Total Sulfhydryl Research Articles

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 Pectin Coating Infused with Gallic Acid on the Quality and Shelf Life of Japanese Sea Bass (Lateolabrax japonicas) Fillets

In the present study, the effect of a pectin (PE) coating infused with gallic acid (GA) on the quality of fresh Japanese sea bass (Lateolabrax japonicas) fillets stored at 4 °C was evaluated over a 20-day period. PE or GA treatment alone and the PE infused with GA coating (PE-GA) all reduced microbial counts, with the PE-GA providing the greatest reduction. In general, samples of fish fillet treated with PE-GA had significantly lower levels of total volatile basic nitrogen, lipid oxidation, and total sulfhydryls, but higher Ca2+-ATPase activity during the storage period, compared with the untreated (control), PE-coated, and GA-treated fillets. Notably, PE-GA-treated samples also had the highest sensory quality rating. Results of the present study indicate that the PE-GA composite coating represents a promising food-grade biopreservative that can be used for maintaining the storage quality of fresh fish fillet.

Binding of aldehydes to myofibrillar proteins as affected by two-step heat treatments.

The present study investigated the effect of two-step heat treatments on the structure of grass carp myofibrillar proteins (MPs) and their binding ability for selected aldehydes (hexanal, heptanal, octanal and nonanal). Within 30 min of the first heating step at 40 °C and 5-10 min of the second heating step at 90 °C, the enhancement of the flavor-binding ability was likely explained by the increases in surface hydrophobicity and total sulfhydryl content due to the unfolding of secondary structures of MPs through exposure of hydrophobic amino acids and sulfhydryl groups. Nevertheless, lengthy heating at 90 °C accelerated the aggregation of unfolded MPs and reduced the hydrophobic bonding sites, thus weakening the hydrophobic interactions and decreasing the resultant binding ability of MPs with aldehydes. The binding ability of aldehydes to MPs was found to be strongly influenced by changes in protein structure and surface during the two-step heating process. The results provided insight into improving the flavor characteristics of freshwater fish surimi products. © 2019 Society of Chemical Industry.

Edaravone reduces oxidative stress and intestinal cell apoptosis after burn through up-regulating miR-320 expression

BackgroundIntestinal mucosa barrier dysfunction after burn injury is an important factor for causing mortality of burn patients. The current study established a burn model in rats and used a free radical scavenger edaravone (ED) to treat the rats, so as to investigate the effect of edaravone on intestinal mucosa barrier after burn injury.MethodsAnesthetized rats were subjected to 40% total body surface area water burn immediately, followed by treatment with ED, scrambled antagomir, or antagomiR-320. Intestinal mucosa damage was observed by hematoxylin-eosin staining and graded by colon mucosal damage index (CMDI) score. The contents of total sulfhydryl (TSH), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were determined by spectrophotometry. Cell apoptosis, protein relative expression,and the in situ expressions of p-Akt and p-Bad were detected by flow cytometry, Western blotting and immunohistochemistry, respectively. The miR-320 expression was determined by quantitative real-time polymerase chain reaction.ResultsED alleviated intestinal mucosal damage caused by burn injury, down-regulated the levels of MDA, cytochrome C, cleaved caspase-9 and cleaved caspase-3, but up-regulated the levels of TSH, SOD, CAT and Bcl-2. We also found that ED could reduce oxidative stress, inhibit cell apoptosis, increase the expressions of p-Akt, p-Bad and miR-320, and decrease PTEN expression. PTEN was predicted to be the target gene for miR-320, and cell apoptosis could be promoted by inhibiting miR-320 expression.ConclusionED regulates Akt/Bad/Caspase signaling cascade to reduce apoptosis and oxidative stress through up-regulating miR-320 expression and down-regulating PTEN expression, thus protecting the intestinal mucosal barrier of rats from burn injury.

Taurine attenuates Cr(VI)-induced cellular and DNA damage: an in vitro study using human erythrocytes and lymphocytes.

