The effect of oxidation on the structure of G-actin and its binding ability with aroma compounds in carp grass skeletal muscle

The revelation of characteristic volatile compounds in egg powder and analysis of their adsorption rules based on HS-GC-IMS technology

The study constructed fingerprints and analyzed adsorption rules of volatile compounds (VOCs) in egg powder (EP) under different production processes, including egg white powder (EWP), egg yolk powder (EYP) and whole egg powder (WEP) by HS-GC-IMS. The 29 VOCs identified were primarily ketones and aldehydes. Characteristic VOCs responsible for flavor differences were clarified by difference comparison, clustering and PCA analysis. Additionally, variations in lipid and protein were the primary causes of the VOCs differences in EP through microscopy imaging, infrared and fluorescence spectroscopy. EWP's stretched structure favored fishy-smelling VOCs adsorption but limited total aldehyde binding due to strong hydrophobic interaction. EYP's higher β-sheet ratio and fewer hydrogen bond sites weakened its alcohol VOCs binding capacity. The abundance of ketone VOCs in EP was linked to their low steric hindrance. Therefore, this study elucidated the flavor differences reasons among EWP, EYP and WEP, laying foundation for EP applications in food industry.

Synergistic rosemary extract with TBHQ and citric acid improves oxidative stability and shelf life of peanut

Lipid oxidation often accompanies the processing and storage of peanuts, which causes a serious waste of peanut resources. To solve the problem of being prone to oxidation in peanut processing, a ternary complex antioxidant based on rosemary extract (RE) was constructed to investigate its effect on the oxidative and thermal stability of peanuts, and the inhibition of peanut oxidation by compound antioxidants was revealed by dynamic Arrhenius formula and complexation theory. The results showed that there was a synergistic effect between RE and Tert-butyl hydroquinone (TBHQ), and the antioxidant effects of RE and TBHQ were 4.86 and 1.45 times higher when used in combination than when used alone, respectively. In addition, RE-TBHQ-CA (citric acid) effectively inhibited primary and secondary oxidation of peanuts with a shelf life 8.7 times longer than that of control peanuts. This study provides a novel antioxidant compounding idea, which has a positive effect on improving the quality of peanut and other nut products, prolonging the shelf life and reducing the waste of resources. PRACTICAL APPLICATION: Compounding a complex antioxidant that permits its use in peanuts. It was found that rosemary and TBHQ might have synergistic antioxidant effects. Meanwhile, this combination of RE-TBHQ-CA effectively inhibited the oxidation of peanut oils and prolonged the shelf life of peanuts. RE-TBHQ-CA is a highly efficient complex antioxidant that can reduce the amounts of antioxidants added while maintaining high antioxidant efficiency, which may be useful for the future preservation and storage of nut products as it positively affects the quality and shelf life of the product.

Understanding the Role of Filamentous Actin in Food Quality: From Structure to Application

Actin, a multifunctional protein highly expressed in eukaryotes, is widely distributed throughout cells and serves as a crucial component of the cytoskeleton. Its presence is integral to maintaining cell morphology and participating in various biological processes. As an irreplaceable component of myofibrillar proteins, actin, including G-actin and F-actin, is highly related to food quality. Up to now, purification of actin at a moderate level remains to be overcome. In this paper, we have reviewed the structures and functions of actin, the methods to obtain actin, and the relationships between actin and food texture, color, and flavor. Moreover, actin finds applications in diverse fields such as food safety, bioengineering, and nanomaterials. Developing an actin preparation method at the industrial level will help promote its further applications in food science, nutrition, and safety.

Recent advances and challenges in the interaction between myofibrillar proteins and flavor substances

Myofibrillar proteins are an important component of proteins. Flavor characteristics are the key attributes of food quality. The ability of proteins to bind flavor is one of their most fundamental functional properties. The dynamic balance of release and retention of volatile flavor compounds in protein-containing systems largely affects the sensory quality and consumer acceptability of foods. At present, research on flavor mainly focuses on the formation mechanism of flavor components, while there are few reports on the release and perception of flavor components. This review introduces the composition and structure of myofibrillar proteins, the classification of flavor substances, the physical binding and chemical adsorption of myofibrillar proteins and volatile flavor substances, as well as clarifies the regulation law of flavor substances from the viewpoint of endogenous flavor characteristics and exogenous environment factors, to provide a theoretical reference for the flavor regulation of meat products.

