Total Sulfhydryl Research Articles

Labeling and Determination of Total Sulfhydryl Content in Protein

Labeling and Determination of Total Sulfhydryl Content in Protein

Cytoprotective effect of taurine against sodium chlorate-induced oxidative damage in human red blood cells: an ex vivo study.

Sodium chlorate (NaClO3) is a common non-selective herbicide that is also used in paper and pulp mills and is produced as a by-product during drinking water disinfection by chlorine dioxide. Here, we report the effect of dietary antioxidant taurine on NaClO3-induced cytotoxicity in human red blood cells (RBC). RBC were treated with 5mM NaClO3, either alone or in presence of 1, 2.5 and 5.0mM taurine. Incubation of RBC with NaClO3 alone caused hemolysis, increased oxidation of lipids and proteins, methemogobin level and decreased total sulfhydryl and glutathione content. It lowered the activities of antioxidant enzymes thioredoxin reductase, glutathione peroxidase, catalase and glutathione reductase, while Cu-Zn superoxide dismutase activity was increased. The antioxidant capacity of RBC was impaired. This strongly suggests that NaClO3 causes the induction of oxidative stress condition in RBC. The specific activities of lactate dehydrogenase, glucose 6-phosphate dehydrogenase and plasma membrane bound enzymes, were also greatly altered. However, prior treatment of RBC with taurine conferred significant protection against NaClO3-induced oxidative damage and also improved the antioxidant defence system of cells. These results were supported by electron microscopy images of RBC. Treatment with NaClO3 alone converted the normal biconcave discoidal RBC to acanthocytes and echinocytes but this transformation was greatly prevented in the presence of taurine. Thus, taurine mitigates the cytotoxicity of NaClO3 in human RBC and can function as an effective chemoprotectant.

Independent and combined effects of ultrasound and transglutaminase on the gel properties and in vitro digestion characteristics of bay scallop (Argopecten irradians) adductormuscle

The effects of transglutaminase (TGase) addition (0.4–1.2 g/100g), ultrasound (120–720 W, 20 min), and their combination on the gel properties and in vitro digestion characteristics of bay scallop adductor muscle were studied. The gel strength of the gel sample with TGase content of 0.8 g/100g (TG-0.8) was 58.2% higher than that of the control sample (CON). The gel sample treated with ultrasound at 480 W (UT-480) had the highest gel strength. The strength of the gel prepared by combination of 0.8 g/100g TGase and 360 W ultrasound (UT-TG) was 82.3% higher than that of CON. The whiteness and water holding capacity of the gel increased regardless of the addition of TGase or ultrasound treatment. SDS-PAGE patterns showed that the myosin heavy chain of the treated samples became thinner, and the changes of actin and tropomyosin were not significant. The scanning electron microscopy results of gel samples prepared by ultrasound combined with TGase showed a denser structure, which was related to the lowest total sulfhydryl content and TCA-soluble peptide content. The results of dynamic rheology show that the UT-TG sample had the highest G′ value, followed by TG-0.8. The in vitro digestion characteristics of the selected gel samples were also discussed. The degree of protein hydrolysis and the content of free amino acids in TG-0.8 samples were the lowest, which improved after ultrasound treatment. Overall, the combination of appropriate ultrasound treatment and TGase addition provides an effective means for improving gel properties and digestibility of scallop surimi product.

Transcranial Direct Current Stimulation Increases Total Sulfhydryl Content in the Spinal Cord of Rats with Neuropathic Pain

Transcranial Direct Current Stimulation Increases Total Sulfhydryl Content in the Spinal Cord of Rats with Neuropathic Pain

Role of oxidant-antioxidant enzymes in managing the cardiovascular risks in nephrotic syndrome patients

