•We examined phase behaviors of myofibrillar protein/κ-carrageenan mixtures.•Phase separation was enhanced as the polysaccharide ratio and temperature increased.•Carrageenan decreased the gelation temperature but increased the storage modulus.•The gel networks were significantly influenced by the κ-carrageenan concentration.Phase behaviors of mixtures of myofibrillar protein and κ-carrageenan at different mixing ratios and temperatures were examined by digital images and confocal scanning laser microscopy, showing that that the extent of phase separation was enhanced as the ratio of polysaccharides and temperature increased. The zeta potential of the mixtures became less negative as the protein ratio increased, and the complex became saturated at or above the protein/κ-carrageenan ratio of R4 (3.2%:0.8%). Gelation process performed by dynamic rheological analysis demonstrated that the presence of carrageenan decreased the gelation temperature but increased the storage modulus. Analysis of the microstructures of the mixed gels showed that the networks were significantly influenced by the concentrations of κ-carrageenan. The present work could be applied to evaluate the mechanism of competition between phase separation and gelation in mixtures of proteins and polysaccharides.Download high-res image (246KB)Download full-size image

•Konjac glucomannan chain stretched better in proteins induced by microwave heating.•Interactions between polysaccharide and protein were stronger in microwave-heated mixed gels.•Microwave heating for 5 or 10 min improved the gel strength of surimi protein-polysaccharide gels.•Microwave heating improved the water-holding capacity of mixed surimi gels.The effects of two heating methods on structure and various quality parameters of polysaccharide-protein mixed gels have been investigated in this study. Confocal laser scanning microscopy and scanning electron microscopy were used for the determination of the micromorphology, stretching, and dispersion of konjac glucomannan (KGM) chains in the proteins, and the microstructure of mixed gels. Double staining was used in this study to observe the microstructure and the interactions between the molecular chains of polysaccharides and proteins. Microwave-heated KGM chains were shown to have the higher rates of stretching, and they contributed to the formation of polysaccharide-protein network, while the polysaccharides in the water bath-heated gels were observed as aggregates inserted in proteins. Dynamic viscoelastic measurements showed that microwave-heated gels had considerably greater gel strength, and that the interactions between their molecular chains were much stronger. Additionally, microwave heating was shown to strengthen the texture properties and improve the water-holding capacity of the gels.Download high-res image (150KB)Download full-size image

•Alginates with different M/G ratios can encapsulate fish oil in core–shell beads by co-extrusion.•A low G content (70.4%) alginate contributed to the better stability of core-shell beads.•Oxidative stability of the fish oil decreases in the order of core-shell beads > free oil > emulsion.Feasibility of encapsulating fish oil in core–shell beads using alginates with different M/G ratios was investigated for improving the stability of fish oil in an acidic solution and the effect of alginate properties on the stabilization of fish oil core–shell beads. Core–shell beads were placed into buffer solutions with different pH values. At equivalent alginate concentrations, the beads exhibited marginal shrinkage in an acidic solution. At pH 9–11, the beads were swollen. At all pH values, the amount of leaked oil increased with decreasing alginate concentration. All three types of alginates with different M/G ratios (70.4%; 79.4%; 88.0%) can encapsulate fish oil in core–shell beads. The results obtained from the stability treatment of three core–shell beads containing different α-l-guluronic acid contents indicated that the wall materials of beads with low G content were viscous. Therefore, it (G = 70.4%) can be a suitable material for improving the oxidation stability of fish oil in an acidic medium. Based on the obtained peroxide and p-anisidine values, it can be suggested that core–shell beads are beneficial for improving the oxidative stability and retention rate of polyunsaturated fatty acids in an acidic solution.