Interactions between phosvitin and aldehydes affect the release of flavor from Russian sturgeon caviar

The release mechanism of flavor during caviar storage was studied by the interaction between phosvitin and four aldehydes. Gas chromatography-mass spectrometry showed that the binding rate of phosvitin with 3-methylbutanal, nonanal, (E,Z)-2,6-nonadienal, and (E)-2-octenal decreased with an increase in the aldehyde concentrations. Among them, (E,Z)-2,6-Nonadienal (0.5 mM) had the highest binding rate (84.47%). The main quenching mechanism of (E,Z)-2,6-nonadienal with phosvitin was static quenching and the binding force comprised spontaneous hydrophobic interactions. An increase in the aldehyde concentrations reduced the α-helix content of phosvitin and led to aggregation of the microstructure of phosvitin. The results of molecular docking showed that tyr residue contributed the most to the binding of phosvitin to aldehydes. This study has elucidated the mechanism of the effect of caviar protein on changes in the caviar flavor during storage and provides effective strategies for regulation of caviar flavor during storage.

Effects of konjac glucomannan as a freeze-denaturation inhibitor or binder on the physiochemical properties of heat-induced gel of freeze-dried duck blood

During freeze-drying, the degradation or eutectic melting of duck blood proteins can reduce the quality of duck blood gels. However, the interaction between proteins and polysaccharides during drying can improve protein-based gel quality. Therefore, here, we investigated the physicochemical properties of heat-induced gels of freeze-dried duck blood (FDB) and FDB with different proportions of the polysaccharide konjac glucomannan (KG), which serves as a freeze-denaturation inhibitor agent (FDA) or binder (BG). The pH and water-holding capacity (WHC) of FDB + KG gels were higher than those of FDB gel without KG (control). Especially, the WHC increased from 11.00% for control to 55.65% for FDB gel with 1% KG as a BG. Consequently, cooking loss and texture parameters of FDB + KG gels decreased. The hardness of control was 2.14 kg, which significantly reduced to 0.12-0.87 kg with KG addition. The highest carbonyl content was observed in control gel, and the thiobarbituric acid reactive substance content was reduced by the addition of 1% KG as an FDA (T1) or 0.8% KG as an FDA with 0.2% KG as a BG (T2) (p < 0.05). These changes might be induced by the alteration of tertiary structure and thermodynamic stability of gels. In conclusion, 1% KG can be used as an FDA to improve the quality and physicochemical properties of heat-induced gels of FDB. Optimized FDB gels with KG can be used as an innovative food ingredient to fortify nutrition and develop special dietary purposes.

Binding of Selected Aroma Compounds to Myofibrillar Protein, Sarcoplasmic Protein, and Collagen during Thermal Treatment: Role of Conformational Changes and Degradation of Proteins

To investigate the effects of conformational changes and thermal degradation of myofibrillar protein (MP), sarcoplasmic protein (SP), and collagen (CO) on the binding ability for aroma compounds during heating. Using SDS-PAGE, HPLC, and LC-MS/MS, a consistent rise in the total concentration of peptides and free amino acids formed by the thermal degradation of proteins was observed. The surface hydrophobicity, total sulfhydryl content, particle size, and secondary structure content of proteins changed significantly over time. Furthermore, the aroma binding ability of proteins was determined by gas chromatography-mass spectrometry. The results revealed an increase in binding ability during 5 or 10 min of heating due to protein unfolding and the accumulation of degradation products. However, the binding ability decreased due to protein aggregation with prolonged heating. Notably, all proteins exhibited strong affinity toward (E)-2-octenal, (E,E)-2,4-decadienal, 2-methyl-3-furanthiol, and dimethyl trisulfide. The binding ability of MP and SP was similar but differed significantly from that of CO, which had lower binding ability for hexanal, (E)-2-octenal, (E,E)-2,4-decadienal, and dimethyl trisulfide compared to MP and SP.

Inhibition mechanism of membrane-separated silver carp hydrolysates on ice crystal growth obtained through experiments and molecular dynamics simulation

The membrane-separated silver carp hydrolysates (>10 k_D, 3-10 k_D and < 3 k_D) displayed abilities to mitigate oxidation and denaturation of myofibrillar protein and cryoprotective activities for frozen surimi. However, the mechanism of the membrane-separated fractions on ice crystal growth in the system is still unknown. Therefore, the cryoprotective activities (recrystallization inhibition, RI and thermal hysteresis activity, THA) of the fractions were investigated and the mechanism was explored by molecular dynamics (MD) simulation to predict the probable binding sites and model the possible interactions between the peptides and water/ice. The fractions < 3 k_D displayed remarkable RI activity, with significantly higher THA (0.60 ± 0.13 °C) and lower amount of ice nuclei (4.74 ± 0.53%) than that of fractions > 10 k_D and 3-10 k_D. The results of MD simulation certified that the main peptides in the fractions < 3 k_D interacted firmly with water molecules and inhibited growth of ice crystals with mechanism compatible with Kelvin effect. Hydrophilic and hydrophobic amino acid residues in the membrane-separated fractions offered synergistic effects on the inhibition of ice crystals.