Increased reactive oxygen species (ROS) in nephrotic syndrome (NS) are involved in the oxidation of membrane proteins, lipoproteins and several receptor molecules ultimately leading to their functional deficit. It is involved in the pathogenesis of dyslipidemia in NS and also increases the oxidation of LDL (oxLDL), which is an important risk factor in thrombus generation and atherosclerosis. Myeloperoxidase (MPO) is an early predictor of myocardial infarction and adverse cardiac events in patients with chest pain. MPO can also foresee the recurrent acute coronary syndrome (ACS) and myocardial infarction in patients. ‘MPO oxidized LDL’ also induces ROS production, lipid accumulation and reduces the antioxidant response in macrophages, however in an augmented way by using different pathways and might be more atherogenic. Paraoxonase 1 (PON1) prevents the oxidative modification of serum lipoproteins, which is one of the crucial steps in the initiation of atherogenesis. PON1 also contributes to the anti-atherogenic effect of HDL-c. Adult NS patients have increased lipid hydroxide levels and significantly decreased PON1 activity and total sulfhydryl levels when compared to healthy controls. While the increased risk of cardiovascular disease in NS patients is well documented, the exact etiology still remains controversial. This prevents the development of a specific treatment modality for the same. MPO as well as PON1 were found as important markers for the management of cardiovascular risk in NS patients. Estimation of these enzymes can therefore be performed in routine clinical practice as prognostic markers, owing to its ease of estimation and cost effectiveness.

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.

Effect of high-intensity ultrasonic treatment on the physicochemical, structural, rheological, behavioral, and foaming properties of pumpkin (Cucurbita moschata Duch.)-seed protein isolates

Pumpkin-seed protein isolates were treated with high-intensity ultrasound (HIU). The effects of different ultrasound powers at the same treating time on the physicochemical, structure and foaming properties of pumpkin-seed protein isolates (PSPIs) were investigated. The results showed that the ultrasound treatment transformed the PSPI aggregates into smaller aggregates with a more uniform distribution. When the pH value increased, the solubility and foaming ability of the protein also increased significantly. Increasing the ultrasound power also increased the surface hydrophobicity of the PSPIs and the total sulfhydryl contents, while the active sulfhydryl content decreased. The most significant effect on the total sulfhydryl content occurred when 500 W ultrasonic power was used. The ultrasound treatment also had a significant effect on the chromaticity and turbidity of the pumpkin-seed protein isolates. With an increase in ultrasonic power, scanning electron microscopy (SEM) showed that the sizes of particles decreased as their distribution increased. Moreover, ultrasound treatment was found to be beneficial for enhancing and improving foaming performance. Ultrasound modification affected the protein's physicochemical properties and structure, which contributed greatly to the corresponding functional and nutritional properties of the protein. It would be, therefore, useful to develop and utilize plant protein and to improve its added-value.

Ultrasound treatment can increase digestibility of myofibrillar protein of pork with modified atmosphere packaging

We explored whether ultrasound treatment affected digestibility of myofibrillar protein (MP) isolated from modified atmosphere packed (MAP, 70% N2 and 30% CO2) pork. MP digestibility under pepsin and pancreatin treatments decreased significantly with storage time. Ultrasound treatment increased the digestibility and produced a greater number of smaller peptides. However, the total peptide count and unique peptide counts were significantly reduced. Moreover, active sulfhydryl, total sulfhydryl, particle size, turbidity and surface hydrophobicity of MP increased with time, while protein solubility and ATPase activity decreased. Compared with the untreated samples, ultrasound treatment increased protein solubility, surface hydrophobicity, and active sulfhydryl content, but decreased total sulfhydryl content (except 10 d), particle sizes, turbidity and ATPase activity. Ultrasound treatment resulted in a decline in β-turn and α-helix contents. Therefore, ultrasound is conducive to the digestion. Additionally, structural and functional properties of protein in MAP were less stable than those in vacuum-packed pork reported before.

