Effects of preheat treatment and syringic acid binding on the physicochemical, antioxidant, and antibacterial properties of black soybean protein isolate before and after in vitro digestion.

This study investigated the effects of preheat treatment (70-100 °C) and syringic acid (SA) grafting on the antioxidant, antibacterial, and physicochemical properties of black soybean protein isolate (BSPI) before and after in vitro digestion. The results revealed that both preheat treatment and SA grafting increased the digestibility and the absolute zeta potential value of BSPI. However, as the preheating temperature increased, the antioxidant ability of BSPI decreased, which was improved by SA grafting. During in vitro digestion, the absolute zeta potential and antioxidant activities of preheated BSPI and preheated BSPI-SA complex followed the order: intestine > gastric > before digestion. Compared with before digestion, preheated BSPI with its SA complex after in vitro digestion exhibited excellent antibacterial activities. Importantly, the preheated BSPI-SA complex enhanced the SA recovery rate during digestion and SA stability, with the highest recovery rate observed for the SA-grafted BSPI with preheat treatment at 100°C (BSPI100-SA). The principal component analysis sufficiently distinguished preheated BSPI and preheated BSPI-SA complexes. There were partitions between BSPI and BSPI-SA treated at different preheating temperatures. This study contributes to expanding the potential applications of BSPI with its SA complex in food products and offers guidance for designing SA delivery systems. PRACTICAL APPLICATION: Preheated BSPI-SA complexes could serve as functional ingredients in food or health products. Besides, preheated BSPI has application potential as a carrier for SA delivery.

Enzymatic hydrolysis pretreatment combined with glycosylation for soybean protein isolate applying in dual-protein yogurt.

This research investigated the viability of replacing milk protein with glycosylated soybean protein isolate (SPI) treated with different enzymatic hydrolysis times (0, 10, 20, 30, 40, and 50 min) in yogurt. The results showed that enzymatic hydrolysis pretreatment combined with glycosylation for SPI exhibited elevated grafting and solubility. Additionally, the high solubility of SPI (94.77 %) at 40 min facilitates the preparation of dual-protein yogurt (DPY). Compared to ESPI0-G, DPY that incorporates ESPI40-G through partial substitution of milk protein is capable of forming a denser and more stable gel matrix. Especially, the syneresis of DPY40 was reduced by 7.61 % compared to DPY0, which more closely approximates the texture properties of traditional yogurt. Meanwhile, glycosylated SPI treated with enzymatic hydrolysis can effectively degrade the beany flavor and slightly bitter taste in DPY. This study could provide a solid theoretical basis for the broader application and industrialization of plant-based yogurt.

Insights into the soybean protein isolate hydrolysates: Performance characterization, emulsion construction and in vitro digestive behavior.

In this experiment, the co-constructed O/W emulsions of different soy protein hydrolysates (SPHs) and gum arabic (GA) were investigated. SPHs were prepared by hydrolyzing soy protein isolate (SPI) using different enzymes, and investigated the effects of enzyme types and hydrolysis time on the physicochemical properties of SPHs. Moreover, SPI/GA and SPHs/GA were prepared and used as hydrophilic emulsifiers to construct O/W emulsions. The results showed that the optimal hydrolysis times for bromelain, pepsin and trypsin were 2 h (BSPH2), 3 h (PSPH3) and 3 h (TSPH3), respectively. Compared with SPI/GA emulsions, SPHs/GA emulsions had smaller particle size, more negative charge, higher interfacial adsorbed protein, and more stable emulsion systems. During the digestion process, SPHs/GA emulsions were effective in realizing the release of bioactives. In conclusion, enzymatic hydrolysis can be an effective modification technique, and SPHs/GA can be used as an effective emulsifier for the emulsion system.

Enzymatic Preparation, Identification by Transmembrane Channel-like 4 (TMC4) Protein, and Bioinformatics Analysis of New Salty Peptides from Soybean Protein Isolate.

