Food protein aggregation and its application

Inhibitory effect of L-arginine on the oxidative aggregation behavior of myofibrillar proteins in the Antarctic krill (Euphausia superba): pH and antioxidation

In this study, the effect of L-arginine (L-Arg) on the oxidative aggregation of myofibrillar proteins (MPs) in Antarctic krill was evaluated. The results showed that the oxidized aggregation of MPs was significantly inhibited after the addition of 20 mM L-Arg compared to the oxidized group, the solubility of MPs significantly increased by 25.74 %, the turbidity reduced from 0.56 to 0.18. These effects were primarily attributed to the addition of L-Arg, which prevented the unfolding of the spatial structure of MPs after oxidation, inhibited the formation of disulfide bonds and dityrosine, and improved the stability of MPs structure. Analysis of carbonyl content and hydroxyl radical (•OH) inhibitory capacity showed that carbonyl formation and hydroxyl radicals were effectively reduced by the pH and guanidinium group of L-Arg. The pH of L-Arg exhibited a significantly higher effect than the guanidinium group in inhibiting the oxidative aggregation of MPs.

The matrix effect derived from proteins in fluorescence detection for ciprofloxacin residues in eggs

Based on the previously developed Al3+/CuNCs probe, the matrix effect (ME) derived from protein was investigated in the fluorescence determination of fluoroquinolones (FQs) residues in eggs, and a sample pretreatment method was established to rapidly reduce the ME. Molecular docking results indicated that the three main egg proteins and FQs were bound by hydrogen bond, van der Waals force, and alkyl groups, leading to the loss of FQs response signal, and then produced ME. After trichloroacetic acid treatment, the mean particle size of egg matrix decreased, the protein secondary structure changed, and the crystal structure was destroyed. The corresponding ME of the supernatant obtained by centrifugation was only 0.7 %. The standard addition experiment confirmed that the proposed pretreatment method improved the accuracy and reliability of the fluorescence probe. This work is helpful to promote the practical application of fluorescence analysis in the rapid monitoring of food safety hazard factors.

Modulating allergenicity of prawn tropomyosin (penaeus chinensis) via pulsed electric field-induced conformational changes

The effect of electric field intensities (EFIs, 5-20 kV/cm) and treatment times (0.5-2 h) on allergenicity and spatial conformation of prawn tropomyosin was evaluated. The results demonstrated that the IgG and IgE binding capacity of tropomyosin maximally increased by 24.34 % and 29.16 % respectively, followed by a subsequent decrease after 20 kV/cm treatment for 1 h. Interestingly, 5-10 kV/cm treatments significantly decreased the α-helix content (P < 0.05) and fluorescence intensity, while 20 kV/cm treatment promoted extensive spiralization, resulting in a tightly packed structure. The increased flexibility further exposed the hydrolysis sites and strengthened the gastrointestinal digestibility of tropomyosin. Additionally, molecular dynamic simulation indicated that extended EFIs increased structural flexibility and depolymerized the tropomyosin dimers through destroying intermolecular hydrogen bonds (formed within arginine and glutamate), which allowed tropomyosin to be easily recognized by IgG/IgE. Whereas, decrease of solvent-accessibility surface area (SASA), hydrophobic surface area induced conformation folded and caused epitopes masked.

High-pressure homogenization transformed salmon protein filament into micelle structure: Improvement on the stability and swallowing rheology of dysphagia-oriented salmon emulsion gels

The aging population is stimulating increased demand for dysphagia-oriented foods, yet most current options are made of ultra-processed macronutrients and lack high-quality protein and ω-3 fatty acids. This study explores the use of whole salmon fillets as a myofibrillar protein source to stabilize salmon backbone oil, creating ω-3-rich emulsion gels (50-60 vol%) for dysphasia individuals. Two-step high-pressure homogenization (HPH; 50 MPa) improved emulsion texture, storage stability, and swallowability (IDDSI level 4) by reducing oil droplet size (from 20 to 2 μm) and increasing elastic modulus by 6-8 times and viscosity by more than 10 times. These emulsion gels, rich in PUFAs, support cardiovascular health. HPH altered the structure of salmon myofibrillar proteins, transforming from micro-sized filament (2.5 μm) to assembled nano-sized micelle aggregate (400 nm) through reducing α-helix structure, crystallization, particle size, and aggregation. The protein interfacial stiffness and stability were improved, thus exhibiting greater oil droplet stabilization. The study offers a compelling reference for applying HPH in producing dysphagia-oriented products.

Cupin-1.1 Adsorption Layers at the Surface of 8 M Urea Solutions

The adsorption layers of cupin-1.1, one of the two evolutionary conserved β-barrel domains of vicilin─the garden pea storage globulin─at the liquid-gas interface were studied by a few methods of the surface chemistry. The kinetic dependencies of the surface pressure of cupin-1.1 solutions in 8 M urea overlap in a single master curve if the surface pressure is plotted as a function of the normalized time. The analysis of the master curve allows separation of a few adsorption steps including the induction period, the regions of the diffusion-controlled and barrier-controlled adsorption kinetics, and a plateau region of slow adsorption. Another master curve can be constructed from the dependencies of the dynamic surface elasticity on surface pressure. This curve has some similarities with the corresponding results for recently studied cupin-1.1 spread layers on the surface of urea solutions and gliadin adsorption layers. There are also important distinctions with the master curve for adsorption layers of cupin-1.1 in the system without denaturants. This difference can be connected with the formation of larger and more rigid aggregates in pure water than the aggregates in urea solutions.

Physicochemical Properties and Metal Ion-Binding Capacity of Thermal-Induced Antarctic Krill Protein Aggregates under Different pH Conditions

Protein properties can be modified by thermal treatment at different pH values, resulting in the formation of protein aggregates with diverse morphologies and functionalities. This study investigated the morphology of aggregates of Antarctic krill protein (AKPS) formed by thermal treatment (90 °C, 15 min) at pH 2, 3, 4, and 6-12, characterized the different morphologies of AKPS, and determined the metal ion (Ca2+, Fe2+, and Zn2+)-binding capacities. Results showed that heat treatment with different pH values generated various AKPS with distinct morphology and metal ion-binding abilities. AKPS have formed fibrils at pH ≤ 3, particles at pH 4-7, and amorphous aggregates at pH ≥ 8. Fibrous AKPS (pH 2) exhibited a high solubility (80.36%) and strong reducing effect on iron. The binding capacities of Ca2+ and Fe2+ reached 36.08% and 66.75%. Particulate AKPS (pH 6 and 7) primarily only showed Zn2+-binding capacity similar to that of casein phosphopeptide (17.33%). Amorphous AKPS (pH 9-11) displayed the optimal capacity to bind Zn2+ and Fe2+ (26.90% and 74.94%). The alterations in morphology and functional characteristics of AKPS permit the design of various nanostructures for food-derived mineral supplements, thus developing their potential for application in functional foods.