Effect of Sous-vide cooking on the quality and digestion characteristics of braised pork

This study aimed to evaluate the effect of Sous-vide (SV) cooking on the quality, flavor and digestion characteristics of braised pork. Traditional (TD) sample had the highest fat content and malondialdehyde (MDA) value, but the lowest protein content and total sulfhydryl (SH) content (P < 0.05). The SH content in SV samples decreased with the heating time, but MDA content increased (P < 0.05). In addition, α-helix content of TD samples was higher but β-sheet content was lower than SV samples. LC-MS/MS indicated that SV samples at 65 °C for 8 h had potential bioactive and antioxidant peptides. GC–MS mainly identified 395 volatile components and SV samples at 70 °C for 8 h and 75 °C for 8 h had similar flavor compounds to TD samples. Thus, Sous-vide cooking produced better quality and digestion characteristics of braised pork. These findings give a new insight into the associations of processing methods with meat quality.

Protective effect of Myrcia pubipetala Miq. against the alterations in oxidative stress parameters in an animal model of depression induced by corticosterone

Depression is a debilitating disorder in humans that significantly affects quality of life. As such, alternative therapies are highly sought after by patients seeking treatment for depression. Experimentally, the chronic administration of corticosterone (CORT) in rodents has been reported to promote depressive-like behaviors. Herein, animals received saline or CORT for 21 days and, during the last 7 days, they were treated with the crude hydroalcoholic extract (CHE) of Myrcia pubipetala Miq (50, 100 or 150 mg/Kg), or vehicle (distilled water), by oral route. After 24 h, animals were subjected to the open field (OFT) and forced swimming tests (FST), and then sacrificed for the removal of the hippocampus and cerebral cortex for biochemical analysis. Results showed enhanced catalase (CAT) and superoxide dismutase (SOD) activities, as well as an elevated formation of thiobarbituric acid reactive substances (TBARS), in the cerebral cortex of CORT-treated mice. The chronic administration of the CHE (100 and 150 mg/Kg) reduced TBARS and the increased total sulfhydryl content, and also reversed the increase in TBARS induced by CORT. In the hippocampus, CORT increased CAT and SOD activities and reduced glutathione peroxidase (GSH-Px) (C) activity, while Myrcia pubipetala Miq. CHE (100 and 150 mg/Kg) increased GSH-Px activity when administered alone and reversed decreased GSH-Px (100 and 150 mg/Kg) activity when given during CORT administration. Neither CORT administration nor CHE treatment significantly altered the immobility time of the animals in FST and no changes were observed in the locomotor activity of the animals in the OFT. Findings indicate that the CHE of Myrcia pubipetala Miq. exerts antioxidant effects in the cerebral cortex and hippocampus of mice induced to depression by CORT. Since phenolic compounds are reported to have antioxidant effects in this species, the effects of the CHE may be, at least in part, mediated by the presence of these compounds in Myrcia extract.

Effects of freeze-thaw cycles of Pacific white shrimp (Litopenaeus vannamei) subjected to radio frequency tempering on melanosis and quality

This study was conducted to investigate the effects of different tempering methods and freeze-thaw cycles on melanosis and quality parameters of pacific white shrimp. Frozen pacific white shrimps tempered with radio frequency tempering (RFT) were compared to that in water tempering (WT) and refrigerator tempering (RT) in terms of temper loss, total volatile base nitrogen (TVBN), polyphenol oxidase (PPO) activity, melanosis, total sulfhydryl contents, differential scanning calorimetry (DSC), and texture properties after 0, 1, 3, 5 freeze-thaw cycles. Results showed that crushed ice was effective as an effective surrounding medium for six layers of frozen shrimp reaching −2 °C within 6 min in RFT. For quality attributes, the temper loss of samples tempered with radio frequency is lower than that of RT and WT after all freeze-thaw cycles, and RFT resulted in the lowest TVBN value (9.17 mgN/100 g) of shrimps after the 5th freeze-thaw cycle. The PPO activity and melanosis of samples increased as the number of freeze-thaw cycles increased, and RFT effectively inhibited the development of melanosis. After the 3rd freeze-thaw cycle, the enthalpy change (△H) and the sulfhydryl content (0.16 mmol/gprot) of radio frequency tempered samples was significantly higher (p < 0.05) than that of WT and RT. RFT retained the hardness and chewiness of shrimp samples in all freeze-thaw cycles. Therefore, RFT effectively inhibited melanosis and reduce protein oxidation in Pacific white shrimp during freeze-thaw cycles with its fast and uniform heating characteristics.