Hexavalent chromium [(Cr(VI)] is widely used in several industries, but human exposure results in multiple organ toxicity. Enhanced generation of free radicals and reactive species is thought to play a key role in Cr(VI)-induced toxicity. We have examined the effect of taurine, a simple sulphur-containing amino acid and an antioxidant, on potassium dichromate [K2Cr2O7, a Cr(VI) compound]-induced cytotoxicity and genotoxicity in human blood cells. Erythrocytes were treated with K2Cr2O7, either alone or after incubation with different concentrations of taurine. Treatment of erythrocytes with K2Cr2O7 alone led to marked increase in generation of reactive oxygen and nitrogen species, lipid and protein oxidation. This was accompanied by decrease in total sulfhydryl and glutathione content and lowered antioxidant power of the cells. This suggests that Cr(VI) induces oxidative stress in the cells. Incubation of erythrocytes with taurine prior to addition of K2Cr2O7, resulted in a concentration-dependent decrease in the generation of reactive oxygen and nitrogen species, mitigation of oxidative stress and amelioration of antioxidant power of these cells. It also restored the activities of several metabolic, antioxidant and membrane-bound enzymes. Cr(VI)-induced damage to erythrocyte membrane and lymphocyte DNA was also significantly attenuated by prior administration of taurine. These results suggest that taurine can function as a chemoprotectant against Cr(VI)-induced oxidative injury and can be potentially used to mitigate the toxic effects of this transition metal ion.

Effects of Ultrasonic-Assisted Extraction on the Physicochemical Properties of Different Walnut Proteins.

The effects of ultrasonic-assisted extraction (UAE, 200 W, 20 min) on the yield and physicochemical properties of different walnut proteins (WNPs, including albumin, globulin, and glutelin) were investigated. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that UAE could result in protein molecular fragmentation of albumin, but did not affect the major bands of globulin and glutelin. The CD spectra demonstrated that different WNPs obtained by UAE had different changes in their secondary structure. Under UAE, there was an increase in surface hydrophobicity (H0) of albumin and gluten and no change in the fluorescence intensity, while decreases were observed in the H0 and fluorescence intensity of globulin; and the contents of total and surface free sulfhydryl in albumin dramatically decreased. UAE reduced the size of the particles and the dimension of the microstructures in albumin and gluten, indicating that ultrasound could unfold protein aggregates. In addition, UAE increased the solubility, emulsifying activity (EA), foaming capacity (FC), and foam stability (FS) of the obtained proteins. The above results indicate that ultrasound extraction is a promising approach to improve the extraction yield and properties of walnut proteins.

Effects of high pressure on biochemical properties and structure of myofibrillar protein from Tegillarca granosa

SummaryThe effects of high‐pressure (HP) treatment parameters (300 MPa for 5 min, 350 MPa for 3 or 5 min and 400 MPa for 1 min) on the biochemical properties and structure of myofibrillar protein (MP) from Tegillarca granosa were investigated. The results showed that HP significantly affected the biochemical properties of MP. Under the HP treatment at 400 MPa for 1 min, the MP extraction yield was reduced from 32.21 to 18.34 mg g−1, and its surface hydrophobicity was increased from 89.29 to 104.69 µg. Ca2+‐ATPase activity of MP decreased from 0.019 to 0.011 µmol (pi) mg−1 (pro) min−1, and both total and reactive sulfhydryl contents significantly declined. Furthermore, HP caused MP to undergo conformational changes. This study provides a reference data for the processing of T. granosa using HP treatment.

Nigella sativa oil and thymoquinone reduce oxidative stress in the brain tissue of rats exposed to total head irradiation

Purpose: To evaluate the antioxidant and radio-protective effects of Nigella sativa oil (NSO) and thymoquinone (TQ) on radiation-induced oxidative stress in brain tissue.Materials and methods: Fifty-four Sprague-Dawley rats were divided into six groups to test the radio-protective effectiveness of Nigella sativa oil and thymoquine administered by either orogastric tube or intraperitoneal injection. Appropriate control groups were also studied.Results: Brain antioxidant capacity, as measured by the levels of total superoxide scavenger activity (TSSA), non-enzymatic superoxide scavenger activity (NSSA), superoxide dismutase, paraoxonase (PON) activities, total antioxidant status and total sulfhydryl (-SH) group, were lower in the irradiation (IR) only group while xanthine oxidase (XO) activity, total oxidant status (TOS), oxidative stress index (OSI) and lipid hydroperoxide (LOOH) levels were higher in the group compared with all other groups. Brain glutathione-S-transferase (GST) activity significantly decreased in the IR only group when compared with the control groups. Glutathione peroxidase (GSH-Px) activity was lower in the IR only, NSO plus IR, TQ plus IR groups when compared with the control group of TQ. Arylesterase (ARYL) activity was not statistically significant in the IR only group compared with all other groups.Conclusions: The results suggest that Nigella sativa oil (NSO) and its active component, TQ, clearly protect brain tissue from radiation-induced oxidative stress.