To address the public health challenges posed by high-salt diets, this study utilized pepsin and flavourzyme for the continuous enzymatic hydrolysis of a soy protein isolate (SPI). The separation, purification, and identification of salt-containing peptides in SPI hydrolysate were conducted using ultrafiltration (UF), gel filtration chromatography (GFC), and Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS). Subsequently, a molecular docking model was constructed between salt receptor protein transmembrane channel 4 (TMC4) and the identified peptides. Basic bioinformatics screening was performed to obtain non-toxic, non-allergenic, and stable salt peptides. After the enzymatic hydrolysis, separation, and purification of SPI, a component with a sensory evaluation score of 7 and an electronic tongue score of 10.36 was obtained. LC-MS/MS sequencing identified a total of 1697 peptides in the above component, including 84 potential salt-containing peptides. A molecular docking analysis identified seven peptides (FPPP, GGPW, IPHF, IPKF, IPRR, LPRR, and LPHF) with a strong theoretical salty taste. Furthermore, residues Glu531, Asp491, Val495, Ala401, and Phe405 of the peptides bound to the TMC4 receptor through hydrogen bonds, hydrophobic interactions, and electrostatic interactions, thereby imparting a significant salty taste. A basic bioinformatics analysis further revealed that IPHF, LPHF, GGPW, and IPKF were non-toxic, non-allergenic, and stable salt-containing peptides. This study not only provides a new sodium reduction strategy for the food industry, but also opens up new avenues for improving the public's healthy eating habits.

Preparation, characterization, and binding mechanism of quercetin-loaded composite nanoparticles based on zein-soybean protein isolate.

In this study, quercetin (Que) was encapsulated for controlled release during gastrointestinal digestion using zein-soy isolate protein (SPI) composite nanoparticles that were made following an antisolvent precipitation technique. The average particle size of the composite nanoparticles ranged from 182.1 to 230.9 nm, and the polydispersity index (PDI) was small (0.105-0.323). The microstructure revealed that the composite nanoparticles were spherically distributed and that Que. was embedded on the surface of the nanoparticles. Que. has an encapsulation efficiency of up to 93.3 %. Spectrum analysis, molecular docking and zeta potential measurements revealed that the interactions between the composite nanoparticles and Que. occurred mainly through hydrophobic interactions, hydrogen bonding, and electrostatic interactions. Compared with single zein nanoparticles, the composite nanoparticles showed a significant and controlled release of Que. during the whole simulated gastrointestinal digestion process. This study provides a novel method for the development of a controlled-release drug delivery system for controlling the release of Que.

Lignin and green solvent extracted phenolic compounds from date palm leaves as functional ingredients for the formulation of soy protein isolate biocomposite packaging materials: A circular packaging concept.

The current study investigated valorization of lignin nanoparticles (LNPs) and phenolic compounds loaded in chitosan (DLECNPs) extracted from date palm leaves into the soy protein isolate (SPI) biocomposite films. The mechanical, structural, barrier, physiochemical, thermal, optical, antioxidant, and antimicrobial properties of the formulated composite films were investigated. The findings showed that the incorporation of DLECNPs into the SPI films significantly improved the film's antioxidant properties by more than 3 times and showed antibacterial inhibition zone in the range of 10-15 mm against six pathogenic bacteria. Further, incorporating LNPs into SPI-DLECNPs films notably improved the mechanical properties from 4.32 MPa and 29.27 % tensile strength and elongation at break, respectively to 10.13 MPa and 54.94 %, the water vapor permeability from 7.38 g/Pa s m to 5.59 g/Pa s m, and the antibacterial inhibition zone from a range of 10.2 mm to 15.0-21.5 mm as well as making the films more heterogeneous and stronger than control SPI film. Moreover, LNPs changed the initial films' color from light yellow to dark red and reduced the films' transparency. The results indicated that LNPs reinforced SPI composite films showed significant improvements in several properties and thus can be used as a potential ingredient for formulation of biodegradable packaging films.

Effect of Corynebacterium glutamicum Fermentation on the Volatile Flavors of the Enzymatic Hydrolysate of Soybean Protein Isolate.

This study focused on improving the flavor quality of seasonings, and enzymatic hydrolysis of soybean protein isolate (SPI) seasoning via traditional technology may lead to undesirable flavors. Herein, we aimed to develop a new type of SPI seasoning through microbial fermentation to improve its flavor quality. The effect of Corynebacterium glutamicum fermentation on the flavoring compounds of seasonings in SPI enzymatic hydrolysate was examined. Sensory evaluation showed that the SPI seasoning had mainly aromatic and roasted flavor, and the response signals of S18 (aromatic compounds), S24 (alcohols and aldehydes), and S25 (esters and ketones) sensors of the electronic nose differed significantly. Overall, 91 volatile compounds were identified via gas chromatography-mass spectrometry. SPI seasonings contained a higher number of alcohols, ketones, aromatics, and heterocyclic compounds than traditional seasonings, which had stronger cheese, fatty, and roasted aromas. According to the relative odor activity value (ROAV) analysis, n-pentylpyrzine, 2,6-dimethylpyrazine, and tetramethylpyrazine are the key flavoring compounds (ROAV ≥ 1) of SPI seasoning, which may impart a unique roasted and meaty aroma. Therefore, the fermentation of SPI enzymatic hydrolysate with C. glutamicum may improve the flavor quality of its products, providing a new method for the development and production of new seasoning products.

