Revealing the mechanism beneath the effects of starch-amino acids interactions on starch physicochemical properties by molecular dynamic simulations

New insight into amino acids on the structure and rheological properties of rice starch via ultra-high pressure processing

There is a lack of research on the effects of amino acid starch interaction on the functional properties of products during Ultra-high pressure (UHP) processing. The functional properties of rice starch with the addition of Glu, Ala and Lys were studied under UHP processing. At 400 MPa, all amino acids reduced G' and weakened the gel strength, and the gel strength order was as follows: Control > Ala > Glu > Lys. At 500 MPa, Glu increased G' and G″, and enhanced the strength of the gel, but the addition of Lys had the opposite effects, the gel strength order was as follows: Glu > Ala > Control > Lys. With the increased of treatment pressure and time, the G' and G″ of all samples treated at 500 MPa decreased, and the gel strength weakened. This study will expand the application scope of rice starch as food gelling agents and functional food.

Experimental characterization and dual-temperature molecular dynamics simulation on the intervention of tea saponin in starch chain dynamic behavior

In this work, the typical properties of starchy products were innovatively described as six types of chain dynamic behaviors. Dual-temperature molecular dynamic simulations, alongside multi-experimental methods, were employed to tandemly explore the intervention effect and mechanism of tea saponin (TS, 0 %-40 % w/w) on these behaviors. The findings reveal that the hydrophilic and hydrophobic ends of TS provide numerous sites for hydrogen bonding and steric hindrance, respectively, which hinder the formation of hydrogen bonds between starch chains. This interaction mode facilitated the chain unwinding (pasting temperature: 79.8 → 76.4 °C) and movement (viscosity: 267.67 → 38.92 Pa.s), and also retarded chain short/long-term reassociation (elastic modulus: 0.41 → 0.14 Pa/min; hardening rate: 2.72 → 0.07 gf/d) and rearrangement (hardness: 15.50 → 10.00 gf). Notably, a critical TS content was observed between 10 % and 20 % w/w, beyond which textural collapse (hardness: 15.50 → 10.00 gf) occurred. This research offers a new strategy and relevant theoretical backing for the property regulation of starch products.

Experimental and computational insights into starch pasting as influenced by amino acids with different R-groups

The effects of amino acids with different R-groups, namely glutamic acid (GLU), glutamine (GLN), and theanine (THE), on the pasting and structure properties of corn starch (CS) were investigated. During gelatinization, GLU decreased viscosity of CS. GLN and THE increased pasting enthalpy of CS from 7.62 to 8.72 and 9.50 J/g, respectively. All starch-amino acid systems had higher storage and loss modulus. Amino acids could adhere to starch granule surface. After co-gelatinization, GLU increased short-range order degree of starch, while GLN and THE decreased. Both infrared spectroscopy and quantum computation showed that non-covalent interaction occurred between amino acids and starch. Molecular dynamics revealed that the interaction between GLU and starch weakened hydrogen bonding between starch and water, promoting cross-linking between starch chains. GLN and THE changed dihedral angle torsion of glycoside bonds, and mainly interacted with starch by electrostatic interaction (50.06 kJ/mol) and van der Waals force (50.30 kJ/mol), respectively.

Highly cost-effective wheat starch-stearic acid complexes enabled by microwave processing: Structural properties, anti-digestion, and molecular dynamics simulation

