Colour improvement of common carp (Cyprinus carpio) fillets by hydrogen peroxide for surimi production

The preferred colour for surimi is white, but surimi prepared from light fillets of common carp (Cyprinus carpio) is slightly pink. Hydrogen peroxide (H₂O₂; 1–3% v/v) with and without sodium tri‐polyphosphate (STP; 1–2% w/v) was added to a sodium carbonate bath (pH 7.0–11.5) resulting in a final pH range of 4.4–10.1 which was injected into carp fillets. After soaking and tumbling for 30 min at 4–10 °C, the fillets were evaluated for colour and water holding capacity (WHC). Fillets tumbled with treatment solution with different pH levels (7.0–11.5), but with no H₂O₂ or STP added, had improved colour with significantly (P < 0.05) higher L* compared with untreated fillets as the control. However, the colour improvement [(L* and colour deviation (ΔE)] was not significantly different (P > 0.05) within the pH levels (7.0–11.5) trialled. With increasing H₂O₂ levels (1–3%), fillets became lighter and ΔE increased significantly (P < 0.05), especially with a 3% H₂O₂ treatment at pH of 10.5 (adjusted pH before H₂O₂ addition, actual pH after H₂O₂ addition was 8.2). The whiteness (L*?3b*) of kamaboko produced from treated (3% H₂O₂, pH 10.5) common carp light fillets was not significantly different to that of kamaboko from Alaska pollock and threadfin bream. Treatments combining H₂O₂ (3%) with STP (1–2%) significantly reduced the L* value obtained in comparison with fillets treated with only H₂O₂ (3%). Similarly, fillets treated with STP (1%) alone, resulting in lower L* values, irrespective of treatment pH (7.0–11.5). WHC, an indicator of the quality of the fillet texture, increased from 816 g/kg at pH 7.0 without STP to 841 g/kg at pH 11.5 with 1% STP. Treatment with H₂O₂ (without STP) decreased the WHC of the fillets.     

Changes in the lipid components of minced carp (Cyprinus carpio) following cooking

The changes in weight, moisture, lipid content and composition, thiobarbituric acid (TBA) and carbonyl values were determined in minced carp following cooking by baking and deep-frying. Baked samples lost lipid via drip while the deep-fried samples absorbed oil. Free fatty acids decreased following cooking. Thiobarbituric acid (TBA) values increased following cooking by either method. Antioxidants (TBHQ and BHA) inhibited the production of TBA-reactive compounds though the production of carbonyls during deep-frying was enhanced. Tertiary butylhydroquinone (TBHQ) was slightly more effective than BHA in inhibiting the formation of TBA-reactive compounds.     

Debromination of the flame retardant decabromodiphenyl ether by juvenile carp (Cyprinus carpio) following dietary exposure

The congener 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE 209) is the primary component in a commonly used flame retardant known as decaBDE. This flame retardant constitutes approximately 80% of the world market demand for polybrominated diphenyl ethers (PBDEs). Because this compound is very hydrophobic (log K(ow) approximately 10), it has been suggested that BDE 209 has very low bioavailability, although debromination to more bioavailable metabolites has also been suggested to occur in fish tissues. In the present study, juvenile carp were exposed to BDE 209 amended food on a daily basis for 60 days, followed by a 40-day depuration period in which the fate of BDE 209 was monitored in whole fish and liver tissues separately. No net accumulation of BDE 209 was observed throughout the experiment despite an exposure concentration of 940 ng/day/fish. However, seven apparent debrominated products of BDE 209 accumulated in whole fish and liver tissues over the exposure period. These debrominated metabolites of BDE 209 were identified as penta- to octaBDEs using both GC/ECNI-MS and GC/HRMS. Using estimation methods for relative retention times of phenyl substitution patterns, we have identified possible structures for the hexa- and heptabromodiphenyl ethers identified in the carp tissues. Although exposure of carp to BDE 209 did not result in the accumulation of BDE 209 in carp tissues, our results indicate evidence of limited BDE 209 bioavailability from food in the form of lower brominated metabolites.     

Changes in functional properties of common carp (Cyprinus carpio) myofibrillar protein as affected by ultrasound-assisted freezing

Ultrasound-assisted freezing (UF) has proven to be a method that can effectively increase the freezing rate of frozen food and improve its quality. The functional properties of myofibrillar proteins (MP) are important factors that affect the further processing quality of meat products. At present, the effect of UF on the functional properties of frozen MP is not yet clear. Therefore, in the present study, changes in the functional properties (emulsifying and gel properties) of MP in common carps (Cyprinus carpio) frozen with UF at different power levels were investigated. The results revealed that, compared with immersion freezing (IF), UF at 175 W (UF-175) effectively inhibited the decrease in protein solubility, absolute Zeta potential, emulsion activity index, storage modulus (G'), and loss modulus (G'') caused by freezing. UF-175 sample had lower protein turbidity, and smaller protein particle size than any other frozen samples (P < 0.05), which suggested that UF-175 inhibited protein aggregation induced by freezing. In addition, shorter T₂₁ and T₂₂ relaxation times were obtained in UF-175 sample than other frozen samples, indicating that UF-175 reduced the mobility of immobilized and free water. Accordingly, UF-175 sample had higher gel strength and water holding capacity than other frozen samples (P < 0.05). A denser and more uniform gel network structure was also found in UF-175 sample than other frozen samples. In general, improved functional properties of common carp MP can be achieved by optimal UF.     