Constructing soybean protein isolate /bacterial cellulose co-assemblies by pH shifting treatment: Molecular conformation and physicochemical properties.

The study elucidates that the pH shifting treatment unfolds the conformation of soybean protein isolate (SPI), enabling it to intertwine with bacterial cellulose (BC) and form SPI/BC co-assemblies. Results from intrinsic fluorescence spectroscopy and surface hydrophobicity indicate that the SPI with pH shifting treatment shows a notable blue shift in maximum emission wavelength and increased surface hydrophobicity. It demonstrates that pH shifting treatment facilitates the unfolding of SPI's molecular conformation, promoting its entanglement with high aspect ratio BC. Particle size distribution and microstructural analysis further demonstrate that the pH shifting treatment facilitates the formation of SPI/BC co-assemblies. Evaluation of processing properties reveals that the SPI/BC co-assemblies exhibited exceptional gel and emulsification properties, with gel strength and emulsifying activity respectively six and two times higher than natural SPI. This enhancement is attributed to the thickening properties of BC with a high aspect ratio and the superior hydrophobicity of SPI in its molten globule state.

Comparison of intestinal absorption of soybean protein isolate-, glutenin- and peanut protein isolate-bound Nε-(carboxymethyl) lysine after in vitro gastrointestinal digestion.

Advanced glycation end products (AGEs), a heterogeneous compound existed in processed foods, are related to chronic diseases when they are accumulated excessively in human organs. Protein-bound Nε-(carboxymethyl) lysine (CML) as a typical AGE, is widely determined to evaluate AGEs level in foods and in vivo. This study investigated the intestinal absorption of three protein-bound CML originated from main food raw materials (soybean, wheat and peanut). After in vitro gastrointestinal digestion, the three protein-bound CML digests were ultrafiltered and divided into four fractions: less than 1 kDa, between 1 and 3 kDa, between 3 and 5 kDa, greater than 5 kDa. Caco-2 cell monolayer model was further used to evaluate the intestinal absorption of these components. Results showed that the absorption rates of soybean protein isolate (SPI)-, glutenin (Glu)-, peanut protein isolate (PPI)-bound CML were 30.18%, 31.57% and 29.5%, respectively. The absorption rates of components with MW less than 5 kDa accounted for 19.91% (SPI-bound CML), 22.59% (Glu-bound CML), 23.64% (PPI-bound CML), respectively, and these samples were absorbed by paracellular route, transcytosis route and active route via PepT-1. Taken together, these findings demonstrated that all three protein-bound CML digests with different MW can be absorbed in diverse absorption pathways by Caco-2 cell monolayer model. This research provided a theoretical basis for scientific evaluation of digestion and absorption of AGEs in food.

Transcriptomic and Metabolomic Analyses of Soybean Protein Isolate on Monascus Pigments and Monacolin K Production.

Monascus pigments (MPs) and monacolin K (MK) are important secondary metabolites produced by Monascus spp. This study aimed to investigate the effect of soybean protein isolate (SPI) on the biosynthesis of MPs and MK based on the analysis of physiological indicators, transcriptomes, and metabolomes. The results indicated that the growth, yellow MPs, and MK production of Monascus pilosus MS-1 were significantly enhanced by SPI, which were 8.20, 8.01, and 1.91 times higher than that of the control, respectively. The utilization of a nitrogen source, protease activity, the production and utilization of soluble protein, polypeptides, and free amino acids were also promoted by SPI. The transcriptomic analysis revealed that the genes mokA, mokB, mokC, mokD, mokE, mokI, and mokH which are involved in MK biosynthesis were significantly up-regulated by SPI. Moreover, the glycolysis/gluconeogenesis, pyruvate metabolism, fatty acid degradation, tricarboxylic acid (TCA) cycle, and amino acid metabolism were effectively up-regulated by SPI. The metabolomic analysis indicated that metabolisms of amino acid, lipid, pyruvate, TCA cycle, glycolysis/gluconeogenesis, starch and sucrose, and pentose phosphate pathway were significantly disturbed by SPI. Thus, MPs and MK production promoted by SPI were mainly attributed to the increased biomass, up-regulated gene expression level, and more precursors and energies.

