Search

Summary: Textural deterioration is a severe problem in fish industry. In order to study the role of structural proteins in refrigerated grass carp, myofibrillar proteins and collagen degradation were investigated at different stages. Results revealed that connective tissues of fish muscle disintegrated from day 1, failing to hold muscle myotomes together, with a decrease of shear force. Meanwhile, collagen solubility increased from day 1 and degradation of nebulin was observed after 3 days, while there was no obvious change in the bands of myosin heavy chain and actin. Furthermore, Pearson coefficient analysis revealed that insoluble collagen (ISC) and nebulin were significantly correlated with shear force. Negative correlation was established between drip loss and contributing factors (ISC, titin and nebulin). All results suggested that textural loss of post‐mortem grass carp fillets was mainly mediated by the degradation of collagen and to a lesser extent by myofibrillar proteins at the early storage. [ABSTRACT FROM AUTHOR]

Here, a nontoxic antibacterial material based on Chitosan Oligosaccharide-N-Chlorokojic acid Mannich base (COS-N-MB) that was synthesized by using the selective partial alkylation reaction displaying excellent activity against bacterial infection. The proposed mechanism of the action of COS-N-MB is that this antibacterial material with positive charge and synergistic antibacterial effects can promote it’s adsorption to bacterial cell wall through electrostatic interaction and chelating metal cations. It changed the permeability of the membrane, caused cellular leakage, and destroyed the membrane integrity, leading to complete membrane disruption and eventually death of the bacteria. Besides, COS-N-MB can interact with membrane proteins, causing deformation in the structure and functionality. The good biocompatibility, noncytotoxic, and low hemolysis made this novel material a promising and effective compound for antibacterial applications. [ABSTRACT FROM AUTHOR]

Chitosan coating and plastic wrap coating were investigated for their effects on the quality of grass carp fillets stored at 4 ± 1ºC for a period of 20 days. The fillets were divided into groups of untreated (Control), wrapped with sterile preservative film (PE), and chitosan-treated (1, 2, and 2.5% w/v corresponding to CH1, CH2, and CH2.5, respectively). The final result demonstrated that chitosan coating has positive effects on the microbial inhibition of total volatile count (TVC), lactic acid bacteria (LAB),Enterobacteriaceae, Pseudomonas, H2S-producing bacteria (includingShewanella putrefaciens), andStaphylococcus. With regard to the results of biogenic amines (BAs), putrescine (PUT) and histamine (HIS) were the major amines, and their concentration was significantly (p< 0.05) higher in Control and PE than in chitosan-coated fillets at the end of storage. The final concentration in Control, PE, CH1, CH2, and CH2.5 was 143.7, 160.1, 83.0, 59.4, and 44.2 mg/kg for PUT and 228.0, 57.1, 4.1 3.2, and 2.9 for HIS, respectively. Chitosan coating was found to inhibit the increase of total volatile base nitrogen (TVB-N), microbial population, and total BAs and prolong the shelf life of grass carp fillets. However, sterile plastic wrap coating had little positive effect on maintaining the quality of grass carp fillets during refrigerated storage. [ABSTRACT FROM PUBLISHER]

Previous studies have verified the protective role of n3 polyunsaturated fatty acids (PUFAs) in cancer. Fish brain lipids are rich in n3 PUFAs. However, the action and mechanism of their potent anticancer activities remain unclear. In this study, polar lipids (PLs) and neutral lipids (NLs) were isolated from the total lipids (TLs) of the silver carp brain, and the anticancer effects of the lipid fractions (LFs) were examined in a human breast cancer cell line (MCF-7). The LFs effectively inhibited the cell proliferation of MCF-7 cells in a time- and concentration-dependent manner by cell cycle arrest at the S stage and induction of apoptosis. Further analyses showed that the apoptotic effect of the LFs on MCF-7 cells was associated with the accumulation of elevated levels of reactive oxygen species and the loss of mitochondrial membrane potential. Among the TLs, PLs were more effective at causing breast cancer cell death than NLs. Our study showed that the LFs from silver carp brains may aid the prevention and treatment of human breast cancer. [ABSTRACT FROM AUTHOR]

The effect of mixed starter cultures isolated from Suanyu on flavor compounds development has been researched. Microorganism, pH, TA, sugars, nonvolatile organic acids and volatile compounds were analyzed in Suanyu with or without starters. In inoculated samples, a higher growth of lactic acid bacteria (LAB) and a declining rate of pH were determined when compared with the controlled samples. Besides, higher levels of volatile compounds were detected in inoculated Suanyu (19342.47, 19852.74 × 106 area units for PS) than those in controlled samples. During the process, aldehydes, acids, alcohols, esters and ketones were formed and increased continuously. Especially in Suanyu with PS, higher levels of ethanol (6973.8, 6549.9 × 106 area units) and acetic acid (2116.8, 2471.1 × 106 area units) were detected, which could produce unique wine flavor and moderate acid taste. Furthermore, high content of hexanal was generated through the addition of PS, which could contribute to a green grass odor. Practical Applications In this study, microorganism, pH, TA, sugars, nonvolatile organic acids and volatile compounds were analyzed in Suanyu with autochthonous starter cultures. The results showed that the generative stability of Suanyu can be assured and the product quality can be advanced by adding autochthonous starter cultures compared with that of noninoculated samples. There is a need to add modern processing technology such as microbial fermentation of the fermentation process to achieve effective control to ensure product flavor and product quality stability. In this study, autochthonous starter cultures isolated from Suanyu, which were propitious to the demand of industrialization. Besides, once the research is applied in the industrialized production, and considerable social and economic benefits can be obtained. Therefore, this study has a good prospect in application. [ABSTRACT FROM AUTHOR]

The hydrolysis of sarcoplasmic proteins during the growth of Lactobacillus plantarum 120 originally isolated from Suanyu, a traditional Chinese low salt fermented fish, was evaluated. Fermentation was carried out in a fish meat model system at 30C for 96 h. Proteolytic activity of this strain on fish muscle sarcoplasmic protein was determined by proteins, peptides and free amino acids analyses. There was a pronounced hydrolysis of almost all protein bands in electrophoretic pattern by L. plantarum 120. It also resulted in the generation of new peptides and disappearance of original peaks. In addition, the studied strain generated greater amounts of free amino acids than the control, especially for alanine, glutamic acid, phenylalanine, valine, methionine, aspartic acid, isoleucine and leucine. In general, proteolysis of fish sarcoplasmic proteins by L. plantarum 120 occurred during fermentation, resulting in increase in peptides and free amino acids, which may contribute to the taste and aroma of Suanyu. Practical Applications Suanyu is one of the Chinese traditional fermented fish products in South China. According to its characteristic flavor and high nutrition value, Suanyu has been accepted around China in recent year. However, Suanyu is still manufactured on a small scale by spontaneous fermentation. It is difficult to guarantee product quality and increase the efficiency. Lactic acid bacteria is one of the essential agents of the meat fermentation process that contribute to the hygienic and sensory qualities of meat products. Lactobacillus plantarum 120, isolated from Suanyu, exhibited optimal properties as a potential starter in our previous work. Once L. plantarum 120 is used as an industrial starter, it will promote fish muscle proteolysis, shorten the fermentation period and then improve product quality assurance activity. [ABSTRACT FROM AUTHOR]

