Total Sulfhydryl Group Content Research Articles

Cryoprotective effect of glycopeptide complex from abalone viscera on frozen surimi and its underlying mechanism

AbstractFreezing technology is important for the long‐term preservation of aquatic products such as surimi. However, mechanical damage caused by ice crystals would lead to quality deterioration. Abalone viscera glycopeptide (AVGP) complex was prepared by hydrolysis technology, which exhibited ice recrystallization ability and antioxidant activity. Moreover, effects of AVGP on Ca2+‐ATPase activity, total sulfhydryl content, secondary structure of myofibrillar protein (MP), rheological properties, and gel properties of surimi frozen were investigated. Results showed that surimi treated with AVGP could improve the gel strength and rheological properties of surimi, reduce the gel ice crystal holes, and improve the degradation of gel matrix caused by freeze–thaw. AVGP can significantly inhibit the decrease of Ca2+‐ATPase activity and total sulfhydryl group content. When the addition of AVGP exceeded 4% (w/w), its freezing protection effect on MP was better than that of commercial antifreeze agents. Moreover, the α‐helix and β‐fold contents in the 4% AVGP group were significantly higher than those in the control group, indicating that the addition of an appropriate amount of AVGP can protect the secondary structure of MP. Therefore, AVGP could serve as a new food ingredient with antifreeze and antioxidant functions for frozen surimi.

Cryoprotective effect of epigallocatechin gallate replacing sucrose on Hypophythalmichthys molitrix surimi during frozen storage.

The present study aimed to investigate the cryoprotective effect of epigallocatechin gallate (EGCG) replacing sucrose on surimi during frozen storage. Substitution or partial substitution of 0.1% EGCG for sucrose (1.5%) was added to surimi, and the surimi samples without and with commercial cryoprotectants (4% sucrose and 4% sorbitol) were used as the control group. The results obtained suggest that, with the increase in frozen storage time, the structural performance of surimi protein gradually weakened (e.g. the decrease in the surface hydrophobicity, the increase in the total sulfhydryl and solubility, and the protein myosin heavy chain bands became shallow) and surimi gel quality gradually deteriorated (e.g. the decrease in water-holding capacity, gel strength and all texture profile attributes). However, compared with the other three group surimi samples during the frozen period, the surimi proteins with partial replacement of sucrose by EGCG had a higher total sulfhydryl group content and solubility of proteins, as well as lower surface hydrophobicity of protein, suggesting that the addition of EGCG as a partial substitute for sucrose can enhance the antifreeze ability of surimi. Meanwhile, the surimi gel with the partial replacement of sucrose by EGCG had a higher water retention capacity, gel strength and texture attributes (e.g. hardness, springiness, cohesiveness, chewiness, and resilience), indicating that the addition of EGCG as a partial substitute for sucrose can inhibit the deterioration of surimi gel quality. Overall, EGCG partially replacing sucrose can play an alternative cryoprotectant with a lower sweetness to prevent the quality of surimi from deteriorating. © 2024 Society of Chemical Industry.

Insight into the allergenicity and structure changes of parvalbumin from Trachinotus ovatus induced by dense-phase carbon dioxide

Parvalbumin (PV) is a major allergen in fish, and traditional treatments cannot reduce its sensitization. The effects of dense-phase carbon dioxide (DPCD) treatment on the sensitization and spatial structure of PV in Trachinotus ovatus were evaluated in this study. Western blotting and indirect ELISA were used to determine the allergenicity changes and spatial conformations of PV treated by DPCD. Tris-tricine-SDS-PAGE, circular dichroism, surface hydrophobicity, endogenous fluorescence, UV spectrophotometry, free amino group, total sulfhydryl group and SEM analyses were applied to characterize PV structure. The results showed that DPCD treatment (15 MPa, 30 min, 50 °C) could reduce PV-induced allergic reactions by 39–41 %, which destroyed the normal conformational epitopes and reduced the risk of PV-induced allergy. The secondary structure changed from ordered to disordered with a decreased content of α-helical groups, while the internal hydrophobic groups were exposed. The total sulfhydryl group content decreased significantly (P < 0.05). The surface hydrophobicity and ultraviolet absorption spectrum were enhanced, and the endogenous fluorescence peak shifted to a long wavelength. Meanwhile, the content of free amino groups increased significantly (P < 0.05). This study could provide a theoretical basis and a promising technical approach for reduction of PV allergenicities.