Influences of ultrasonic treatment on the physicochemical properties and microstructure of diacylglycerol-loaded emulsion stabilized with soybean protein isolate and sodium alginate.

This study examined the impacts of ultrasonic power (0, 150, 300, 450, 600, and 750 W) and ultrasonic durations (3, 6, 9, 12, and 15 min) on the physicochemical properties and microstructure of diacylglycerol (DAG)-loaded emulsions stabilized with soybean protein isolate (SPI) and sodium alginate (SA). The findings indicated that the smallest particle size, zeta potential, and contact angle for SPI-SA-DAG emulsions were respectively 5.58 µm, -49.85 mV, and 48.65°, achieved at an ultrasonic power of 450 W. The emulsification properties, loss modulus, storage modulus, and apparent viscosity of the emulsions were optimal at this power setting and at a duration of 9 min. Analytical techniques, including confocal laser scanning-, scanning electron-, and atomic force microscopy, revealed that ultrasonication significantly altered emulsion aggregation state, with the surface roughness (Rq) being minimized at 450 W. These results demonstrated that the stability of SPI-SA-DAG emulsions can be effectively enhanced by an appropriate ultrasonic treatment at 450 W for 9 min. This research provides theoretical support for the broad application of sonication techniques in the food industry.

Soybean protein isolate-sodium alginate double network emulsion gels: Mechanism of formation and improved freeze-thaw stability.

Soybean protein isolate (SPI) is widely used in the food industry. However, SPI-based emulsion gels tend to aggregate and undergo oiling-off during freeze-thawing. In this study, emulsion gels were prepared by a combination of heat treatment and ionic cross-linking using SPI and sodium alginate (SA) as raw materials. The focus was on exploring the mechanistic effects of the SPI-SA double network structure on the freeze-thaw stability of emulsion gels. The results showed that the addition of SA could form different types of network structures with SPI, due to different degrees of phase separation. In addition, SA appearing on the SPI network indicated that the addition of Ca2+ shielded the electrostatic repulsion between SPI and SA to form SPI-SA complexes. The disappearance of the characteristic peaks of SA and SPI in Fourier transform infrared spectroscopy analysis also confirmed this view. Low-field nuclear magnetic resonance data revealed that SA played a role in restricting water migration within the emulsion gels, increasing bound water content, and thereby improving the water-holding capacity of the emulsion gels. Therefore, the incorporation of SA improved the freeze-thaw stability of SPI emulsion gels. These findings offer a theoretical basis and technical support for SPI application in frozen products.

Ultrasound-assisted modification of soybean protein isolate with L-histidine: Relationship between structure and function.

Herein, the effects of ultrasound-assisted L-histidine (L-His) on the physicochemical properties and conformation of soybean protein isolate (SPI) were investigated. Particle size, zeta potential, turbidity, and solubility were used to evaluate protein aggregation, and the relationship between structural and functional changes of the proteins was characterized using spectral analysis, surface hydrophobicity, emulsification, and antioxidant properties. After ultrasound-assisted L-His treatment, SPI exhibited a smaller particle size, higher solubility, and more homogeneous micromorphology owing to the decrease in alpha-helix content and subsequent increases in zeta potential and active sulfhydryl content. In addition, spectral analysis showed that L-His and SPI could form a complex, which changed the microenvironment of the amino acid residues in SPI, thus improving its emulsification and antioxidant properties. At the concentration of L-His was 0.3 % w/w, the nanocomplex had a smaller particle size (140.03 nm), higher ζ-potential (-23.63 mV), and higher emulsification stability (22.48 min).

Structural, physicochemical and digestive properties of non-covalent and covalent complexes of ultrasound treated soybean protein isolate with soybean isoflavone.

The non-covalent and covalent complexes of ultrasound treated soybean protein isolate (SPI) and soybean isoflavone (SI) were prepared, and the structure, physicochemical properties and in vitro digestion characteristics of SPI-SI complexes were investigated. Ultrasonic treatment increased the non-covalent and covalent binding degree of SPI with SI, and the 240 W ultrasonic covalent complexes had higher binding efficiency. Appropriate ultrasonic treatment caused more uniform particle size distribution, lower average particle size and higher surface charge, which enhanced the free sulfhydryl groups and surface hydrophobicity, thus improving the stability, solubility and emulsifying properties of complexes. Ultrasonic treatment resulted in more disordered secondary structure, tighter tertiary conformation, higher thermal stability and stronger SPI-SI covalent interactions of complexes. These structural modifications of particles had important effects on the chemical stability and gastrointestinal digestion fate of SI. The ultrasonic covalent complexation had a greater resistance to heat-induced chemical degradation of SI and improved its chemical stability. Furthermore, the 240 W ultrasonic covalent complexes showed lower protein digestibility during digestion, and provided stronger protection for SI, which improved the digestion stability and antioxidant activity. Therefore, appropriate ultrasound promoted SPI-SI interactions to improve the stability and functional properties of complexes, which provided a theoretical basis for the development of new complexes and their applications in functional foods.