Mulberry fruit powder enhanced the antioxidant capacity and gel properties of hammered minced beef: Oxidation degree, rheological, and structure

The effects of mulberry fruit powder on the antioxidant capacity and gel properties of hammered minced beef, including oxidation degree, texture properties, rheological properties and protein structure, were investigated. The results manifested that the total antioxidant capacity (T-AOC) and DPPH free radical scavenging rate of minced beef were remarkably enhanced (P < 0.05) when the addition of mulberry fruit powder was 0.6%, while the contents of carbonyl and total sulfhydryl groups were reduced. Higher storage modulus (G′) and lower tanδ demonstrated that mulberry fruit powder conduced to the formation of a denser gel network structure and improved rheological properties. Furthermore, the improvement of hardness and resilience as well as the reduction of cooking loss rate suggested that mulberry fruit powder had a positive effect on maintaining the gel textural properties. Surface hydrophobicity and FT-IR analysis elucidated that mulberry fruit powder promoted the unfolding of protein structure and the transformation from α-helix to β-sheet structure. Nevertheless, a high concentration of mulberry fruit powder (≥1.0%) could jeopardize the structural properties and quality of minced meat gels. Thus, to maintain the good quality of meat products, both the addition of mulberry fruit powder and the oxidation degree should be controlled simultaneously.

Anti-leukemogenic Efficacy of Aloe vera Gel on Benzene-induced Leukemia in Wistar Rats

Backgroud: The toxicity of benzene leading to leukemia induction has been well documented in animal model. Aloe vera is a succulent perennial evergreen flowering plant used traditionally in the treatment of jaundice and was found to have potent cytotoxic effect against HL60 human acute myeloid leukemia. The present study investigated the in vivo chemoprotective effects of Aloe vera gel on benzene-induced leukemia in rats.&#x0D; Methodology: Leukemia was induced in male Wistar rats of 80-90g weight by intravenously administered 0.2ml benzene solution alternate days for four weeks. Following induction, leukemic rats and normal baseline control rats were randomly assigned into four experimental groups of 6 animals each as follows: Group CTRL (control), normal baseline control rats; Group AVG (Aloe vera gel), normal baseline rats treated with Aloe vera gel (150 mg/kg) for 7 days, Group LKR (leukemic rats), untreated leukemic rats serving as leukemia control and Group LKR + AVG, leukemic rats treated with Aloe vera gel (150 mg/kg) for 7 days.&#x0D; Results: Leukemic rats showed altered hematology and morphological deformations such as anisocytosis, poikilocytosis and blast cells occurrence in peripheral blood. Also hypercellularity, severe dysplasia and significantly elevated micronucleated polychromatic erythrocyte were observed in marrow of leukemic rats. Moreover, benzene caused a significant elevation in plasma level of advanced oxidation protein products (AOPPs) with concomitant reduction in total sulfhydryl and arylesterase activity. However, treatment with Aloe vera gel restored blood hematology to near normal and mitigated the deformities in blood cell morphology induced by benzene. Aloe vera supplementation also effected a disappearance of dysplasia and diminution in the frequency of micronucleus in the bone marrow of treated leukemic rats. It also enhanced plasma antioxidant capability by restoring sulfhydryl content and arylesterase activity of the blood and abrogated the increase in plasma content of AOPPs.&#x0D; Conclusion: Overall, Aloe vera gel offered chemoprotective effect on Benzene-induced leukemia in rats.