Insight into the protein oxidation impact on the surface properties of myofibrillar proteins from bighead carp

The objective of this study was to elucidate the influence of oxidative modifications of myofibrillar proteins (MPs) on their surface properties. Oxidative modifications (deamination, formation of disulfide bonds and Schiff bases), particle size, net surface charge, and binding ability of volatiles (2-enthylfuran, 1-octen-3-ol, hexanal, and octanal) of oxidized MPs was measured. Molecular docking of volatiles with actomyosin was performed using Qvina-W program and the specific oxidative modifications (monoxidation and deamination) of MPs were determined using LC-MS/MS. Results showed that oxidation of Cys (forming sulfinic, sulfonic, sulfenic acid, and disulfide bonds), monoxidation of Ala, Lys, Glu, and Asn, and deamination of Lys changed the surface properties of oxidized MPs including enhanced surface hydrophobicity and decreased affinity to volatile compounds and water. Overall, this study gives evidence of how protein oxidation affects the properties of MPs and therefore deteriorates fish meat quality.

Insights on the binding mechanism between specified aldehydes and flaxseed protein using multispectral image and molecular docking

The binding and release behavior of flaxseed proteins to aldehydes is significant for the sensory properties of flaxseed foods. The key aldehydes of flaxseed were selected by headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and odor activity value (OAV) method, and the interaction between flaxseed protein and flaxseed protein was investigated by multispectral, molecular docking, molecular dynamics simulation, and particle size techniques. The results showed that 2,4-decadienal presented a higher binding capability and a higher Stern-Volmer constant with flaxseed protein than pentanal, benzaldehyde, and decanal. Thermodynamic analysis revealed that hydrogen bonding and hydrophobic interactions were the main forces. Aldehydes contributed to a certain reduction in radius of gyration (Rg) value and α-helix content of flaxseed protein. In addition, the results of particle size showed that aldehydes caused the proteins to aggregate toward larger particles. This study could provide new insights into the interactions between flaxseed food and flavor.

Characteristics and antioxidant properties of Harpadon nehereus protein hydrolysate-xylose conjugates obtained from the Maillard reaction by ultrasound-assisted wet heating in a natural deep eutectic solvents system

BACKGROUND

Harpadon nehereus is a high-protein marine fish. A valuable way to add value to H. nehereus is to convert it into protein hydrolysate. The Maillard reaction is an effective way to improve the functional properties of peptides and proteins, which are affected by many factors such as reactant concentration, water activity, pH, temperature, and heating time. However, the traditional Maillard reaction method is inefficient. The purpose of this study was therefore to explore the effect of the ultrasound-assisted wet heating method on the Maillard reaction of H. nehereus protein hydrolysate (HNPH) in a new-type green solvent - a natural hypereutectic solvent (NADES).

RESULTS

Harpadon nehereus protein hydrolysate-xylose (Xy) conjugates were prepared via a Maillard reaction in a NADES system using an ultrasound-assisted wet heating method. The effects of different treatment conditions on the Maillard reaction were studied. The optimized glycation degree (DG) of HNPH-Xy conjugates was obtained with a water content of 10%, a reaction temperature of 80 °C, a reaction time of 35 min, and an ultrasonic power level of 300 W. Compared with HNPH, the structure of HNPH-Xy conjugates were significantly changed. Moreover, the functional properties and antioxidant activity of HNPH-Xy were all superior to the HNPH.

CONCLUSIONS

An ultrasound-assisted wet-heating Maillard reaction between HNPH and Xy in the NADES system could be a promising way to improve the functional properties of HNPH. © 2023 Society of Chemical Industry.