Development and characterization of adhesives constructed by soy protein isolate and tea polyphenols for enhanced tensile strength in plant-protein meat applications.

The study aimed to evaluate a food adhesive developed using tea polyphenols (TPs) with soybean protein isolate (SPI) to create a cohesive bond between soy protein gel and simulated fat. Upon the addition of 5.0 % TPs, significant increases in viscosity, thermal stability, and crystallinity were noted in adhesives, suggesting the formation of a cohesive network. Furthermore, TPs effectively enhanced adhesion strength, with the optimal addition being 5.0 %. This enhancement can be attributed to hydrogen bonding, hydrophobic and electrostatic interactions between TPs and SPI molecules. TPs induced a greater expansion of the protein structure, exposing numerous buried hydrophobic groups to a more hydrophilic and polar environment. However, excessive TPs were found to diminish adhesion strength. This can be attributed to enhanced reactions between TPs and SPI, where high molecular weight SPI-TPs cooperatively aggregate to form agglomerates that eventually precipitated, rendering the adhesive network inhomogeneous, less stable, and more prone to disruption.

Effects of preheat treatment and syringic acid modification on the structure, functional properties, and stability of black soybean protein isolate.

This study investigated preheated (25-100°C) black soybean protein isolate (BSPI) conjugated with syringic acid (SA) (25 and 50 µmol/g protein) under alkaline conditions, focusing on the structure, functional properties, and storage stability. The results revealed that the SA binding equivalent and binding rate on BSPI increased continuously as the preheat temperature increased. Additionally, preheating positively impacted the surface hydrophobicity (H0) of BSPI, with further enhancement observed upon SA binding. Preheating and SA binding altered the secondary and tertiary structure of BSPI, resulting in protein unfolding and increased molecular flexibility. The improvement in BSPI functional properties was closely associated with both preheating temperature and SA binding. Specifically, preheating decreased the solubility of BSPI but enhanced the emulsifying activity index (EAI) and foaming capacity (FC) of BSPI. Conversely, SA binding increased the solubility of BSPI with an accompanying increase in EAI, FC, foaming stability, and antioxidant activity. Notably, the BSPI100-SA50 exhibited the most significant improvement in functional properties, particularly in solubility, emulsifying, and foaming attributes. Moreover, the BSPI-SA conjugates demonstrated good stability of SA during storage, which positively correlated with the preheating temperature. This study proposes a novel BSPI-SA conjugate with enhanced essential functional properties, underscoring the potential of preheated BSPI-SA conjugates to improve SA storage stability. PRACTICAL APPLICATION: Preheated BSPI-SA conjugates can be used as functional ingredients in food or health products. In addition, preheated BSPI shows potential as a candidate for encapsulating and delivering hydrophobic bioactive compounds.

pH-regulated Tannic acid and soybean protein isolate adhesive for enhanced performance in plant-based meat analogues.

A food adhesive comprising tannic acid (TA) and soybean protein isolate (SPI) was developed to establish a cohesive bond between soy protein gel and simulated fat. The impact of varying TA concentrations and pH levels on the adhesive's rheology, thermal stability, chemical structure, and tensile strength were investigated. Rheological results revealed a gradual decrease in adhesive viscosity with increasing TA content. Differential scanning calorimetry (DSC) and thermal gravimetric (TG) results indicated that the stability of the adhesive improved with higher TA concentrations, reaching its peak at 0.50% TA addition. The incorporation of TA resulted in the cross-linking of amino group in unfolded SPI molecules, forming a mesh structure. However, under alkaline conditions (pH 9), adhesive viscosity and stability increased compared to the original pH. This shift was due to the disruption of the SPI colloidal charge structure, an increase in the stretching of functional groups, further unfolding of the structure, and an enhanced binding of SPI to TA. Under the initial pH conditions, SPI reacted with TA's active site to form covalent crosslinked networks and hydrogen bonds. In alkaline condition, beyond hydrogen and ionic bonding, the catechol structure was oxidized, forming an ortho-quinone that crosslinked SPI and created a denser structure. Tensile strength measurements and freeze-thaw experiments revealed that the adhesive exhibited maximum tensile strength and optimal adhesion with 0.75% TA at pH 9, providing the best overall performance. This study provides a new formulation and approach for developing plant-based meat analogues adhesives.