Quality changes and storage life of common carp (Cyprinus carpio) at various storage temperatures

The shelf life and freshness changes in pond-grown common carp (Cyprinus carpio L) during storage at 0–2°C, 5–6°C and room temperature (26–29°C) were investigated by sensory, microbiological, physical and chemical analyses. The effect of gutting on the shelf life during storage at 0–2°C was examined. Iodine/starch and potassium sorbate were examined for their effects on shelf life of whole fish stored at 0–2°C and 5–6°C. Sensory results indicated that the whole fish had a maximum shelf life of 24 to 25 days at 0– 2°C. The life of the fish to the point beyond which it would be unsuitable for sale (commercial shelf life) was 17 days at 0–2°C. Storage at 5–6°C shortened shelf life 2- to 2.5-fold. At room temperature (26–29°C), spoilage was evident after 13 h. Gutting the carp shortened its storage potential at 0–2°C. Iodine treatment of this species stored at 0–2°C and at 5–6°C did not extend shelf life. The maximum shelf life of sorbate-treated fish at 0–2°C and 5–6°C was extended by 1–2 days, commercial shelf life by 3–4 days. Total volatile basic nitrogen, pH and penetrometer analyses were not reliable indicators of changes in freshness during shelf life. Thiobarbituric acid values were not useful as rancid odours or flavours were not detected during storage.     

Biogenic amines in vacuum-packed and non-vacuum-packed flesh of carp (Cyprinus carpio) stored at different temperatures

Samples of carp flesh (Cyprinus carpio), vacuum-and non-vacuum-packed were stored at 3 and 15 °C. Chemical, sensory and microbial qualities were measured throughout the storage time to determine the changes that took place and to evaluate the effects of both storage temperature and the means of packaging. Seven biogenic amines (putrescine, cadaverine, spermidine, spermine, histamine, tyramine and tryptamine) were determined. Putrescine and cadaverine showed the best correspondence with the sensory and microbial states of the samples. Low storage temperature had a dominant effect, resulting in low biogenic amine content and better quality of samples. The effect of vacuum-packaging was less obvious, especially in samples kept at 15 °C. Application of vacuum-packaging at 3 °C prolonged the shelf life by about 4–5 days.     

The inhibition mechanism of carp (Cyprinus carpio) stefin to cathepsin B and their tertiary structures

Carp is a major economic species. However, fish or surimi gel will easily soften during processing or storage due to its abundant endogenous protease, which will seriously affect the product quality. Because of the high inhibitory activity to cysteine protease, stefin has great potential as an additive for the improvement of fish softening. In this study, molecular dynamics simulation was used to explore the inhibition mechanism of carp stefin to cathepsin B (CTS B) and their tertiary structures. The results showed that carp stefin is a single domain protein with four stranded β-sheets and a α-helix. CTS B is a typical papain-like fold containing two domains. During the inhibition process, the wedge-shaped structure created by N-terminal trunk and the two hairpin loops of stefin would insert into the groove between two domains of CTS B. Besides, the inhibition can be spontaneous in pure water through hydrogen bonding, VDW and electrostatic interactions. And the Cys3, His83 and Val49 of carp stefin were the critical residues for the inhibition to CTS B. The results may provide a theoretical reference for the application of stefin in the processing and storage of fish products.     

Post-thawing quality changes of common carp (Cyprinus carpio) cubes treated by high voltage electrostatic field (HVEF) during chilled storage

In recent years, high voltage electrostatic field (HVEF) technology has been demonstrated to be a viable alternative to high-temperature treatments in processing for inhibiting microbial growth and maintaining post-thawing quality of foods. In this study, common carp (Cyprinus carpio) meat cubes were treated with HVEF, and compared to air-thawed and running tap water-thawed controls to investigate how HVEF affects common carp meat quality after thawing and low-temperature storage (4 °C). The results showed that thawing under − 6, − 12 kV HVEF and running tap water significantly decreased the thawing time by 30, 50 and 45 min, respectively, compared to air thawing control. In addition, − 12 kV HVEF treatment also reduced the moisture loss, which the initial drip loss of it was lower by 2.95% than CK. The initial total viable counts, Aeromonas, Pseudomonas, and lactic acid bacteria were 3.58, 3.15 2.88 and 3.25 log CFU/g in CK after thawing, respectively, which were higher than that in the cube thawed by − 12 kV HVEF (3.11, 2.93 2.71 and 2.91 log CFU/g). Additionally, − 12 kV HVEF treatment enhanced adenosine monophosphate deaminase (AMP-deaminase) activity, reduced acid phosphatase (ACP) activity and delayed the degradation of inosine monophosphate (IMP) to hypoxanthine (Hx). These results suggested that HVEF treatment could be useful in the thawing and storage of frozen common carp fish.Industrial relevanceThe study investigated the effects of high voltage electrostatic field (HVEF) thawing on the water-holding capacity, adenosine triphosphate degradation and microbial community changes of frozen common carp (Cyprinus carpio) cubes when stored at 4 °C. HVEF under − 12 kV was found to have positive influence on reducing the thawing time, maintaining water-holding capacity, decreasing the level of microbe, and delaying adenosine triphosphate (ATP) degradation. A potential application for HVEF in the thawing and storage of frozen aquatic product was highlighted in food industry.     