Fabrication of depolymerized zein films via high-intensity ultrasound for ethylene adsorption packaging

The aim of the study was to prepare depolymerized zein (D-zein) films for fruit packaging. High-intensity ultrasound (HIU) treatment was employed to stretch the chemical structure of zein protein, and improve the ethylene adsorption efficiency of D-zein films. The study of circular dichroism spectra, fluorescence spectra, particle size, zeta-potential, and total sulfhydryl group content revealed that the depolymerized zein had stretched structure via a moderate HIU treatment (400 W, 15 min). The structural, mechanical, barrier properties, ethylene adsorption efficiency, and application were used to analyze the performance of the D-zein films. In all treatment groups, bananas coated with the D-zein-15 film exhibited favorable browning rate, weight loss rate, flesh hardness, and sensory properties during storage at 25 °C for 10 d. The results indicated that depolymerized zein films could improve the ethylene adsorption efficiency and effectively prolong the shelf life of bananas.

Effect of cryoprotectants on physicochemical and structural changes in repeated freeze–thawed egg white protein

The effect of cryoprotectants on the changes of physicochemical and structural properties of egg white protein (EWP) caused by repeated freeze-thaw (F-T) cycles was investigated. The cryoprotectants (4% trehalose + 0.3% carrageenan, TC; 1% xylo-oligosaccharide + 0.3% carrageenan, XC; 4% trehalose + 1% xylo-oligosaccharide, TX) were added to the egg white, and stored at F-T for 1, 3, and 5 cycles. The freezing protection effect of cryoprotectants on EWP was discussed by detecting carbonyl contents, total sulfhydryl group content, surface hydrophobicity, water-holding capacity (WHC) of heat-induced gel, SDS-PAGE and the secondary and tertiary structure of protein. The results showed that cryoprotectants could effectively inhibit the increase in surface hydrophobicity and carbonyl contents, and restrict the decrease in total sulfhydryl group content, WHC of heat-induced gel and endogenous fluorescence intensity (p < 0.05). The results can provide reference for the application of cryoprotectants in frozen EWP using in food industry.

The influence of Klotho protein and prooxidant-antioxidant balance combination on the mortality of HD patients.

End-stage renal disease patients on chronic hemodialysis (HD) have a shortened life expectancy compared to the general population. The aim of this study was to evaluate a possible link between three new and emerging factors in renal pathophysiology: Klotho protein, telomere length in peripheral blood mononuclear cells (TL) and redox status parameters before HD (bHD) and after HD (aHD), and to test mortality prediction capability of these emerging parameters in a population of HD patients. The study included 130 adult patients with average age 66 (54-72), on HD (3 times per week; 4-5h per session). Klotho level, TL, routine laboratory parameters, dialysis adequacy and redox status parameters: advanced oxidation protein products (AOPP), prooxidant-antioxidant balance (PAB), superoxide anion (O2.-), malondialdehyde (MDA), ischemia-modified albumin (IMA), total sulfhydryl group content (SHG), and superoxide dismutase (SOD) were determined. Klotho concentration was significantly higher aHD; 68.2 (22.6-152.9) vs. bHD 64.2 (25.5-119.8) (p = 0.027). The observed increase in TL was not statistically significant. AOPP, PAB, SHG, and SOD activity were significantly increased aHD (p > 0.001). The patients with the highest mortality risk score (MRS) had significantly higher PAB bHD (p = 0.002). Significantly lower O2.- (p < 0.001), SHG content (p = 0.072), and IMA (p = 0.002) aHD were found in patients with the lowest MRS values. Principal component analysis revealed redox balance-Klothofactor as a significant predictor of high mortality risk (p = 0.014). Decreased Klotho and TL attrition as well as redox status disturbance could be connected with higher mortality rate in HD patients.

