Sulphydryl Group Content Research Articles

Effects of thermal treatment on the physicochemical and structural properties of wheat gluten proteins: insights from gluten, glutenin, and gliadin fractions

SummaryThis study examined changes in heat‐induced gluten proteins, focusing on their structure, physicochemical properties, and molecular analysis. The results demonstrated that gliadin had a high denaturation temperature (68.04 °C) and minimal aggregation during heating (25 °C–95 °C), yet it hindered thermal reaction progress of gluten effectively. Heating caused a shift from α‐helical structure to random coil and β‐turn structures, with a decrease in fluorescence intensity. High temperature reduced sulphydryl groups in gluten and glutenin, reaching 0.64 and 0.58 mmol L−1, respectively. However, the content of sulphydryl groups in gliadin remained relatively stable at around 0.37 mmol L−1. Notably, the configuration of disulphide bonds in gliadin, particularly in the g‐g‐g configuration, displayed greater stability. Microstructure analysis revealed increased compactness in all protein fractions as temperature rose. Overall, gliadin had greater thermal stability, impeding glutenin aggregation and gluten network formation. These findings provide valuable insights for cooking, processing, and storage of gluten proteins.

Structural characterization and functional properties of egg white protein treated by electron beam irradiation

This study investigated the functional properties and structural characteristics of egg white protein (EWP) powder treated by electron beam irradiation (EBI) at the doses of 5, 10, 20, 30, 50, 70 and 100 kGy. In comparison with the untreated sample (0 kGy), the EBI-induced EWP showed generally better solubility and higher antioxidant capacity by ABTS•+ radical scavenging assay. Furthermore, the emulsifying activity index of EBI-induced EWP increased with increased EBI dose, reaching the maximum value of 15.8 ± 0.4 m2/g at 100 kGy. The emulsifying stability index and ϛ-potential of EBI-induced EWP showed fluctuating tendencies. These functional property changes of protein were attributed to the conformational changes caused by EBI. SDS-PAGE patterns confirmed that high-dose EBI would result in protein depolymerization to low-mass molecules at 11 kDa, contributing to the increased solubility. Circular dichroism data demonstrated that EBI-induced EWP exhibited partial denaturation and a flexible structure, which was responsible for the improved emulsifying properties. Fluorescence spectra revealed that high EBI doses led to an increase in the polar environment around tryptophan, which could enhance the solubility and antioxidant activity of EWP. In addition, high EBI doses decreased the content of free and total sulphydryl groups, and changed the intermolecular forces of protein, including ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bonds. These findings can provide solid support for practical applications of EBI technology in EWP food processing.

Effects of innovative gelation and modified tapioca starches on the physicochemical properties of surimi gel during frozen storage

SummaryThis study presented a comparative evaluation of the effects of 5% tapioca starch, acetylated distarch phosphate and hydroxypropyl distarch phosphate (HPDSP) on the changes in surimi gel quality after the traditional gelation procedure (suwari‐cooking‐freezing) and a novel gelation procedure (suwari‐freezing‐cooking, SFC). Overall, subjected to the SFC procedure, lower hydrophobic interactions, lower total sulphydryl group content, higher disulphide bond content and a more orderly protein conformation was observed in the HPDSP‐surimi gel. These changes resulted in smaller drip loss, stabler breaking force and deformation, and less structural damage during frozen storage. Since the strongest hydrophilicity of HPDSP and the lowest gelatinisation temperature (63.15 °C), when it was reheated and then gelatinized, it interacted more closely with the protein. These findings indicated that subjected to the SFC procedure, the addition of 5% HPDSP effectively decreased the changes in the quality of the surimi gel.

Optimization of High Hydrostatic Pressure Treatments on Soybean Protein Isolate to Improve Its Functionality and Evaluation of Its Application in Yogurt.