Understanding interactions among flavor compounds from spices and myofibrillar proteins by multi-spectroscopy and molecular docking simulation

Influence of the constant heating treatment on structural and adsorption properties of myofibrillar proteins (MPs) of chicken was investigated. The results showed that heat treatment enhanced the exposure of sulfhydryl groups and improved hydrophobicity of MPs surface. Particle size distribution of MPs significantly varied depending on heat treatment duration. Also, heat treatments resulted in significant changes in the α-helix and β-sheet structures of MPs. Besides, the MPs formed larger, irregular, and cluster-like aggregates after heat treatments. Moreover, heat treatments increased viscosity and surface roughness of MPs, while zeta potential value was reduced after heat treatments. Furhthermore, binding interactions between the MPs and spices flavors signifcanlty varied relying on nature of MPs and flavor compounds, as well as heat treatments duration. Amino acid residues were interacted with flavor compounds of spices via a variety of bonds and a stable MPs-flavors complex was performed. The obtained results provide a basis for understanding structural and physicochemical changes that occur in MPs during cooking and the interactions between MPs and flavors of spices.

Physicochemical and Antioxidant Properties of Nanoliposomes Loaded with Rosemary Oleoresin and Their Oxidative Stability Application in Dried Oysters

Lipid and protein oxidation is a main problem related to the preservation of dried aquatic products. Rosemary oleoresin is widely used as an antioxidant, but its application is limited due to its instability and easy degradation. Nanoliposome encapsulation is a promising and rapidly emerging technology in which antioxidants are incorporated into the liposomes to provide the food high quality, safety and long shelf life. The objectives of this study were to prepare nanoliposome coatings of rosemary oleoresin to enhance the antioxidant stability, and to evaluate their potential application in inhibiting protein and lipid oxidation in dried oysters during storage. The nanoliposomes encapsulating rosemary oleoresin were applied with a thin-film evaporation method, and the optimal amount of encapsulated rosemary oleoresin was chosen based on changes in the dynamic light scattering, Zeta potential, and encapsulation efficiency of the nanoliposomes. The Fourier transform-infrared spectroscopy of rosemary oleoresin nanoliposomes showed no new characteristic peaks formed after rosemary oleoresin encapsulation, and the particle size of rosemary oleoresin nanoliposomes was 100-200 nm in transmission electron microscopy. The differential scanning calorimetry indicated that the nanoliposomes coated with rosemary oleoresin had better thermal stability. Rosemary oleoresin nanoliposomes presented good antioxidant stability, and still maintained 48% DPPH radical-scavenging activity and 45% ABTS radical-scavenging activity after 28 d of storage, which was 3.7 times and 2.8 times higher than that of empty nanoliposomes, respectively. Compared with the control, the dried oysters coated with rosemary oleoresin nanoliposomes showed significantly lower values of carbonyl, sulfhydryl content, thiobarbituric acid reactive substances, Peroxide value, and 4-Hydroxynonenal contents during 28 d of storage. The results provide a theoretical basis for developing an efficient and long-term antioxidant approach.

Hydrophobic bonds-dominated key off-odors/silver carp myofibrillar protein interactions, and their binding characteristics at cold storage and oral temperatures

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Off-odors binding to MP via hydrophobic forces is a spontaneous process.

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Nonanal had the strongest binding ability to MP among the three off-odors.

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MD method provided a structural basis for the fluorescence spectroscopic analysis.

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Three off-odors, especially nonanal, could change the conformation of MP.

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Compared with others, nonanal formed more binding sites to Trp residues in Myosin1.

This study revealed the interaction mechanism between silver carp myofibrillar protein (MP) and key off-odors by combining fluorescence spectroscopy with molecular dynamics (MD) simulation. Spectroscopic results exhibited a dynamic quenching mechanism between MP and off-odors. Thermodynamic analysis indicated that the MP/off-odors interaction was spontaneous (ΔG° < 0) and dominated by hydrophobic interactions (ΔH° > 0, ΔS° > 0). Meanwhile, the binding affinity was in the order of nonanal (n = 1.38) > hexanal (n = 0.89) > 1-octen-3-ol (n = 0.65), which was further verified by the MD results. Among off-odors, nonanal had the highest binding energy with myosin (8105.66 kJ/mol) and formed more hydrophobic binding sites to Trp residues in myosin head (e.g., Trp820 and Trp822), thereby changing myosin conformations via both physical and chemical interactions. Additionally, higher binding energies of myosin/off-odors were observed at oral temperature (37 °C) than at cold storage temperature (4 °C), implying that less off-odors were released at 37 °C.