Proteolytic changes in Suanyu, a traditional fermented fish product of China, were determined during 6 weeks of fermentation. The gradual decrease of pH value andawwas detected, accompanied with an increasing trend detected in trichloroacetic acid–soluble C-1: peptides concentration. Protein composition changed throughout the fermentation. A decrease in sarcoplasmic and myofibrillar protein fractions was accompanied by an increase in the insoluble fraction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed most bands of sarcoplasmic, myofibrillar, and insoluble proteins lightened or disappeared due to proteolysis or denaturation. New bands emerged especially in insoluble proteins. Fluctuation of molecular weight distribution of the water-soluble nitrogen in Suanyu was found during fermentation. The highest percentage in Suanyu end-products was observed in the fraction of <0.18 kDa, followed by 0.18–0.5 kDa, 66.02 ± 0.38% and 10.79 ± 0.27%, respectively. Free amino acids analysis showed that nearly all amino acids increased, especially for Asp, Glu, Met, Phe, Leu, Val, and Ile. Overall, intense proteolysis in Suanyu brought numerous of small peptides and free amino acids, which contribute to the taste and flavor of Suanyu. [ABSTRACT FROM AUTHOR]

Effect of endogenous proteolysis on myofibrillar conformational changes under acidic condition was investigated by spectroscopic techniques. The result of intrinsic tryptophan fluorescence showed that tryptophan residues were exposed to polar environment by acid denaturation of protein and participation of endogenous proteolysis. Extrinsic fluorescence indicated that average surface hydrophobicity (ShANS) decreased by reduction of pH but increased by endogenous proteolysis. Second-derivative UV-spectroscopy implied that the decrease of ShANS under acidic condition may be due to burying of some aromatic amino acid residues into hydrophobic cores induced by acid-induced aggregation, such as tyrosine, while ShANS increased by exposure of some hydrophobic amino acids due to the effect of endogenous proteases. Raman spectra verified the changes in microenvironment of tryptophan and tyrosine residues, and showed that aliphatic amino acids were mainly exposed to polar solvent by both acid denaturation and endogenous proteolysis. In addition, new disulphide bonds were less likely to form by acid-induced aggregation and proteolytic cleavage, while random coils increased and smaller water domains were found. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the thermophysical properties of bighead carp (Aristichthys nobilis) fillets after curing and deep-fat frying. The kinetics of simultaneous curing and deep-fat frying and mass transfer models were utilized to study the predicted models programmed by Matlab and thermophysical models. The results show that the effective salt and water diffusion coefficient models for curing areand, respectively, which correspond to the multivariate nonlinear regression models. The specific rate and effective moisture diffusion coefficient models for frying based on the Arrhenius equation areand, respectively, which are fitted to accurately calculate the mass transfer processes. Moreover, the changes of thermophysical properties—including thermal conductivity, specific heat, and thermal diffusivity of the processed bighead carp muscle—were successfully predicted by incorporating the mass transfer models, the thermophysical properties models, and the components conversion equations into a Matlab program. [ABSTRACT FROM PUBLISHER]

Our work here, for the first time, reported the antibacterial activity of kojic acid-grafted-chitosan oligosaccharides (COS/KA) against three gram-positive and three gram-negative bacteria. Integrity of cell membrane, outer membrane (OM) and inner membrane (IM) permeabilization assay, alkaline phosphatase (ALP) and glucose-6-phosphate dehydrogenase (G6PDH) assay, and SDS-PAGE assay techniques were used to investigate the interactions between COS/KA and bacterial membranes. The antibacterial activity of COS/KA was higher than those of unmodified COS. The electric conductivity of bacteria suspensions increased, followed by increasing of the units of average release for ALP and G6PDH. COS/KA can also rapidly increase the 1- N -phenylanphthylamine (NPN) uptake and the release of β-galactosidase via increasing the permeability of OM and IM in Escherichia coli . SDS-PAGE indicated the content of cellular soluble proteins decreased significantly in COS/KA-treated bacteria. Hence, COS/KA has potential in food industry and biomedical sciences. [ABSTRACT FROM AUTHOR]

In this study,Lactobacillus plantarum 120, Lactobacillus plantarum 145,andPediococcus pentosaceus 220, which exhibit optimal properties among those isolated from the traditional fermented fish products, were selected as the starter cultures for the preparation of fermented whole carp. During the fermentation, samples inoculated with different single starter cultures showed rapid growth of lactic acid bacteria (LAB), decline in pH, suppression in the growth of main microflora, as well as increase of thiobarbituric acid reactive substances (TBARS) values and total volatile base nitrogen (TVB-N). Quantities of nonprotein nitrogen (NPN) and free amino acids (FAA) were higher in whole carp with starter cultures compared to those in the control. Severe hydrolysis of protein was observed utilizing sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis during fermentation. Moreover, sensory evaluation indicated the higher acceptability of fermented products. The results show that inoculation with the autochthonous starter cultures reduced fermentation time and improved the quality of samples. Therefore, isolates of the strains could be used as potential starters for the fermentation of whole carp. [ABSTRACT FROM AUTHOR]

In this paper, a novel chitosan oligosaccharides derivative-chitosan oligosaccharides-kojic acid graft copolymer (COS/KA), COS, and KA were selected to investigate the binding to bovine serum albumin (BSA) using UV-Vis spectroscopy, fluorescence, synchronous fluorescence, and circular dichroism (CD) at pH 7.4. The results indicated that the tryptophan residues of BSA to the distance of COS/KA, COS, and KA were <8 nm, the quenching constants K were decreased, and the value of Kq were much >2.0 × 10 L mols for COS/KA-BSA, COS-BSA, and KA-BSA at 298, 302, 306, 310 K, respectively, those confirmed that the quenching process belongs to static quenching. The thermodynamic parameters ∆H°, ΔG°, ΔS° at different temperatures were calculated and indicated that hydrophobic and electrostatic forces played important roles in the binding process, and the enhanced binding affinity mainly associated with the increase of the hydrophobicity. Moreover, the CD data demonstrated that the secondary structure of BSA was slightly altered in the presence of COS/KA, COS, and KA, with different reduced α-helix contents (46.30 ± 0.20, 48.60 ± 0.40, 50.70 ± 0.20), respectively. The work provides basic data for the binding mechanism of COS/KA with BSA in vitro. [ABSTRACT FROM AUTHOR]