This work aimed to improve the functional properties of soybean protein isolate (SPI) by high hydrostatic pressure (HHP) and develop SPI incorporated yogurt. Response surface methodology (RSM) was used to optimize the HHP treatment parameters, including pressure, holding time, and the ratio of SPI/water. Water holding capacity, emulsifying activity index, solubility, and hardness of SPI gels were evaluated as response variables. The optimized HPP treatment conditions were 281 MPa of pressure, 18.92 min of holding time, and 1:8.33 of SPI/water ratio. Water and oil holding capacity, emulsifying activity, and stability of SPI at different pH were improved. Additionally, relative lipoxygenase (LOX) activity of HHP treated SPI (HHP-SPI) was decreased 67.55 ± 5.73%, but sulphydryl group content of HHP-SPI was increased 12.77%, respectively. When incorporating 8% of SPI and HHP-SPI into yogurt, the water holding capacity and rheological properties of yogurt were improved in comparison with yogurt made of milk powders. Moreover, HHP-SPI incorporated yogurt appeared better color and flavor.

Effects of the enzymatic hydrolysis treatment on functional and antioxidant properties of quinoa protein acid-induced gels

Partial enzymatic hydrolysis is frequently used as strategy to improve the functional and nutritional properties of vegetable proteins. The aim of this work was to evaluate the hydrolysis of quinoa proteins, as well as the functional and antioxidant properties of their acid-induced gels. In order to fulfil this purpose, quinoa protein hydrolysates were obtained using a fungal serin protease. The hydrolysis degree, surface hydrophobicity, sulphydryl group content and the electrophoretic profile of hydrolysates were assayed. Hydrolyzed quinoa protein acid-induced gels were carried out and gels obtained were tested for their textural characteristics, water holding capacity, appearance (color and microstructural properties) as well as for their in vitro antioxidant activity. The changes occurring during the enzymatic hydrolysis affected the gel-forming ability of quinoa proteins and therefore the characteristics of gels. After 3 h of proteolysis, protein hydrolysates with 17 ± 2% hydrolysis degree and low surface hydrophobicity were obtained. Gels obtained of these hydrolysates presented less interconnected protein network and thus, lower textural parameters and lower water holding capacity than control gels. In conclusion, even though the hydrolysis treatment negatively affects the gelling properties of the quinoa proteins, limited hydrolysis enables us to obtain gels with antioxidant capacities which present differential characteristics.

Physical properties and chemical forces of extruded corn starch fortified with soy protein isolate

SummaryThe effect of soy protein addition on physical properties of extruded corn starch was studied. The correlations between the chemical bonds in proteins and the physical properties of extrudates were analysed. Increasing soy protein isolate content resulted in higher expansion ratio (ER) but lower bulk density (BD), hardness, water solubility index (WSI), degree of starch gelatinisation (DSG), content of sulphydryl (SH) groups and protein solubility in phosphate buffer. In the other hand, increasing the processing temperature resulted in higher ER, water absorption index, DSG, contents of the SH group and disulphide (SS) bond but in lower specific mechanical energy, BD, hardness and WSI. The results indicated that changes in the chemical bonds in proteins had a significant effect on the apparent physical properties of extrudates. More protein–protein and protein–starch cross‐linking reactions occurred through new chemical linkages, such as the nondisulphide covalent bonds and hydrogen bonds, which are beneficial to the expansion of starch‐based products.

Effects of ultrasound treatment on physicochemical and emulsifying properties of whey proteins pre- and post-thermal aggregation

The aim of this study was to determine the effect of high intensity ultrasound on physicochemical and emulsifying properties of thermally aggregated whey proteins. Whey protein isolate (WPI) solutions were sonicated for 20 min using an ultrasonic probe (frequency: 20 kHz; amplitude: 20%) pre- and post-thermal treatment (85 °C for 30 min). Changes in particle size, zeta-potential, surface hydrophobicity, free sulphydryl group content, turbidity, thermal denaturation properties, rheological properties, and emulsifying properties were studied. Soluble aggregates prepared with ultrasound treated post-thermal aggregation resulted in significantly smaller particle size and broader size distribution compared with those prepared by untreated or ultrasound treated pre-thermal aggregation (P < 0.05). It was suggested that surface hydrophobicity of the soluble aggregates was significantly increased by ultrasound applied post-thermal aggregation (P < 0.05). There was a significant reduction in turbidity of whey protein solutions by ultrasound applied post-thermal aggregation (P < 0.05). The apparent viscosity of whey protein soluble aggregate model systems has been decreased significantly by ultrasound pre- and post-thermal aggregation (P < 0.05). Emulsion activity index and emulsion stability index of soluble aggregates were increased significantly by ultrasound applied post-thermal aggregation (P < 0.05). There were no significant changes in zeta-potential, total free sulphydryl group by ultrasound either pre-or post-thermal aggregation (P > 0.05). We conclude that ultrasound treatment on post-thermal aggregation has improving effect on physiochemical and emulsifying properties of whey protein soluble aggregates for potential industrial applications.