The comparison of largemouth bass (Micropterus salmoides) fed trash fish and formula feeds: Growth, flesh quality and metabolomics

This study compared the growth, flesh quality and metabolomics of largemouth bass (Micropterus salmoides) fed trash fish and formula feeds. Trash fish (TF), self-made feed (SF) and commercial feed (CF) were prepared with crude protein levels of 172.2 g/kg, 503.5 g/kg and 504.1 g/kg (666.2 g/kg, 547.3 g/kg and 535.1 g/kg based on dry matter), respectively. Then, the three diets were fed to largemouth bass with an initial body weight of 75.0 ± 0.1 g for 12 weeks. SF and CF groups presented significantly lower feed intake (FI), feed conversion ratio (FCR) and higher protein efficiency ratio (PER) than TF group based on dry matter basis without affecting the weight gain (P &lt; 0.05). The yellowness (b*) in dorsal muscle, flesh heat-insoluble collagen and free flavor amino acids contents in SF group were significantly higher (P &lt; 0.05), while drip loss were significantly lower (P &lt; 0.05) than those of TF group. Compared to TF group, SF and CF groups showed significantly higher flesh polyunsaturated fatty acids (PUFAs), n-3 PUFAs and n-6 PUFAs contents, flesh hardness, shear force and muscle fiber density (P &lt; 0.05), and lower flesh total free amino acids, essential amino acids, muscle fiber diameter, intestine villus height and muscular thickness (P &lt; 0.05). The serum total protein, triglyceride and cholesterol levels in SF group were significantly lower than those in TF and CF groups (P &lt; 0.05). In the muscle metabolomics, 177 differential metabolites were detected between SF and TF groups, which mainly enriched in pathways as biosynthesis of amino acid, histidine metabolism, glycine, serine and threonine metabolism, etc. Conclusively, feeding largemouth bass with formula feeds improved flesh fatty acid profile and flesh texture without negative effects on the growth, but the flesh free amino acids contents were lower than the fish fed trash fish.

The Texture Change of Chinese Traditional Pig Trotter with Soy Sauce during Stewing Processing: Based on a Thermal Degradation Model of Collagen Fibers

In order to clarify the influence of the thermal degradation of collagen fibers on the texture profile analysis (TPA) parameters of pig trotter stewed with soy sauce (PTSWSS), TPA (springiness, chewiness, hardness, and gumminess), the secondary structures, the cross-linkage, decorin (DCN) and glycosaminoglycan (GAG) levels, and the histochemical morphology of collagen fibers during the stewing process (0, 30, 60, 120 min) were assessed. The springiness and hardness increased after 30 min of stewing, along with the denaturation of collagen proteins. TPA parameters improved with the prolonged stewing times of 60 and 120 min, along with the ultra-structural dissolution of collagen fibers, and a substantial reduction in cross-linkage, DCN, and GAG levels, and the unfolded triple-helix structure. This study concluded that the TPA parameters of PTSWSS were dependent on the stewing time, and that the improvement in TPA parameters with longer stewing time could primarily be attributed to the thermal degradation of collagen fibers.

Influence of Proteolysis on the Binding Capacity of Flavor Compounds to Myofibrillar Proteins

Proteolysis occurs extensively during postmortem aging, enzymatic tenderization and fermentation of meat products, whereas less is understood regarding how proteolysis affects meat flavor. Myofibrillar proteins (MP) were extracted from beef longissimus dorsi muscle and subsequently treated with three commercial proteases. The effect of proteolysis on the interactions between the treated MP and butyraldehyde, 2-pentanone, octanal and 2-octanone was investigated. The progress of proteolysis increased the degree of hydrolysis (DH) and the surface hydrophobicity but decreased the turbidity and particle size. Fluorescence-quenching analysis results indicated that the enzymatic treatment generally increased the quenching constant (Ksv) between the treated MP and ketones but decreased the Ksv between the treated MP and aldehydes, and the papain treatment changed the Ksv value to a larger degree than treatment with proteinase K and bromelain. The adsorption assay showed that the proteinase K treatment largely increased the adsorption capacity of the MP to octanal (by 15.8−19.3%), whereas the bromelain treatment significantly reduced the adsorption capacity of the treated MP to butyraldehyde (by 6.0−7.9%) and 2-pentanone (by 9.7−11.9%). A correlation analysis demonstrated a strong positive correlation (0.859, p < 0.05) between the DH of the MP and the adsorption ability of the treated MP to octanal. This study highlighted the significant but complex influence of proteolysis on MP binding capacity to flavor compounds.