The effect of media milling on lipid-lowering and antioxidant activities of chitosan was studied in rats fed high-fat diets. Results showed that media-milled chitosan was more effective than chitosan in reducing body weight gain and liver fat accumulation of rats. Compared with chitosan, the reducing effects of media-milled chitosan on serum triacylglycerol (TG), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) were increased by 10.1, 7.5 and 10.2%, and liver TG and TC-reducing effects were increased by 16.2 and 14.6%, respectively. Rats fed media-milled chitosan showed decreased levels of free fatty acid (FFA) and thiobarbituric acid-reactive substances (TBARS) and increased superoxide dismutase (SOD) activity. The cholesterol and fat in feces of rats fed media-milled chitosan were higher than those of rats fed chitosan. These results suggested media milling enhanced the lipid-lowering and antioxidant activities of chitosan, and the reason might be partly due to its effect on strengthening the ability of chitosan in promoting fecal lipid excretions. [ABSTRACT FROM AUTHOR]

In this study, a traditional Chinese dish, a ready-to-eat sweet and sour carp was developed. The effects of sterilization temperature (110, 115, 121, and 130°C) on the selected properties, including heat penetration characteristics, as well as rheological, instrumental color, texture, and sensory attributes, were investigated at the same lethality value (F0) of 4.5 min. The results showed that the heat penetration parameters of cooking value (C-value) and the ratio of C-value to F0value (C-value/F0) exhibited an inverse relationship with processing temperature. The color and rheological properties of the sauce and the texture of the fish sterilized at 130°C were better preserved compared to those sterilized at other temperatures. The sensory attributes of the product sterilized at 130°C scored highest among the final products sterilized at the four temperatures. This study suggested that short-time sterilization at a high temperature can minimize the negative thermal impact on sweet and sour carp product, which would be feasible in the practical production. [ABSTRACT FROM PUBLISHER]

Abstract: A total of 21 Lactobacillus plantarum were isolated from a Chinese traditional low salt fermented whole fish product “Suan yu” and identified by biochemical and molecular methods. The isolates were screened for acidifying and amino-biogenic ability for proteolysis, lipolysis, antimicrobial activity, and sensory in order to select the most suitable candidates as the starter cultures. All the strains had high acidifying activities and were able to reduce the pH to lower than 4.5 in 36, 24 and 16 h at 15, 25 and 37 °C respectively. Major strains showed antimicrobial activities against Listeria monocytogenes, Staphylococcus aureus and Escherichia coli, and ten L. plantarum strains could produce bacteriocins. Five L. plantarum strains exhibited weak proteolytic activities against myofibrillar proteins, as evidenced by the agar plate assay and sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE). None of the strains showed lipolytic activity. Major L. plantarum strains displayed different enzymatic profiles. Besides, the isolates mostly showed negative-decarboxylase activities, but Lp-10 had a decarboxylase activity against l-tyrosine. Furthermore, the fermented fish surimi inoculated with Lp-15 and Lp-21 strains respectively scored high for overall acceptability. Therefore, Lp-15 and Lp-21 presented the best technological properties, which should be given first priority as the starter culture for manufacturing fermented fish products. [Copyright &y& Elsevier]

Silver carp ( Hypophthalmichthys molitrix) is one of the major species of freshwater fish in China. Modification of myofibrillar proteins induced by high pressure processing (HPP) has been investigated at pressures ranging from 200 to 500 MPa for 10 min at 20 °C. Influence of high pressure on conformational changes of myofibrils was studied by means of differential scanning calorimetry (DSC), surface hydrophobicity measurement, ultraviolet absorption spectra and second-derivative spectroscopy, intrinsic spectrofluorimetry, Raman spectroscopic analysis and circular dichroism (CD). DSC analyses revealed that the conformational stability of myofibrils is reduced to different extents when they are exposed to a pressure over 200 MPa. More sulfydryl groups as well as hydrophobic regions and amino acid residues which had ultraviolet absorbance had been found significantly after HPP (≥300 MPa). Changes in the Raman spectra were interpreted as the occurrence of secondary structural changes in pressure-induced myofibrillar proteins. CD analysis results demonstrated that α-helix was destroyed after processed at 400 MPa for 10 min. The results implicated that HPP can be used as a possible means of improving the functional properties for growing demand for healthier fish products. [ABSTRACT FROM AUTHOR]

Abstract: In this study, three groups of mixed starter cultures (S1: Lactobacillus plantarum 120, Staphylococcus xylosus 135 and Saccharomyces cerevisiae 31; S2: L. plantarum 145, S. xylosus 135 and S. cerevisiae 22; S3: Pediococcus pentosaceus 220; S. xylosus 135 and S. cerevisiae 22), isolated from Suan yu, were inoculated to produce the traditional fermented fish. After 42 days fermentation at 24 °C, Suan yu inoculated with different mixed starter cultures underwent rapid growth of lactic acid bacteria (LAB), declined pH, suppressed increase of thiobarbituric acid (TBARS) and total volatile base nitrogen (TVB-N) as well as growth of spoilage bacteria and pathogens. Besides, Suan yu had higher contents of non-protein nitrogen (NPN) and total free amino acids (FAA) compared to the control (P < 0.05). The muscle proteins were severely hydrolyzed during fermentation (SDS-PAGE). Moreover, the sensory evaluation indicates the fermented fish was more widely accepted than the control. The results suggest that the inoculation with S1, S2 and S3 reduced the lag time that fermentation began and improved the quality of Suan yu. [Copyright &y& Elsevier]