Combined effect of squid ink tyrosinase and tannic acid on heat induced aggregation of natural actomyosin from sardine

The mixture of squid ink tyrosinase (SIT) at 300 and 500 U/g protein and tannic acid (TA) at 0.5 and 1% (based on protein) increased the turbidity and surface hydrophobicity of natural actomyosin (NAM) from sardine (Sardinella albella) in a dose dependent manner. Total sulphydryl group content decreased in the NAM solutions with coincidental increase in disulphide bond content, when added with SIT/TA mixture. Ca2+-ATPase activity was also lower in NAM solutions added with SIT/TA mixture. Higher aggregation of protein filaments was noticeable in NAM added with SIT at 500 U/g protein and 1% TA, which also had the highest storage modulus (G′) and largest particle size. Negative charge of NAM was decreased when SIT/TA mixture was incorporated. Therefore the mixture of SIT and TA, particularly at higher level, could be used as the novel protein cross-linker in fish mince and surimi.

Optimization of arachin extraction from defatted peanut (Arachis hypogaea) cakes and effects of ultra-high pressure (UHP) treatment on physiochemical properties of arachin

A process for the optimization of arachin from defatted peanut cakes had been developed. The process included pre-treatment, extraction by Tris–HCl buffer solution, pH adjustment and final separation by centrifugation. A Box–Behnken design including independent variables such as extraction temperature (x1), extraction pH (x2) and liquid–solid ratio (x3) was used. The variable with the largest effect was extraction pH. The optimum extraction conditions were found to be extraction temperature 56.0°C, extraction pH 8.7 and liquid–solid ratio 14:1, under which the arachin yield could reach 310.4g/kg defatted peanut cakes. The effect of ultra-high pressure treatment on the physiochemical properties of arachin was also evaluated. After processing, solubility, emulsifying activity, emulsifying stability and surface hydrophobicity changed significantly. The content of free sulphydryl groups, which were often associated with aggregation and gelation of proteins, also decreased. All the processes widened the utilization of by-products generated from oil extraction as a source of protein in human diet.

Modulation of cardiac mitochondrial permeability transition and apoptotic signaling by endurance training and intermittent hypobaric hypoxia

BackgroundModulation of the mitochondrial permeability transition pore (MPTP) and inhibition of the apoptotic signaling are critically associated with the cardioprotective phenotypes afforded by both intermittent hypobaric-hypoxia (IHH) and endurance-training (ET). We recently proposed that IHH and ET improve cardiac function and basic mitochondrial capacity, although without showing addictive effects. Here we investigate whether a combination of IHH and ET alters cardiac mitochondrial vulnerability to MPTP and related apoptotic signaling. MethodsMale Wistar rats were divided into normoxic-sedentary (NS), normoxic-exercised (NE, 1h/day/5week treadmill-running), hypoxic-sedentary (HS, 6000m, 5h/day/5weeks) and hypoxic-exercised (HE) to study susceptibility to calcium-induced cardiac MPTP opening. Mitochondrial cyclophilin D (CypD), adenine nucleotide translocator (ANT), Bax and Bcl-2 protein contents were semi-quantified by Western blotting. Cardiac caspase 3-, 8- and 9-like activities were measured. Mitochondrial aconitase and superoxide dismutase (MnSOD) activity and malondialdehyde (MDA) and sulphydryl group (–SH) content were determined. ResultsSusceptibility to MPTP decreased in NE and HS vs. NS and even further in HE. The ANT content increased in HE vs. NS. Bcl-2/Bax ratio increased in NE and HS compared to NS. Decreased activities in tissue caspase 3-like (HE vs. NS) and caspase 9-like (HS and HE vs. NS) were observed. Mitochondrial aconitase increased in NE and HS vs. NS. No alterations between groups were observed for caspase 8-like activity, MnSOD, CypD, MDA and –SH. ConclusionsData confirm that IHH and ET modulate cardiac mitochondria to a protective phenotype characterized by decreased MPTP induction and apoptotic signaling, although without visible addictive effects as initially hypothesized.