•The paper demonstrated the identification of sia 2-6 hexose by ESI-MS/MS.•The cleavage pathway of sulfated sialic acid was proposed.•The retention versus ceramide carbon numbers were fitted to exponential equations.Sea urchin gangliosides have been proved to contain neuritogenic activities, which related to their molecular compositions. This study reports a method utilizing reversed-phase chromatography coupled to mass spectrometry for structure investigation and molecular species determination of the monosialogangliosides from sea urchin Strongylocentrotus nudus. Two types of sulfated and nonsulfated monosialogangliosides were isolated from the sea urchin ovary. In MS2 spectra of both nonsulfated monosialoganglioside and sulfated monosialoganglioside, 2-6 linked sialic acids were identified by the characteristic fragments of 0,4A2-CO2 and 0,2A1. Fragment ions at m/z 139.1 and m/z 169.1 of nonsulfated monosialoganglioside might be characteristic for 8-sulfated sialic acid residue. Retention time of the molecules was effectively used in the characterization of unknown molecules, and molecules that differ in mass by only 0.04 Da were easily differentiated.

There is mounting evidence demonstrating causative links between hyperglycemia, oxidative stress, and insulin resistance, the core pathophysiological features of type 2 diabetes mellitus. Using a combinational approach, we synthesized a vanadium–antioxidant (i.e., l-ascorbic acid) complex and examined its effect on insulin resistance and oxidative stress. This study was designed to examine whether vanadyl(IV)-ascorbate complex (VOAsc) would reduce oxidative stress, hyperglycemia, and insulin resistance in high-fat high-sucrose diet (HFSD)-induced type 2 diabetes in mice. Male C57BL/6J mice were fed a HFSD for 12 weeks to induce insulin resistance, rendering them diabetic. Diabetic mice were treated with rosiglitazone, sodium l-ascorbate, or VOAsc. At the end of treatment, fasting blood glucose, fasting serum insulin, homeostasis model assessment-insulin resistance index, and serum adipocytokine levels were measured. Serum levels of nitric oxide (NO) parameters were also determined. The liver was isolated and used for determination of malondialdehyde, reduced glutathione, and catalase levels, and superoxide dismutase and glutathione peroxidase activities. VOAsc groups exhibited significant reductions in serum adipocytokine and NO levels, and oxidative stress parameters compared to the corresponding values in the untreated diabetic mice. The results indicated that VOAsc is non-toxic. In conclusion, we identified VOAsc as a potentially effective adjunct therapy for the management of type 2 diabetes.

Metabolic syndrome (MS) is a cluster of metabolic disorders such as abdominal obesity, hypertension, glucose intolerance, dyslipidemia and hepatic steatosis that contribute to increased cardiovascular morbidity and mortality. There is an urgent need for strategies to prevent this emerging global epidemic. Recently, growing interest in discovering food functional nutrients for the prevention and treatment of MS has generated. In the present study, sea cucumber cerebrosides (SCC) and the main structural units, long-chain bases (LCB), were prepared from Acaudina molpadioides and then administered to high fat (HF) diet-induced obese C57BL/6J mice at a diet supplement dosage of 0.025% for 5 weeks to evaluate their effects on obesity-related metabolic disorders. SCC and LCB significantly decreased epididymal adipose tissue weights, lowered hepatic triacylglycerol levels, and reduced serum glucose, insulin levels and HOMA-IR index in mice. The activities of hepatic lipogenetic enzymes including FAS, ME and the mRNA levels of SREBP-1c and FAS were reduced by SCC and LCB treatment. However, SCC and LCB showed no effect on the hepatic lipolysis pathway. Besides, SCC and LCB also efficiently up-regulated the gene expression of SREBP-1c, FAS, ACC, ATGL and HSL, and down-regulated the gene expression of LPL and VLDL-r in the adipose tissue. These results demonstrated that SCC and LCB were efficacious in suppressing hepatic SREBP-1c mediated lipogenesis, inhibiting lipid uptake and increasing TG catabolism in the adipose tissue. The ameliorative degree and regulatory mechanisms of these two compounds were basically the same, suggesting that LCB are the key active structural units. Such findings would offer new insight into the application of SCC or LCB in the development of functional foods for preventing MS in humans.