Impact of salt content and hydrogen peroxide-induced oxidative stress on protein oxidation, conformational/morphological changes, and micro-rheological properties of porcine myofibrillar proteins

Salting and rehydration of myofibrils can be interfered with free radical diffusion process. This study investigated the effects of salt content (0, 1, 3 and 5%) and H₂O₂/ascorbate-based hydroxyl radical (OH)-generating system (1, 10, 20 mM H₂O₂) on the oxidation, conformation, aggregation, and thermal stability of porcine myofibrillar proteins (MPs). Results showed that 5% of salt inhibited carbonylation of MPs with intensive sulfhydryl loss and tryptophan quenching. Fourier transform infrared (FTIR), laser light scattering, and scanning electron microscopy (SEM) suggested that 20 mM H₂O₂ transformed more α-helix into β-sheet of MPs, favoring larger aggregates being selectively exposed towards solvent during salt-induced fiber swelling. Oxidized MPs brined with ≤1% salt underwent partial unfolding with higher flexibility, while up to 5% of salt greatly hampered their hydration potential and weakened inter-fibrillar hydrogen bond with an improved protein solubility. Micro-rheology revealed that 1% of salt and 10 mM H₂O₂ rendered a denser structure of heat-set MPs gels.

Mechanisms of Change in Emulsifying Capacity Induced by Protein Denaturation and Aggregation in Quick-Frozen Pork Patties with Different Fat Levels and Freeze-Thaw Cycles

Herein, we discuss changes in the emulsifying properties of myofibrillar protein (MP) because of protein denaturation and aggregation from quick-frozen pork patties with multiple fat levels and freeze-thaw (F-T) cycles. Protein denaturation and aggregation were confirmed by the significantly increased surface hydrophobicity, turbidity, and particle size, as well as the significantly decreased solubility and absolute zeta potential, of MPs with increases in fat levels and F-T cycles (p < 0.05). After multiple F-T cycles, the emulsifying activity and emulsion stability indices of all samples were significantly reduced (p < 0.05). The emulsion droplets of MP increased in size, and their distributions were dense and irregular. The results demonstrated that protein denaturation and aggregation due to multiple F-T cycles and fat levels changed the distribution of surface chemical groups and particle sizes of protein, thus affecting the emulsifying properties.

Investigation of molecular mechanisms of interaction between myofibrillar proteins and 1-heptanol by multiple spectroscopy and molecular docking methods

In this study, we investigated the interaction between myofibrillar proteins (MPs) and selected alcohols (1-pentanol, 1-hexanol, and 1-heptanol). Only 1-heptanol exhibited the binding ability to MPs, and the binding ability significantly increased with increasing protein concentration (p < 0.05). In addition, both static and dynamic quenching occurred during the interaction, with a red shift of the maximum absorption peak in the synchronous fluorescence spectra indicating a change in the microenvironment of the MPs. The results of circular dichroism measurements suggested that the interaction between MPs and 1-heptanol altered the secondary structure of the MPs. Furthermore, thermodynamic analysis showed that hydrogen bonding and van der Waals forces dominated the interaction between MPs and 1-heptanol, which was confirmed by the results of molecular docking/dynamics simulations. This study provides an in-depth understanding of the interaction between MPs and alcohols, which can help to improve the flavor control in meat.

Changes in the digestion properties and protein conformation of sturgeon myofibrillar protein treated by low temperature vacuum heating during in vitro digestion

The digestion properties of sturgeon myofibrillar protein (MF) treated by low temperature vacuum heating (LTVH) at different processing temperatures (50, 60 and 70 °C) and times (15 and 30 min) were studied and compared with those of sturgeon MF treated by traditional cooking (TC). The results showed that as the temperature and time increased, the protein digestibility decreased, whereas the particle size and protein aggregation increased. It was observed that the band intensity of myosin heavy chain and myosin heavy chain 7 weakened; however, the band intensity of actin showed little change. MALDI-TOF-MS analysis revealed that the digested products of the samples treated by LTVH had a larger proportion of 750-1000 Da peptides than those treated by TC, which was consistent with the trend of the number of unique peptides identified in each group. Fourier transmission infrared (FT-IR) spectroscopy showed that the contents of α-helices and β-sheets exhibited negative and positive correlations with the temperature, respectively. Overall, compared to TC, LTVH can relieve the heat stress of protein conformation, reduce protein aggregation to improve the accessibility of the protein to digestive protease, and increase digestibility.

