Comparison of the molecular structure of heat and pressure-treated corn starch based on experimental data and molecular dynamics simulation

Multiscale insights into the role of water content in the extrusion-crosslinked starch

Water content is a key factor in the extrusion-crosslinking process, profoundly influencing the modification and structural properties of starch. The specific effects of water content have not been sufficiently emphasized in the extrusion-crosslinking process, limiting the high-value utilization of starch. This study elucidates the mechanisms of extrusion crosslinking under varying water contents through multiscale analysis, revealing that water content directly affects starch modification. As water content increases, starch crystallinity and molecular degree of order decrease, while the proportion of short-chain structures increases. Higher water content (≥45 %) improves starch melt fluidity and molecular chain mobility, promotes crosslinking, and results in starch gels with superior viscoelastic properties. However, excessive water content (85 %) decreases gel strength and crosslinking efficiency. Molecular simulations complemented the experimental results, showing that water modulates hydrogen bonding and starch molecular mobility. At 65 % moisture content, the crosslinking bonds exhibited the highest and narrowest peak, indicating a higher proportion of crosslinking bonds and greater bond stability. This multiscale analysis highlights the importance of combining molecular simulations and experimental methods to better understand the role of water in starch modification. These results provide insights into the optimization of starch processing and guidance for the sustainable use of starch applications.

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.

Mechanistic understanding of changes in physicochemical properties of different rice starches under high hydrostatic pressure treatment based on molecular and supramolecular structures

The molecular and supramolecular structures of japonica and waxy rice starches under high hydrostatic pressure treatment (450 MPa) were studied and the changes in physicochemical properties were analyzed based on these structures. The molecular structures of japonica and waxy rice starch cause differences in the lamellar structure and physicochemical properties. The thickness of amorphous lamella of japonica rice starch increased at 5 min (2.95 nm) followed by a gradual collapse of lamellar structure. Whereas the thickness of crystalline lamellae of waxy rice starch increased at 15 min (5.92 nm) and the lamellae collapsed suddenly at 20 min. The pasting, rheological and textural characteristics of both starches increased significantly within 10 to 15 min. The decreasing onset temperature and enthalpy of high hydrostatic pressure-treated starches indicated easier gelatinization. High hydrostatic pressure-treatment offers potential for developing starch-based products with low swelling capacity, easy gelatinization, high viscosity and hardness.

Effects of Fermentation Modification and Combined Modification with Heat-Moisture Treatment on the Multiscale Structure, Physical and Chemical Properties of Corn Flour and the Quality of Traditional Fermented Corn Noodles

This study investigates the effects of fermentation modification and combined modification with heat-moisture treatment (HMT) on the multiscale structure, physical and chemical properties, and quality of corn flour in the production of traditional fermented corn noodles (TFCNs). The results indicate that after fermentation modification, the starch granule size decreased while the amylopectin proportion increased. Fermentation also enhanced the relative crystallinity and short-range order of the starch, along with an increase in resistant digestion components and ester content in the noodles. After combined modification with HMT, starch granules lost their spherical, intact structure, underwent melting and reorganization, and displayed an increase in particle size. These changes led to a significant improvement in the thermal stability and textural properties of corn flour, resulting in noodles with enhanced cooking quality. Furthermore, the combined modification significantly increased the contents of flavor compounds such as aldehydes, acids, and alcohols in the noodles while reducing olefin and alkane levels, thus contributing to improved flavor development. These findings demonstrate that fermentation modification and combined modification with HMT play a crucial role in enhancing the multiscale structure and physical and chemical properties of corn starch, thereby improving the quality of TFCN.

Impact of ultra-high pressure on the microstructure, emulsification, and physicochemical properties of rice starch

Ultra-high pressure (UHP) treatment is considered a non-thermo physical treatment technology with a "clean label". Starch is an ideal stabilizer for food-grade Pickering emulsions. This study aimed to investigate the effects of ultra-high pressure (UHP) modification of rice starch on its structure, water/oil absorption, and emulsification properties under different pressure treatments (100-500 MPa), the results showed that the morphology of the starch granules and crystalline structure did not change significantly at lower pressures. Conversely, the particle size of starch increased significantly from 4.85 to 110.13 μm, the relative crystallinity (RC) obviously decreased from 18.89 % to 9.18 %, and the starch granules were destroyed and formed more fragments at higher pressure (500 MPa). The results of water/oil absorption indicated that the oil absorption slightly increased under UHP treatment, but water absorption intensively increased under higher pressure (500 MPa). The emulsifying capacity was significantly enhanced at 500 MPa after 8, 16, and 24 min. The UHP treatment induced swelling and disruption of starch granules at higher pressure (500 MPa). The starch fragments and the released starch molecules stabilized the droplets. This study provides a reference for the application of UHP processing in the starchy foods.