Microwave (MW) heating shows higher efficiency in preparing wheat starch-stearic acid (WS-SA) complexes than the traditional water bath (WB) heating method, while the detailed "time-energy-quality" evaluations and the potential anti-digestion mechanism of the MW-processed WS-SA remain further exploration. In this study, 95 % time cost and 73 % energy consumption were saved when using MW processing WS-SA, and the MW-processed complexes were verified to show significantly higher relative crystallinity, short-range ordered structure degree, thermal stability, complex index, and resistant starch content. Molecular dynamics (MD) simulation demonstrated that MW treatment notably facilitated the binding rate of amylose and SA molecules, generating a tight and stable helical structure through hydrogen bonds and van der Waals forces. Analyses of solvent-accessible surface area and water status cross-verified that the denser structure could endow the MW-processed complexes with higher resistance to water solvation effects and correspondingly reduce the water mobility for enzymatic hydrolysis reactions, ultimately making the MW-processed complexes more undigestible. This study provides a further understanding of the anti-digestion mechanisms of the MW-processed WS-SA from the molecular level, and it is expected that the current work could attract more concerns to the highly cost-effective MW heating method for processing starchy food.

Intervention mechanism of amphiphilic natural sweeteners on starch chain dynamic behavior: Computational and experimental insights

Amphiphilic natural sweeteners (i.e. steviol glycosides (STE) and glycyrrhizic acid (GA)) have been adopted to improve the quality of various starchy products, which can fundamentally be characterized as the intervention of the former in the chain dynamic behavior of the latter. However, these phenomena and related mechanisms still lack systematic insights. Herein, dual-temperature molecular dynamic simulations combined with experimental analysis were used to tandemly investigate the intervention of sweeteners in six types of chain dynamic behaviors that are strongly correlated with starch properties, including unwinding, movement, long/short-term reassociation, rearrangement, and depolymerization. The results show that STE and GA both promoted the chain unwinding and movement, and also retarded the chain short/long-term reassociation and rearrangement. Besides, GA exhibited a greater role than STE in facilitating chain unwinding and movement. Peculiarly, GA (0 %-40 % w/w) collaborated with starch to form a new microstructure, especially at high content (≥ 20 % w/w), which endowed starch with exceptionally high hardness (15.50 gf→189.36 gf) and hardening rate (2.72 gf/d→17.76 gf/d), and also placed a physical barrier to retard starch depolymerization (slowly digestible starch: 11.26 %→20.62 %). This work contributes data and theoretical support for the development of starch/amphiphilic natural sweetener composite matrices.

Effect of transglutaminase on the interaction of protein and rice starch

The present study aims to investigate the effects of endogenous protein (rice protein, RP) and exogenous proteins (corn protein, CP, and wheat protein, WP) on the physicochemical properties of rice starch under the action of transglutaminase (TG). The findings indicate that, the interactions between exogenous proteins with rice starch are relatively weak. However, with the catalysis of TG, both endogenous and exogenous proteins tightly encapsulate rice starch granules, forming a dense microporous network structure. This phenomenon led to a reduction in starch expansion coefficient and amylose leaching, resulting in an increase in the onset temperature and a notable decrease in viscosity and digestibility. Among them, endogenous protein exerted the greatest influence on the gelatinization properties of rice starch, whereas exogenous protein had the most significant impact on its digestibility. Specifically, the order of influence on the gelatinization characteristics is RP > CP > WP, and for digestibility, it is WP > CP > RP. Furthermore, under the action of TG, both endogenous and exogenous proteins significantly enhanced the short-range ordered structure of starch molecules, contributing to higher crystallinity and a more ordered A-type structure. In conclusion, this study provides a theoretical basis for the construction of starch functional foods.

Assessing the influences of β-glucan on highland barley starch: Insights into gelatinization and molecular interactions

Developing highland barley products is complex, possibly due to the presence of β-glucan in highland barley. This study aims to investigate the impact of β-glucan on the physicochemical properties, microstructure, and molecular interactions of highland barley starch (HBS) during gelatinization and aging. Increasing the β-glucan content significantly reduced peak viscosity, setback viscosity, and breakdown viscosity, indicating altered gelatinization behavior. The β-glucan content increase caused a significant drop in peak viscosity. With 20% β-glucan addition, it reduced by 883 mPa·s, nearly 38%. Rheological analysis showed a transition from a solid-like to a liquid-like texture or quality, ultimately leading to a shear-thinning behavior. Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) confirmed the interaction between HBS and β-glucan via intermolecular hydrogen bonding, promoting the formation of double helical structures in starch. These findings provide a deeper understanding of the role of β-glucan in the processing of highland barley, highlighting its influence on the starch's properties.