Covalent Interaction between High Hydrostatic Pressure-Pretreated Rice Bran Protein Hydrolysates and Ferulic Acid: Focus on Antioxidant Activities and Emulsifying Properties

Rice bran protein hydrolysates (RBPH) pretreated with high hydrostatic pressure (HHP) covalently interacted with ferulic acid (FA) (0.5 to 2.5 mg/mL) under alkaline conditions. The structural and functional properties of the conjugates were investigated. The results revealed that the FA binding equivalent on RBPH increased from 6.03 to 207.64 nmol/mg. FTIR spectral analysis indicated that the content of α-helix increased, whereas the contents of β-sheet, β-turn, and random coil decreased. The surface hydrophobicity (H₀) of RBPH increased, the fluorescence intensity decreased, and the tertiary structure changed because of covalent interactions between RBPH and FA. The emulsifying activity index of RBPH-FA (1.5 mg/mL) was 35.10% higher than that of the control, whereas FA concentrations higher than 1.5 mg/mL had a negative effect on emulsifying properties. RBPH-FA (2.5 mg/mL) exhibited the strongest antioxidant activity. This study provides a new reference for the application of RBPH-FA conjugates in food processing.

Characterization of the Striatal Extracellular Matrix in a Mouse Model of Parkinson's Disease

Parkinson’s disease’s etiology is unknown, although evidence suggests the involvement of oxidative modifications of intracellular components in disease pathobiology. Despite the known involvement of the extracellular matrix in physiology and disease, the influence of oxidative stress on the matrix has been neglected. The chemical modifications that might accumulate in matrix components due to their long half-live and the low amount of extracellular antioxidants could also contribute to the disease and explain ineffective cellular therapies. The enriched striatal extracellular matrix from a mouse model of Parkinson’s disease was characterized by Raman spectroscopy. We found a matrix fingerprint of increased oxalate content and oxidative modifications. To uncover the effects of these changes on brain cells, we morphologically characterized the primary microglia used to repopulate this matrix and further quantified the effects on cellular mechanical stress by an intracellular fluorescence resonance energy transfer (FRET)-mechanosensor using the U-2 OS cell line. Our data suggest changes in microglia survival and morphology, and a decrease in cytoskeletal tension in response to the modified matrix from both hemispheres of 6-hydroxydopamine (6-OHDA)-lesioned animals. Collectively, these data suggest that the extracellular matrix is modified, and underscore the need for its thorough investigation, which may reveal new ways to improve therapies or may even reveal new therapies.

Effect of deacetylated konjac glucomannan on heat-induced structural changes and flavor binding ability of fish myosin

This work investigated the effects of deacetylated konjac glucomannan (DKGM) on heat-induced structural changes and flavor binding in bighead carp myosin. DKGM could cross-link with fish myosin to form a thermostable complex and improve the gel strength of myosin. The incorporation of DKGM increased the surface hydrophobicity and total sulfhydryl content of heat-induced myosin. Increasing DKGM concentrations resulted in a decrease in the absolute zeta potential and a continuous increase in particle size. DKGM addition significantly reduced the α-helical content of myosin with a concomitant increase in β-sheet, β-turn, and random coil content. The binding abilities of myosin to flavors were significantly enhanced by increasing amounts of DKGM, attributing to the accelerative unfolding of myosin secondary structures and the exposure of additional hydrophobic and thiol binding sites. Increased numbers of available hydroxyl groups after DKGM treatment could also cause an increase of flavor adsorption by hydrogen bonding.

Capacity of myofibrillar protein to adsorb characteristic fishy-odor compounds: Effects of concentration, temperature, ionic strength, pH and yeast glucan addition

The capacity of myofibrillar protein (MP) to adsorb fishy-odors (hexanal, nonanal, 1-octen-3-ol) was investigated under the influences of concentration, temperature, pH, ionic strength and yeast glucan (YG) addition. The adsorption of MP for fishy-odors was in the order of nonanal > hexanal > 1-octen-3-ol. With increasing MP concentration, the binding of protein-aldehydes was facilitated, in contrast to a decrease trend in binding to 1-octen-3-ol. Meanwhile, MP adsorption capacity for off-odors peaked at 40 °C. Additionally, low ionic strength (0.2 mol/L) could promote MP adsorption for off-odors, while high ionic strength (0.6-1.0 mol/L) could reduce its adsorption for hexanal and 1-octen-3-ol. Moreover, MP had higher adsorption capacity under extreme pH values (pH 3 and 11). Furthermore, YG was shown as an ideal additive to adsorb off-odors due to its large specific surface area and good stability. This work provides useful information on how to deodorize fishy-odors in fish products.

