Structural characterization and physicochemical properties of protein extracted from soybean meal assisted by steam flash-explosion with dilute acid soaking

Improved nutritional and functional properties of plant protein isolate blends through steam infusion: A study on chickpea, brown rice and defatted peanut protein blends

This study examined the impact of steam-infusion on defatted peanut (Pn), chickpea (Cp), and rice (R) protein isolates (PI) and their blends. Steam infusion significantly increased protein content (up to 83.13 % in PnPI, 75.25 % in CpPI, 76.13 % in RPI) and digestibility (98.92 % in peanut, 98.84 % in chickpea) and improved protein solubility. Steam-infused protein blends (SIPB) showed higher protein content (84.44 %), digestibility (89.61 %), improved EAA scores, and enhanced functional properties compared to non-steam infused protein blends (NSIPB). SEM revealed porous, serrated structures in SIPB, while FTIR analysis showed higher β-turn content corroborated with higher protein digestibility. Also found higher β-sheet content that enabled high emulsion protein stability as revealed by analysis of emulsion proteins by TEM and optical microscopy. Herschel-Bulkley modelling demonstrated improved rheological properties, including shear-thinning behaviour [flow index (α < 1)]. Due to enhanced protein digestibility properties, SIPB can serve as a novel plant protein ingredient in protein-food industry.

Effects of arabinoxylan extracted from vinegar residue on physicochemical and structural properties of gluten proteins obtained from freeze-thaw wheat dough

BACKGROUND

Arabinoxylan is commonly used as a hydrocolloid in frozen dough to improve the texture and the sensory qualities of the products. The effects of vinegar residue arabinoxylan (VRAX) on the secondary structures and microstructures of gluten proteins during freeze-thaw storage were studied, and the underlying mechanism governing these effects was clarified.

RESULTS

The results revealed that VRAX improved the textural properties of gluten proteins, but had a negative impact on their viscoelasticity. Additionally, the addition of VRAX increased the number of disulfide bonds and also improved the freezing tolerance of the gluten proteins. It was found that the enthalpy of the gluten proteins decreased by 19.78% following VRAX addition. As a result of the use of VRAX, the freezing procedure resulted in reduced formation of ice crystals, protecting the gluten network structure and preserving the dough's elasticity. The network structure of gluten proteins after VRAX treatment was more ordered and integrated relative to that of frozen blank control gluten proteins.

CONCLUSION

Overall, the freeze-thaw stability of the gluten proteins was enhanced by VRAX. These results suggest that VRAX has potential as an effective cryoprotectant in frozen dough. © 2024 Society of Chemical Industry.

Okara protein extracted by alternating ultrasonic/alkali treatment and its improved physicochemical and functional properties

Okara protein (OP) is a potential plant-based protein that is beneficial to human health. In this work, an alternating ultrasonic/alkali treatment method with non-continued cavitation and thermal energy output was used to extract protein (AUA-OP) from okara to enhance the functional properties of OP and improve the stability of OP-based emulsions. The purity of AUA-OP was greater than 80%. Compared with traditional (physical-assisted) alkali treatment, FTIR and SDS-PAGE revealed that AUA-OP retained the chemical structure of the protein, but the number of ultrasound-induced exposure sites increased, with increased fluorescence intensity, surface hydrophobicity, and absolute ζ-potential. After alternating ultrasonic/alkali treatment, the protein particles were looser and smaller. In addition, the water/oil holding capacity, EAI, and ESI of AUA-OP further increased. The viscosity of the AUA-OP-stabilized emulsion was also greater. Finally, a 28-day emulsion storage assay revealed that the AUA-OP-stabilized emulsion was stable with a relatively low droplet size and creaming index, indicating great potential for the development of stable protein-based emulsions.

A comprehensive review on composition to application of pea protein and its components

Pea protein, a valuable plant-based protein source, is notable for its nutritional value, essential amino acids, and low allergenicity, making it widely applicable in food, medicine, and materials. It consists mainly of globulin and albumin, which influence its functional properties and applications. However, there is a lack of comprehensive reviews on its extraction methods, functional properties, modification techniques, and applications in food. This paper aims to fill these gaps by detailing pea protein composition, extraction methods, functional properties, and modification impacts while summarizing its food applications and proposing future research directions. The goal is to enhance pea protein's functionality and expand its applications through optimized extraction and advanced technology. By improving extraction techniques and adapting pea protein for better functionality, we aim to develop high-quality market applications, ensuring the growth and sustainability of the pea protein industry globally. This approach promises a flourishing future for pea protein, meeting global competition demands and driving industry advancement.