Preferential Binding of Cations Modulates Electrostatically Driven Protein Aggregation and Disaggregation

Protein aggregation resulting in either ordered amyloids or amorphous aggregates is not only restricted to deadly human diseases but also associated with biotechnological challenges encountered in the therapeutic and food industries. Elucidating the key structural determinants of protein aggregation is important to devise targeted inhibitory strategies, but it still remains a formidable task owing to the underlying hierarchy, stochasticity, and complexity associated with the self-assembly processes. Additionally, alterations in solution pH, salt types, and ionic strength modulate various noncovalent interactions, thus affecting the protein aggregation propensity and the aggregation kinetics. However, the molecular origin and a detailed understanding of the effects of weakly and strongly hydrated salts on protein aggregation and their plausible roles in the dissolution of aggregates remain elusive. In this study, using fluorescence and circular dichroism spectroscopy in combination with electron microscopy and light scattering techniques, we show that the ionic size, valency, and extent of hydration of cations play a crucial role in regulating the protein aggregation and disaggregation processes, which may elicit unique methods for governing the balance between protein self-assembly and disassembly.

Effect of sodium metabisulfite-mediated self-assembly on the quality of silver carp myofibrillar protein-EGCG composite gels

Myofibrillar protein (MP) gels are susceptible to oxidation, which can be prevented by complexing with hydrophilic polyphenols, but may cause gel deterioration. Sodium metabisulfite (Na2S2O5) has been used to induce self-assembly of MP and analyze the impact of self-assembly on the quality of composite gels containing high amounts of (-)-epigallocatechin gallate (EGCG). Hydrophobic forces were confirmed as the main driver of self-assembly. Self-assembly reduced the size of the MP-EGCG complex to approximately 670 nm and increased the gel's hydrophobic force by approximately 3.6-fold. The maximum hardness of the Na2S2O5-treated MP-EGCG composite gel was 52.43 g/kg, which was approximately 49% greater than pure MP gel. After oxidative treatment, the Na2S2O5-treated MP-EGCG composite gel had considerably lower carbonyl and dityrosine levels (2.47-μmol/g protein and 450 a.u.) than the control (8.37-μmol/g protein and 964 a.u.). Therefore, Na2S2O5 shows potential as a cost-effective additive for alleviating MP limitations in the food industry.

Elucidating the effects of precooked treatments on the quality attributes of red swamp crayfish (Procambarus clarkia): Insights from water boiling vs. microwaving

Precooked treatments are essential in food processing, extending beyond mere sterilization to include the enhancement of nutritional value, flavor profile, and digestibility. This research scrutinizes the effects of water boiling and microwaving on red swamp crayfish, two distinct precooked methodologies. A comparative analytical framework has been employed to assess the efficacy of two precooked methods across a spectrum of quality indicators, including aerobic plate counts, texture, nutrient composition, volatile compound characterization, protein oxidation, and digestive properties. The findings revealed that both water boiling and microwaving effectively reduced bacterial counts to a safe level of 500 CFU/g. Microwave precooking facilitated a moderate oxidation of lipids in crayfish, preferentially liberating flavor compounds, thereby enhancing their sensory attributes. The boiling process imparted a pronounced denaturation to proteins, consequently augmenting the hardness of the crayfish. Notably, the enhanced digestibility of boiled crayfish proteins results from the denaturing action of boiling, promoting efficient protein digestion.

Effect of electrohydrodynamic (EHD) drying on active ingredients, textural properties and moisture distribution of yam (Dioscorea opposita)

This paper systematically investigates the changes in material properties during electrohydrodynamic (EHD) drying, the discharge characteristics of the EHD system as well as the active ingredients, textural properties (hardness, adhesiveness, etc.) and moisture distribution of yam under EHD, air drying and hot air drying were investigated. The results showed that the active particles and the ionized wind generated during the discharge process of the electrohydrodynamic drying device had a significant effect on the drying. Compared to thermal drying, 21 kV drying resulted in the most complete cellular structure, the best internal bound water content as well as textural properties of yam. It played a positive role in the retention of internal nutrients in yam, and the total phenol and allantoin contents were increased by 25.74% and 81.99%, respectively. These results elucidate the advantages of electrohydrodynamic drying in yam drying and provide a reference for the application of EHD in drying.

Effect of NaCl partial replacement by KCl, Ca-ascorbate, and spent hen meat hydrolysate on the physicochemical properties and quality of Cantonese sausage

A large amount of NaCl is usually used to provide a unique flavor and extend the shelf life of meat products. However, excessive sodium intake may cause diseases such as cardiovascular diseases. Spent hen meat hydrolysate (SHH) as an efficient NaCl substitute was developed with inefficient research related to SHH application in food systems. Therefore, the effects of NaCl replacement with SHH, KCl, and Ca-ascorbate on the quality of low-sodium Cantonese sausage were investigated. Four groups of salt formulation, I (100% NaCl), II (NaCl/KCl/Ca-ascorbate = 60%/30%/10%), III (NaCl/KCl/Ca-ascorbate/SHH = 50%/30%/10%/10%), and IV (NaCl/KCl/Ca-ascorbate/SHH = 30%/30%/10%/30%), were used to produce Cantonese sausages. The moisture and nitrite content decreased, the microbiological growth was inhibited, and the protein content increased after adding SHH for Cantonese sausages with NaCl substitution degrees of 50% and 70%. The saltiness, overall flavor, color, and texture of low-sodium Cantonese sausages with SHH were maintained or improved compared to the Cantonese sausage without sodium replacement. The proportion of peptides with molecular weight <1 kDa in Cantonese sausages increased after adding SHH, which may improve the overall flavor by interacting with peptides or other compounds. SHH combined with KCl and Ca-ascorbate is an efficient NaCl substitute, which can maintain and even improve Cantonese sausage quality and reduce sodium content up to 70%. These findings offer a promising reference for SHH application in the food industry and promote the development of salt taste-enhancing hydrolysate in food science.

The Effect of Reduced Nitrogen Fertilizer Application on japonica Rice Based on Volatile Metabolomics Analysis

Nitrogen is critical for rice yield and quality, but its overuse can be detrimental to efficiency and the environment. To identify changes in the quality of rice in response to the reduced application of nitrogen fertilizer, we carried out a comprehensive metabolomics study of SuiJing 18 using volatile metabolomics methods. Our results showed that SuiJing 18 had a total of 358 volatile metabolites, mainly lipids (16.25%), terpenoids (15.41%), heterocyclic compounds (15.13%), and hydrocarbons (13.45%). SuiJing 18 underwent significant changes in response to the reduced application of nitrogen fertilizer. Key sweet volatile compounds such as 4-methyl-benzeneacetaldehyde, hexyl acetate, and 2-methylnaphthalene were present at significantly higher levels when nitrogen fertilizer was applied at a rate of 68 kg of pure nitrogen per hectare, and their flavor characteristics also differed significantly from the compounds resulting from the other two treatments. Focusing on 16 differential volatile metabolites, we further investigated their effects on flavor and quality, thus laying the foundation for a greater understanding of the biomarkers associated with changes in rice quality. This study contributes to a better understanding of the mechanisms underlying changes in rice quality after reduced nitrogen fertilizer application.