Investigation of starch hierarchical structure in relation to physicochemical properties and digestive behavior under different high hydrostatic pressure treatment time

Changes and causal relationships in the hierarchical structure, thermal, pasting and rheological properties, as well as the digestive behavior of starch under different high hydrostatic pressure (HHP) treatment time were investigated. At 5 min, the thickness of amorphous lamellae increased (2.76 nm) and the content of B2 and B3 chains in the amorphous lamellae decreased significantly (10.78 % and 9.08 %). As the treatment time increased, the crystalline lamellae swelled and tightly arranged double helices located in the crystalline lamellae were disturbed, resulting in a decrease in the content of double helices (12.16 %) and relative crystallinity (16.96 %). Helix dissociation, crystal disruption, lamellar collapse and granule deformation were observed at 20 min. These structural changes were closely linked to variations in the physicochemical behaviors. The thermal parameters decreased gradually, accompanied by a decrease in double helix stability. The swollen crystalline lamellae provided more space for molecular stretching, thus enhancing the pasting characteristics. Regarding the digestive behavior, the swollen amorphous lamellae facilitated the invention of enzyme molecules to hydrolyze the starch at 5 min. The digestion rate coefficient and rapidly digestible starch content increased significantly until 15 min, which demonstrated that starch was more easily digested while retaining its intact granular form.

Understanding the multiscale structure and in vitro digestibility changes of corn starch-ferulic acid complexes induced by high hydrostatic pressure

High hydrostatic pressure (HHP) was used to synthesize corn starch (CS) and ferulic acid (FA) complex (CS-FA). Its effects on the structure of the complex at multiple scales and its digestibility were examined. The results demonstrated that HHP significantly influenced the digestibility of the CS-FA complex, decreasing the content of rapidly digestible starch (RDS) while increasing slowly digestible starch (SDS) and resistant starch (RS). Notably, the combined SDS and RS content in the HHP-treated CS-FA complex with 2.0 % FA addition (38.13 %) was significantly higher (p < 0.05) than those in the CS-FA complex without HHP treatment (29.21 %) and pure CS (21.72 %). The results indicated that HHP treatment reduced the enthalpy change (ΔH), number of short-range order structures, and relative crystallinity (RC) while increasing the average particle size of these CS-FA complexes. This treatment also increased the proportion of amorphous starch regions and the degree of agglomeration between the starch and FA. HHP treatment-induced CS-FA complexes exhibited a denser fractal structure and higher short-range order, affecting the interaction sites between the starch and digestive enzymes. These findings suggest the potential application of HHP treatment and FA in modulating the postprandial glycemic response to starchy food.

Recent advances in the impact of gelatinization degree on starch: Structure, properties and applications

During home cooking or industrial food processing operations, starch granules usually undergo a process known as gelatinization. The starch gelatinization degree (DG) influences the structural organization and properties of starch, which in turn alters the physicochemical, organoleptic, and gastrointestinal properties of starchy foods. This review summarizes methods for measuring DG, as well as the impact of DG on the starch structure, properties, and applications. Enzymatic digestion, iodine colorimetry, and differential scanning calorimetry are the most common methods for evaluating the DG. As the DG increases, the structural organization of the molecules within starch granules is progressively disrupted, the particle size of the granules is altered due to swelling and then disruption, the crystallinity is decreased, the molecular weight is reduced, and the starch-lipid complexes are formed. The impact of DG on the starch structure and properties depends on the processing method, operating conditions, and starch source. The starch DG affects the quality of many foods, including baked goods, fried foods, alcoholic beverages, emulsified foods, and edible inks. Thus, a better understanding of the changes in starch structure and function caused by gelatinization could facilitate the development of foods with novel or improved properties.

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.

Unveiling the impact of high-pressure processing on anthocyanin-protein/polysaccharide interactions: A comprehensive review

Anthocyanins, natural plant pigments responsible for the vibrant hues in fruits, vegetables, and flowers, boast antioxidant properties with potential human health benefits. However, their susceptibility to degradation under conditions such as heat, light, and pH fluctuations necessitates strategies to safeguard their stability. Recent investigations have focused on exploring the interactions between anthocyanins and biomacromolecules, specifically proteins and polysaccharides, with the aim of enhancing their resilience. Notably, proteins like soy protein isolate and whey protein, alongside polysaccharides such as pectin, starch, and chitosan, have exhibited promising affinities with anthocyanins, thereby enhancing their stability and functional attributes. High-pressure processing (HPP), emerging as a non-thermal technology, has garnered attention for its potential to modulate these interactions. The application of high pressure can impact the structural features and stability of anthocyanin-protein/polysaccharide complexes, thereby altering their functionalities. However, caution must be exercised, as excessively high pressures may yield adverse effects. Consequently, while HPP holds promise in upholding anthocyanin stability, further exploration is warranted to elucidate its efficacy across diverse anthocyanin variants, macromolecular partners, pressure regimes, and their effects within real food matrices.