Extraction and improvement of protein functionality using steam explosion pretreatment: advances, challenges, and perspectives

Protein has become an increasingly valuable food component with high global demand. Consequently, unconventional sources, such as industrial and agroindustrial wastes and by-products, emerge as interesting alternatives to meet this demand, considering the UN Sustainable Development Goals and the transition to a circular economy. In this context, this work presents a review of the use of Steam Explosion (SE), a green technique that can be employed as a pretreatment for various waste materials, including bones, hide/leather, feathers, and wool, aimming the extraction of protein compounds, such as low molecular weight biopeptides, gelatin, and keratin, as well as to enhance the protein functionality of grains and meals. The SE technique and the main factors affecting the process's efficiency were detailed. Promising experimental studies are discussed, along with the mechanisms responsible for protein extraction and functionality improvement, as well as the main reported and suggested applications. In general, steam explosion favored yields in subsequent extraction processes, ranging from 27 to 95%, in addition to enhancing solubility and functional protein properties. Nonetheless, it is crucial to maintain the continuity of research on this topic to drive advancements in ensuring the safety of the extracted compounds for use in consumable products and oral ingestion.

Comparison of ovalbumin glycation induced by high-temperature steaming and high-temperature baking: A study combining conventional spectroscopy with high-resolution mass spectrometry

High-temperature steaming (HTS) and high-temperature baking (HTB)-induced ovalbumin (OVA)-glucose glycation (140 °C, 1-3 min) were compared, and the different mechanisms were evaluated by changes in protein conformation, glycation sites and average degree of substitution per peptide molecule (DSP) values as well as the antioxidant activity of glycated OVA. Conventional spectroscopic results suggested that in comparison with HTB, HTS promoted protein expansion, increased β-sheet content and made OVA structure more orderly. Liquid chromatography-high resolution mass spectrometry (LC-HRMS) analysis showed that 10 glycation sites were found under HTB, while 4 new glycation sites R111, R200, R219 and K323 appeared under HTS, and 2 of them (R219 and K323) were located in internal β-sheet chains. The antioxidant activities of glycated OVA increased with increasing treatment time, and HTS showed stronger enhancement effect than HTB. Furthermore, the DSP values were generally higher under HTS than HTB. Compared with HTB, HTS with high penetrability could enhance the change of OVA primary structure and spatial conformation, making the protein structure more unfolded and stable, leading to more protein-sugar collisions occurred in inner OVA molecular and significantly promoted glycation. In conclusion, HTS is a promising method for high-temperature short-time glycation reaction, with drastically increasing the protein antioxidant activities.

Effects of hydrocolloids as fat-replacers on the physicochemical and structural properties of salt-soluble protein isolated from water-boiled pork meatballs

Konjac glucomannan (KGM), xanthan gum (XG), guar gum (GG), and κ-carrageenan (KC), as substituent, are commonly used in ground pork products. Here, the content of these (0.5, 1.0, 1.5, and 2.0%, w/w) on the gel properties, thermal properties, and interaction forces of salt-soluble protein (SSP) isolated from water-boiled pork meatballs were investigated. We found 1.0% KGM, 0.5% XG, 0.5-2.0% GG, and 0.5-2.0% KC to water-boiled pork meatballs exerted a positive effect on the denaturation temperature, hydrogen bonds, hydrophobic interactions, disulfide bonds, α-helix, and β-sheet content of SSP, as well as the strength and storage modulus of the modified protein gel. The addition of these hydrocolloids with the addition of 1.0% aggregated myosin and actin, led to the enhancement of the bands corresponding to myosin heavy chain and actin. The prediction model of gel strength showed that the gel strength was negatively correlated with Tpeak1, Tpeak2, and ionic bond. This study provides theoretical guidance for improving the application of hydrocolloids in pork-based foods.

The Effect of High Pressure Homogenization on the Structure of Dual-Protein and Its Emulsion Functional Properties

It has been proven that high-pressure homogenization (HPH) could improve the functional properties of proteins by modifying their structure. This study researched the effect of HPH on the structural and functional properties of whey-soy dual-protein (Soy Protein Isolation-Whey Protein Isolation, SPI-WPI). Different protein solution samples were treated with HPH at 30, 60, 90, 120 and 150 MPa, and the structure changed under different pressures was analyzed by measuring particle size, zeta potential, Fourier infrared spectrum (FTIR), fluorescence spectrum and scanning electron microscope (SEM). The results showed that HPH significantly reduced the particle size of SPI-WPI, changed the secondary and tertiary structures and improved the hydrophobic interaction between molecules. In addition, HPH significantly improved the solubility and emulsification of all proteins, and the improvement effect on SPI-WPI was significantly better than SPI and WPI. It was found that SPI-WPI treated with 60 MPa had the best physicochemical properties. Secondly, we researched the effect of HPH by 60 MPa on the emulsion properties of SPI-WPI. In this study, the SPI-WPI had the lowest surface tension compared to a single protein after HPH treatment. The emulsion droplet size was obviously decreased, and the elastic properties and physical stability of SPI-WPI emulsion were significantly enhanced. In conclusion, this study will provide a theoretical basis for the application of HPH in modifying the structure of dual-protein to improve its development and utilization in liquid specialty food.