Peanut de-oiling at room temperature by micro-aqueous hydration: Co-destabilization driven by oleosome coalescence and protein aggregation

The peanut de-oiling industry currently lacks efficient processing technologies for de-oiling at low or room temperatures. A novel method, micro-aqueous extraction (MAE), offers over 93 % de-oiling efficiency at room temperature and is also effective for other oilseeds like sesame, camellia, and rapeseed. Despite its effectiveness, the exact mechanism behind oleosomes destabilization at a critical hydration level or oil volume fraction (φ ∼ 0.75) is not fully understood. This study investigates how MAE affects peanut oleosome size, paste stability, and the interfacial properties of surfactant proteins. Results showed that micro-aqueous hydration and agitation caused small droplets (85.6 vol% < 10 μm) to coalesce into larger droplets (90.0 vol% > 30 μm) due to press-induced rupture of the liquid film. Simultaneously, agitation decreased water mobility and protein intrinsic fluorescence, while increasing paste viscosity, leading to protein aggregation. This aggregation further promoted oleosome coalescence. Additionally, hydration and agitation weakened the ability of membrane proteins to stabilize oleosomes by increasing interfacial tension and decreasing dilatational storage modulus. The insights into the peanut oleosome destabilization mechanism for MAE provide a foundation for scaling up the process, with the potential to replace current hot and cold pressing techniques.

Stable, porous, light-emitting post-modification covalent organic frameworks conjugated molecularly imprinted polymers for selective detection of pyrraline in salami products

Molecular imprinting is one of the most frequently occurring post-modification in the preparation of covalent organic frameworks (COFs) to enhance selectivity and specificity. In this study, we prepared a 2D layer structure of methoxy-conjugated COFs with the modification of azide (4-azido-L-phenylalanine), named [4-ALP]0.17-COFs, which exhibited a large specific surface area of 827.6 m2/g, good stability of water, polar solvents, chemistry, and thermodynamics. Fluorescent COF nanosheets ([4-ALP]0.17-CONs) obtained by liquid-assisted ultrasonic stripping have excellent blue luminescence properties and ultra-high absolute fluorescence quantum yield of 33.34 %. The modifiable functional groups in the surface of [4-ALP]0.17-CONs interacted with the targets and functional monomers of molecularly imprinted polymers (MIPs) through hydrogen bonding interactions, to form the 3D holes with recognition sites. The quantitative detection of pyrraline (PRL) could be achieved in the concentration range of 0.05-4 μg/L with the LOD was 34.81 ng/L. The spiked recovery of PRL in meat products was 88.01-106.00 %. The [4-ALP]0.17-CONs@MIPs sensing system showed excellent stability, reliability, reusability, and practicability, promising its potential for targeted monitoring of trace molecules in real matrices.

Conjugation prepared by wet-Maillard reactions improves the stability and properties of lutein and lycopene loaded nanoparticles

In this study, lutein and lycopene were encapsulated in plant protein (faba bean protein concentrate, (FPC))-carrageenan (Car) conjugates prepared by Maillard reaction in an aqueous media. The conjugation improved encapsulation yield that reached to 82.69% and 93.07%, for lycopene and lutein, respectively. The mean particle diameters for lutein loaded nanoparticles observed smaller in FPC-Car conjugates (66.60 nm) than FPC (71.49 nm). Scanning electron microscopy images showed that FPC-Car conjugates were more spherical and no fractures or fissures on the surface, revealing that wall materials provided better protection and retention for core materials. The diameter of lycopene nanoparticles coated with FPC remained constant between pH 3-4 and 7-9 but increased to 220 nm at pH 4-6. Even though the diameter of lutein nanoparticles coated with FPC remains steady between pH 5 and 9, increased to 953 nm at pH 3. The bioaccessibility of the lutein or lycopene samples encapsulated by FPC were found as higher than FPC-Car conjugates. These findings suggest that protein-polysaccharide conjugates could be used as a wall material to encapsulate lipophilic lutein and lycopene in order to improve their stability, property and bioaccessibility. As a result, FPC-Car conjugates may be an alternative for the formation of functional beverages as well as other nutraceutical products.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05976-4.

Evaluation of antinutrients, nutritional, and functional properties in sacha inchi (Plukenetia volubilis L) cake treated with hydrothermal processes

Applying heat treatments using an autoclave and hot air sterilization can alter the proximal composition, technofunctional properties, and antinutrient content of Sacha inchi (P. volubilis) oil press cake. The autoclave and hot air treatments significantly reduced antinutrients compared to the control. The samples treated with autoclave and hot air sterilization exhibited a significant decrease in alkaloids, nitrates, tannins, saponins, and trypsin inhibitors compared to the control sample. However, the 20-min autoclave treatment did not significantly reduce the saponin antinutrients. Phytic acid significantly decreased in the 30-min hot air sample and autoclave 20-min/hot air treatments, respectively. On the other hand, the levels of antinutrients oxalate and thiocyanates did not significant difference between the control and hot air treatments. However, the autoclave treatment resulted in a significant reduction in oxalates. The study found that hydrotreatments at temperatures of 121 °C with humid heat - autoclave showed significant differences in protein content compared to the control sample, with content of 37.75 + 0.2 g/100g. Samples treated with an autoclave for 10, 20, and 30 min showed values of protein 53.19 + 0.28, 66.08 + 2.6, and 70.12 + 0.48 g/100g, respectively. Meanwhile, samples treated with dry heat showed significant differences with the sample treated for 10 min having a protein content of 60.21 + 6.80 g/100g. The techno-functional properties analyzed in the study demonstrated a significant decrease in hydrating properties such as water holding capacity (WHC), water retention capacity (WRC), and swelling capacity (SC) due to changes in the solubility of proteins for the two treatments and the oil holding capacity (OHC) property showed a significant increase. Finally, water's presence during hydrothermal treatments significantly reduces antinutrients, providing guidance for analyzing other study variables.

Exploring the effect of high-pressure processing conditions on the deaggregation of natural major royal jelly proteins (MRJPs) fibrillar aggregates

High pressure processing is a safe and green novel non-thermal processing technique for modulating food protein aggregation behavior. However, the systematic relationship between high pressure processing conditions and protein deaggregation has not been sufficiently investigated. Major royal jelly proteins, which are naturally highly fibrillar aggregates, and it was found that the pressure level and exposure time could significantly promote protein deaggregation. The 100-200 MPa treatment favoured the deaggregation of proteins with a significant decrease in the sulfhydryl group content. Contrarily, at higher pressure levels (>400 MPa), the exposure time promoted the formation of disordered agglomerates. Notably, the inter-conversion of α-helix and β-strands in major royal jelly proteins after high pressure processing eliminates the solvent-free cavities inside the aggregates, which exerts a 'collapsing' effect on the fibrillar aggregates. Furthermore, the first machine learning model of the high pressure processing conditions and the protein deaggregation behaviour was developed, which provided digital guidance for protein aggregation regulation.