Preparation, structural analysis of alcohol aroma compounds/β-cyclodextrin inclusion complexes and the application in strawberry preservation

The dynamic combination of aromas and cyclodextrins is an important means to achieve their stability and controllability, and accurately revealing their interaction rules is the key to designing and constructing high-quality aroma nanocarriers. In this study, the inclusion mechanism between alcohol aroma compounds with different structures and β-cyclodextrin (β-CD) was studied by combining molecular dynamics simulation and experimental methods. Results showed that the selected alcohol aroma compounds formed inclusion complexes (ICs) with β-CD in a 1:1 ratio, while alcohol aroma compounds containing cyclic structures were more tightly bound to β-CD. Van der Waals forces were the primary forces driving the formation and stabilization of the ICs. Cinnamyl alcohol/β-CD ICs showed the most significant antimicrobial effect and notably prolonged the shelf life of strawberries. This study aimed to provide theoretical support for precisely designing and preparing highly stable flavours and fragrances, as well as expanding their application range.

Application of the molecular dynamics simulation GROMACS in food science

Food comprises proteins, lipids, sugars and various other molecules that constitute a multicomponent biological system. It is challenging to investigate microscopic changes in food systems solely by performing conventional experiments. Molecular dynamics (MD) simulation serves as a crucial bridge in addressing this research gap. The Groningen Machine for Chemical Simulations (GROMACS) is an open-source, high-performing molecular dynamics simulation software that plays a significant role in food science research owing to its high flexibility and powerful functionality; it has been used to explore the molecular conformations and the mechanisms of interaction between food molecules at the microcosmic level and to analyze their properties and functions. This review presents the workflow of the GROMACS software and emphasizes the recent developments and achievements in its applications in food science research, thus providing important theoretical guidance and technical support for obtaining an in-depth understanding of the properties and functions of food.

Insights into formation and stability mechanism of V7-type short amylose-resveratrol complex using molecular dynamics simulation and molecular docking

Pre-formed V-type amylose as a kind of wall material has been reported to carry polyphenols, while the interaction mechanism between V-type amylose and polyphenol is still elusive. In this work, the formation and stability mechanism of a V7-type short amylose-resveratrol complex was investigated via isothermal titration calorimetry, molecular dynamics, and molecular docking. The results presented that two stoichiometric ratios of resveratrol to short amylose were calculated to 0.120 and 0.800, and the corresponding main driving force was hydrogen bonding and hydrophobic interaction, respectively. The folding and unfolding conformation of V7-type short amylose chains appeared alternately during the simulation. Resveratrol tended to be bound in the short amylose helix between 40 ns and 80 ns to form a more stable complex. Hydrogen bonds between resveratrol molecule and O6 at the 22nd glucose molecule/O2 at the 24th glucose molecules and hydrophobic interaction between resveratrol molecule and glucose molecules (19th, 20th, 21st and 23rd) could be found.

Mechanism of interaction between L-theanine and maize starch in ultrasonic field based on DFT calculations: Rheological properties, multi-scale structure and in vitro digestibility

The digestibility of starch-based foods is receiving increased attention. To date, the full understanding of how including L-theanine (THE) can modify the structural and digestive properties of starch has not been fully achieved. Here, we investigated the multi-scale structure and digestibility of maize starch (MS) regulated by THE in ultrasound field and the molecular interactions. Ultrasound disrupted the structure of starch granules and opened the molecular chains of starch, promoting increased THE binding and producing more low-order or disordered crystal structures. In this case, the aggregation of starch molecules, especially amylose, was reduced, leading to increased mobility of the systems. As a result, the apparent viscosity, G', and G" were significantly decreased, which retarded the starch regeneration. Density functional theory calculations indicated that there were mainly non-covalent interactions between THE and MS, such as hydrogen bonding and van der Waals forces. These interactions were the main factors contributing to the decrease in the short-range ordering, the helical structure, and the enthalpy change (ΔH) of MS. Interestingly, the rapidly digestible starch (RDS) content of THE modified MS (MS-THE-30) decreased by 17.89 %, while the resistant starch increased to 26.65 %. These results provide new strategies for the safe production of resistant starch.