Changes in glycated myofibrillar proteins conformation on the formation of Nε-carboxymethyllysine under gradient thermal conditions

N^ε-carboxymethyllysine (CML), a frequently used marker of advanced glycation end products (AGEs) in food, was generated in food processing easily and caused changes in myofibrillar proteins (MPs) characterization. The relevance between glycosylated MPs structure alternation and CML formation under thermal conditions have been reported. However, the correlation mechanism was not clear yet. In this work, the influence of gradient heating (50℃, 60℃, 70℃, 80℃, and 90℃) on the different degrees of glycated MPs, which determined the correlation with CML formation in protein structural changes of MPs. In the rising stage of the CML level, glycation accelerated the fibrillation and aggregation behavior of MPs during heating and increased surface hydrophobicity and particle size. The protein cross-linking affected the protein modification caused by heating and glycation. This work highlights the substantial influences of glycosylation and thermal treatments on MPs, which transformed the MPs structural characteristics and CML level.

Supplemental methionine selenium effects on egg yolk physicochemical, functional, and protein structure during storage

To clarify the effect of the addition of methionine selenium on the physicochemical, functional, and protein structural properties of egg yolk during storage. We analyzed the changes in the main indicators of egg yolks stored at 4°C and 25°C for 28 days. The results showed that the increase in water content and pH, and the decrease in absolute zeta potential and apparent viscosity of the selenium-rich egg yolks (Se-group) during storage were smaller than those of the control group egg yolks (C-group). In addition, the antioxidant capacity and emulsifying ability of the Se-group during storage were better than those of the C-group. Simultaneously, the hardness and chewiness of the Se-group gel during storage were lower than those of the C-group. The protein structure results showed that selenium rich treatment did not affect the secondary structure of egg yolk protein during storage but could improve the fluorescence intensity of the egg yolk protein. Therefore, the addition of methionine selenium can reduce the degree of deterioration in the physicochemical properties of egg yolk during storage and extend its shelf life.

Formation of Nε-Carboxymethyl-Lysine and Nε-Carboxyethyl-Lysine in Heated Fish Myofibrillar Proteins with Glucose: Relationship with Its Protein Structural Characterization

The formation of advanced glycation end products (AGEs), including N^ε-carboxymethyl-lysine (CML) and N^ε-carboxyethyl-lysine (CEL), in a fish myofibrillar protein and glucose (MPG) model system at 80 °C and 98 °C for up to 45 min of heating were investigated. The characterization of protein structures, including their particle size, ζ-potential, total sulfhydryl (T-SH), surface hydrophobicity (H₀), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR), were also analyzed. It was found that the covalent binding of glucose and myofibrillar protein at 98 °C promoted protein aggregation when compared with the fish myofibrillar protein (MP) heated alone, and this aggregation was associated with the formation of disulfide bonds between myofibrillar proteins. Furthermore, the rapid increase of CEL level with the initial heating at 98 °C was related to the unfolding of fish myofibrillar protein caused by thermal treatment. Finally, correlation analysis indicated that the formation of CEL and CML had a significantly negative correlation with T-SH content (r = -0.68 and r = -0.86, p ≤ 0.011) and particle size (r = -0.87 and r = -0.67, p ≤ 0.012), but was weakly correlated with α-Helix, β-Sheet and H₀ (r² ≤ 0.28, p > 0.05) during thermal treatment. Overall, these findings provide new insights into the formation of AGEs in fish products based on changes of protein structure.

Impact of Cavitation Jet on the Structural, Emulsifying Features and Interfacial Features of Soluble Soybean Protein Oxidized Aggregates

A cavitation jet can enhance food proteins' functionalities by regulating solvable oxidized soybean protein accumulates (SOSPI). We investigated the impacts of cavitation jet treatment on the emulsifying, structural and interfacial features of soluble soybean protein oxidation accumulate. Findings have shown that radicals in an oxidative environment not only induce proteins to form insoluble oxidative aggregates with a large particle size and high molecular weight, but also attack the protein side chains to form soluble small molecular weight protein aggregates. Emulsion prepared by SOSPI shows worse interface properties than OSPI. A cavitation jet at a short treating time (<6 min) has been shown to break the core aggregation skeleton of soybean protein insoluble aggregates, and insoluble aggregates into soluble aggregates resulting in an increase of emulsion activity (EAI) and constancy (ESI), and a decrease of interfacial tension from 25.15 to 20.19 mN/m. However, a cavitation jet at a long treating time (>6 min) would cause soluble oxidized aggregates to reaggregate through an anti-parallel intermolecular β-sheet, which resulted in lower EAI and ESI, and a higher interfacial tension (22.44 mN/m). The results showed that suitable cavitation jet treatment could adjust the structural and functional features of SOSPI by targeted regulated transformation between the soluble and insoluble components.