The contrasting roles of co-solvents in protein formulations and food products

Protein aggregation is a major hurdle in developing biopharmaceuticals, in particular protein formulation area, but plays a pivotal role in food products. Co-solvents are used to suppress protein aggregation in pharmaceutical proteins. On the contrary, aggregation is encouraged in the process of food product making. Thus, it is expected that co-solvents play a contrasting role in biopharmaceutical formulation and food products. Here, we show several examples that utilize co-solvents, e.g., salting-out salts, sugars, polyols and divalent cations in promoting protein-protein interactions. The mechanisms of co-solvent effects on protein aggregation and solubility have been studied on aqueous protein solution and applied to develop pharmaceutical formulation based on the acquired scientific knowledge. On the contrary, co-solvents have been used in food industries based on empirical basis. Here, we will review the mechanisms of co-solvent effects on protein-protein interactions that can be applied to both pharmaceutical and food industries and hope to convey knowledge acquired through research on co-solvent interactions in aqueous protein solution and formulation to those involved in food science and provide those involved in protein solution research with the observations on aggregation behavior of food proteins.

Effect of exogenous selenium on physicochemical, structural, functional, thermal, and gel rheological properties of mung bean (Vigna radiate L.) protein

Selenium (Se) biofortification during the growth process of mung bean is an effective method to improve the Se content and quality. However, the effect of Se biofortification on the physicochemical properties of mung bean protein is unclear. The objective of this study was to clarify the changes in the composition, Se forms, particle structure, functional properties, thermal stability, and gel properties of mung bean protein at four Se application levels. The results showed that the Se content of mung bean protein increased in a dose-dependent manner, with 7.96-fold (P1) and 8.52-fold (P2) enhancement at the highest concentration. Exogenous Se application promotes the conversion of inorganic Se to organic Se. Among them, selenomethionine (SeMet) and methyl selenocysteine (MeSeCys) replaced Met and Cys through the S metabolic pathway and became the dominant organic Se forms in Se-enriched mung bean protein, accounting for more than 80 % of the total Se content. Exogenous Se at 30 g/hm2 significantly up-regulated protein content and promoted the synthesis of sulfur-containing protein components and hydrophobic amino acids in the presence of increased levels of SeMet and MeSeCys. Meanwhile, Cys and Met substitution altered the sulfhydryl groups (SH), β-sheets, and β-turns of protein. The particle size and microstructural characteristics depend on the protein itself and were not affected by exogenous Se. The Se-induced increase in the content of hydrophobic amino acids and β-sheets synergistically increases the thermal stability of the protein. Moderate Se application altered the functional properties of mung bean protein, which was mainly reflected in the significant increase in oil holding capacity (OHC) and foaming capacity (FC). In addition, the increase in SH and β-sheets induced by exogenous Se could alter the protein intermolecular network, contributing to the increase in storage modulus (G') and loss modulus (G″), which resulted in the formation of more highly elastic gels. This study further promotes the application of mung bean protein in the field of food processing and provides a theoretical basis for the extensive development of Se-enriched mung bean protein.

Transglutaminase cross-linking ovalbumin-flaxseed oil emulsion gels: Properties, microstructure, and performance in oxidative stability

This study prepared emulsion gels by modifying ovalbumin (OVA)-flaxseed oil (FSO) emulsions with transglutaminase (TGase) and investigated their properties, structure and oxidative stability under different enzyme reaction times. Here, we found prolonged reaction times led to the transformation of α-helix and β-turn into β-sheet and random coil. The elasticity, hardness and water retention of the emulsion gels increased significantly, but the water-holding capacity decreased when the reaction time exceeded 4 h. Confocal laser scanning microscope (CLSM) indicated extended enzyme reaction time fostered oil droplet aggregation with proteins. Emulsion gel reduced FSO oxidation, especially after 4 h of the enzyme reaction, the peroxide value (PV) of the emulsion gel was reduced by 29.16% compared to the control. In summary, the enzyme reaction time of 4 h resulted in the formation of a dense gel structure and enhanced oxidative stability. This study provides the potential applications in functional foods and biomedical fields.

High pressure-assisted enzymatic hydrolysis potentiates the production of quinoa protein hydrolysates with antioxidant and ACE-inhibitory activities

The impact of different pressure levels in the HHP-assisted hydrolysis by Alcalase of quinoa proteins on the catalytic efficiency, peptide release, phenolic compounds content, and biological activities was investigated. The protein profile (SDS-PAGE) showed a more extensive peptide breakdown for the HHP-assisted proteolysis at 300-400 MPa, which was confirmed by the higher extent of hydrolysis and peptide concentration. Quinoa protein hydrolysates (QPH) produced at 200 and 300 MPa exhibited higher total phenolic contents and antioxidant activities (methanol-acetone and aqueous extracts) when compared to the non-hydrolyzed (QPI) and non-pressurized hydrolyzed samples. Kaempferol dirhamnosyl-galactopyranoside was the prevalent phenolic compound in those samples, increasing total flavonoids by 1.8-fold over QPI. The QPH produced at 300 MPa inhibited ACE more effectively, exhibiting the greatest anti-hypertensive potential, along with the presence of several ACE-inhibitory peptides. The peptide sequences GSHWPFGGK, FSIAWPR, and PWLNFK presented the highest Peptide Ranker scores and were predicted to have ACE inhibitory, DPP-IV inhibitory, and antioxidant activities. Mild pressure levels were effective in producing QPH with enhanced functionality due to the effects of bioactive soluble phenolics and low molecular weight peptides.

Impact of Fava Bean (Vicia faba) Processing on Quality Characteristics and Digestibility of a Protein-Rich Snack

The impact of fava bean processing methods (soaking, autoclaving, fermentation) on a legume-based bars' quality, protein characteristics, and digestibility was shown. The antioxidant and the angiotensin-converting enzyme-inhibitory capacity before and after in vitro digestion were investigated to reveal the potential advantages of fava bean usage for snacks. All bars have demonstrated high protein content, varying from 22.1 to 25.1 g/100 g DB. Based on the fermented fava beans of Pleurotus ostreatus, the samples were characterized by a higher concentration of essential amino acids by 8.6% and a reduction of tannins by 18.5% compared with bars based on soaked fava beans. Sensory evaluation improved the color, texture, and overall acceptability of the bars with fermented legumes. Various types of bean processing did not significantly affect the protein digestibility of the bars. The fermentation method positively affected the angiotensin-converting enzyme-inhibitory properties of bars and increased by 16.5% (before digestion) and 15% (after digestion) compared with other samples. After digestion, samples were characterized by a high level of Fe bioaccessibility (100, 83, and 79% for the bars based on soaked, autoclaved, and fermented fava beans, respectively) and increased total phenolic content. These findings highlight the potential health benefits of fava bean usage for snack products.

Revolutionizing food science with mass spectrometry imaging: A comprehensive review of applications and challenges

Food science encounters increasing complexity and challenges, necessitating more efficient, accurate, and sensitive analytical techniques. Mass spectrometry imaging (MSI) emerges as a revolutionary tool, offering more molecular-level insights. This review delves into MSI's applications and challenges in food science. It introduces MSI principles and instruments such as matrix-assisted laser desorption/ionization, desorption electrospray ionization, secondary ion mass spectrometry, and laser ablation inductively coupled plasma mass spectrometry, highlighting their application in chemical composition analysis, variety identification, authenticity assessment, endogenous substance, exogenous contaminant and residue analysis, quality control, and process monitoring in food processing and food storage. Despite its potential, MSI faces hurdles such as the complexity and cost of instrumentation, complexity in sample preparation, limited analytical capabilities, and lack of standardization of MSI for food samples. While MSI has a wide range of applications in food analysis and can provide more comprehensive and accurate analytical results, challenges persist, demanding further research and solutions. The future development directions include miniaturization of imaging devices, high-resolution and high-speed MSI, multiomics and multimodal data fusion, as well as the application of data analysis and artificial intelligence. These findings and conclusions provide valuable references and insights for the field of food science and offer theoretical and methodological support for further research and practice in food science.