Genipin-Aided Protein Cross-linking to Modify Structural and Rheological Properties of Emulsion-Filled Hempseed Protein Hydrogels.

Genipin, a natural electrophilic cross-linker, was applied (5, 10, 20, and 30 mM) to modify hempseed protein isolate (HPI). Genipin treatments resulted in general losses of total sulfhydryls (up to 2.9 nmol/mg) and free amines (up to 77.3 nmol/mg). Surface hydrophobicity decreased by nearly 90% with 30 mM genipin, corresponding to similar tryptophan fluorescence quenching. The genipin treatment converted HPI into highly cross-linked polymers. Hydrogels formed with such polymers when also incorporated with hemp oil emulsions exhibited substantially enhanced gelling ability: up to 3.3- and 2.6-fold increases, respectively, in gel strength and gel elasticity over genipin-untreated protein. The genipin-modified composite gels also exhibited superior water-holding capacity. Microstructural analysis revealed a compact gel network filled with protein-coated oil globules that interacted intimately with the protein matrix when treated with genipin. Such gels remained readily digestible. Hence, genipin-treated hemp protein hydrogels show promise as functional food components.

Some indices of the cats’ protein metabolism under the obesity

Obesity is one of the most widely-distributed metabolic disturbances in cats, herewith the animals’ number with a given pathology is constantly increasing. The excess mass and obesity lead to the extreme metabolic disturbances including all the chains of metabolism. The cats belong to wild animals and are characterized by a high level of protein metabolism, herewith they are incapable to keep up with the level of the particular amino acids under their constant introduction into the feeds. The intensity of glucogenesis for which the amino acids are viscous material and are involved into the process of dissemination under the obesity is constantly increasing. It results in increasing the amount of final product of nitrogen metabolism. The paper researches the total protein content as well as that of albumin, ammonia, urine, creatinine and creatine kinase activity of the cats’ blood which had the excess mass or obesity. In addition, it has become necessary to determine the content of amino acids cysteine sulfhydryl groups, which essentially contributes to the process of cats’ metabolism. To perform the research two groups of cats (female and male) aged 3–7 were formed, the control group consists of 7 clinically healthy animals that corresponds to the BCS 4–5 index according to the nine grading scale, the experimental group consists of 5 animals of the same age and they have BCS – 7–9 index, that testifies to the excess mass and obesity processes. The concentration of the total protein, albumin, ammonia, urine, creatinine as well as of creatine kinase activity of the total and free(nonprotein) sulfhydryl groups was found in the cats’ blood. The significant decreasing of the albumin part has been revealed in cats with the excess mass and obesity that causes the liver function disturbances and results in increasing of its protein decomposition. The increasing quality of the ammonia content by 31% and urine by 21% has been revealed in cats of the experimental group, however the individual ranges of given indexes within both control and experimental groups were considerable ones. The creatinine concentration and creatine kinase activity in cats with the obesity increases, that testifies to the destructive processes intensification in the muscular tissues. Sulfhydryl groups of the cysteine are of great importance for the metabolic processes in particular in the processes of detoxication, disease-resistance as well as of antioxidant processes. The total concentration of SH-blood groups made no essential difference in cats of the control and experimental groups, while the concentration of free SH-blood groups of experimental animals was by 31% less than in its control analogues. Thus, the obesity has an essential effects on the protein metabolism that causes the amino acids decomposition processes as well as the accumulation of the metabolic final products and free sulfhydryl groups reducing.

Effects of low frequency magnetic field on myoglobin oxidation stability

The effects of low frequency magnetic field on myoglobin (Mb) oxidation stability were evaluated by treatments at 0, 3, 6, 9, 12 mT and storage for 10 h. The results showed that Mb oxidation was inhibited under all magnetic field treatments, due to the increase of total sulfhydryl and free amino groups (9 or 12 mT) from unfolding of Mb clusters (3, 9, 12 mT) as well as β-turn and β-sheet structures (9 or 12 mT). The unfolding also induced (i) the destruction or burial of iron porphyrin and tyrosine residues; (ii) the exposure of tryptophan; (iii) more uniform Mb particle size distribution (3, 9, 12 mT) and increased zeta potential (3, 6, 12 mT). Overall, magnetic field promoted exposed active groups as the preferred oxidation target, thus decreasing the oxidation rate of central iron atoms. It also promoted Mb stability by redistributing particle size and increasing zeta potential.