Comparison of Arrhenius model and artificial neuronal network for predicting quality changes of frozen tilapia (Oreochromis niloticus)

The objectives of this study were to study the quality changes (ice crystal morphology, Ca2+-ATPase activity, total sulfhydryl [SH] content, intrinsic fluorescence intensity [IFI], and K value [freshness determination]) of tilapia at different storage temperatures for 112 days, and kinetic models and artificial neuronal network (ANN) were developed to predict the changes. There was a dramatic increase in cross-section area and equivalent diameter and a sharp decrease in Ca2+-ATPase activity and SH content during the first 4 weeks (p < 0.05). IFIλmax decreased by 43.95%, 29.77%, 28.97% and 18.58% after 16 weeks at 265 K, 259 K, 253 K, and 233 K. The kinetic model established by IFIλmax could be accurately described the quality changes during storage at 233–265 K. However, the prediction accuracy established by other indices decreased at later stages (14–16 weeks). The ANN model was superior to Arrhenius models and performed better for all indicators.

The anti-cancer potential of 2,4,6 tris-methyphenylamino1,3,5-triazine compound against mammary glands cancer: Via down-regulating the hormonal, inflammatory mediators, and oxidative stress

Aim of the studyBreast cancer is caused by abnormal growth of the cells and progressed due to the over-expression of estrogen (ER) and progesterone (PR). The current study was designed to evaluate the anti-tumor activity of 2,4,6 tris-methyphenylamino1,3,5-triazine compound (MPAT) in N-nitroso, N-methyl urea (NMU)-induced mammary gland cancer. MethodsMolecular docking and in-vitro studies were conducted before the in-vivo analysis. Female Albino rats were divided into 5 groups (n = 6). Group I received Carboxymethylcellulose (CMC) (1 mL/100 g). Group II (diseased group) received NMU 50 mg/kg. Group III (standard group) received tamoxifen (5 mg/kg). Group IV–V received MPAT at doses of 30 and 60 mg/kg respectively. All groups received NMU intraperitoneally except the control group at 3 weeks intervals for 12 weeks. After 12 weeks of NMU dosing, MPAT was given for 15 consecutive days. Biochemical, oxidative stress markers, hormonal profile, and inflammatory mediators were analyzed. Key findingsMPAT showed significant interaction with the selected targets in docking studies. An over-expression of ER and PR was observed in NMU-treated rats which were restored significantly after MPAT administration. Nitrite and MDA levels were high in the diseased group and MPAT treatment attenuated the oxidative damage after treatment. Antioxidants such as superoxide dismutase (SOD), Catalase (CAT), total sulfhydryl (TSH), glutathione (GSH), and Lactate dehydrogenase (LDH) values were low in NMU-treated rats. SignificanceThis study concluded that MPAT can be used as an anticancer agent due to its significant effects on down-regulating the hormonal profile and oxidative stress markers.

Cardioprotective Effect of Maternal Supplementation with Resveratrol on Toxicity Induced by Doxorubicin in Offspring Cardiomyocytes.