Effect of addition of methionine and histidine on physicochemical and rheological characteristics of water chestnut starch as revealed by molecular dynamic simulations

The effect of addition of amino acids including methionine (Met) and histidine (His) at selected concentrations (2, 6, 10, and 15%) on the physicochemical, pasting, and rheological properties of water chestnut starch (WS) was evaluated. A higher quantity of amino acids considerably (p < 0.05) inhibited the ability of starch-amino acid blends to expand their solubility index and swelling capacity. The addition of amino acids also significantly decreased peak viscosity (952.33-540.67 cP), hot paste viscosity (917-528 cP), cold paste viscosity (1209.67-659 cP), and setback (277.67-131 cP) of WS. Addition of amino acids enhanced the stability ratio (SR) of WS. All the studied samples displayed storage moduli (G') values higher than loss moduli (G'') but rheologically weak gel characteristics. Molecular dynamics simulation studies revealed that interactions between amino acids and water greatly reduced the number of starch-water hydrogen bonds while preserving a higher number of starch-starch intramolecular interactions. This study could provide important insights for better understanding of modification of water chestnut starch functionality under the influence of amino acid residues.

The anti-digestibility mechanism of soy protein isolate hydrolysate on natural starches with different crystal types

The effects of soy protein isolate hydrolysate (SPIH) on the physicochemical properties and digestive characteristics of three starch types (wheat, potato, and pea) were investigated. Fourier-transform infrared spectroscopy and molecular dynamics simulations showed that hydrogen bonds were the driving force of the interaction between SPIH and starch. Furthermore, the SPIH was predicted to preferentially bind to the terminal region of starch using molecular dynamics simulations. Compared to pure starch, adding 20 % SPIH to wheat starch, potato starch, and pea starch, the content of resistant starch increased by 39.71 %, 125.66 % and 37.83 %, respectively. Both the radial distribution function (RDF) and low field-nuclear magnetic resonance (LF-NMR) showed that SPIH reduced the flow of water molecules in starch, indicating that SPIH competed with starch for water molecules. Multiple characterization experiments and molecular dynamics simulations confirmed that the anti-digestibility mechanism of SPIH on natural starches with different crystal types could be attributed to the interaction between starch and SPIH, which decreased the catalytic efficiency of amylase. This study clarified the anti-digestibility mechanism of SPIH on natural starches, which provides new insights into the production of low-glycemic index foods for the diabetic population.

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.

Harnessing nitrogen-doped graphene quantum dots for enhancing the fluorescence and conductivity of the starch-based film

The flexible film is widely applied in the modern electronic industry, whilst it is still challenging to use biopolymer substrates (e.g., starch) to prepare flexible film well-performed in conductivity and fluorescence. In the study, a novel conductive, fluorescent, and flexible biopolymer film was prepared via a cost-effective method by fabricating the nitrogen-doped oxide-reduced graphene quantum dots (N-rGO-QDs) into the thermoplastic starch (TPS) substrate. TPS/N-rGO-QDs film with 10 wt% N-rGO-QDs showed the desirable lowest resistivity (0.082 Ω·m), acceptable light transmittance (60-80 %), and durable fluorescence intensity (9000 CPS). The results reveal a novel starch-based multifunctional film with satisfactory electrical and fluorescent performances, which is hypothesized potential to be applied in some frontier domains, like human wearable devices.

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.

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...