Oleic Acid Facilitates Cd Excretion by Increasing the Abundance of Burkholderia in Cd-Exposed Mice

As a global pollutant, cadmium (Cd) can easily enter the body through food chains, threatening human health. Most Cd is initially absorbed in the gut, with the gut microbiota playing a pivotal role in reducing Cd absorption and accumulation. This study assessed the effects of three fatty acids on Cd accumulation and toxicity in Cd-exposed mice. The results showed that oleic acid (OA) was the most effective in facilitating Cd excretion in mice among these fatty acids. The use of OA led to reduced Cd accumulation in the organs and increased Cd content in the feces. The metagenomic analysis of the gut microbiota showed that the genus Burkholderia was the most significantly restored by OA in Cd-exposed mice. Burkholderia cepacia, as the type species for the genus Burkholderia, also exhibited strong Cd tolerance after treatment with OA. Furthermore, the electron microscopy analysis showed that most of the Cd was adsorbed on the surface of B. cepacia, where the extracellular polymeric substances (EPSs) secreted by B. cepacia play a key role, displaying a strong capacity for Cd adsorption. The peak at 2355 cm-1 and the total sulfhydryl group content of EPSs showed significant increases following co-treatment with Cd and OA. The results demonstrated the potential roles that gut Burkholderia may play in OA-mediated Cd excretion in mice.

Modification of functional properties of mussel actomyosin by ultrasound treatment and the appplication at O/W emulsion

Effects of ultrasonication (0 W, 150W, 300 W, 450 W, 600 W) for 16 min on the functional properties of mussels actomyosin (MAP) and the application at oil-in-water emulsion were investigated. Ultrasonication modified the physicochemical properties of MAP, consequently improving the emulsifying properties of MAP. Particle size and total sulfhydryl group content of ultrasonicated MAP decreased. However, free sulfhydryl content, absolute zeta-potential (from 17.18 to 41.00) and surface hydrophobicity increased. Ultrasonication improved solubility (from 38.5% to 57.1%) and emulsifying properties of MAP. In addition, the interfacial tension of MAP after ultrasonic treatment was reduced, which improved its adsorption rate at the oil-water interface (from 14.5% to 32.8%). Rheological properties of emulsion were improved after ultrasonication at 300 W. However, when the ultrasonic power increased from 300 W to 600 W, the emulsifying properties of MAP of the emulsion decreased. This may be due to excessive ultrasound treatment leading to protein aggregation and larger particle size, thereby reducing the protein adsorption rate at the oil-water interface. The results of this research suggested that ultrasound treatment has great potential in modifying emulsifying properties of shellfish muscle proteins, and ultrasound treatment at 20 kHz, 300W for 16 min was the optimum condition for modification.

Effect of ultrasonic thawing on the physicochemical properties, freshness, and protein-related properties of frozen large yellow croaker (Pseudosciaena crocea).