Stability of Protein Pharmaceuticals: Recent Advances

There have been significant advances in the formulation and stabilization of proteins in the liquid state over the past years since our previous review. Our mechanistic understanding of protein-excipient interactions has increased, allowing one to develop formulations in a more rational fashion. The field has moved towards more complex and challenging formulations, such as high concentration formulations to allow for subcutaneous administration and co-formulation. While much of the published work has focused on mAbs, the principles appear to apply to any therapeutic protein, although mAbs clearly have some distinctive features. In this review, we first discuss chemical degradation reactions. This is followed by a section on physical instability issues. Then, more specific topics are addressed: instability induced by interactions with interfaces, predictive methods for physical stability and interplay between chemical and physical instability. The final parts are devoted to discussions how all the above impacts (co-)formulation strategies, in particular for high protein concentration solutions.'

Effects of sturgeon oil and its Pickering emulsion on the quality of sturgeon surimi gel

This study aimed to extract sturgeon oil (SO) from the sturgeon head and apply it to sturgeon meat to produce surimi gel. The effects of SO and its Pickering emulsion on the qualities of surimi gel were investigated. The results demonstrated that Pickering emulsions improved the quality deterioration of the gel caused by the direct addition of SO, especially the soy isolate protein (SPI) emulsion and the pea isolate protein (PPI) emulsion. Pickering emulsions contributed to a more uniform and compact network structure of the gel, improved the texture properties, enhanced the freeze-thaw stability, and reduced lipid oxidation. Additionally, compared to the addition of exogenous lipids such as peanut oil and linseed oil, SO and its Pickering emulsion better maintained the characteristic flavor of sturgeon surimi gel. This study provides valuable data and feasible ideas for expanding the utilization of sturgeon by-products and developing new types of surimi gel products.

Mining Bovine Milk Proteins for DPP-4 Inhibitory Peptides Using Machine Learning and Virtual Proteolysis

Dipeptidyl peptidase-IV (DPP-4) enzyme inhibitors are a promising category of diabetes medications. Bioactive peptides, particularly those derived from bovine milk proteins, play crucial roles in inhibiting the DPP-4 enzyme. This study describes a comprehensive strategy for DPP-4 inhibitory peptide discovery and validation that combines machine learning and virtual proteolysis techniques. Five machine learning models, including GBDT, XGBoost, LightGBM, CatBoost, and RF, were trained. Notably, LightGBM demonstrated superior performance with an AUC value of 0.92 ± 0.01. Subsequently, LightGBM was employed to forecast the DPP-4 inhibitory potential of peptides generated through virtual proteolysis of milk proteins. Through a series of in silico screening process and in vitro experiments, GPVRGPF and HPHPHL were found to exhibit good DPP-4 inhibitory activity. Molecular docking and molecular dynamics simulations further confirmed the inhibitory mechanisms of these peptides. Through retracing the virtual proteolysis steps, it was found that GPVRGPF can be obtained from β-casein through enzymatic hydrolysis by chymotrypsin, while HPHPHL can be obtained from κ-casein through enzymatic hydrolysis by stem bromelain or papain. In summary, the integration of machine learning and virtual proteolysis techniques can aid in the preliminary determination of key hydrolysis parameters and facilitate the efficient screening of bioactive peptides.

Microbial β C-S Lyases: Enzymes with Multifaceted Roles in Flavor Generation

β C-S lyases (β-CSLs; EC 4.4.1.8) are enzymes catalyzing the dissociation of β carbon-sulfur bonds of cysteine S-conjugates to produce odorant metabolites with a free thiol group. These enzymes are increasingly studied for their role in flavor generation in a variety of food products, whether these processes occur directly in plants, by microbial β-CSLs during fermentation, or in the mouth under the action of the oral microbiota. Microbial β-CSLs react with sulfur aroma precursors present in beverages, vegetables, fruits, or aromatic herbs like hop but also potentially with some precursors formed through Maillard reactions in cooked foods such as meat or coffee. β-CSLs from microorganisms like yeasts and lactic acid bacteria have been studied for their role in the release of polyfunctional thiols in wine and beer during fermentation. In addition, β-CSLs from microorganisms of the human oral cavity were shown to metabolize similar precursors and to produce aroma in the mouth with an impact on retro-olfaction. This review summarizes the current knowledge on β-CSLs involved in flavor generation with a focus on enzymes from microbial species present either in the fermentative processes or in the oral cavity. This paper highlights the importance of this enzyme family in the food continuum, from production to consumption, and offers new perspectives concerning the utilization of β-CSLs as a flavor enhancer.

Could 'Isochoric Freezing' Revolutionise Food Preservation?

The present article responds to the food engineering community's growing interest in an emerging and lauded approach to food preservation, popularised by its developers as 'isochoric freezing'. A strong campaign in the scientific literature and mass media has recently promoted this technique as a universal replacement for traditional food freezing and the frozen supply chain by highlighting a number of alleged advantages of 'isochoric freezing'. Some of these claims therefore require a more neutral and critical assessment against the background of the today's state of the art in food freezing technologies. Hence, this article spotlights several concerns regarding the plausibility, energy expenditure, resource efficiency, process rate, throughput and safety of 'isochoric freezing', as well as the correct use of food refrigeration terminology. The aspects considered are intended to make food scientists, technologists and engineers more aware of the real capabilities and the application perspectives of this still immature mode of refrigerated food processing.

Effect of staphylococci fermentation and their synergistic Lactobacillus on the physicochemical characteristics and nonvolatile metabolites of Chinese bacon

The impacts of Staphylococcus cohnii, S. saprophyticus and their synergistic Lactobacillus plantarum on the quality and flavor of Chinese bacon were investigated by monitoring the physicochemical characteristics and characterizing metabolites with non-targeted metabolomics. Results showed that S. cohnii could increase the tenderness and decrease the oxidation of muscle, while S. saprophyticus stabilized the springiness and increased the proteolysis. The metabolites produced by the co-fermentation of S. cohnii and S. saprophyticus showed a higher hierarchy, then exhibited the highest hierarchy in synergy with L. plantarum. The promising flavor may be related to the arginine biosynthesis, nicotinic acid and nicotinamide metabolism, and pyrimidine metabolism pathways. Staphylococcus contributed to flavor by promoting the accumulation of di- and tripeptides and activating the amino acid metabolic pathway through arginine metabolism. These findings provide thoughts for understanding the fermentation mechanism of Staphylococcus and the targeted modulation of the flavor of Chinese bacon.

