanism of arrowhead starch-lipid complexes

Multi-scale structural interactions of the arrowhead starch-linoleic/stearic acid complexes under different durations (20, 40 & 60 min) of dual-frequency power ultrasound (DFPU, 20/40 kHz) and their underlying mechanisms were discussed. Differential scanning calorimetry and X-ray diffraction (XRD) revealed V6 type (V6-I, II) crystalline structure for ultrasonically-treated arrowhead starch-linoleic acid (UTAS-LA) complexes. An increased degree of short-range molecular order as IR ratios of 1045/1022 cm^-1 was evident from the FTIR results. The complexing index (CI) values of the complexes were greater than 65%, and the highest CI values of 83.04% and 81.26% were found in the case of UTAS-LA40 and UTAS-LA60, respectively. SEM results showed that LA-complexes had a sponge-like structure with smooth surfaces, while the SA-complexes exhibited flaky structures with irregular shapes and rough surfaces. The V-type complexes exhibited a higher digestion resistance than native AS and un-sonicated AS-LA/SA complexes due to partial RDS convention to RS.

Effect of Endogenous Lipids and Proteins on the Antioxidant, in vitro Starch Digestibility, and Pasting Properties of Sorghum Flour

This study evaluated the effect of endogenous lipids and proteins on the antioxidants, starch digestibility, and pasting properties of sorghum (Sorghum bicolor) flour (SF). Endogenous lipids and/or proteins were removed from different portions of SF to obtain defatted (DF), deproteinized (DP), and defatted and deproteinized (DF-DP) flours. Bioactive constituents (total phenolics, tannins, flavonoids, saponins, and anthocyanins), antioxidant activities [2,2-Azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation (ABTS*+) and 2, 2-Diphenyl-2-picrylhydrazyl radical (DPPH*) scavenging activities, reducing power, and Fe2+ chelating capacity], starch, amylose, starch hydrolysis index (HI), estimated glycemic index (eGI), and pasting properties of treated and control (untreated) flours were determined. The control flour (SF) had significantly higher (p < 0.05) levels of all the bioactive constituents and antioxidant activity tested than the DF, DP, and DF-DP flours, while the DF-DP flour had the least levels of bioactive constituents and antioxidant activity. In contrast, the starch, amylose, HI, and eGI were consistently in the order of DF-DP > DF > DP > control flour (p < 0.05). The control flour had the highest (p < 0.05) peak viscosity, and the least peak time and pasting temperature, while the DF flour had the highest final viscosity. Therefore, endogenous lipids and proteins contribute to the antioxidant, starch digestibility, and pasting properties of sorghum flour.

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.