Development of acceptable high‐quality noodles using nonglutinous rice cultivar Akitakomachi flours

AbstractBackground and objectivesTo elucidate the effects of four different particle sizes of flour from the nonglutinous rice cultivar Akitakomachi on noodle quality and the factors that affect the production of acceptable high‐quality noodles.FindingsThe damaged starch content was lowest in the flour with a particle size range of 53–212 μm, and the water absorption rate increased as the flour particle size ranges decreased. By textural and sensory analyses, noodles made from flour with a particle size range of 53–212 μm showed high breaking strength, cohesiveness, smoothness, gelatinization degree, and acid solubility and low adhesiveness. The expansion rate of noodle strands after cooking, especially noodle width and thickness, was fairly high, and the solubility of proteins and sugars was low in strands made with 0.5% grain vinegar compared to those made without grain vinegar. The total and surface SH group contents in different protein fractions were not different between noodles produced with and without grain vinegar.ConclusionsAcceptable high‐quality noodles were produced using flour with a particle size range of 53–212 μm and 0.5% grain vinegar. The high‐order structural changes in the rice protein molecules by grain vinegar treatment significantly contributed to noodle quality, particularly their satisfactory firm texture.Significance and noveltyThe use of flour with a particle size range of 53–212 μm and the addition of grain vinegar were important factors for the production of high‐quality noodles with flour from the nonglutinous rice cultivar Akitakomachi. These results provide useful information for rice flour noodle industries.

Bitter peptides increase engulf of phagocytes in vitro and inhibit oxidation of myofibrillar protein in peeled shrimp (Litopenaeus vannamei) during chilled storage

We have shown that bitter peptides derived from the hydrolysates of pepsin digested fish protein can increase lymphocytes and lysozyme activity and improve fish survival in aquaculture. In this study, we investigated how the immune function of bitter peptides increases the phagocytes’ engulf of latex beads, and analyzed the antioxidation of myofibrillar protein in peeled shrimp during chilled storage with /without bitter peptides by evaluating the activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, and the effects of the total carbonyl and sulfhydryl. Also, the bitter peptides’ effect on the structural stability of muscles protein throughout oxidation was examined in vitro by both scanning electron microscope (SEM) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The engulf assay demonstrated phagocytosis increased from the control group to the highest bitter peptide concentration of 1.2 mg/ml; the bitter peptides had a significant DPPH radical-scavenging activity, reducing the power of ferric ions and metal chelating ability. Chemical analysis showed that myofibrillar protein in chilled storage was highly susceptible to oxidation, and the results indicate that treating peeled shrimp with bitter peptides before chilled storage significantly decreases the formation of carbonyl derivatives and reduces the loss of thiol groups when compared with the water treated sample. In addition, the results of both SEM and SDS-PAGE confirm that there was less distortion of tissue structure and less degradation of the protein in the samples treated with bitter peptides. Bitter peptides are both beneficial for fish disease control and preservation of marine food.

EFFECTS OF AEROBIC EXERCISE TRAINING ON OXIDATIVE STRESS IN THE SKELETAL MUSCLES OF OBESE RATS

ABSTRACT Introduction Obesity is a complex and multifactorial metabolic disorder characterized by the accumulation of body fat; physical exercise increases energy expenditure and promotes a reparative effect through modulation of endogenous antioxidant defenses. Objective To evaluate the effects of the high-fat diet (HFD) on oxidative stress parameters in skeletal muscles of rats using aerobic exercise training protocols (AETP), moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT). Methods The study was quantitative and experimental. Animals received 8 weeks of HFD or normal diet (ND), followed by 9 weeks of HFD or ND and the two AETPs. Results HFD did not alter the formation of thiobarbituric acid reactive substances (TBA-RS), total sulfhydryl and protein carbonyl content in the soleus and plantaris muscles; in contrast, the protocols caused a decrease in TBA-RS levels in the plantaris muscle and increased the sulfhydryl content in the soleus muscle, while MICT increased the sulfhydryl content in the plantaris muscle and reduced protein carbonyl content in both muscles. HFD reduced SOD activity in the plantaris muscle while the MICT protocol enhanced SOD in the soleus muscle and both protocols reversed the decrease in SOD in the plantaris muscle. HFD increased CAT activity in the soleus muscle, the HIIT protocol prevented this alteration and both protocols increased CAT in the plantaris muscle. HFD reduced GSH-Px activity in both muscles, and the MICT protocol prevented this reduction in the soleus muscle, while the HIIT protocol partially prevented this decrease. The MICT protocol did not prevent the reduction of GSH-Px and the HIIT protocol partially prevented this decrease in the plantaris muscle. Conclusions HFD elicited oxidative stress in the skeletal muscle of rats, and both protocols were able to prevent most of the alterations in oxidative stress parameters caused by the HFD. Level of evidence IV; Investigation of treatment outcomes.