Effect of Steam Flash-Explosion on Physicochemical Properties and Structure of High-Temperature Denatured Defatted Rice Bran Protein Isolate

The effects of Steam Flash-Explosion (SFE) on the physicochemical properties and molecular structure of high-temperature denatured defatted rice bran protein isolate (RBPI) were investigated. The mechanism of SFE treatment on high-temperature denatured defatted RBPI was revealed. The analysis of the physical and chemical properties of RBPI showed that the surface hydrophobicity, characteristic viscosity, and thermal stability of rice bran protein isolate were significantly affected by the pressure of saturated steam and pressure holding time. Under the conditions of 2.1 MPa and 210 s, the surface hydrophobicity index decreased significantly from 137.5 to 17.5, and the characteristic viscosity increased significantly. The peak temperature of denaturation decreases from 114.2 to 106.7 °C, and the enthalpy of denaturation decreases from 356.3 to 231.4 J/g. The higher structure (circular dichroic spectrum and endogenous fluorescence spectrum) of rice bran protein isolate was analyzed by volume rejection chromatography (SEC). The results showed that steam flash treatment could depolymerize and aggregate RBPI, and the relative molecular weight distribution changed greatly. The decrease in small molecules with poor solubility was accompanied by the increase in macromolecules (>550 kDa) soluble aggregates, which were the products of a Maillard reaction. The contents of free sulfhydryl and disulfide bonds in high-temperature rice bran meal protein isolate were significantly increased, which resulted in the increase in soluble aggregates containing disulfide bonds. Circular dichroism (CD) analysis showed that the α-helix content of the isolated protein was significantly decreased, the random curl content was increased, and the secondary structure of the isolated protein changed from order to disorder. The results of endogenous fluorescence spectroscopy showed that the high-temperature rice bran meal protein isolate was more extended, tryptophan was in a more hydrophilic microenvironment, the fluorescence intensity was reduced, and the tertiary structure was changed. In addition, the mean particle size and net surface charge of protein isolate increased in the aqueous solution, which was conducive to the development of the functional properties of the protein.

Effects of CaCl2 on salting kinetics, water migration, aggregation behavior and protein structure in rapidly salted separated egg yolks

Salted egg yolks are valued by consumers for their delicious taste good processing characteristics. To improve the quality of rapidly salted separated egg yolks, we compared changes in the salting kinetics, textural properties, water migration, protein aggregation and structure of salted egg yolks in the presence or absence of CaCl₂ for 24 h. CaCl₂ increased the mass transfer driving force and diffusion coefficient during the salting process; as a result, the salted egg yolks exhibited increased hardness and decreased springiness and cohesiveness. Through low field nuclear magnetic resonance (LF NMR), it was confirmed that CaCl₂ promoted the precipitation of lipids and the dehydration of egg yolk. Furthermore, CaCl₂ promoted the bulk aggregation of proteins. The analyses of protein structures showed that the contents of β-sheets and irregular curls in CaCl₂-salted egg yolk protein increased, while the contents of α-helices and β-turns decreased. CaCl₂ affected the microenvironment of tryptophan residues and embedded these residues, enhancing protein aggregation. Based on the comprehensive information obtained in this study, adding CaCl₂ to the salting solution improved the degree of protein polymerization in egg yolk; thus, this method might be used to improve the quality of egg yolks separated by salt.

Correlation of steam explosion severity with morphological and physicochemical characterization of soybean meal

Steam explosion, a novel effective technology for cereal modification, integrates high-temperature autohydrolysis and structural disruption, which can significantly influence the morphological and physicochemical characterization of the feedstocks. The deep knowledge of the structural changes that are brought about by the treatment severity is connected with the technological demands to improve the processing efficiency and to increase the industrial application of the feedstocks by steam explosion. In this study, the changes in morphological and physicochemical properties of soybean meal induced by steam explosion were investigated. The correlation of steam explosion severity with soybean meal's final quality was also analyzed. The results showed that steam explosion effectively increased the fractal dimension from 1.6553 to 1.8871, the glycinin content from 151.38 to 334.94 mg/g, and the 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging activity from 28.69 to 63.78%. The gray value, color (L* and a* values), and the total phenol and polysaccharide contents of soybean meal were reduced with greater steam explosion severity. Steam explosion severity had a remarkable positive correlation with the fractal dimension and DPPH radical scavenging activity. However, steam explosion severity had no significant correlation with the textural and adsorption properties of the soybean meal. This study focused on the morphological and physicochemical property changes of the soybean meal during a steam explosion process, which could guide the application of steam explosion in food systems.