Abstract: Silver carp (Hypophthalmichthys molitrix) is a popular cultured freshwater fish in China, and becomes a potential raw material for surimi product. However, silver carp surimi exhibits considerable gel softening (modori) and myofibril-bound serine proteinases (MBSP) involved in the degradation of myofibrillar proteins have been assumed to be crucial to the modori phenomenon. High-pressure technology has demonstrated its potential application to control enzyme-related seafood texture deterioration. Herefrom, it could be further applied to the freshwater fish processing and the effect of high pressure treatments on the activity of MBSP implicated in texture deterioration in myofibrils and crude enzyme extracts was evaluated. The inactivation kinetics of MBSP pressured from 200MPa to 500MPa at room temperature (20°C) were fitted first-order kinetics, The extent of enzyme inactivation was lower in silver carp myofibrils in comparison with the crude enzyme extracts from myofibrils showing a protective effect against the high pressure treatment. The effect of HHP on MBSP myofibrillar degradation shown by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was associated with a corresponding decrease coincided with the elevated high pressure levels in intensity of myosin heavy chain (MHC). Dynamic rheological measurements indicated that high-pressure treatment exerted considerable influence on MBSP activities as well as proteins (mainly myofibrils), resulting in structural modifications and texture changes. In this study, 300MPa (≥10min) was the process condition (pressure and time) that caused apparent MBSP inactivation derived from the first order kinetic model and had the efficacy in controlling silver carp texture deterioration both verified by SDS-PAGE and dynamic rheological measurements. [Copyright &y& Elsevier]

Inactivation kinetics of endogenous lipoxygenase in crude silver carp ( Hypophthalmichthys molitrix) extract was studied for thermal (50-80 °C, ambient pressure) and high hydrostatic pressure combined with heat treatment (300-700 MPa at 50-80 °C) process conditions. Lipoxygenase ( LOX) inactivation followed first-order kinetics at all pressure-temperature combinations used. Moreover, LOX inactivation rates became less pressure dependent with increasing pressure at all temperatures studied and also showed less temperature dependence of the enzyme inactivation rate at various high pressure levels tested. It is evident that inactivation kinetics is complex affected by both pressure and temperature. Therefore, response surface methodology ( RSM) was attempted to investigate combined temperature-pressure processing conditions on LOX inactivation kinetics in crude silver carp extract samples. In conclusion, the LOX inactivation rate constant was modelled as a function of both temperature and pressure conditions by a quadratic polynomial equation as follows: [ABSTRACT FROM AUTHOR]

A diffusion model has been developed for predicting the change of moisture content in lightly salted grass carp fillets under the consideration of shrinkage and variable volumetric effective diffusivity. The established relationship between moisture content, temperature, and effective diffusivity validated the effectiveness of considering the variable volumetric effective diffusivity. The appearance of shrinkage during drying and the shrinkage coefficient have been determined for better predicting the variation of moisture content during drying to provide a thorough theoretical basis for industrial processes. [ABSTRACT FROM PUBLISHER]

In this study, two groups of mixed starter cultures ( S1, S2), which were isolated from Suan yu, were inoculated for this experimental product, and a batch without starters was used as the control. The effect of the mixed starter cultures on the suppression of biogenic amine ( BA) produced during the ripening of Suan yu was investigated. Changes in BA, p H, total volatile base nitrogen ( TVB-N), microbial counts and free amino acids ( FAA) contents were detected during ripening. The results show that the mixed starter cultures rapidly decreased p H, inhibited the growth of contaminant microorganisms emerged in the sample and drastically reduced the accumulations of tyramine, putrescine and cadaverine. However, histamine and spermine were not produced in any batch. Besides, p H, FAA and BA production were not directly correlated. The study suggests that inoculation with S1 and S2 inhibited BA, thereby improving the product safety. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the first study on the chemical and microbial properties of Suan yu, a sanitary Chinese traditional low-salt fermented whole fish product of high nutrition, unique flavor, and long-storage capability. Six brands of Suan yu from different locations in China were studied. Significant differences were observed in some characteristics of this traditional fermented fish, raw material and other spontaneously fermented fish. The values of Enterobacteria and Pseudomonads were under the detection limits in six different brands. In addition, the products contained higher protein and lower moisture ranging from 17.2% to 22.9% and 52.9%–58.1%, respectively. The pH values ranged between 4.27 and 5.18, and lactic acid was the major organic acid. The proteolysis of the myosin heavy chain and actin chain were observed through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Moreover, low concentrations of biogenic amine (BA) and thiobarturic acid (TBARS) values were found in all samples. The characteristics of the six Suan yu brands were all influenced by raw materials, ingredients, and fermentation processes and conditions. [Copyright &y& Elsevier]

Abstract: The structural changes and aggregation properties of silver carp actomyosin acidified with d-gluconic acid-δ-lactone (GDL) were investigated. Results showed that silver carp actomyosin underwent aggregation and formation of precipitate as indicated by turbidity and centrifugation coupled electrophoresis analysis. Circular dichroism indicated that myosin rod unfolded during acidification, resulting in a gradual decrease in α-helical content. The changes in tertiary structure of actomyosin under acidic conditions were demonstrated by second-derivative UV spectra and intrinsic fluorescence. Tyrosine residues were exposed to the surface of proteins when pH was decreased to 5.5, and were buried inside the protein aggregates with further reduction in pH. In contrast, more tryptophan residues were exposed to the polar environment with decreasing pH. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide crosslinking experiments showed that the intensity of myosin heavy chain (MHC) bands decreased sharply with decreasing pH and the actin bands decreased more slowly, suggesting that MHC is the major protein component involved in the non-covalent cross-linking and formation of aggregates during acidification of silver carp actomyosin. [Copyright &y& Elsevier]

In the current study, bighead carp fish were used in conjunction with the flavourzyme enzyme to obtain (FPH) fish protein hydrolysates. The optimum conditions of the hydrolysis process included an enzyme/substrate ratio of 4% and a temperature of 50 °C and pH of 6.5. The hydrolysis time was studied and investigated at 1, 3, and 6 h, and the (DH) degree of hydrolysis was recorded at 16.56%, 22.23%, and 25.48%, respectively. The greatest yield value was 17.83% at DH 25.48%. By increasing the DH up to 25.48%, the crude protein and total amino acid composition of the hydrolysate were 88.19% and 86.03%, respectively. Moreover, more peptides with low molecular weight were formed during hydrolysis, which could enhance the functional properties of FPH, particularly the solubility property ranging from 85% to 97%. FTIR analysis revealed that enzymatic hydrolysis impacted the protein's secondary structure, as indicated by a remarkable wavelength of amide bands. Additionally, antioxidant activities were investigated and showed high activity of DDPH radical scavenging, and hydroxyl radical scavenging demonstrated remarkable activity. The current findings demonstrate that the functional, structural, and antioxidant characteristics of FPH might make it an excellent source of protein and suggest potential applications in the food industry. [ABSTRACT FROM AUTHOR]