Effect of ferulic acid incorporation on structural, rheological, and digestive properties of hot-extrusion 3D-printed rice starch

The influence of ferulic acid (FA) on rice starch was investigated by incorporating it at various concentrations (0, 2.5, 5, 7.5, and 10 %, w/w, on dry starch basis) and subjecting the resulting composites to hot-extrusion 3D printing (HE-3DP) process. This study examined the effects of FA addition and HE-3DP on the structural, rheological, and physicochemical properties as well as the printability and digestibility of rice starch. The results indicated that adding 0-5 % FA had no significant effect; however, as the amount of FA increased, the printed product edges became less defined, the product's overall stability decreased, and it collapsed. The addition of FA reduced the elasticity and viscosity, making it easier to extrude the composite gel from the nozzle. Moreover, the crystallinity and short-range ordered structure of the HE-3D printed rice starch gel decreased with the addition of FA, resulting in a decrease in the yield stress and an increase in fluidity. Furthermore, the addition of FA reduced the digestibility of the HE-3D-printed rice starch. The findings of this study may be useful for the development of healthier modified starch products by adding bioactive substances and employing the 3D printing technology.

Structural changes of thermally treated starch during digestion and the impact on postprandial glucose homeostasis

Intake of foods upon thermal treatment is typically associated with an elevated postprandial glycemic response, which is one of the risk factors for type 2 diabetes development and progression. In this study, rice starch was thermally treated using aqueous phase (boil), air phase (bake), and lipid phase (fry). Peak blood glucose levels in C57 mice increased by 16.94 %, 12.60 %, and 8.1 % after ingestion of thermally treated starch (20.23, 19.48, and 18.70 mmol/L), compared with raw starch (17.30 mmol/L). The insulin response to the intake of thermally treated starch increased (4.73 %-6.83 % higher than the control), whereas the concentration of GLP-1, a hormone used to promote insulin secretion, decreased (1.54 %-8.56 % lower than the control). Furthermore, thermally treated starch accelerated food absorption by enhancing gastrointestinal digestion, exacerbating postprandial glucose fluctuation at the next meal. Structural characterization showed thermal treatment reduced starch branching density and degree of structure order, which were not conducive to preventing the attack of enzymes. During digestion, they were highly hydrolyzed into low-molecular-weight fragments, and the proportion of ultrashort chains substantially increased. These findings provide a better understanding of the fine structure of starch that promotes hypoglycemia and initially explain how diets high in thermally treated starch impair glucose balance.

Increasing the pressure during high pressure homogenization regulates the starch digestion of the resulting pea starch-gallic acid complexes

The pea starch-gallic acid (PS-GA) complexes were prepared using high pressure homogenization (HPH), then the effect and underlying mechanism of pressure on multi-scale structure and digestibility of complexes were investigated. Results showed that HPH promoted the formation of PS-GA complexes, reaching the maximum complex index of 7.74 % at the pressure of 90 MPa, and the main driving force were hydrophobic interactions and hydrogen bonding. The interaction between PS and GA facilitated the formation of surface reticular structures to encapsulate gallic acid molecules, further entangled into bigger size aggregates. The enhancement of rearrangement and aggregation of starch chains during HPH developed a dense hierarchical structure of PS-GA complexes, including short-range ordered structure, V-type crystal structure, lamellar and fractal structure, thus increasing gelatinization temperature. The digestibility of PS-GA complexes substantially changed in reducing rapidly digestible starch content from 29.67 % to 17.07 %, increasing slowly digestible starch from 53.69 % to 56.25 % and resistant starch from 16.63 % to 26.67 %, respectively. Moreover, the resulting complexes exhibited slower digestion rates compared with native PS. Furthermore, the regulating mechanism of pressure during HPH on starch digestibility was the formation of ordered multi-scale structure and inhibition of GA on digestive enzymes.

Effect of pre-gelatinization on α-amylase-catalyzed hydrolysis of corn starch under moderate electric field

This study aimed to explore the roles of starch structure in α-amylase-catalyzed hydrolysis under moderate electric field (MEF). Corn starch was gelatinized by controlling the temperature procedure of rapid viscos-analysis, and then the pre-gelatinized starch (3.0 g) was treated by MEF (2.5 and 5 V/cm) in the presence of α-amylase (1.5 mL). Only a slight hydrolysis occurred for native starch, showing minor increases in reducing sugar content (RSC, ∼0.19 mg/mL), slight changes in granular and semicrystalline structure, and decreases in thermostability (the maximum decomposition temperature (T_max) decreased from 322 to 300 °C). The densely-packed semicrystalline within starch granules was destroyed by pre-gelatinization, thus enhancing the hydrolysis and further decreasing the thermostability, presenting RSC values of 0.63-0.92 mg/mL and T_max of 291-292 °C. Moreover, some special crystals were formed by IEF-induced orientation of hydrolyzed starch chains. Overall, these results confirmed that the semicrystalline structure of starch dominated in MEF-assisted hydrolysis, which could provide guidance for the application of electro-based techniques in starch modification.