ResumoFundamentoA doxorrubicina (DOX) é frequentemente usada para tratar muitos tipos de cânceres, apesar da cardiotoxicidade dose-dependente. Como alternativa, o resveratrol é um polifenol que tem demonstrado efeitos cardioprotetores em vários modelos de disfunção cardíaca.ObjetivoEste estudo investigou se o tratamento com resveratrol em ratas gestantes protege contra toxicidade induzida por doxorrubicina em cardiomiócitos da ninhada.MétodosRatas Wistar (n-8) receberam sresveratrol como suplemento alimentar durante a gestação. No nascimento da ninhada, os corações (9-11) foram usados para se obter a cultura primária de cardiomiócitos. A cardiotoxicidade induzida por DOX e os efeitos da suplementação com resveratrol foram avaliados por marcadores de stress oxidativo, tais como oxidação da diclorofluoresceína diacetato, diminuição da atividade de enzimas antioxidantes, e oxidação do teor total de grupos sulfidrila, além da avaliação da viabilidade celular, geração de danos ao DNA, bem como a resposta de reparo aos danos ao DNA. Um valor de p <0,05 foi considerado estatisticamente significativo.ResultadosOs cardiomiócitos de neonatos de ratas que receberam suplemento resveratrol apresentaram um aumento (p <0,01) na viabilidade das células, e diminuição (p <0,0001) de células apoptóticas/necróticas após o tratamento com DOX, o que está correlacionado às atividades de enzimas antioxidantes e produção de diclorofluoresceína. Além disso, o resveratrol protegeu os cardiomiócitos de danos ao DNA induzidos por DOX, apresentando uma diminuição (p <0,05) nas quebras de DNA induzidas por stress oxidativo, avaliadas pela atividade de enzimas reparadoras do DNA endonuclease III e formamidopirimidina glicosilase. A suplementação com resveratrol aumentou (p <0,05) a expressão da proteína reparadora Sirt6 nos cardiomiócitos dos filhotes.ConclusãoEssa pesquisa indica que a suplementação com resveratrol durante o período gestacional tem um efeito cardioprotetor no coração da ninhada contra a toxicidade induzida por DOX, o que pode se dever a sua função antioxidante, e o aumento na resposta de danos ao DNA.

Effect of Physical and Enzymatic Pre-Treatment on the Nutritional and Functional Properties of Fermented Beverages Enriched with Cricket Proteins.

The aim of this study was to evaluate the effects of γ-irradiation (IR), ultrasound (US), and combined treatments of ultrasound followed by γ-irradiation (US-IR), ultrasound followed by enzymatic hydrolysis with and without centrifugation (US-E and US-EWC, respectively), and ultrasound followed by γ-irradiation and enzymatic hydrolysis (US-IRE), on the digestibility and the nutritional value of fermented beverages containing probiotics. Results showed that US (20 min), IR (3 kGy) and US-IR (tUS = 20 min, dose = 3 kGy) treatments raised protein solubility from 11.5 to 21.5, 24.3 and 29.9%, respectively. According to our results, these treatments were accompanied by the increased amount of total sulfhydryl groups, surface hydrophobicity and changes to the secondary structure of the proteins measured by Fourier-transform infrared spectroscopy (FTIR). Fermented probiotic beverages, non-enriched (C) and enriched with untreated (Cr) or treated cricket protein with combined treatments were also evaluated for their in vitro protein digestibility. Results showed that the soluble fraction of US-IRE fermented beverage had the highest digestibility (94%) as compared to the whole fermented tested beverages. The peptides profile demonstrated that US-IRE had a low proportion of high molecular weight (MW) peptides (0.7%) and the highest proportion of low MW peptides by over 80% as compared to the other treatments.

Effects of Repeated Freezing-thawing on Water Holding Capacity, Protein Oxidation and Dissolution Characteristics of Tibetan Mutton during Chilled Storage

The purpose of this study was to investigate the effects of repeated freeze-thaw phenomenon on on water holding capacity, myofibrillar protein oxidation and dissolution characteristics of Tibetan mutton during chilled storage. Tibetan mutton was as the research objects and after repeated freezing-thawing for 0, 1, 3 and 5 times, the mutton was refrigerated at 4 ℃ for 1, 3, 5 and 7 days. And then the water holding capacity, myofibril oxidation characteristics, protein solubility and muscle fiber microstructure were determined. The results showed that compared with T3 group, the thawing loss rate of T5 group was significantly increased by 63.08%, 43.20%, 20.58% and 16.20%, and compared with T0 group, the drip loss rate of T5 group was significantly increased by 29.16%, 21.09%, 22.16% and 25.47%, respectively and the pressure loss rate significantly increased by 23.76%, 20.45%, 21.17% and 20.15% (P<0.05) during chilled storage. The carbonyl content and surface hydrophobicity all presented a significant increase and total sulfhydryl content presented a significant decrease (P<0.05), meanwhile, with the increase of freezing-thawing cycles the protein solubility decreased significantly as well as the damage degree of muscle fiber microstructure increased gradually. The correlation results showed that freezing-thawing cycles times were significantly correlated with the degree of protein oxidation and protein solubility (P<0.01), and the water holding capacity also had significant correlation with the above indexes (P<0.01). The above results indicated that the more times of freezing-thawing cycle, the more serious oxidative degree of myofibril protein, the more serious damage to muscle fiber microstructure, and the lower protein solubility, which was therefore not conducive to the maintenance of meat water holding capacity. At the same time, the refrigeration process also had adverse effects on water holding capacity, myofibril oxidation, protein solubility and muscle fiber microstructure. Therefore, the control of temperature fluctuation during meat storage, transportation and production is of great significance to maintain meat quality.