Amyloid-like Aggregation of Wheat Gluten and Its Components during Cooking: Mechanisms and Structural Characterization

Amyloid-like aggregation widely occurs during the processing and production of natural proteins, with evidence indicating its presence following the thermal processing of wheat gluten. However, significant gaps remain in understanding the underlying fibrillation mechanisms and structural polymorphisms. In this study, the amyloid-like aggregation behavior of wheat gluten and its components (glutenin and gliadin) during cooking was systematically analyzed through physicochemical assessment and structural characterization. The presence of amyloid-like fibrils (AFs) was confirmed using X-ray diffraction and Congo red staining, while Thioflavin T fluorescence revealed different patterns and rates of AFs growth among wheat gluten, glutenin, and gliadin. AFs in gliadin exhibited linear growth curves, while those in gluten and glutenin showed S-shaped curves, with the shortest lag phase and fastest growth rate (t1/2 = 2.11 min) observed in glutenin. Molecular weight analyses revealed AFs primarily in the 10-15 kDa range, shifting to higher weights over time. Glutenin-derived AFs had the smallest ζ-potential value (-19.5 mV) and the most significant size increase post cooking (approximately 400 nm). AFs in gluten involve interchain reorganization, hydrophobic interactions, and conformational transitions, leading to additional cross β-sheets. Atomic force microscopy depicted varying fibril structures during cooking, notably longer, taller, and stiffer AFs from glutenin.

Investigation of the Effects of Phenolic Extracts Obtained from Agro-Industrial Food Wastes on Gelatin Modification

In this study, modified bovine gelatin was produced using the alkaline technique with four different oxidized agro-industrial food waste (pomegranate peel (PP), grape pomace and seed (GP), black tea (BT), and green tea (GT)) phenolic extracts (AFWEs) at three different concentrations (1, 3, and 5% based on dry gelatin). The effect of waste type and concentration on the textural, rheological, emulsifying, foaming, swelling, and color properties of gelatin, as well as its total phenolic content and antioxidant activity, was investigated. Significant improvement in gel strength, thermal stability, and gelation rate of gelatin was achieved by modification with oxidized agro-industrial waste extracts. Compared to the control sample, 46.24% higher bloom strength in the GT5 sample, 5.29 and 6.01 °C higher gelling and melting temperatures in the PP5 sample, respectively, and 85.70% lower tmodel value in the GT3 sample were observed. Additionally, the total phenolic content, antioxidant activity, foam, and emulsion properties of the modified gels increased significantly. This study revealed that gelatins with improved technological and functional properties can be produced by using oxidized phenolic extracts obtained from agricultural industrial food wastes as cross-linking agents in the modification of gelatin.

Extraction, Modification, Biofunctionality, and Food Applications of Chickpea (Cicer arietinum) Protein: An Up-to-Date Review

Plant-based proteins have gained popularity in the food industry as a good protein source. Among these, chickpea protein has gained significant attention in recent times due to its high yields, high nutritional content, and health benefits. With an abundance of essential amino acids, particularly lysine, and a highly digestible indispensable amino acid score of 76 (DIAAS), chickpea protein is considered a substitute for animal proteins. However, the application of chickpea protein in food products is limited due to its poor functional properties, such as solubility, water-holding capacity, and emulsifying and gelling properties. To overcome these limitations, various modification methods, including physical, biological, chemical, and a combination of these, have been applied to enhance the functional properties of chickpea protein and expand its applications in healthy food products. Therefore, this review aims to comprehensively examine recent advances in Cicer arietinum (chickpea) protein extraction techniques, characterizing its properties, exploring post-modification strategies, and assessing its diverse applications in the food industry. Moreover, we reviewed the nutritional benefits and sustainability implications, along with addressing regulatory considerations. This review intends to provide insights into maximizing the potential of Cicer arietinum protein in diverse applications while ensuring sustainability and compliance with regulations.

Preventing thermal aggregation of ovalbumin through dielectric-barrier discharge plasma treatment and enhancing its emulsification properties

The impact of Dielectric-Barrier Discharge (DBD) plasma treatment on the prevention of heat-induced aggregation of Ovalbumin (OVA) and improvement in emulsification properties was investigated. Results highlighted the effective inhibition of thermal aggregation of OVA following exposure to plasma. Structural analysis revealed that the plasma-induced oxidation of sulfhydryl and intermolecular disulfide bonds played a pivotal role in inhibiting the thermal aggregation, considered by Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), multiplies spectroscopy, and analysis of dynamic exchange of sulfhydryl-disulfide bonds. Meanwhile, the oxidation of exposed hydrophobic sites due to plasma treatment resulted in the transformation of the OVA molecule's surface from hydrophobic to hydrophilic, contributing significantly to the aggregation inhibition. Additionally, compared to an untreated sample of OVA, almost one-fold increase in emulsifying ability (EAI) and 1.5-fold in emulsifying stability (ESI) was observed after 4 min of plasma treatment. These findings demonstrated that plasma treatment not only enhanced the thermal stability of OVA, but also improved its emulsification properties.

Widely Targeted Metabolomic Analysis Revealed the Diversity in Milk from Goats, Sheep, Cows, and Buffaloes and Its Association with Flavor Profiles

The milk flavor can be attributed to the presence of numerous flavor molecules and precursors. In this study, we employed widely targeted metabolomic analysis techniques to analyze the metabolic profiles of various milk samples obtained from goats, sheep, dairy cows, and buffaloes. A total of 631 metabolites were identified in the milk samples, which were further categorized into 16 distinct classes. Principal component analysis (PCA) suggested that the metabolite profiles of samples from the same species exhibit clustering, while separated patterns of metabolite profiles are observed across goat, sheep, cow, and buffalo species. The differential metabolites between the groups of each species were screened based on fold change and variable importance in projection (VIP) values. Five core differential metabolites were subsequently identified, including 3-(3-hydroxyphenyl)-3-hydroxypropanoic acid, inosine 5'-triphosphate, methylcysteine, N-cinnamylglycine, and small peptide (L-tyrosine-L-aspartate). Through multiple comparisons, we also screened biomarkers of each type of milk. Our metabolomic data showed significant inter-species differences in the composition and concentration of some compounds, such as organic acids, amino acids, sugars, nucleotides, and their derivatives, which may affect the overall flavor properties of the milk sample. These findings provided insights into the molecular basis underlying inter-species variations in milk flavor.

Inhibition of water-diluted precipitate formation from egg whites by ultrasonic pretreatment: Insights from quantitative proteomics analysis

The formation of the egg white precipitate (EWP) during dilution poses challenges in food processing. In this paper, the effects of 90 W and 360 W ultrasonic intensities on the inhibition of EWP formation were investigated. The findings revealed that 360 W sonication effectively disrupted protein aggregates, decreasing the dry matter of EWP by 5.24 %, particle size by 57.86 %, and viscosity by 82.28 %. Furthermore, the ultrasonic pretreatment unfolded protein structures and increased the content of β-sheet structures. Combined with quantitative proteomics and intermolecular forces analysis, the mechanism by which ultrasonic pretreatment inhibited water-diluted EWP formation by altering protein interactions was proposed: ultrasonic pretreatment disrupted electrostatic interactions centered on lysozyme, as well as hydrogen-bonding interactions between ovomucin and water. In conclusion, our research provides valuable insights into the application of ultrasonic pretreatment as a means to control and improve the quality of egg white-based products.