Improvement of gel properties of mackerel mince by phlorotannin extracts from sporophyll of Undaria pinnatifidai and UVA induced cross-linking.

The effects of phlorotannin extracts (PTE) (from sporophyll of Undaria pinnatifida) added at different concentration (0, 1.6, 8, and 40 mg/g protein) with and without ultraviolet A (UVA) irradiation treatment on gel properties of mackerel (Scomberomorus niphonius) mince (MM) were investigated. The results indicated that both the breaking force and water-holding capacity (WHC) of the MM gel increased with addition of PTE, and the highest breaking force and WHC were observed with 40 mg/g PTE under UVA irradiation. Low-field nuclear magnetic resonance revealed that free water significantly decreased in this PTE-MM gel as well. UVA irradiation treatment led to reduction of total sulfhydryls and free amines in the PTE-MM gel, indicating more cross-linking between proteins. Electrophoresis results indicated that myosin heavy chains were aggregated in the UVA-treated PTE-MM gel. The microstructure of the UVA-treated PTE-MM gel showed that protein formed more evenly distributed cross-linked structures and was more compact than the untreated control gel. As a conclusion, PTE addition with UVA irradiation is shown to improve gelling properties of mackerel mince.

Molecular characteristics and foaming properties of ovalbumin-pullulan conjugates through the Maillard reaction

The aim of this research was to synthesize ovalbumin-pullulan conjugates through the Maillard reaction and compare the molecular characteristics of native ovalbumin (N-OVA), heated ovalbumin (H-OVA) and glycosylated ovalbumin (G-OVA). The glycosylation was monitored by the degree of graft and Amadori compound. Covalent binding between ovalbumin and pullulan was confirmed by SDS-PAGE and FTIR. CD spectra showed that glycosylation could inhibit the heat-induced formation of β-sheet. Due to the shielding effect of polysaccharide, H0 and fluorescence intensity of G-OVA were lower than those of heated group. Meanwhile, zeta potential values of G-OVA at three different pH were extreme small, close to zero. Compare with N-OVA, the free exposed sulfhydryl contents of conjugates increased and total free sulfhydryl contents decreased. For G-OVA, foaming stability was 50.5%, which was a factor of 7.1 higher than the value of N-OVA (7.1%). G-OVA foam displayed smaller and more homogeneous bubble size than N-OVA and H-OVA. In addition, G-OVA foam presented the slowest rate of the bubble size increase over time. Overall, Maillard reaction was proven to be successful in enhancing the foaming properties of ovalbumin.

Effects of Glazing with Preservatives on the Quality Changes of Squid during Frozen Storage

This study aimed to investigate the effects of glazing with sodium polyacrylate (SP) and D-sodium erythorbate (DSE) on the quality changes of squid during frozen storage. Frozen squid samples were randomly divided into seven groups: (1) CK (unglazed); (2) WG (distilled water-glazed); (3) SG (0.1% SP -glazed); (4) SG-1DSE (0.1% SP with 0.1% DSE -glazed); (5) SG-3DSE (0.1% SP with 0.3% DSE-glazed); (6) SG-5DSE (0.1% SP with 0.5% DSE-glazed); (7) WG-1DSE (0.1% DSE-glazed). The efficacy of the different coatings was evaluated using various indicators, such as water holding capacity (WHC), pH value, low field nuclear magnetic resonance (LF-NMR), color, malondialdehyde (MDA) content value, free amino acids (FAAs) content, intrinsic fluorescence intensity (IFI) and the total sulfhydryl content (SH) content. Intrinsic fluorescence intensity (IFI) and low field nuclear magnetic resonance (LF-NMR) were used as fast monitoring techniques to monitor changes in quality of squid samples. The results showed that compared with the CK and WG groups, coating with either SG or DSE alone resulted in reduced rate of moisture loss (p < 0.05), lipid oxidation (p < 0.05) protein degradation (p < 0.05) and prolonged its shelf-life. The combination of glazing treatment with SG and DSE (groups SG-1DSE, SG-3DSE and SG-5DSE) further improved the protective effects of coating, particularly in the SG-3DSE group. Therefore, the glazing of SG-3DSE is recommended to be used to control the quality of frozen squid and to prolong its shelf-life during frozen storage.