Conformational Changes in Proteins Caused by High-Pressure Homogenization Promote Nanoparticle Formation in Natural Bone Aqueous Suspension

As a natural calcium resource, animal bone needs to be miniaturized to the nanoscale to improve palatability and absorption capacity. To explore the mechanism of high-pressure homogenization (HPH) in preparing natural bone aqueous nanosuspensions, the relationships between the changes in protein conformation, solubility and quality characteristics of rabbit bone aqueous suspensions (RBAS) prepared by different HPH cycles were studied. The results showed that the improvements in particle size, stability and calcium solubility of RBASs could be mainly attributed to the improvement of protein solubility induced by the changes in protein conformation. HPH treatment led to the denaturation and degradation of protein in rabbit bone, generating soluble peptides and improving the stability of the suspensions by enhancing the surface charge of the particles. When collagen as the main protein was partially degraded, the hydroxyapatite in the bone was crushed into tiny particles. The increase in the particle-specific surface area led to the release of calcium ions, which chelated with the peptides to produce peptide calcium. However, excessive HPH treatment caused the production of protein macromolecular aggregates and affected the quality of RBASs. This study is helpful to promote the application of HPH technology in animal bone nanoprocessing.

Improving bioaccessibility and physicochemical property of blue-grained wholemeal flour by steam explosion

Whole grain contains many health-promoting ingredients, but due to its poor bioaccessibility and processibility, it is not widely accepted by consumers. The steam explosion was exploited to modify the nutritional bioaccessibility and the physicochemical properties of wholemeal flour in this study. In vitro starch digestibility, in vitro protein digestibility of wholemeal flour, total flavonoids content, and total phenolics content of digestive juice were used to evaluate the bioaccessibility, and a significant variation (p < 0.05) was noted. Results showed that steam explosion enhanced the gastric protein digestibility ranged from 5.67 to 6.92% and the intestinal protein digestibility ranged from 16.77 to 49.12%. Steam-exploded wholemeal flour (0.5 MPa, 5 min) had the highest protein digestibility and rapidly digestible starch content. Compared with native flour, steam explosion (0.5 MPa, 5 min) contributed to a 0.72-fold and 0.33-fold increment of total flavonoids content and total phenolics content in digestible juice. Chemical changes of wholemeal flour, induced by steam explosion, caused the changes in the solvent retention capacity, rheological property of wholemeal flour, and altered the falling number (and liquefaction number). An increasing tendency to solid-like behavior and the gel strength of wholemeal flour was significantly enhanced by the steam explosion at 0.5 MPa for 5 min, while the gluten was not weakened. This study indicated that steam-exploded wholemeal flour (0.5 MPa, 5 min) could serve as a potential ingredient with the noticeable bioaccessibility and physicochemical properties in cereal products.

Effect of Steam Explosion on Structural Characteristics of β-Conglycinin and Morphology, Chemical Compositions of Soybean Meal

In this study, steam explosion was applied as a means to degrade β-conglycinin. We investigated changes in morphology, the chemical composition of soybean meal, and the structural characteristics of β-conglycinin. The results showed that steam explosion at 0.7 MPa for 8 min could effectively decrease the β-conglycinin content of soybean meal while the histamine content was not increased. The structural characteristics of soybean meal proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and X-ray diffraction (XRD). Steam explosion caused the degradation of high weight proteins and reduced the band density of α', α, and β subunits in β-conglycinin. The micro-surface of soybean meal seemed to be in the cracked or puffed stage and the color became brown or dark after steam explosion. Steam explosion facilitated the dissolution of water-extractable arabinoxylans, which are 4.81 fold higher than that of native soybean meal. Phytic acid was exposed to the hydrothermal environment of the steam explosion process and consequently degraded by 12.95-24.69%. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of soybean meal extract was gradually increased from 20.70 to 33.71% with the rising of treated pressure from 0.3 to 0.7 MPa, which was 1.11-1.81 fold of native extract. The steam explosion may be a new modification technology that could decrease antigenicity, and steam-exploded soybean meal (0.7 MPa, 8 min) with lower β-conglycinin and phytic acid content that could be widely used in food products.

Interaction mechanism between ZnO nanoparticles-whey protein and its effect on toxicity in GES-1 cells

The interaction between zinc oxide nanoparticles (ZnO NPs) and whey protein (WP) was studied. The gastric epithelial cell line (GES-1) was used to evaluate the toxicity intensity of ZnO NPs. The interaction mechanism of ZnO NPs and WP was studied by spectroscopic techniques. The results showed that the inhibitory effect of ZnO NPs on cells activity could be reduced when added to ZnO NPs at a concentration of 50 µg/ml. The fluorescence quenching mechanism of ZnO NPs on WP is a combination of dynamic and static quenching. The interaction force between ZnO NPs and WP can be considered as H-bond and VdW force, and they have two binding sites. The interaction between WP and ZnO NPs leads to the loosening of the structural skeleton of WP and the extension of peptide chain, which exposes the tyrosine (Tyr) and tryptophan (Trp) hydrophobic groups in the hydrophobic region of protein molecules and reduces the hydrophobicity of the microenvironment. The ZnO NPs might form a complex with WP through H-bond, hydrophobic interactions, and so on, leading to peptide chain rearrangement, and finally causing changes in the secondary structure of α-helix. Practical Application This study provides a theoretical basis for future research on the interaction between food ingredients and nanomaterials, the evaluation of toxicity of nanomaterials and the application scope of nanomaterials in food field.