Abstract: Acid-induced denaturation and aggregation properties of silver carp actomyosin added with d-gluconic acid-δ-lactone (GDL) during incubation at chilled temperature (4 °C) were studied. Actomyosin underwent aggregation with decreasing pH, as evidenced by increased turbidity and decreased protein solubility in 0.6 M NaCl solution. Ca2+-ATPase activity decreased continually with increasing incubation time in the presence of GDL, accompanied by an initial increase in surface reactive sulphydryl (SH) content, indicating the conformation changes of actomyosin during acidification. Protein solubility in selected solvents and electrophoresis analysis showed that the major myofibrillar proteins, particularly, myosin heavy chain and actin were involved in the formation of protein aggregates mainly through noncovalent bonds including hydrophobic interactions and hydrogen bonds during acidification. The slight decrease in total SH content during acidification suggested that disulphide bonds were also involved in acid-induced aggregation of silver carp actomyosin to a lesser extent. [Copyright &y& Elsevier]

Abstract: Chitosan has excellent emulsifying properties. Emulsifying activity and stability of chitosan were determined by integrated light scattering technique and turbidimetric method. The effects of concentration, degree of deacetylation and molecular weight on emulsifying properties of chitosan were systematically studied in the paper. Emulsifying activity of chitosan initially increased, arrived at the peak at 0.75% and then declined, while emulsifying stability continuously increased with a rise of chitosan concentration from 0.25% to 1.25%. Emulsifying activity and stability of chitosan initially decreased and reached the minimum, then increased with the rise of degree of deacetylation. Chitosan with DD 60.5% and 86.1% showed superior emulsifying activity and stability. Chitosan with low Mw exhibited better emulsifying activity than those with high Mw. Chitosan with Mw 410kDa and 600kDa showed superior emulsifying activity in the test range. Emulsifying stability of chitosan increased with a rise of Mw. [Copyright &y& Elsevier]

Abstract: Chitosan and its oligosaccharides, which are known to possess multiple functional properties, have attracted considerable interest due to their biological activities and potential applications in the food, pharmaceutical, agricultural and environmental industries. Many researchers have focused on chitosan as a potential source of bioactive materials in the past few decades. This review focuses on the biological activities of chitosan and chitooligosaccharides based on our and others’ latest research results, including hypocholesterolemic, antimicrobial, immunostimulating, antitumor and anticancer effects, accelerating calcium and iron absorption, anti-inflammatory, antioxidant and Angiotensin-I-converting enzyme (ACE) inhibitory activities and so on, which are all correlated with their structures and physicochemical properties. The bioactivities summarized here may provide novel insights into the functions of chitosan, its derivatives or oligosaccharides and potentially enable their use as functional-food components and additives. [Copyright &y& Elsevier]

Abstract: A novel water-soluble chitosan derivative, O-fumaryl-chitosan (OFCS), was prepared by using the selective partial acylation of chitosan and fumaric acid in the presence of H2SO4. The chemical structure and physical properties of OFCS were characterized by FTIR, 1H NMR, 13C NMR, and TG techniques. Our results showed that the degree of substitution (DS) for the chitosan derivatives was from 0.07 to 0.48 and the prepared derivatives had good solubility over a wide pH range, for example, the solubility of OFCS increased from 10.5 to 52.6mg/ml as the DS increased. The antibacterial activity of chitosan and OFCS was investigated against Escherichia coli and Staphylococcus aureus. The results indicated that the antibacterial activity of OFCS was much stronger than that of chitosan and it increased with increasing DS increasing. These findings suggest that the OFCS with a DS of 0.48 is preferable for use as a food preservative. [Copyright &y& Elsevier]

Abstract: Chitosans (CHI) with different degree of deacetylation (DD) (60.5%, 65.4%, 70.8%, 77.3%, 86.1%) and different molecular weight (MW) (299, 410, 600, 706, 880kDa) were obtained. Heat-induced composite gels were prepared from 4% salt-soluble meat proteins (SSMP) with chitosans at 0.6mol/L NaCl, pH 7.0. Penetration forces and storage modulus of SSMP–CHI composite gels increased proportionally with increasing amount of molecular weight. Gel containing chitosan with DD 77.3% exhibited the highest penetration force and storage modulus. The SEM observations showed that SSMP–CHI incorporated gels were compact and fine compared with that of SSMP. Chemical forces involved in SSMP–CHI composite gels were investigated by determining the effects of NaCl, urea, propylene glycol, and 2-MeSH on penetration forces. Results of these studies demonstrated that interaction between CHI and SSMP contributed to the enhancement of texture of the SSMP–CHI composite gels by electrostatic interactions and hydrogen bonds. [ABSTRACT FROM AUTHOR]

Abstract: Changes in protein composition and physicochemical properties of silver carp sausages during fermentation were investigated. As fermentation progressed, the amount of salt-soluble and water-soluble proteins decreased gradually with a concomitant increase in insoluble proteins and non-protein constituents. The rapid reduction in pH to 4.5 within 48h of fermentation coincided with a progressive increase in titratable acidity. The increasing content of TCA-soluble peptides during fermentation indicated intensive degradation of muscle proteins. SDS–PAGE showed that muscle proteins tended to aggregate into large polymers through disulphide bonds and non-disulphide covalent bonds during fermentation, which may be responsible for the formation of superior textural properties of silver carp sausages. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Abstract: The effect of fermentation with Pediococcus pentosaceus at different temperatures ranging from 15 to 37°C on the quality characteristics of silver carp sausages was investigated. Higher temperature stimulated the rapid growth of lactic acid bacteria, resulting in a rapid decline in pH, and consequently suppressed the growth of Pseudomonas, Micrococcaceae and Enterobacteriaceae. However, increasing fermentation temperature gave a progressive increase in total volatile basic nitrogen and biogenic amines in fermented silver carp sausages. Histamine was the main biogenic amine, exceeding 100mg/kg after 48h of fermentation at temperatures above 30°C. Higher content of non-protein nitrogen and α-amino nitrogen correlated with the electrophoretic studies, which showed that proteolysis of high molecular weight myofibrillar and sarcoplasmic proteins was more prominent at higher fermentation temperatures. Products fermented at 23–30°C showed greatest consumer preference and most favourable textural properties. [Copyright &y& Elsevier]