Electrical Fields in the Processing of Protein-Based Foods

Electric field-based technologies offer interesting perspectives which include controlled heat dissipation (via the ohmic heating effect) and the influence of electrical variables (e.g., electroporation). These factors collectively provide an opportunity to modify the functional and technological properties of numerous food proteins, including ones from emergent plant- and microbial-based sources. Currently, numerous scientific studies are underway, contributing to the emerging body of knowledge about the effects on protein properties. In this review, "Electric Field Processing" acknowledges the broader range of technologies that fall under the umbrella of using the direct passage of electrical current in food material, giving particular focus to the ones that are industrially implemented. The structural and biological effects of electric field processing (thermal and non-thermal) on protein fractions from various sources will be addressed. For a more comprehensive contextualization of the significance of these effects, both conventional and alternative protein sources, along with their respective ingredients, will be introduced initially.

Pulse Protein Isolates as Competitive Food Ingredients: Origin, Composition, Functionalities, and the State-of-the-Art Manufacturing

The ever-increasing world population and environmental stress are leading to surging demand for nutrient-rich food products with cleaner labeling and improved sustainability. Plant proteins, accordingly, are gaining enormous popularity compared with counterpart animal proteins in the food industry. While conventional plant protein sources, such as wheat and soy, cause concerns about their allergenicity, peas, beans, chickpeas, lentils, and other pulses are becoming important staples owing to their agronomic and nutritional benefits. However, the utilization of pulse proteins is still limited due to unclear pulse protein characteristics and the challenges of characterizing them from extensively diverse varieties within pulse crops. To address these challenges, the origins and compositions of pulse crops were first introduced, while an overarching description of pulse protein physiochemical properties, e.g., interfacial properties, aggregation behavior, solubility, etc., are presented. For further enhanced functionalities, appropriate modifications (including chemical, physical, and enzymatic treatment) are necessary. Among them, non-covalent complexation and enzymatic strategies are especially preferable during the value-added processing of clean-label pulse proteins for specific focus. This comprehensive review aims to provide an in-depth understanding of the interrelationships between the composition, structure, functional characteristics, and advanced modification strategies of pulse proteins, which is a pillar of high-performance pulse protein in future food manufacturing.

Structural, kinetic, and thermodynamic aspects of insulin aggregation

Given the significance of protein aggregation in proteinopathies and the development of therapeutic protein pharmaceuticals, revamped interest in assessing and modelling the aggregation kinetics has been observed. Quantitative analysis of aggregation includes data of gradual monomeric depletion followed by the formation of subvisible particles. Kinetic and thermodynamic studies are essential to gain key insights into the aggregation process. Despite being the medical marvel in the world of diabetes, insulin suffers from the challenge of aggregation. Physicochemical stresses are experienced by insulin during industrial formulation, storage, delivery, and transport, considerably impacting product quality, efficacy, and effectiveness. The present review briefly describes the pathways, mathematical kinetic models, and thermodynamics of protein misfolding and aggregation. With a specific focus on insulin, further discussions include the structural heterogeneity and modifications of the intermediates incurred during insulin fibrillation. Finally, different model equations to fit the kinetic data of insulin fibrillation are discussed. We believe that this review will shed light on the conditions that induce structural changes in insulin during the lag phase of fibrillation and will motivate scientists to devise strategies to block the initialization of the aggregation cascade. Subsequent abrogation of insulin fibrillation during bioprocessing will ensure stable and globally accessible insulin for efficient management of diabetes.

Physicochemical properties and in vitro digestion behavior of emulsion gels stabilized by rice bran protein aggregates: Effects of heating time and induction methods

To investigate the effects of heating time and induction methods on the physicochemical properties and in vitro digestion behavior of emulsion gels, rice bran protein aggregates (RBPAs) were formed by acid-heat induction (90 °C, pH 2.0) and the emulsion gels were further prepared by adding GDL or/and laccase for single/double cross-linked induction. Heating time affected the aggregation and oil/water interfacial adsorption behavior of RBPAs. Suitable heating (1-6 h) was conducive to faster and more adsorption of aggregates at the oil/water interface. While excessive heating (7-10 h) resulted in protein precipitation, which inhibited the adsorption at the oil/water interface. The heating time at 2, 4, 5 and 6 h was thus chosen to prepare the subsequent emulsion gels. Compared with the single cross-linked emulsion gels, the double-cross-linked emulsion gels showed higher water holding capacity (WHC). After simulated gastrointestinal digestion, the single/double cross-linked emulsion gels all exhibited slow-release effect on free fatty acid (FFA). Moreover, the WHC and final FFA release rate of emulsion gels were closely related to the surface hydrophobicity, molecular flexibility, sulfhydryl, disulfide bond and interface behavior of RBPAs. Generally, these findings proved the potential of emulsion gels in designing fat alternatives, which could provide a novel technique for the fabrication of low-fat food.

Hydrogen peroxide oxidation modifies the structural properties and allergenicity of the bee pollen allergen profilin

Bee pollen is a byproduct of pollination, which is a necessary process to produce foods. However, bee pollen can induce significant food-borne allergies. We previously identified a bee pollen-derived pan-allergen in the profilin family, Bra c p. Herein, we aimed to reduce Bra c p allergenicity via protein oxidation with hydrogen peroxide and explore the changes induced. Ion-mobility mass spectrometry revealed aggregation of the oxidized product; we also found irreversible sulfonation of the free sulfhydryl group of the Bra c p Cys98 residue to a more stable cysteine derivative. A significant proportion of the α-helices in Bra c p were transformed into β-sheets after oxidation, masking the antigenic epitopes. An immunoassay demonstrated that the IgE-binding affinity of Bra c p was decreased in vitro after oxidation. To our knowledge, this is the first report describing the application of protein oxidation to reduce the allergenicity of profilin family member in foods.

Electrostatics-Induced Nucleated Conformational Transition of Protein Aggregation

Despite the wide existence of protein aggregation in nature and its intimate connection to many human diseases, the underlying mechanism remains unclear. Here, we develop a molecular theory by systematically incorporating the self-consistent field theory for charged macromolecules into the dilute solution thermodynamics. The kinetic pathway is tracked without any restriction on the morphology of the aggregates. We find that protein aggregation at low salt concentrations is via a two-step nucleated process involving a conformational transition from metastable spherical oligomer to elongated fibril. The scaling analysis elucidates the electrostatic origin of the conformational transition: the fibril enters the screening region much earlier than the spherical aggregate. As salt concentration increases, the classical mode of one-step nucleation corresponding to macroscopic liquid-liquid phase separation is recovered. Our results reveal that the screened electrostatic interaction is essential for the existence of the metastable oligomer and its subsequent conformational transition to fibril. The theoretical predictions of the kinetic pathway and the morphology of the aggregates are in good agreement with the experimental observations of real proteins.