Effects of "nine steaming nine sun-drying" on proximate composition, protein structure and volatile compounds of black soybeans

Nine steaming nine sun-drying is a traditional processing technology for food or medicinal materials. The dynamic changes of the proximate composition, protein structure and volatile compounds during nine-time steaming and sun-drying of black soybeans (BS) were studied. The proximate composition results showed that the content of protein, carbohydrate and fat of BS decreased after processing, whereas the relative content of amino acids remained basically unchanged. Protein structure was evaluated using Fourier transform infrared spectroscopy (FT-IR), Ultraviolet absorption spectroscopy (UV) and Fluorescence spectroscopy. FT-IR result revealed that the relative contents of β-sheet and β-turn of the secondary structure of black soybean protein isolate (BSPI) decreased but the relative contents of α-helix and random coil increased after steaming and sun-drying. The results of UV and fluorescence spectroscopy confirmed changes in the protein conformation. In addition, SPME-GCMS analysis demonstrated that hydrocarbons, alcohols and aldehydes were the main volatile compounds. The relative contents of 1-octen-3-ol and hexanal, which are the main sources of beany flavor decreased significantly compared with raw BS. Principal component analysis (PCA) results showed that the volatile compounds of nine steamed and nine sun-dried BS could be well distinguished during the process. These findings may therefore provide a scientific basis for the application of nine-time steamed and sun-dried BS in food industry and contribute to the understanding of process-induced chemical transformations in this ancient processing technique.

Effects of acid-hydrolyzed soybean meal on growth performance, jejunal morphology, digestive enzyme activities, nutrient utilization, and intestinal microbial population in broiler chickens

The objective of this study was to investigate the effects of soybean meal (SBM) treated with acetic or citric acids on growth performance, microbial population, digestive enzyme activities, nutrient digestibility, and jejunal morphology in broiler chickens. A total of 350 one-day-old male broiler chicks (Ross 308) were randomly distributed into 7 experimental groups with 5 replicates per each. Experimental treatments were diets containing untreated SBM (control) and SBM treated with two acid sources and their concentrations including 5, 10, and 15% acetic acid (A1, A2, and A3) or 0.25, 0.50, and 0.75% citric acid (C1, C2, and C3). Results showed that trypsin inhibitors and lectins as the main SBM anti-nutrients significantly reduced in acid-treated SBM compared with untreated SBM (P < 0.05). During 1-24 days, body weight gain increased in chicks fed the C2 diet (P < 0.05). Feeding of the C2 diet increased feed intake compared with A1, A2, and C3 groups (P < 0.05). Feed conversion ratio improved in chicks fed with C2, C3, and A2 diets compared with the control group (P < 0.05). The greatest villus length, villus length to crypt depth ratio, and villus surface area were observed in the C2 diet (P < 0.05). A significant increase in protease and lipase activity was found in broilers which received a C2 diet compared with the control group (P < 0.05). Broiler chickens fed with the C2 diet had a higher organic matter and crude protein digestibility than the chicks which received the control diet (P < 0.05) and dry matter digestibility was the lowest in broilers fed with the A3 diet (P < 0.05). In conclusion, the acid hydrolyzing process had a beneficial effect on the nutritional value of SBM. In addition, data showed that acid-hydrolyzed SBM had the potential to exert positive influences on growth performance, jejunal morphology, and nutrient utilization in broiler chickens.

Studying the effects of high pressure-temperature treatment on the structure and immunoreactivity of β-lactoglobulin using experimental and computational methods

The effects of high hydrostatic pressure (HHP) on the conformation and immunoreactivity of bovine β-lactoglobulin (BLG) were studied. BLG was treated under 100-600 MPa at the temperature of 20-60 °C. The immunoglobulin E (IgE) binding ability of BLG decreased when the pressure increased from 0.1 to 200 MPa. However, the IgE binding increased with the increase in pressure from 200 to 400 MPa, followed by a gradual decrease until a pressure of 600 MPa. The IgE binding ability continuously decreased with an increase in pressure at 60 °C. The conformation of HHP-treated BLG was evaluated using fluorescence spectroscopy, circular dichroism spectroscopy and molecular dynamics (MD) simulation. Increasing the temperature and pressure promoted the unfolding of BLG, causing the disappearance of some α-helixes and some β-sheets. Based on ELISA analysis, it was revealed that HHP-termperature treatment altered the immunoreactivity of BLG by altering the structures and conformational states of BLG.