Modeling relationship between protein oxidation and denaturation and texture, moisture loss of bighead carp (Aristichthys Nobilis) during frozen storage.

To evaluate the effects of protein oxidation and denaturation on the fish texture and moisture loss during frozen storage, we measured the changes of protein oxidation and denaturation (salt-soluble protein (SSP), total sulfhydryl (SH), disulfide (SS), carbonyl contents and Ca2+ -ATPase activity), texture (hardness), and moisture loss (drip loss) of bighead carp fillets stored at -12, -20 and -28°C during 16weeks. These data were employed to develop partial least squares regression (PLSR) model, radial basis function neural network (RBFNN) model, PLSR-RBFNN (PR) model and RBFNN-PLSR (RP) model. The results showed that the RP model provided no enhancement to RBFNN model because it had the exactly same root mean square error (RMSE) and R2 . PLSR model showed better performance than other models when predicting hardness. More appropriate linear or linearity-dominant hybrid model needed to be explored to establish the relationship between protein oxidation and denaturation and texture. The PR model performed better than other models in predicting drip loss with its lower RMSE and higher R2 , which revealed both linear and nonlinear relationship between protein oxidation and denaturation and moisture loss. Therefore, the PR model was a promising and encouraging tool to provide a more comprehensive understanding of the relationship between protein oxidation and denaturation and moisture loss of fish during frozen storage. PRACTICAL APPLICATION: The study explored the effects of protein oxidation and denaturation on the texture and moisture loss of bighead carp during frozen storage (-12 to -28°C). PLSR model showed better performance than other models when predicting the relationship between protein oxidation and denaturation and texture. The PR model was an available tool for manufacturers to predict the relationship between protein oxidation and denaturation and moisture loss.

Synergistic Effect of Enzyme Hydrolysis and Microwave Reactor Pretreatment as an Efficient Procedure for Gluten Content Reduction

In this study, we assessed the effects of microwave irradiation of wheat gluten proteins as a pretreatment performed in a microwave reactor that could accurately control process parameters as a function of power and temperature, as well as comparing it with conventional heat treatment. The aim was to identify suitable combinations of partial enzymatic hydrolysis and microwave pretreatment parameters to produce gluten hydrolysates with reduced allergenicity and conserved techno-functional features for food application. FTIR analysis, and total and reactive SH group contents confirmed that the microwave-controlled heating can significantly change the secondary structure and conformation of gluten protein. The microwave treatment had the largest effect at 200 W and 100 °C, at which the content of gluten has been reduced by about 2.5-fold. The microwave pretreatment also accelerated the enzymatic hydrolysis of gluten, changing the kinetic profile. The apparent hydrolysis rate constants (k2) were 1.00, 3.68, 3.48, 4.64 and 4.17 min−1 for untreated gluten, and those pretreated with microwave power of 200, 400, 600 and 800 W, respectively. Compared to the heat treatment, it appeared that microwave specific non-thermal effects had a significant influence on the gluten structure and allergenicity and, in combination with the enzymatic hydrolysis, ultimately yielded protein hydrolysates with enhanced antioxidant and functional properties.