Ultrasonic treatment (UT) was used to thaw large yellow croaker in this study, and the effect of various ultrasonic power levels on the quality of large yellow croaker was evaluated after thawing. The effects of ultrasonic on water holding capacity (WHC), moisture distribution, thiobarbituric acid-reactive substance (TBARs), total volatile base nitrogen (TVB-N), ATP degradation (related to K value), surface color change, free amino acid (FAA) content, total sulfhydryl group (SH) content, Fourier transform infrared absorption spectra (FT-IR), fluorescence emission spectra, and microscopic observations of large yellow croaker myofibrillar proteins were investigated. The thawing times of the control sample, 200UT, 240UT, 280UT, and 320UT samples were 1750, 1190, 810, 580, and 570 s, respectively, which indicated that ultrasonic radiation could improve thawing efficiency. Additionally, ultrasonic thawing maintained better freshness and color and inhibited lipid oxidation. Compared with fresh samples, the TVB-N of large yellow croaker thawed by ultrasonication increased by 12.68%, and the K value increased by 0.9%. The 240UT sample had tightly arranged myofibrils and fewer changes in the structures of myogenic fibrillar proteins than the fresh samples, and the SH content of 240UT was decreased by 8.17%. Use of excessive ultrasonic power (320 W) damaged the protein microstructure and the microstructure of large yellow croaker. In conclusion, sample 240UT maintained the quality of large yellow croaker better with minimal damage, which is recommended for rapid thawing. PRACTICAL APPLICATION: Ultrasonic waves improve the thawing efficiency of large yellow croaker and maintain the freshness and color of the fish. According to results, sample 240UT exhibited slight changes in the structure of the myofibril protein, but excessive ultrasonic power destroyed the microstructure and protein structure. Appropriate ultrasonic treatment to the thawing of fish has good prospects.

Rice Bran Hydrolysates Minimize Freeze-Denaturation of Washed Fish Mince during Extended Freeze-Thaw Cycles

ABSTRACT Rice bran hydrolysate (RBH) was produced from hexane-defatted rice bran using subcritical alkaline water followed by enzymatic hydrolysis (Protease G6 at 2% for 6 hr). The RBH was added to Pacific whiting washed mince. The physicochemical and rheological properties of the mince with and without RBH or commercial cryoprotectants (sucrose-sorbitol (S/S)) were evaluated after 0, 7, and 14 freeze-thaw (FT) cycles. The protein solubility and total sulfhydryl group content of all samples decreased as the number of FT cycles increased, while surface hydrophobicity increased. Samples prepared with 2% RBH mixed with 4% S/S (RBH+S/S) and 2% RBH exhibited higher total sulfhydryl group content and protein solubility than 8% S/S and a control. Samples prepared with RBH+S/S and 2% RBH exhibited lower surface hydrophobicity than control but slightly higher than 8% S/S sample. The elastic modulus (G′) of samples prepared with RBH and S/S was higher than that of the control. After gelation was completed, the sample with RBH+S/S showed the highest G′. RBH showed a significant ability to maintain the quality of frozen fish proteins, especially when blended with S/S. This study suggests RBH can effectively protect fish myofibrillar proteins from denaturation during frozen storage and further contribute to reducing sugar/sorbitol.

Effect of ultrasound pretreatment on structural, physicochemical, rheological and gelation properties of transglutaminase cross-linked whey protein soluble aggregates

A solution (10%, w/v) of whey protein soluble aggregates (WPISA) was pretreated with high-intensity ultrasound (HUS, 20 kHz) for different durations (10–40 min) before incubation with transglutaminase (TGase) to investigate the effect of HUS on the structural, physicochemical, rheological, and gelation properties of TGase cross-linked WPISA. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results showed that HUS increased the amounts of high-molecular-weight polymers/aggregates in WPISA after incubation with TGase. HUS significantly increased (P < 0.05) the degree of TGase-mediated cross-linking in WPISA, as demonstrated by a reduction in free amino group contents. HUS significantly increased (P < 0.05) the particle size, intrinsic fluorescence intensity, and surface hydrophobicity of TGase cross-linked WPISA, but had no significant impact (P > 0.05) on the zeta-potential or total free sulfhydryl group content of TGase cross-linked WPISA. The apparent viscosity and the consistency index of TGase cross-linked WPISA were significantly increased by HUS (P < 0.05), which indicated that HUS facilitated the formation of more high-molecular-weight polymers. HUS significantly increased (P < 0.05) the water holding capacity and gel strength of glucono-δ-lactone (GDL)-induced TGase cross-linked WPISA gels. The results indicated that HUS could be an efficient tool for modifying WPISA to improve its degree of TGase-mediated cross-linking, which would lead to improved rheological and gelation properties.