Changes in the content of free sulphydryl groups during postharvest wheat and flour maturation and their influence on technological quality

The main aim of this study was to determine the changes in free sulphydryl content during postharvest wheat and flour maturation. The content of free sulphydryl groups was determined from wet gluten over 50 days of wheat postharvest maturation and over 14 days of flour maturation by varying incubation temperatures (30 and 37 °C) and incubation times (0, 45, 90 and 135 min). The amount of free sulphydryl groups increased during postharvest wheat and flour maturation as well as with the increase in temperature and gluten incubation time. The additional aim of this study was to find the interrelation between the content of free sulphydryl groups and selected parameters of technological quality by means of Principal Component Analysis. During wheat/flour maturation, the strengthening of protein structure was observed manifested by the increase in gluten index and Mixolab protein network weakening (C2), and changes in dough resistance as well. The incubation temperature of 37 °C affected the weakening of protein structure manifested by the decrease in gluten index and resistance, and increase in extensibility. Strong differentiation of examined varieties in terms of selected quality indicators was observed upon pre-defined maturation period, probably due to the expression of their intrinsic properties.

Effect of freeze–thaw cycles on the molecular weight and size distribution of gluten

Freezing processing is widely used in food industry, but some key scientific issue is still unclear. In this paper, the effects of freeze–thaw cycles on the molecular weight, radius of gyration, free amino group content, free sulphydryl group content and molecular conformation of gluten were investigated by size-exclusion chromatography in conjunction with multi-angle laser light scattering (SEC–MALLS), spectrophotometry and atomic force microscopy (AFM). The results showed that during the freeze–thaw cycles (frozen at −18°C with cycling to 0°C for 12h and then back to −18°C per 10days) the molecular weight and radius of gyration of the gluten proteins decreased with the increase in freeze–thaw cycles, implying a depolymerisation in the high-molecular-weight fraction of the gluten. The free amino group content changed only slightly, and the free sulphydryl group content of the gluten increased from 9.8μmol/g for the control to 13.87μmol/g for the gluten stored for 120days and submitted to 12 times freeze–thaw cycling, indicating that the depolymerisation of the gluten during freeze–thaw cycling was due to the breakage of disulphide bonds. AFM images showed that the gluten chain formed a fibril-like branched network which was weakened with increasing freeze–thaw cycles storage time. Some aggregation of the gluten chains was also observed in the AFM images.

Cryoprotectants Reduce Protein Oxidation and Structure Deterioration Induced by Freeze-Thaw Cycles in Common Carp (Cyprinus carpio) Surimi

The objective of the present study was to investigate the effects of a cryoprotectant (a mixture of sucrose and sorbitol) on protein and lipid oxidation and structural changes in common carp (Cyprinus carpio) surimi subjected to different numbers of freeze-thaw (FT) cycles. Increased numbers of FT cycles were accompanied by increases in carbonyl content and thiobarbituric acid-reactive substances values and concomitant decreases in sulphydryl group (P<0.05) content, revealing that multiple FT cycles could cause protein and lipid oxidation in the carp tissue. Myofibrillar protein isolated from FT surimi also showed a reduced ATPase activity (P<0.05), increased hydrophobicity (P<0.05), and enhanced susceptibility to thermal aggregation. The addition of cryoprotectants significantly inhibited carbonyl formation and lipid oxidation (P<0.05), and its good protective effect on protein denaturation was demonstrated by its efficacy in maintaining Ca-ATPase activity, reducing the rapid exposure of hydrophobic and sulphydryl groups on the protein surface, and decreasing the degree of protein aggregation. Overall, the use of cryoprotectants reduced protein oxidation and structural deterioration induced by freeze-thaw in common carp surimi.