Effect of sarcoplasmic proteins oxidation on the gel properties of myofibrillar proteins from pork muscles

This study investigated the influence of sarcoplasmic proteins (SPs) treated by the oxidation system (0.1 mmol/L FeCl₃ , 0.1 mmol/L ascorbic acid, and 0, 1, 5, 10 mmol/L H₂ O₂ ) on the properties of pork myofibrillar proteins (MPs) gel. After oxidation treatment, the SPs showed an increased in carbonyl content and a decreased in total sulfhydryl content, coupled with the cross-linking of protein components by disulfide bonds and covalent bonds. The MPs gel with SPs oxidized at 1 mmol/L H₂ O₂ exhibited the maximal strength while the minimal water holding capacity (WHC). The WHC of MPs gel was significantly decreased with increasing SPs oxidation, leading to the increase of free water and the decrease of immobilized water in the gel system. The microstructures of MPs gels with moderately (1 mmol/L H₂ O₂ ) oxidized SPs showed a more compact and smaller pore gel network than MPs alone, suggesting adding oxidized SPs can expel water trapped in the gel. Furthermore, the environmental polarity of aliphatic C-H groups increased with SPs oxidation.

Molar mass effect in food and health

It is demanded to supply foods with good quality for all the humans. With the advent of aging society, palatable and healthy foods are required to improve the quality of life and reduce the burden of finance for medical expenditure. Food hydrocolloids can contribute to this demand by versatile functions such as thickening, gelling, stabilising, and emulsifying, controlling texture and flavour release in food processing. Molar mass effects on viscosity and diffusion in liquid foods, and on mechanical and other physical properties of solid and semi-solid foods and films are overviewed. In these functions, the molar mass is one of the key factors, and therefore, the effects of molar mass on various health problems related to noncommunicable diseases or symptoms such as cancer, hyperlipidemia, hyperglycemia, constipation, high blood pressure, knee pain, osteoporosis, cystic fibrosis and dysphagia are described. Understanding these problems only from the viewpoint of molar mass is limited since other structural characteristics, conformation, branching, blockiness in copolymers such as pectin and alginate, degree of substitution as well as the position of the substituents are sometimes the determining factor rather than the molar mass. Nevertheless, comparison of different behaviours and functions in different polymers from the viewpoint of molar mass is expected to be useful to find a common characteristics, which may be helpful to understand the mechanism in other problems.

Effect of incubation temperature on the binding capacity of flavor compounds to myosin

This study was aimed to investigate the effect of incubation temperature on the binding of hexanal, octanal and 3-methylbutyraldehyde to myosin. Fluorescence quenching, Fourier transform infrared spectroscopy, surface plasmon resonance (SPR), isothermal titration calorimetry (ITC) and gas chromatography-mass spectrometry (GC-MS) were employed. An increase in aldehyde concentration led to a reduction in fluorescence intensity in myosin. SPR revealed that the interactions were involved in a rapid combination and dissociation, and the dissociation constants significantly decreased from 25 to 37 °C. ITC showed that the values of entropy, enthalpy and Gibbs free energy were negative. The interactions were driven by hydrogen bonds and van der Waals forces. GC-MS further demonstrated that the highest binding capacity occurred at 37 °C between myosin and aldehydes. The findings provide a new insight into the mechanism on controlling or maintaining meat flavor.

Effect of heat treatment duration on the interaction between fish myosin and selected flavor compounds

BACKGROUND

Interactions between flavor compounds and proteins during food processing are critical to flavor perception of the final product. Here, we investigated the effect of the duration of heat treatment on the interaction between bighead carp myosin and selected flavor compounds including hexanal, heptanal, octanal, nonanal, (E)-2-heptenal, and 1-octen-3-ol.

RESULTS

The binding of flavor compounds to native myosin was strong and decreased in the order nonanal > octanal > (E)-2-heptenal > heptanal > hexanal >1-octen-3-ol. The aldehydes, especially trans-2-undecenal, were more conducive to hydrophobic binding to myosin than alcohols. Within the initial 5 min of heating, the surface hydrophobicity and total sulfhydryl exposure increased, while α-helix turned into β-sheets, β-turns, and random coils. However, upon further heating, the hydrophobicity and sulfhydryl contents declined, β-sheets, β-turns and random coils shifted to α-helix. Throughout the heating process, the particle size increased, and the absolute zeta potential decreased continuously, indicating that thermal aggregation of myosin occurred simultaneously. Changes in binding capacities of flavor compounds to myosin were consistent with changes in hydrophobicity and sulfhydryl contents.

CONCLUSION

The initial enhancement of the flavor-binding capacity of myosin was attributed to the unfolding of secondary structures by exposing more hydrophobic bonding sites and hydrogen bonding sites. The rebuilding and aggregating of myosin was enhanced upon prolonged heating, thus favoring hydrophobic protein-protein interactions and weakening the resultant flavor binding capacity of myosin.