Effects of Gallic Acid by Ultrasound on Physicochemical Properties of Lateolabrax Japonicas Myofibrillar Protein

The effects of different concentrations of gallic acid (0 mg/g, 1 mg/g, 2 mg/g, 4 mg/g, and 6 mg/g) on the physicochemical properties of Lateolabrax japonicas myofibrillar protein were studied with 400 W ultrasound. The results showed that gallic acid decreased the particle size, total sulfhydryl group, carbonyl and dimer tyrosine content and Ca2+-ATPase activity (P&lt;0.05) of myofibrillar protein, however, increased the zeta potential. Ultrasonic wave could cooperate with gallic acid to slow down protein oxidation and make the protein solution system more stable. When the concentration of gallic acid was 2 mg/g, the indicators of protein solution were most favorable, which improved the properties of protein.

Impact of chitosan-based coatings on myofibrillar protein denaturation, muscle microstructure and lipid oxidation of oyster (Crassostrea hongkongensis) during 0 °C storage

ABSTRACT The changes in myofibrillar protein, muscle microstructure, and lipid oxidation of oysters (Crassostrea hongkongensis) treated with chitosan-based coatings (CP-0°C) or aseptic water (CG-0°C) for 20 days storage at 0°C were investigated. Compared to the CG-0°C at day 20, the higher total sulfhydryl group content (83.24%), unfrozen water content (39.24%), and Ca2+-ATPase activity (96.79%) along with the lower myofibrillar protein solubility (80.15%) indicated that CP-0°C protected oysters from protein denaturation. Similarly, the CP-0°C better maintained muscle microstructure shown by the relatively higher quality of muscle and less ice crystals. Meanwhile, CP-0°C prevented lipid hydrolysis and oxidation, as evidenced by the lower contents of fatty acid (FA) content (total content of 12.16 ± 1.02 mg/g wet weight at day 20), peroxide value (POV) (15.13 meq oxygen/Kg lipid at day 20), and thiobarbituric acid-reactive substances (TBARS) (1.79 mg MDA eq/Kg sample at day 20) in CP-0°C. These results imply that CP-0°C could protect the quality of chilled oysters stored at 0°C.

Effect of Atmospheric Pressure Cold Plasma on Biophysical Properties and Aggregation of Natural Actomyosin from Threadfin Bream (Nemipterus bleekeri)

Biophysical properties and aggregation of natural actomyosin (NAM) from threadfin bream (Nemipterus bleekeri) subjected to atmospheric pressure cold plasma (APCP) treatment with different contact times were determined. Protein solubility, turbidity, Ca2+-ATPase activity, total sulfhydryl (SH) group content, protein carbonyl content, and SDS-PAGE were monitored. With increasing APCP contact times (from 0 to 30 min), total SH group content (5.74–3.77 mol/105 g protein), Ca2+-ATPase activity (0.32–0.23 μmol Pi/mg protein/min), and solubility (100–92%) of NAM decreased, while protein carbonyl content (1.43–36.47 μmol/g protein) increased to a higher extent. During APCP treatment, cross-linking via disulfide bond as visualized by SDS-PAGE along with increased turbidity of NAM was observed. Therefore, APCP treatment markedly induced biophysical changes and aggregation of NAM which can be used as a possible approach to strengthen the gel formation of threadfin bream surimi.