Effect of Astaxanthin Supplementation on Paraoxonase 1 Activities and Oxidative Stress Status in Young Soccer Players

The purpose of the study was to examine the effects of astaxanthin (Asx) on paraoxonase (PON1) activities and oxidative stress status in soccer players. Forty soccer players were randomly assigned in a double-blind fashion to Asx and placebo (P) group. Blood samples were obtained before, 45 and 90 days after supplementation. PON1 activity was assessed by using two substrates: paraoxon and diazoxon. The oxidative stress biomarkers were also examined: total sulphydryl group content (-SH groups), thiobarbituric acid-reactive substances (TBARS), advanced oxidation protein products and redox balance. The significant interaction effect of supplementation and training (p < 0.05) on PON1 activity toward paraoxon was observed. The PON1 activity toward diazoxon increased in Asx group after 90 days (p < 0.01), while there was no significant difference in P group. SH groups content rose from pre- to post-supplementation period only in Asx group (supplementation and training, p < 0.05; training, p < 0.01). TBARS levels decreased after 45 days and increased after 90 days of regular soccer training in both groups (training, p < 0.001). Redox balance decreased significantly in response to the regular training, regardless of treatment group (training, p < 0.001). Asx supplementation might increase total SH groups content and improve PON1 activity through protection of free thiol groups against oxidative modification.

Influence of time and chloride ions on the interaction of cisplatin with human albumin in-vitro.

The interaction of cis-dichlorodiammineplatinum (II) (cisplatin) with human serum albumin (HSA), dissolved in phosphate buffer with or without sodium chloride (0.1 M) has been examined at pH 7.4 and mu = 0.154. Equal volumes of cisplatin and HSA solutions were incubated at 37 degrees C for various times and filterable platinum concentrations versus time measured by flameless atomic absorption spectrophotometry. Binding kinetics differed depending on the buffer solutions used and on the time elapsing between cisplatin dissolution and outset of incubation with HSA. Experimental data were fitted to a theoretical equation used to calculate the number of nucleophilic sites per HSA molecule. Titrations of the HSA sulphydryl group content before and after incubation with a cisplatin solution were made, from which it was shown that the lone SH-group of the HSA macromolecule is involved in cisplatin binding. We also studied HSA's sensitivity towards denaturing agents when it was complexed with cisplatin. This sensitivity was decreased upon cisplatin binding. Also, the binding capacities of HSA and the HSA-Pt(II) complex to both tryptophan and warfarin were compared to determine the possible influence of cisplatin upon the binding to HSA of other drugs; this influence was negligible.

Purification and Characterizaion of Buffalo Brain Cystatin

Cystatins are thiol proteinase inhibitors ubiquitously present in mammalian body and serve various important physiological functions. To purify and characterize Thiol protease inhibitor from buffalo brain and to compare its properties with respect to tissue and organ difference from other mammalian cystatins. Inhibitor has been isolated and purified using alkaline treatment; ammonium sulphate fractionation and gel filtration chromatography on Sephadex G-75 with a % yield of 64.13 and fold purification of 384.72.The inhibitor was studied by U.V and fluorescence spectroscopy. Papain inhibitory activity was measured using casein as substrate. The molecular weight of the buffalo brain cystatin (BC), determined by gel filtration and SDS PAGE came out to be 43.6 KDa and 44.20 KDa respectively. BC was found to be stable in broad pH and temperature range. The inhibitor was devoid of any sulphydryl group and carbohydrate content. These properties led to conclusion that BC is variant of type-I cystatin. The stokes radius and diffusion coefficient of the inhibitor were found to be 27 A° and 8.1 x 10⁻⁷ cm²/sec respectively, the f/f₀ ratio was 1.12 signifying that purified cystatin is nearly globular in shape. Kinetic data revealed binding stoichiometry of BC with papain as 1:1. The Ki value with papain ficin and bromelain were found to be 1, 1.85 and 2.25 nM respectively suggesting that cystatin has higher affinity with papain as compared to ficin and bromelain. The fluorescence and UV spectra of BC- papain complex showed significant conformational changes indicative of perturbation in the micro environment of aromatic amino acid residues on the formation of complex. This work proliferates our knowledge about cystatins of the mammalian brain on the basis of their physiochemical properties.