Protective characterization of low dose sodium nitrite on yak meat myoglobin in a hydroxy radical oxidation environment: Fourier Transform Infrared spectroscopy and laser Micro-Raman spectroscopy

The effect of NaNO2 in hydroxyl radical-mediated oxidative damage of yak meat myoglobin was investigated. Laser micro-Raman spectroscopy and Fourier Transform Infrared spectroscopy were used to assess protein (carbonyls, total sulfhydryl and Disulfide bonds) oxidation, atomic (or molecular) interactions and secondary structural changes. The addition of NaNO2 during the oxidation of myoglobin significantly reduced the content of carbonyl and disulfide bonds and protected the sulfhydryl groups from hydroxyl radical oxidation (P < 0.05). There was no significant difference in the secondary structure of myoglobin between the control group and the SN treatment group(P > 0.05). At the same time, NaNO2 had an inhibitory effect on the expansion of the hemoglobin center size and the transition of Fe from a low spin state to a high spin state caused by radical-oxidized. These findings suggest that NaNO2 has potential for treatment effects in a hydroxyl radical-oxidized myoglobin.

Comparison of hydrodynamic and ultrasonic cavitation effects on soy protein isolate functionality

In this study, soy protein isolate (SPI) dispersions (3%, w/v) were treated with hydrodynamic cavitation (HC) with a venturi tube (treatment volume: 2 L) and ultrasonic cavitation (UC) (treatment volume: 200 mL and 2 L) under the power of 550 W for 5, 10, 20, and 30 min. The effects of HC and UC treatment on the physicochemical and functional properties of SPI were investigated, and the results were compared to better evaluate the HC effects on food proteins. The results showed that the electrophoretic profile and pH were not affected by UC or HC treatment. The particle size and viscosity of SPI were reduced after UC or HC treatment. Both UC and HC treatment significantly (P < 0.05) increased the surface hydrophobicity. UC treatment at the volume of 2 L did not alter the exposed or total sulfhydryl content; however, UC treatment at the volume of 200 mL and HC treatment altered the exposed sulfhydryl content and decreased the total sulfhydryl content. Moreover, the solubility, emulsifying activity index, emulsion stability index, and foaming capacity were also significantly (P < 0.05) improved; however, foam stability was reduced after UC and HC treatment. Under the conditions investigated in this study, the effect of HC treatment on the physicochemical and functional properties of SPI was more pronounced than that of UC treatment at the volume of 2 L, and was similar to that of UC treatment at the volume of 200 mL. These results suggest that HC could be an effective method to improve the functional properties of food proteins.

Duck egg albumen hydrolysate-epigallocatechin gallate conjugates: Antioxidant, emulsifying properties and their use in fish oil emulsion

Duck albumen hydrolysates (DAH) conjugated with epigallocatechin gallate (EGCG) at various levels (2–5%, w/w) were prepared and characterized. FTIR analysis showed that the conjugation between DAH and EGCG induced the change of secondary structure and modified functional groups of DAH. Furthermore, surface hydrophobicity of DAH was increased, while total sulfhydryl group and total carbonyl contents were decreased when EGCG was conjugated, especially when EGCG at higher levels was used (P < 0.05). Antioxidant activities and emulsifying properties of DAH-EGCG conjugates were enhanced, particularly when DAH conjugated with 4% EGCG (P < 0.05). Storage stability of fish oil emulsion (FOE) stabilized by DAH or DAH-EGCG conjugate was also investigated up to 15 days at 26–28 °C. Emulsion stabilized by DAH-EGCG conjugate had higher magnitude of ζ-potential (negative charge), smaller oil droplets size (d43), as well as lower flocculation and coalescence of oil droplets as compared to those of emulsion prepared using DAH throughout the storage. Moreover, oxidative stability of FOE was improved when DAH-EGCG conjugate was incorporated as evidenced by lowered thiobarbituric acid-reactive substances and peroxide value. Thus, the conjugate between DAH and 4% EGCG could serve as an antioxidant emulsifier for enhancement of physical and oxidative stability of FOE.