Optimization of Enzymatic Hydrolysis Process of Antarctic Krill and Cryoprotective Effect of Enzymatic Hydrolysates on Oyster Meat

In order to develop a safe and efficient non-phosphorus antifreeze agent,enzymatic hydrolysates of Antarctic krill were prepared to evaluate their cryoprotective effects,providing basic data for the development of new antifreeze agents.The alkaline protease was screened from the four proteases as experimental enzymes,and the enzymatic hydrolysis process was optimized by single factor experiment and orthogonal experiment. The freezing protection of oyster meat by enzymatic hydrolysates of Antarctic krill was studied with the indexes of the water loss rate,salt-soluble protein content,total sulfhydryl group content and Ca2+-ATPase activity.The results showed that the optimum conditions for enzymatic hydrolysis of Antarctic krill by alkaline protease were as follows:Temperature 55℃,pH8.5,enzyme dosage 2.6%,enzymatic hydrolysis time 5 h. Under these conditions,the relative molecular weight of enzymatic hydrolysates of Antarctic krill mainly distributed in the range of 100~5500 Da,accounting for 79.69% of the total enzymatic hydrolysates. The enzymatic hydrolysate of Antarctic krill could inhibit the loss of water after freezing storage,retard the decrease of salt-soluble protein content,Ca2+-ATPase activity and total sulfhydryl content,and its effect was better than that of phosphorus-containing antifreeze agent.Therefore,the enzymatic hydrolysate of Antarctic krill had freezing protection activity,which could be further separated and identified.

Thiram-induced cytotoxicity and oxidative stress in human erythrocytes: an in vitro study

Tetramethylthiuram disulfide, commonly known as thiram, is an organosulfur compound which is used as a bactericide, fungicide and ectoparasiticide to prevent disease in seeds and crops. Being a fungicide there is a high probability of human occupational exposure to thiram and also via consumption of contaminated food. In this work, the cytotoxicity of thiram was studied under in vitro conditions using human erythrocytes as the cellular model. Erythrocytes were incubated with different concentrations of thiram (25–500 μM) for 4 h at 37 °C. Control cells (thiram untreated) were similarly incubated at 37 °C. Whole cells and hemolysates were analyzed for various biochemical parameters. Treatment of erythrocytes with thiram increased protein and lipid oxidation and hydrogen peroxide level in hemolysates but decreased glutathione and total sulfhydryl group content. This was accompanied by hemoglobin oxidation, heme degradation and release of free iron. Activities of all major antioxidant enzymes were inhibited. The antioxidant power of thiram treated erythrocytes was lowered resulting in decreased metal reducing and free radical quenching ability. These results suggest that thiram enhances the generation of reactive species that cause oxidative modification of cell components. This was confirmed by experiments that showed enhanced generation of reactive oxygen and nitrogen species in thiram treated erythrocytes. Activities of marker enzymes of glucose metabolism and erythrocyte membrane were also inhibited. All effects were seen in a thiram concentration-dependent manner. Electron microscopy further supported the damaging effect of thiram on erythrocytes. Thus thiram induces oxidative stress condition in human erythrocytes and causes oxidative modification of cell components.

Effect of apple peel extract as natural antioxidant on lipid and protein oxidation of rainbow trout (Oncorhynchus mykiss) mince

The aim of this study was to use apple peel extract (APE) as antioxidant for inhibition of lipid and protein oxidation in rainbow trout (Oncorhynchus mykiss) mince during refrigerated storage. Apple peel extract had high 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azinobios-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and hydroxyl radical scavenging activity and ferric reducing antioxidant power (FRAP) comparable to ascorbic acid. Lipid oxidation was effectively inhibited in mince during 96 h of refrigerated storage as indicated by significantly lower peroxides and thiobarbituric acid-reactive substances (TBARS) (P < 0.05) compared to control. APE could reduce protein oxidation as evidenced by lower protein carbonyls and higher total sulfhydryl group content (P < 0.05) compared to control. This was coincidental with higher polyunsaturated fatty acids (PUFA)/saturated fatty acids (SFA) and eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA)/palmitic acid (C16:0) ratio in mince with added apple peel extract, especially at 20 mg of gallic acid equivalent/kg mince. Apple peel extract retarded fish mince lipid and protein oxidation during refrigerated storage and might be considered as natural antioxidant in rainbow trout mince.

Ultrasound treatment improved the physicochemical characteristics of cod protein and enhanced the stability of oil-in-water emulsion.