The effect of oxidation with ozone on myofibrillar proteins from bighead carp (Hypophthalmichthys nobilis) and its influence on the textural properties of surimi gels of bighead carp were investigated. Treatment with ozone of an appropriate concentration significantly increased the salt extractable protein (SEP), Ca2+-ATPase activity, total sulfhydryl and active sulfhydryl contents, surface hydrophobicity, and carbonyl content of the myofibrillar proteins. The breaking force and deformation of the surimi gels of bighead carp initially increased and subsequently decreased as the extent of oxidation increased. Based on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis, there were no apparent changes in the protein distribution and no new patterns appeared in electrophoresis processing analysis after the ozone treatment. Differential scanning calorimetry (DSC) found that low concentrations of ozone water rinse had slight effects on thermal stabilities of myofibrillar proteins, which coincided with the above results. The present study indicates that ozone treatment is a prospectively mild oxidation protocol for enhancing the physicochemical properties of fish proteins from bighead carp.

•The effects of frequency and temperature on ε of myofibrillar protein were studied.•Linear models were developed for the dielectric properties between 500 and 2500 MHz.•Effects of concentrations and viscosities of protein on ε′ were consistent.The open-ended coaxial probe technique was used to study the effects of frequency (500–2500 MHz), temperature (20–90 °C), concentrations of myofibrillar protein (0.5, 1.5, and 2.5 mg/mL) and NaCl (0.3, 0.45, and 0.6 M) on the dielectric properties of myofibrillar protein. Models describing the behavior of the dielectric constant (ε′), loss factor (ε″) were developed. ε′ decreased as frequency, temperature, and NaCl concentration increased, whereas ε″ decreased with increasing frequency but increased with increasing temperature and NaCl concentration. Minor differences in the effects of myofibrillar protein concentrations were observed; the trend of ε′ changes agreed with viscosity changes, namely the maximum value of ε′ and viscosity were achieved when the myofibrillar protein concentration was 1.5 mg/mL, followed by concentration of 0.5 and 2.5 mg/mL. The penetration depth was estimated under various conditions and decreased with frequency, temperature, and NaCl concentration increasing but increased with myofibrillar protein concentration increasing.

•Ozone for the removal of geosmin in freshwater fish was effective.•The physicochemical properties of myofibrillar protein could be enhanced by ozone.•The mechanism of how ozone-induced oxidation affects the gel structure was shown.Two manners of ozone treatment (washing with ozonized water and ozone-flotation) were selected to remove the geosmin in the fish muscle from bighead carp. A total of 42.09%–54.28% and 42.78%–69.19% geosmin in fish muscle could be eliminated by ozone water and ozone-flotation washing for 5–20 min, respectively. Treatment with ozone of an appropriate condition significantly increased the salt-extractable protein, Ca2 +-ATPase activity, total sulfhydryl and active sulfhydryl contents, carbonyl content of the myofibrillar protein, and gel strength without improving PV and TBA values too much. No apparent changes in the protein distribution and no new patterns appeared in SDS-PAGE after the ozone water treatment. The results indicate that ozone water treatment is a prospectively mild oxidation protocol than ozone flotation to enhance the physicochemical properties of fish protein from bighead carp as well as to eliminate muddy flavours.Industrial relevanceOzonation has been used for years to disinfect water for drinking purposes in Europe. A number of other commercial uses have been found for ozone including disinfection of bottled water, swimming pools, prevention of fouling of cooling towers, and wastewater treatment. Ozone use may have many advantages in the food industry. There are suggested applications of ozone in the food industry such as food surface hygiene, sanitation of food plant equipment, reuse of waste water, and lowering of the biological oxygen demand (BOD) and chemical oxygen demand (COD) of food plant waste.Ozone is a strong oxidant that also has decolorizing and deodorizing effects, and thus offers many advantages in the food industry, and has been traditionally used in freshwater aquaculture systems in the treatment of fish, disinfection of eggs, sterilization of water to improve the water quality, and decomposition of odorous compounds in natural water in addition to its applications for improving the sensory quality and shelf life of fish. Since 1920, scientists have attempted to exploit the wide-range disinfection characteristics of ozone to slow the decomposition for improving the safety of fishing products. A number of commercial uses have been found for ozone, including the disinfection and preservation of aquatic products. In the United States, ozone received Generally Recognized as Safe (GRAS) classification in 1997, and in 2001, the FDA officially approved ozone for use in the food industry and for direct contact with food products, including fish, meat, and poultry. Ozone has continued to gain momentum in the food processing industry as the safest, most cost-effective, and a chemical-free way of dealing with food safety management.