Surface characteristics and emulsifying properties of whey protein/nanoliposome complexes

The surface characteristics and emulsifying properties of whey proteins (WP) after complexation with nanoliposomes (NL) were investigated. WP surface hydrophobicity enhanced after complexation with NL, and it indicated the exposure increase of WP hydrophobic groups. WPNL interfacial tension significantly decreased compared with that of WP. The interfacial protein content of WPNL-stabilized emulsions was slightly different from that of WP-stabilized emulsions. WP emulsifying properties were significantly improved after complexation with NL. The mean sizes and polydispersity indexes of WPNL-stabilized emulsion droplets were smaller than those of WP-stabilized emulsion droplets. The absolute zeta-potential values of WPNL-stabilized emulsions were greater than those of WP-stabilized emulsions. Electrostatic repulsion played a vital role in WPNL-stabilized emulsion stability. Moreover, surface and emulsifying properties of WPNL were changed by exterior factor-induced alteration of protein advanced structures. The emulsifying properties of WP after complexation with NL were improved due to the modification of WP surface characteristics.

Effect of solid-state fermentation by three different Bacillus species on composition and protein structure of soybean meal

BACKGROUND

Fermentation efficiency of thermophiles of Bacillus licheniformis YYC4 and Geobacillus stearothermophilus A75, and mesophilic Bacillus subtilis 10 160 on soybean meal (SBM), was evaluated by examining the nutritional and protein structural changes.

RESULTS

SBM fermentation by B. licheniformis YYC4, B. subtilis 10 160 and G. stearothemophilus A75 increased significantly the crude and soluble protein from 442.4 to 524.8, 516.1 and 499.9 g kg-1 , and from 53.9 to 203.3, 291.3 and 74.6 g kg-1 , and decreased trypsin inhibitor from 8.19 to 3.19, 2.14 and 5.10 mg g-1 , respectively. Bacillus licheniformis YYC4 and B. subtilis 10 160 significantly increased phenol and pyrazine content. Furthermore, B. licheniformis YYC4 fermentation could produce abundant alcohols, ketones, esters and acids. Surface hydrophobicity, sulfhydryl groups and disulfide bond contents of SBM protein were increased significantly from 98.27 to 166.13, 173.27 and 150.71, from 3.26 to 4.88, 5.03 and 4.21 μmol g-1 , and from 20.77 to 27.95, 29.53 and 25.5 μmol g-1 after their fermentation. Fermentation induced red shifts of the maximum absorption wavelength (λmax ) of fluorescence spectra from 353 to 362, 376 and 361 nm, while significantly reducing the fluorescence intensity of protein, especially when B. subtilis 10 160 was used. Moreover, fermentation markedly changed the secondary structure composition of SBM protein. Analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and atomic force microscopy showed that macromolecule protein was degraded into small-sized protein or peptide during fermentation of SBM.

CONCLUSION

Bacillus licheniformis YYC4 fermentation (without sterilization) improved nutrition and protein structure of SBM as B. subtilis 10 160, suggesting its potential application in the SBM fermentation industry. © 2021 Society of Chemical Industry.

Physicochemical, structural and adhesion properties of walnut protein isolate-xanthan gum composite adhesives using walnut protein modified by ethanol

Low-sugar and high-protein adhesives have broad market application prospects, while natural plant proteins have confronted technical bottlenecks due to their poor adhesion. In this study, the effects of ethanol with different concentrations (0-80%) on the adhesion properties of walnut protein isolate-xanthan gum (WNPI-XG) composite adhesives were investigated. Results showed the bonding strength of WNPI-XG treated with 40% ethanol reached 12.55 MPa, the denaturation temperature and the surface hydrophobicity increased to 87.91 and 185.07 respectively, displaying the best rheological and texture properties. It also indicated appropriate concentration of ethanol (40%) didn't change the molecular weight of WNPI-XG, but greatly strengthened the fluorescence intensity, leading changes in contents of reactive sulfhydryl groups, electrostatic forces, hydrophobic interactions, hydrogen bonds and disulfide bonds. Furthermore, the treatment also facilitated a conformation conversion of the secondary structures from β-sheet to α-helix, promoting the full unfolding of protein molecules. The microstructure analysis showed after 40% ethanol treatment, the WNPI structure was uniform, the surface of WNPI-XG adhesive was flat and smooth, combined more closely with water molecules. By analyzing the influence of ethanol treatment on adhesion of WNPI-XG, the research laid a theoretical foundation for protein modification, providing good technical references for its development and utilization.

Effects of High Hydrostatic Pressure on the Conformational Structure and Gel Properties of Myofibrillar Protein and Meat Quality: A Review

In meat processing, changes in the myofibrillar protein (MP) structure can affect the quality of meat products. High hydrostatic pressure (HHP) has been widely utilized to change the conformational structure (secondary, tertiary and quaternary structure) of MP so as to improve the quality of meat products. However, a systematic summary of the relationship between the conformational structure (secondary and tertiary structure) changes in MP, gel properties and product quality under HHP is lacking. Hence, this review provides a comprehensive summary of the changes in the conformational structure and gel properties of MP under HHP and discusses the mechanism based on previous studies and recent progress. The relationship between the spatial structure of MP and meat texture under HHP is also explored. Finally, we discuss considerations regarding ways to make HHP an effective strategy in future meat manufacturing.