Abstract: The recovery of sodium hydroxide from alkali wastewater in chitin processing was investigated using stainless steel ultrafiltration membrane (SSM) and HDS-04 nanofiltration (NF) membranes with membrane area of 0.35m2 and 1.4m2, respectively. Flux behaviors were observed with respect to filtration time, volumetric concentration ratio (VCR), operating pressure, temperature, and cleaning. As the VCR increased, the permeate flux declined while almost the same concentration of NaOH was permeable. The SSM and NF operations end with a concentrated protein solution that needed a small amount of waste acid for neutralization and easy spray drying and the permeate of the NaOH solution can be reused. Concentrations of NaOH that govern reusability of permeate were measured to be independent on VCR. The most suitable VCRs for SSM and NF in terms of maintaining relatively good membrane productivity and high rejection of protein and chemical oxygen demand (COD) were approximately 50. At a VCR of 50, the total rejections of protein, COD and suspended solid (SS) were 82.5%, 94% and 100%, respectively, while total NaOH recovery was 96% with SSM average flux 270LMH and NF average flux 25LMH. SSM filtration was essential for the pretreatment of the alkali wastewater before it was fed into the NF system. [Copyright &y& Elsevier]

Chinese olive ( Canarium album L.), a native and a well-known tropical fruit tree in the southeast of China, contains large amount of phenolics and possesses great pharmacological activities. In this study, phenolics were extracted from Chinese olive fruit pulp using 80% (v/v) aqueous acetone, and acetone extracts were further fractioned with petroleum ether, ethyl acetate and n-butanol sequentially. From n-butanol fraction, a new phenolic compound was isolated and purified through AB-8 adsorption resin column chromatography, polyamide column chromatography and TSK Toyopearl HW-40 (S) column chromatography, and the structure of the new compound was established as 3- O-galloyl quinic acid butyl ester by electrospray ionization mass spectrometry (ESI-MS), 1D- and 2D-NMR (DEPT, COSY, HMBC, HMQC) and UV–vis techniques. [ABSTRACT FROM AUTHOR]

Besides the specific chitinase, chitosanase and lysozyme, chitosan also could be hydrolyzed by some non-specific enzymes such as cellulase, protease, lipase and pepsin, especially cellulase, which show high activity on chitosan. Almost all the cellulases produced by different kinds of microorganisms could degrade chitosan to chitooligomers. The existence of bifunctional enzymes with cellulase and chitosanase activity is one of the reasons for cellulase on chitosan hydrolysis. The bifunctional cellulase–chitosanases mainly belong to glycoside hydrolase family 8 (GH-8), few belong to GH-5 and GH-7, according to the homogeneity analysis of amino acids sequences. Their three dimensional structures however have not been clearly determined. This paper may serve as a guide for a further study on the relationship between structure and function of chitosanolytic cellulases. [Copyright &y& Elsevier]

Abstract: The carboxyl groups of the bifunctional cellulase–chitosanase (CCBE), purified from a commercial cellulase prepared from Trichoderma viride were modified using the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide (EDC). The EDC modified CCBE lost 80–90% of its chitosnase activity and 20% of its carboxylmethyl cellulase (CMCase) activity; meanwhile, its conformation changed slightly, which altered the substrate binding affinity to chitosan, without affecting its binding to CMC. However, the modification did not alter the structure integrity. The dynamic analysis of modification indicated that the CCBE possessed two carboxylates essential for its chitosanase activity and one carboxyl group for its CMCase activity. One of the two carboxylates involved in chitosanase activity was deduced to be the proton donator, and the other may function for substrate recognition, while the only catalytic carboxyl group for CMCase activity probably also acted as a proton donator. [Copyright &y& Elsevier]

Abstract: To improve the characteristics and functionality, and increase the use of fish muscle, three groups mixed starter cultures (group one: Lactobacillus plantarum-15, Staphylococcus xylosus-12 and Pediococcus pentosaceus-ATCC33316 [S-PXP]; group two: Lactobacillus planatrum-15, Staphylococcus xylosus-12 and Lactobacillus casei subs casei-1.001 [S-PXC]; and group three: Staphylococcus xylosus-12, Lactobacillus casei subsp. casei-1.001 and P. pentosaceus-ATCC33316 [S-XCP]) were inoculated in minced silver carp muscle to produce a fermented fish product. During the 48h fermentation at 30°C, silver carp muscle inoculated with mixed starter cultures resulted in a rapid pH decrease, suppression in the increase of thiobarturic acid (TBARS) values, total volatile base nitrogen (TVB-N), trimethylamine (TMA), and the growth of spoilage bacteria and pathogens, and had higher whiteness than the control (without any starter) (P<0.05). The changes in SDS-PAGE indicated extensive hydrolysis of muscle protein occurred during fermentation. This study showed that the mixed starter cultures could substantially improve the flavor, digestibility, and nutritional value of the silver carp muscle. [Copyright &y& Elsevier]

Abstract: Qualitative analysis of acetone extracts from Chinese olive (Canarium album L.) fruit pulp was performed by means of reversed phase high-performance liquid chromatography coupled to diode array detection and electrospray ionization mass spectrometry (RPHPLC–DAD–ESI–MS). Seven phenolic compounds were identified (gallic acid, methyl gallate, ethyl gallate, ellagic acid, brevifolin carboxylic acid, sinapic acid, and hyperin) by comparing their retention times, UV–Vis absorption spectra and mass spectra with authentic standards or literature data. In addition, six other phenolic compounds, including one kaempferol hexoside and five hexahydroxydiphenoyl (HHDP) derivatives, were partially identified. All of these phenolic compounds, except gallic acid, ellagic acid and hyperin, are reported in Canarium album L. for the first time. Quantification of phenolic compounds was performed by HPLC–DAD, which revealed that gallic acid (166mg/100g FW), ellagic acid (87.8mg/100g FW) and HHDP hexose (80.9mg/100g FW) were the major phenolic compounds in Chinese olive fruit. [Copyright &y& Elsevier]

Abstract: The effects of three group mixed starter cultures (group one: Lactobacillus plantarum-15, Staphylococcus xylosus-12 and Pediococcus pentosaceus-ATCC33316, group two: L. plantarum-15, S. xylosus-12 and Lactobacillus casei subsp. casei-1.001, and group three: S. xylosus-12, L. casei subsp. casei-1.001 and P. pentosaceus-ATCC33316) and a batch without starter as control, on biogenic amine formation during the manufacture of silver carp sausage were investigated. Determination of seven different biogenic amines was carried out by reverse-phase high performance liquid chromatography (RP-HPLC) with fluorometric detection. Quality parameters of silver carp sausage, namely pH, water activity, microbial counts, α-amino nitrogen and total volatile base nitrogen, were determined. In addition to these, amino acid contents were analyzed to note changes of amino acids in silver carp sausages. Mixed starter cultures decreased the pH quickly, inhibited the growth of contaminant microorganisms present in the raw materials, and suppressed the accumulation of histamine, cadaverine, putrescine, tryptamine and tyramine. In order to prevent biogenic amine formation, mixed starter cultures with negative-decarboxylate activity should be inoculated into the manufactured food products. [Copyright &y& Elsevier]