Alkali-Induced Phenolic Acid Oxidation Enhanced Gelation of Ginkgo Seed Protein

The effect of alkali-induced oxidation of three phenolic acids, namely gallic acid, epigallocatechin gallate, and tannic acid, on the structure and gelation of ginkgo seed protein isolate (GSPI) was investigated. A mixture of 12% (w/v) GSPI and different concentrations of alkali-treated phenolic acids (0, 0.06, 0.24, and 0.48% w/w) were heated at 90 °C, pH 6.0, for 30 min to form composite gels. The phenolic treatment decreased the hydrophobicity of the GSPI sol while enhancing their rheological properties. Despite a reduced protein solubility, water holding capacity, stiffness, and viscoelasticity of the gels were improved by the treatments. Among them, the modification effect of 0.24% (w/v) EGCG was the most prominent. Through the analysis of microstructure and composition, it was found to be due to the covalent addition, disulfide bond formation, etc., between the quinone derivatives of phenolic acids and the side chains of nucleophilic amino acids. Phenolic acid modification of GSPI may be a potential ingredient strategy in its processing.

Potential of Good's buffers to inhibit denaturation of myofibrillar protein upon freezing

The current systematic study sought to examine the potential use of three Good's buffers (MES, MOPS and HEPES) in inhibiting myofibrillar protein (MFP) denaturation induced by acidity changes. The highest degree of acidity variation was found in the center and bottom of large bottles due to the freeze-concentration effect. Good's buffer tended to basify during freezing, and it could prevent the crystallization of sodium phosphate (Na-P) buffer. Acidification upon freezing Na-P disrupted the natural conformation of MFP and induced the formation of large proteins aggregates with tight packing. The 15 mM MES, 20 mM MOPS, and 30 mM HEPES were respectively added to neutralize the strong acidity drop induced by freezing 20 mM Na-P, and all of them significantly improved the stability of the MFP conformation (P < 0.05). This work is not only critical to meet the growing demand for protein, but also groundbreaking for broadening the applicability of Good's buffers in the food industry.

Proteolysis of Micellar β-Casein by Trypsin: Secondary Structure Characterization and Kinetic Modeling at Different Enzyme Concentrations

Tryptic proteolysis of protein micelles was studied using β-casein (β-CN) as an example. Hydrolysis of specific peptide bonds in β-CN leads to the degradation and rearrangement of the original micelles and the formation of new nanoparticles from their fragments. Samples of these nanoparticles dried on a mica surface were characterized by atomic force microscopy (AFM) when the proteolytic reaction had been stopped by tryptic inhibitor or by heating. The changes in the content of β-sheets, α-helices, and hydrolysis products during proteolysis were estimated by using Fourier-transform infrared (FTIR) spectroscopy. In the current study, a simple kinetic model with three successive stages is proposed to predict the rearrangement of nanoparticles and the formation of proteolysis products, as well as changes in the secondary structure during proteolysis at various enzyme concentrations. The model determines for which steps the rate constants are proportional to the enzyme concentration, and in which intermediate nano-components the protein secondary structure is retained and in which it is reduced. The model predictions were in agreement with the FTIR results for tryptic hydrolysis of β-CN at different concentrations of the enzyme.

The interaction of trehalose and molten globule state soybean 11S globulin and its impact on foaming capacities

BACKGROUND

Soybean 11S globulin has good functional properties, which are widely used in the field of food. However, natural soybean 11S globulin (N-11S) has low flexibility and is easy to aggregate, impacting its foaming process. Studies have shown that soybean 11S globulin in molten globule state (MG-11S) has better molecular flexibility than N-11S, and trehalose has been shown to improve the properties of proteins. Therefore, this study investigated the interaction mechanism between trehalose and MG-11S, and its impact on rheological and foaming properties of MG-11S.

RESULTS

The molecular docking and intrinsic fluorescence results showed that hydrogen bonding was the main interaction force at lower than 0.5 mol L^-1 trehalose added. Meanwhile, rheology and foaming showed that the MG-11S-trehalose complexes had better viscoelasticity, foaming ability (66.67-86.67%) and foaming stability (75.00-89.29%) than N-11S (16.67% foaming ability and 40.00% foaming stability); however, when the trehalose was higher than 0.5 mol L^-1 , molecular crowding occurred and H-bonds were weakened, resulting in reduction of foaming capacities. Microstructure determination showed that trehalose attached to the surface of foam membrane; meanwhile, the foaming structure of the complex with 0.5 mol L^-1 trehalose had a thicker liquid film with decreased drainage rate, less agglomeration and disproportionation of foam, illustrating the best foaming ability and foaming stability.

CONCLUSION

The results suggested that trehalose at different concentrations can interact with MG-11S through different mechanisms, and improve the foaming capacity of MS-11S. This provided a reference for the application of MS-11S in foaming food. © 2022 Society of Chemical Industry.

Effect of Sitophilus zeamais (Coleoptera: Curculionidae) Infestation on the Protein Physicochemical and Structural Properties of Wheat Grain

Boring pests such as Sitophilus zeamais (S. zeamais) are major threats in grain storage. However, how these pests affect the proteins of stored grains remains largely unknown. Here we aimed to investigate the effect of S. zeamais infestation on wheat protein during postharvest storage. In this study, wheat grain infested by S. zeamais was sampled at egg (4 d), larval (20 d), pupal (35 d), and adult stages (45 d), respectively. The protein's physicochemical and structural properties and the edible quality of whole wheat noodle were analyzed. The results showed that S. zeamais infestation significantly decreased the quality of wheat protein by altering its constitution and structure properties. Especially, compared with the control, the content of wet and dry gluten, gluten index, sodium dodecyl sulfate sedimentation volume, sulfhydryl groups, and disulfide bonds in insect-infested wheat decreased by 19.40, 5.42, 18.40, 8.12, 29.13, and 14.30%, respectively, during the storage period of one life cycle of S. zeamais. Additionally, the proportions of wheat protein fractions (albumin [1.16-fold], globulin [0.96-fold], gliadin [1.16-fold], and glutenin [0.95-fold]) and secondary structures (α-helix [0.91-fold], β-fold [0.96-fold], β-turn [1.06-fold], and random coil [1.05-fold]) of protein changed significantly, and the gluten network structure was broken in S. zeamais-infested wheat. Furthermore, the color of whole wheat noodle became darker, cooking loss rate increased, and textural properties (hardness, adhesiveness, springiness, cohesiveness, chewiness, and resilience) decreased as well. The results in the present study provided new insights for analyzing the quality deterioration mechanism and further quality improvement of boring pests-infested wheat grain.

Salt-Induced Dissolution of Protein Aggregates

Protein aggregation is mediated by a complex interplay of noncovalent interactions and is associated with a broad range of aspects from debilitating human diseases to the food industry and therapeutic biotechnology. Deciphering the intricate roles of noncovalent interactions is of paramount importance for the design of effective inhibitory and disaggregation strategies, which remains a formidable challenge. By using a combination of spectroscopic and microscopic tools, here we show that the surfactant-mediated protein aggregation can be modulated by an intriguing interplay of hydrophobic and electrostatic effects. Additionally, our results illuminate the unique role of salt as a potent disaggregation inducer that alters the protein-surfactant electrostatic interactions and triggers the dissolution of preformed protein aggregates resulting in restoring the native protein structure. This unusual salt-induced dissolution and refolding offers a unique approach to regulating the balance between protein self-assembly and disassembly and will offer a potent strategy to design electrostatically targeted inhibitors.