Construction and Properties of Oil-Loaded Soybean Protein Isolate/Polysaccharide-Based Meat Analog Fibers.

Rationally designing the fibrous structure of artificial meat is a challenge in enriching the organoleptic quality of meat analogs. High-quality meat analog fibers have been obtained by wet-spinning technique in our previous study, whereas introducing oil droplets will further achieve their fine design from the insight of microstructure. Herein, in this current work, oil was introduced to the soybean protein isolate/polysaccharide-based meat analog fibers by regulating the oil droplets' size and content, which, importantly, controlled the spinning solution characterization as well as structure-related properties of the meat analog fiber. Results showed that the oil dispersed in the matrix as small droplets with regular shapes, which grew in size as the oil content increased. Considering the effect of oil droplets' size and content on the spinnability of the spinning solution, the mechanical stirring treatment was chosen as the suitable treatment method. Importantly, increasing the oil content has the potential to enhance the juiciness of meat analog fibers through improvements in water-holding capacity and alterations in water mobility. Overall, the successful preparation of oil-loaded plant-based fiber not only mimicked animal muscle fiber more realistically but also provided a general platform for adding fat-soluble nutrients and flavor substances.

Soybean isolate protein complexes with different concentrations of inulin by ultrasound treatment: Structural and functional properties.

The effects of ultrasound and different inulin (INU) concentrations (0, 10, 20, 30, and 40 mg/mL) on the structural and functional properties of soybean isolate protein (SPI)-INU complexes were hereby investigated. Fourier transform infrared spectroscopy showed that SPI was bound to INU via hydrogen bonding. All samples showed a decreasing and then increasing trend of α-helix content with increasing INU concentration. SPI-INU complexes by ultrasound with an INU concentration of 20 mg/mL (U-2) had the lowest content of α-helix, the highest content of random coils and the greatest flexibility, indicating the proteins were most tightly bound to INU in U-2. Both UV spectroscopy and intrinsic fluorescence spectroscopy indicated that it was hydrophobic interactions between INU and SPI. The addition of INU prevented the exposure of tryptophan and tyrosine residues to form a more compact tertiary structure compared to SPI alone, and ultrasound caused further unfolding of the structure of SPI. This indicated that the combined effect of ultrasound and INU concentration significantly altered the tertiary structure of SPI. SDS-PAGE and Native-PAGE displayed the formation of complexes through non-covalent interactions between SPI and INU. The ζ-potential and particle size of U-2 were minimized to as low as -34.94 mV and 110 nm, respectively. Additionally, the flexibility, free sulfhydryl groups, solubility, emulsifying and foaming properties of the samples were improved, with the best results for U-2, respectively 0.25, 3.51 µmoL/g, 55.51 %, 269.91 %, 25.90 %, 137.66 % and 136.33 %. Overall, this work provides a theoretical basis for improving the functional properties of plant proteins.

Deciphering the interaction mechanism between soy protein isolate and fat-soluble anthocyanin on experiments and molecular simulations.

In this work, the acylated anthocyanin (Ca-An) was prepared by enzymatic modification of black rice anthocyanin with caffeic acid, and the binding mechanism of Ca-An to soybean protein isolate (SPI) was investigated by experiments and computer simulation to expand the potential application of anthocyanin in food industry. Multi-spectroscopic studies revealed that the stable binding of Ca-An to SPI induced the folding of protein polypeptide chain, which transformed the secondary structure of SPI trended to be flexible. The microenvironment of protein was transformed from hydrophobic to hydrophilic, while tyrosine played dominant role in quenching process. The binding sites and forces of the complexes were determined by computer simulation for further explored. The protein conformation of the 7S and 11S binding regions to Ca-An changed, and the amino acid microenvironment shifted to hydrophilic after binding. The results showed that more non-polar amino acids existed in the binding sites, while in binding process van der Waals forces and hydrogen bonding played a major role hydrophobicity played a minor role. Based on MM-PBSA analysis, the binding constants of 7S-Ca-An and 11S-Ca-An were 0.518 × 106 mol-1 and 5.437 × 10-3 mol-1, respectively. This information provides theoretical guidance for further studying the interaction between modified anthocyanins and biomacromolecules.