Effects of ultrafine grinding time on the functional and flavor properties of soybean protein isolate

Soybean protein isolate (SPI) powders were prepared at different ultrafine grinding time, and the functional and flavor properties of microparticulation SPI were evaluated. With extending ultrafine grinding time, a narrow and uniform particle size distribution in SPI powders was produced. The particle sizes of protein powders at grinding time 0, 2, 4, 6 and 8 h significantly reduced from 217 ± 16.5-137.5 ± 10.7 nm, while the absolute values of zeta-potential significantly increased from 25 ± 0.93-32.4 ± 117 mV (P < 0.05). The microstructure of SPI at grinding time 0-8 h changed from smooth to irregular. With prolonging the ultrafine grinding processing time, the solubility, foaming and emulsifying properties of SPI powders were improved, the content ofα-helix, β-sheet and random coils increased, while β-turn decreased. Furthermore, the ultrafine grinding time clearly influenced the volatile compounds of SPI powders. The main flavor compounds were aldehydes, alcohols, acids, ketones and alkanes. SPI powders for grinding time 2, 4, 6 and 8 h exhibited the higher total content of volatile compounds compared to that for 0 h. So the ultrafine grinding treatment at appropriate time could affect the functional and flavor properties of SPI.

Optimization of flash extraction, separation of ginsenosides, identification by HPLC-FT-ICR-MS and determination of rare ginsenosides in mountain cultivated ginseng

In this paper, we used the flash extraction method (FEM) to extract ginsenosides from mountain cultivated ginseng (MCG), optimized the FEM process by response surface methodology (RSM), and separated 23 kinds of ginsenosides from MCG, including rare ginsenoside Rg₃, 20(R/S)-Rg₂, Rk₃, 20(S)-Rh₂, 20(R)-Rh₁, F₁ and Rg₆. Among them, notoginsenoside R₁ was isolated from MCG for the first time. Additionally, we established an HPLC-FT-ICR-MS method to accurately identify 20 ginsenosides in MCG, and quantitatively analyzed the differences in the content of rare ginsenosides in MCG and Garden-Cultivated Ginseng (CG) by HPLC-UV. The results showed that the chemical components of MCG and CG were similar, but the ginsenoside content of MCG was double that of CG. Notably, the content of ginsenoside 20 (S)-Rh₂ and 20 (R)-Rh₁ had the largest difference, and the content in MCG was 33 and 24 times higher than that in CG, respectively. Through quantitative analysis, we clarified the reason why the activity of MCG is stronger than that of CG, which provided a theoretical basis for clinical application and further research of MCG.

23 ginsenosides, including rare ginsenosides, were separated from MCG by flash extraction technique. Through quantitative analysis, we found that the content of rare ginsenosides in MCG was higher than that in CG.

Improvement of nutritional quality of soybean meal by Fe(II)-assisted acetic acid treatment

We investigated the effect of Fe(II)-assisted acetic acid treatment on improvement of nutrition quality of soybean meal (SBM) by degrading antinutritional factors (ANFs) and maintaining initial nutrition quality. Fe(II)-assistance reduced trypsin inhibitor (TI) content significantly from 5.20 to 0.86 mg/g, and allergenic proteins were completely degraded at 55 °C, due to changes in the conformation of soybean protein isolate (SPI) that renders proteins more prone to acetic acid-mediated degradation. The red-shift of maximum emission wavelength indicated that Fe(II)-assisted acid induced molecular unfolding of SPI and increased surface hydrophobicity. Investigation of protein secondary structure revealed that Fe(II)-assisted acid treatment decreased the β-sheet structure by 4.65% and increased the α-helical content by 7.37%. This demonstrated that Fe(II) and acetic acid synergistically degrade ANFs by altering protein conformations in SBM.

Functional and conformational changes to soy proteins accompanying anthocyanins: Focus on covalent and non-covalent interactions

The present study was aimed to evaluate the interaction between anthocyanins from black rice and soybean protein isolate (SPI) via non-covalent and covalent bindings and the impact of these interactions on the functional and conformational changes of soybean protein. The conformational changes of the protein structure with different concentrations of anthocyanins (0.05, 0.1%, and 0.2%) were analyzed using three-dimensional fluorescence and Fourier transform infrared spectroscopy. The anthocyanins were more likely to form covalent interactions with SPI instead of non-covalent interactions. The addition of anthocyanins changed the secondary structure of SPI with a decrease in β-sheets and an increase in β-turns and random coils. The emulsifying and foaming properties of SPI were improved after complexation with anthocyanins. This study might be useful for elucidating the mechanisms behind the binding of anthocyanins with SPI and the possible uses of SPI-anthocyanin complexes in food formulations.