Protein molecular interactions involved in the gel network formation of fermented silver carp mince inoculated with Pediococcus pentosaceus

Abstract The types of interactions and the proteins involved in the formation of gel network of fermented silver carp mince were investigated. Results showed that the amount of each type of protein interactions varied significantly depending on fermentation time. The content of sulphydryl groups decreased continually with a concomitant increase in disulphide bonds during fermentation. The higher gel strength and more compact fibrous network of fermented silver carp mince corresponded to a higher percentage of hydrophobic interactions, disulphide bonds and non-disulphide covalent bonds. SDS–PAGE showed that the major myofibrillar proteins, particularly myosin heavy chain were involved in the formation of aggregates through hydrophobic interactions and disulphide bonds during fermentation. Furthermore, low molecular weight proteins probably produced by proteolysis were also involved in the formation of gel matrix.

Association of oxidative stress and paraoxonase status with PROCAM risk score

Objectives Oxidative stress and paraoxonase activity play a significant role in the pathogenesis of cardiovascular disease (CVD). The Prospective Cardiovascular Münster (PROCAM) study evaluated the prevalence of CVD risk factors and postulated the prediction of future CVD events. We therefore investigated the association between plasma markers of oxidative stress and paraoxonase status with PROCAM risk score. Design and methods Oxidative stress status parameters [lipid peroxidation measured as thiobarbituric acid-reacting substances (TBARS), superoxide anion (O 2 −), superoxide dismutase (SOD) activity, total sulphydryl group content] and paraoxonase (PON1) status were assessed in 211 participants. The predicted 10-year risk was calculated according to the PROCAM algorithm. Results As expected subjects with high PROCAM risk score (high CVD risk) had significantly higher concentrations of oxidative stress parameters (TBARS and O 2 − P < 0.001 and P < 0.05, respectively). The PON1 192 phenotype distribution among CVD risk groups was not significantly different. Logistic regression analyses revealed significant associations of all the examined oxidative stress status parameters with calculated CVD risk score. The potential of the parameters for CVD risk prediction was tested via multivariate analysis. Only the O 2 − level retained a strong association with high CVD risk. Conclusions Our study demonstrated that high PROCAM risk score is associated with increased oxidative stress, indicating for the first time that elevated O 2 − is independently associated with high CVD risk.

Activation and conformational changes of mushroom polyphenoloxidase by high pressure microfluidization treatment

Activation and conformational changes of mushroom polyphenoloxidase (PPO) after high pressure microfluidization treatment were observed by means of UV spectrophotometer, far-UV circular dichroism, fluorescence emission spectra, UV absorption spectra and sulphydryl groups detection. The results indicated that, treated under pressures of 90 MPa, 110 MPa, 130 MPa and 150 MPa one pass, and 150 MPa 1, 2 and 3 passes, respectively, mushroom PPO exhibited an increase in activity. The circular dichroism (CD) analysis demonstrated that some of secondary structures such as α-helix were destroyed. There were some indices that the increase of relative activity was accompanied by a decrease in α-helix content. The fluorescence emission spectra analysis indicated that Trp and Tyr residues in mushroom PPO were more or less exposed to solvent, and the result was in good agreement with that of UV absorption spectra analysis. The sulphydryl groups detection showed that the sulphydryl groups content on the surface of mushroom PPO was increased. Results of the present study show that high pressure microfluidization can not be used to inactivate mushroom PPO. However, it provides a new way for enzyme preparation, such as enzyme modification, with higher activity. High pressure microfluidization can be easily operated, with shorter treatment time and higher food safety compared with chemical methods.

The effect of cooking in a steam‐convection oven on the quality of selected dishes

AbstractThe effects of cooking in a steam‐convection (combi) oven in comparison with traditional methods of cooking, such as frying, roasting and boiling, on basic chemical composition and contents of hydroxymethylfurfural (HMF) and sulphydryl (SH) groups of pork, fish and chicken meats, potatoes and carrot were studied. The cooking of pork and fish in a combi oven required a longer time than traditional frying; therefore higher cooking losses were observed, whereas cooking losses in chicken cooked in a traditional oven and the combi oven were comparable. Foods cooked in the combi oven contained more protein and less fat than traditionally cooked samples. Lack of water in the combi oven cooking enabled a higher retention of vitamin C in vegetables. The intensity of HMF forming was higher in products cooked in the combi oven. Changes in proteins were smaller in meats cooked in the combi oven (higher content of total SH groups), whereas they were higher in the combi oven‐cooked vegetables.