Effects of ultrasonic pretreatment on the physicochemical changes of cod protein and the characteristics of subsequent oil-in-water emulsions were investigated. Ultrasonic treatment led to a reduction of particle size of cod protein. With increasing ultrasonic power, a significant increase in surface hydrophobicity of cod protein was found, due to the decrease of aggregates size as well as protein conformational changes of protein, but a decrease in total sulfhydryl group content was observed, probably because of the formation of disulfide bonds. Ultrasonic pretreatment promoted the adsorption of cod protein on oil droplets, resulting in higher ratios of adsorbed proteins. Diagonal electrophoresis illustrated that larger aggregates in adsorbed proteins were composed of cod actin. Reducing SDS-PAGE showed that adsorbed proteins contained a large amount of cod actin and two faint bands of light chains of myosin, and non-adsorbed proteins were composed of actin, tropomyosin, and the three light chains of myosin. More homogenous microstructures with smaller size of oil droplets were observed for the emulsions stabilized by higher intensity ultrasound treated cod protein, and the coalescence effect was improved obviously. The enhancement of the stability of cod protein coated-oil emulsions might be due to the smaller size of oil droplets and reduced oil droplets attraction by higher ratios of adsorbed proteins.

Antigenicity of β-lactoglobulin reduced by combining with oleic acid during dynamic high-pressure microfluidization: Multi-spectroscopy and molecule dynamics simulation analysis

Some food components can modulate the antigenicity of β-lactoglobulin (β-LG). This study investigated the role of oleic acid (OA) in reducing the antigenicity of β-LG. The results indicate the antigenicity of β-LG gradually decreased from 15 (sample with no OA) to 9.86, 7.51, and 6.01 µg/mL when interacting with OA during dynamic high-pressure microfluidization treatment at 0.1, 80, and 160 MPa. Although binding sites (n) of β-LG combined with OA at 0.1, 80, and 160 MPa decreased from 0.79 to 0.5 and 0.66, β-LG had a higher binding affinity (Ka) to OA than that of untreated β-LG. The values of Ka for β-LG/OA at 0.1, 80, and 160 MPa were 5.51 × 106, 17.43 × 106, and 49.75 × 106M-1, respectively. The molecule dynamic simulation showed that the OA molecules located at both β-barrel (site 1) interacted with Lys60, Glu62, and Lys69 and outer surface site 2 consisting of Tyr20, Tyr42, Ser21, Glu157, and His161. Additionally, when binding with OA during the dynamic high-pressure microfluidization treatment, the conformation of β-LG changed, reflected by the decrease of fluorescence intensity and total sulfhydryl group content, the increase of surface sulfhydryl group content, and secondary structure changes of β-LG. These results deduce that some epitopes may be masked by OA or modified by the conformational changes, resulting in the decline of antigenicity of β-LG molecules.

Combined effect of CaCl2 and high pressure processing on the solubility of chicken breast myofibrillar proteins under sodium-reduced conditions

The combined effect of calcium chloride (CaCl2) (20–100 mM) and high pressure processing (HPP, 200 MPa) on the solubility of myofibrillar proteins (MP) was investigated under sodium-reduced conditions (0.3 M sodium chloride). The results revealed that HPP combined with low concentrations (<40 mM) of CaCl2 synergistically increased the solubility of MP, but an antagonistic effect occurred when a high concentration (100 mM) of CaCl2 was present. This synergistic effect could be attributed to a mildly destabilized conformation of myosin, an increased surface hydrophobicity and the decreased total sulfhydryl group content of MP. However, CaCl2 at 100 mM destabilized myosin to a larger extent and induced non-disulfide covalent cross-linking of S-1 subfragment in pressurized MP, thus attenuating the solubilizing effect of HPP on the myosin heavy chain, resulting in the antagonistic effect. Therefore, HPP in combination with low-level CaCl2 (<40 mM) may improve the functional properties of sodium-reduced meat products.