Abstract: The kernels from Canarium album L. (also called Chinese olive), largely cultivated in the southeast of China, were analyzed for their nutritional composition. The kernels had a high percentage of fats (52.8%) and proteins (29.5%). Soxhlet extracted kernel oil presented acid, iodine and saponification values of 0.56, 84.6 and 192, respectively. Gas chromatography–mass spectroscopy (GC–MS) analysis of kernel oil revealed that oleic acid (30.5%) and linoleic acid (41.8%) were the major unsaturated fatty acids, while palmitic acid (18.0%), stearic acid (7.83%) and arachidic acid (0.39%) were the main saturated ones. Potassium, calcium and magnesium were the predominant mineral elements present in the kernels. Sodium, iron, manganese and zinc were also detected in appreciable amounts. The kernel proteins were rich in arginine, glutamic and aspartic acids (3.19%, 5.02% and 2.47%, respectively) while the limiting amino acids were methionine and lysine. [Copyright &y& Elsevier]

Abstract: The selected 11 chitosan samples were evaluated for their fat- and bile acid-binding capacities, physico-chemical properties, and the correlations between each binding capacity and individual physico-chemical properties. The bile acid- and fat-binding capacities were estimated using in vitro assays, whereas the measured physico-chemical properties were deacetylation degree, swelling capacity, and solution viscosity. Chitosan samples might differ in their binding capacities against fat and/or individual bile acids. The bile acid-binding capacities were 0.20–0.61, 0.43–1.63, and 0.61–1.61μmol/g chitosan for cholic, deoxycholic, and chenodeoxycholic acids, respectively. Stronger binding capacity of chitosan against a selected bile acid does not warrant greater binding capacity for other bile acid. The fat-binding capacity ranged from 1077–1239g oil/g for the chitosan samples under the experimental conditions. No correlation was observed between any binding ability and individual physico-chemical properties, although the swelling capacity of chitosan was correlated to the solution viscosity (, ) and deacetylation degree (, ), indicating that none of the measured physico-chemical properties can be used to predict the fat- or bile acid-binding ability of chitosan. [Copyright &y& Elsevier]

Abstract: A bifunctional enzyme with chitosanase and carboxymethyl cellulase (CMCase) activity was purified from commercial cellulase, which was produced by trichoderma viride, through sequential steps of DEAE-Sepharose CL-6B ion-exchange chromatography, Phenyl Sepharose CL-4B hydrophobic interaction chromatography and Sephadxe G-75 gel filtration. The purified hydrolase was homogeneous as examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular mass was 66kDa. The hydrolase exhibited chitosanase activity for chitosan hydrolysis and cellulase activity for carboxymethyl cellulose (CMC) hydrolysis. For chitosan hydrolysis, the enzyme had an optimum pH of 5.2, temperature of 60°C and exhibited typical Michaelis-Menten kinetics with K m value and V max of 10mg/ml and 0.164U/ml, respectively. For CMC hydrolysis, the pH and temperature optima enzyme were 4.0 and 50°C. Heavy metal ions such as Hg2+, Ag+ significantly or completely inhibited the enzyme activity. Identification of glucosamine (GlcN) and N-acetyl-glucosamine (GlcNAc) oligomers as depolymerized products indicated that the enzyme cleaved both GlcN-GlcN and GlcNAc-GlcN linkages. The chitosan hydrolysates were oligomers with one to four glucosamine residues and some oligomers with longer chain length. [Copyright &y& Elsevier]

Phenolic compounds like simple phenols, flavonoids, and phenolic acids are commonly in foods of plant origin. Several studies, including animal and epidemiological investigations, have demonstrated that phenolic compounds in foods possess positive attributes such as anticarcinogenesis, antioxidant potential, antiviral activity, antimicrobial activity, and antimutagenic activity. However, other studies have shown that the same phenolics have negative attributes such as carcinogenic activity and antinutritional activity, as well as imparting negative attributes to foods. This review summarizes the information about food phenolics and presents the most current knowledge with respect to its role in human health, food attributes, and toxicity among others. [ABSTRACT FROM AUTHOR]

Milk contains components that provide critical nutritive elements, immunological protection, and biologically active substances to both neonates and adults. Milk proteins are currently the main source of a range of biologically active peptides. Concentrates of these peptides are potential health-enhancing nutraceuticals for food and pharmaceutical applications. Several bioactive peptides may be used as nutraceuticals, for example, in the treatment of diarrhea, hypertension, thrombosis, dental diseases, as well as mineral malabsorption, and immunodeficiency. Minor whey proteins, such as lactoferrin, lactoperoxidase, lysozyme, and immunoglobulins, are considered antimicrobial proteins. Milk also contains some natural bioactive substances. These include oligosaccharides, fucosylated oligosaccharides, hormones, growth factors, mucin, gangliosides, and endogenous peptides, which are present in milk at secretion. Most of the claimed physiological properties of milk bioactive components have been carried out in vitro or in animal model systems, and these hypothesized properties remain to be proven in humans. Whether these milk bioactive components will replace drugs entirely in the immediate future is still unclear, but the increasing appreciation of “drug foods” or nutraceuticals plays a complementary rather than a substitutional role to the synthetic pharmacological drugs. [ABSTRACT FROM AUTHOR]

Abstract: Aspergillus CJ22-326, a fungi strain capable of utilizing chitosan as a carbon source, was isolated from soil samples. Two types of chitosanase (ChiA and ChiB) produced from the culture supernatant of Aspergillus CJ22-326 were purified to an apparent homogeneity identified by SDS–PAGE through ammonium sulfate precipitation, CM-Sepharose FF chromatography, and Sephacryl S-200 gel filtration. Molecular weights of the enzymes were 109 kDa (ChiA) and 29 kDa (ChiB). Optimum pH values and temperature of ChiA were 4.0 and 50 °C, respectively, those of ChiB were 6.0 and 65 °C. The enzyme activities of ChiA and ChiB were increased by about 0.5-fold and 1.5-fold, respectively, by the addition of 1 mM Mn2+. However, 2.5 mM Ag+, Hg2+ and Fe3+strongly inhibited ChiA and ChiB activities. Viscosimetric assay and analysis of reaction products of these enzymes, using chitosan as a substrate, by TLC indicated endo- and exo-type cleavage of chitosan by ChiB and ChiA, respectively. ChiB catalysed the hydrolysis of glucosamine (GlcN) oligomers larger than pentamer, and chitosan with a low degree of acetylation (0–30%), and formed chitotriose with chitohexaose as the major products. ChiA released a single glucosamine residue from chitosan and glucosamine oligomers. Both of the activities of ChiA and ChiB increased with the degree of deacetylation of chitosan. The enzyme ChiB had a useful reactivity and a high specific activity for producing functional chitooligosaccharides with high degree of polymerization. [Copyright &y& Elsevier]

In this study, we aimed to clone and further investigate the novel chitosanase Po CSN75A from Penicillium oxalicum M2 that we have previously identified and characterized. Sequence alignment and bioinformatics analysis revealed the conserved regions, enzyme classification, and other properties of Po CSN75A. Furthermore, the gene encoding Po CSN75A was heterologously expressed in Pichia pastoris GS115 and successfully purified via Ni-NTA chromatography. The purified recombinant Po CSN75A had an optimum pH and temperature of 5.5 and 60 °C, respectively. The enzyme was stable within a pH range of 3.0–6.0 and thermostable at 45 °C and below. Additionally, treatments with cations (Ca2+, Mn2+), non-ionic surfactants (Tween 20/40/60/80, Triton X-100), and common reducing agents (dithiothreitol [DTT], β-mercaptoethanol [β-ME]) were observed to significantly enhance the catalytic ability of the recombinant protein, which exhibited an obvious substrate preference for chitosan. For the enzyme kinetic parameters, the V max and K m values against colloidal chitosan were determined to be 4.36 U/mL and 0.27 mg/mL, respectively. Molecular docking (MD) for the overall model of enzymes and substrates identified several potentially important amino acid residues (D148, D150, T149 and E159). The recombinant protein was also found to exhibit a typical endohydrolytic pattern, with a chitooligosaccharide dimer and trimer as the final hydrolytic products. [Display omitted] ● A novel chitosanase gene from Penicillium oxalicum M2 was cloned. ● Po CSN75A expression in P. pastoris was 4.62 folds that of the original strain ● MD expanded the understanding of the catalytic mechanism of Po CSN75A. [ABSTRACT FROM AUTHOR]

Summary Brown stain is a major problem for tuna during storage. This study aimed to investigate the impact of antioxidants on myoglobin oxidation and the promotion of metmyoglobin (MetMb) reduction in tuna slices. Response surface methodology (RSM) was used to optimise the formula of the compound antioxidant in yellowfin tuna (YFT) slices, with the percentage of MetMb as the response value. The ratios of ε‐polylysine, sodium lactate and D‐sodium ascorbate were 0.43%, 2.21% and 2.71%, respectively. The interactions between sodium lactate and D‐sodium ascorbate had a greater impact on the percentage of MetMb. Then, verification experiments were conducted, and the results revealed that the samples treated with compound antioxidants had higher a* values, total sulfhydryl content, Ca2+‐ATPase activity, total reducing activity (TRA) and MetMb‐reducing activity (MRA) and lower percentages of MetMb and carbonyl contents than did the control samples. It also helps to maintain the stability of the NADH/NAD+ ratio, which contributes to facilitating MetMb reduction. The results showed that the compound antioxidant significantly inhibited myoglobin oxidation, promoted the reduction of MetMb in tuna slices and significantly enhanced the myoglobin stability of refrigerated YFT slices. [ABSTRACT FROM AUTHOR]

Summary: The impact of κ‐carrageenan on the physicochemical structural characteristics of ready‐to‐eat (RTE) Antarctic krill surimi gel (AKSG) was investigated. The modifications in chemical bonding, protein secondary structure, protein composition and microscopic morphology were compared in both gels with and without κ‐carrageenan. According to the findings, adding 4% (w/w) κ‐carrageenan could reduce the cooking loss of AKSG significantly (P < 0.05), enhance the WHC and textural quality of AKSG and RTE AKSG and increase the amount of hydrophobic and disulfide bonds so that the secondary structure of Antarctic krill proteins could be shifted to the β‐sheet. However, there was little impact on the composition of the protein molecules according to the SDS‐PAGE. In addition, the usage of κ‐carrageenan significantly alleviated the disruption of the protein gel network caused by high‐temperature and high‐pressure treatments (P < 0.05). Therefore, applying κ‐carrageenan could effectively enhance the gel quality of RTE AKSG. [ABSTRACT FROM AUTHOR]

Summary: The effects of different grilling temperatures (220 °C, 250 °C, 280 °C, 310 °C) reaching the central temperature of 70 °C on heterocyclic amines (HAs) formation, moisture content, cooking loss, texture, colour, and sensory properties of grilled grass carp (Ctenopharyngodon idella) were investigated. The grilling condition significantly (P < 0.05) affected cooking loss, moisture content, heterocyclic amines (HAs) formation, texture, colour and sensory properties. The results showed that 5 kinds of free and 9 kinds of protein‐bound heterocyclic amines were detected. The total amount of protein‐bound heterocyclic amines was much higher than that of the free state. Harman and Norharman, belonging to β‐carboline, constituted over 80% of the total content of heterocyclic amines. Considering the HAs formation and quality attributes, when the grilling condition was 280 °C for 10 min, the total content of HAs was the lowest, and the fish had moderate moisture content, firm texture, bright colour, and high sensory evaluation score. [ABSTRACT FROM AUTHOR]

• Aroma of a new fish flavouring was modulated by the cysteine-xylose Maillard reaction. • Response surface methodology assessed the optimum condition of this reaction. • 2-Methyl-3-furanthiol (MFT) and 2-furfurylthiol (FFT) were used as responses. • Heating temperature significantly affected the production of MFT and FFT. Aroma defects limit the application of fish protein hydrolysates as flavourings. This study aimed to develop a flavour concentrate from fermented tilapia fish head hydrolysate by maximising the Maillard reaction production of meaty and roasted aroma associated compounds. We studied the optimal conditions of the Maillard reaction of xylose with cysteine to form meat-like odorants using response surface methodology. A 3-factored and 3-leveled Box Behnken design was employed, where the independent variables were cysteine concentration (A, w/v, %), heating temperature (B, °C) and heating time (C, min). 2-Methyl-3-furanthiol and 2-furfurylthiol were used as response factors. The optimal conditions were obtained as follows: A, 0.80%; B, 183.80 °C; C, 89.34 min. Compared with the controls, Maillard reaction products enriched the meaty and roasted aroma associated compounds in the treated hydrolysate. In conclusion, the treated tilapia fish head hydrolysate may be used as a base in development of new fish-based flavourings. [ABSTRACT FROM AUTHOR]