Physicochemical,micro-structural,and textural properties of different parts from farmed common carp (Cyprinus carpio)

The fish body of cultured common carp (Cyprinus carpio) was divided into six sections, including the upper back, lower back, jaw, chest, belly, and tail. Differences in the physicochemical, micro-structural, and textural properties of different muscle tissues were investigated. The upper and lower back, with high content of protein, low content of fat, high water-holding capacity, and desirable textural properties, was proven to be the most valuable part of common carp from both a nutritional point-of-view and an organoleptic perspective. This could provide a theoretic basis for the comprehensive utilization of freshwater fish.     

Metal speciation dynamics and bioavailability: Zn(II) and Cd(II) uptake by mussel (Mytilus edulis) and carp (Cyprinus carpio)

In the analysis of metal biouptake from complexing environments, both chemical speciation and biological uptake characteristics have to be taken into account. The commonly used free ion activity model is based on equilibrium speciation and implies that diffusion of the bioactive free metal toward the organism is not rate-limiting. In the presence of complexes, however, sufficiently labile species might contribute to the biouptake via preceding dissociation. Coupling of the ensuing diffusional mass transfer flux of metal with the biouptake flux of free metal, the supposedly bioactive species, shows under which conditions labile metal complexes can contribute to the uptake. The goal of the present paper is to apply this type of analysis to experimental data on metal uptake by mussel (Mytilus edulis) and carp (Cyprinus carpio) in complexing environments. These biosystems have fairly well-characterized uptake parameters, but the uptake fluxes cannot be fully explained by considering equilibrium speciation only. For Zn(II) uptake by mussel, evidence was found for diffusional limitation at low concentrations, whereas for Cd(III) uptake by carp, diffusion is not limiting at all. The analysis provides an example of how a more comprehensive treatment of complex systems can be applied to real experimental data.     

鲤鱼肌肉蒸制过程中的品质变化

采用理化检验、光学显微镜和质构分析法(TPA)对新鲜鲤鱼肌肉组织在蒸制过程中理化性质、微观结构和质构特性进行了分析,并采用SDS-PAGE电泳法分析了流失液的蛋白形式,以期明确鲤鱼肌肉在蒸制过程中品质变化规律,提出鲤鱼肌肉组织蒸制的最佳工艺条件。研究表明:随加热时间延长,肌肉组织失重率、失水率和p H值呈上升趋势,肌原纤维蛋白提取率在2 min内迅速降低,而后缓慢降低。鱼肉蒸制后肌浆蛋白等水溶性蛋白流失,随时间延长蛋白质变性程度加深。加热过程中肌肉组织微观结构变化明显,纤维间隙逐渐增大直至纤维断裂。硬度、咀嚼性、回复性及剪切力均随加热时间延长而降低,在4 min后趋于平稳。综合分析,为保证营养价值和质构特性,规格为1.5 cm3的鲤鱼肌肉组织蒸制时间为4 min较好。     

建鲤组织蛋白酶L的克隆表达、纯化及活性特征鉴定

首先采用TA克隆技术克隆建鲤组织蛋白酶L（Cathepsin L,CAT L）成熟肽基因片段并进行双酶切鉴定,进而构建表达载体CAT L-p ET-30a并转入宿主菌E.coli BL21,经1 mmol/L异丙基-β-D-硫代吡喃半乳糖苷（IPTG）在37℃诱导2 h表达重组CAT L蛋白。而后经尿素梯度洗涤和镍离子亲和层析纯化目的蛋白,并利用SDS-PAGE检测诱导效果和纯化过程。最后以荧光合成肽底物（Z-Phe-Arg-MCA）测活法鉴定建鲤重组CAT L的热稳定性、p H稳定性,以及鱼糜生产和冻藏中常用添加剂对其活性稳定性的影响。双酶切鉴定结果表明成功克隆了目的基因片段,与鲤鱼CAT L基因序列相似性为99.11%。SDS-PAGE分析表明经诱导、尿素梯度洗涤及亲和层析后,成功获得高度纯化目的蛋白,分子量约28 ku。活性鉴定结果表明重组CAT L在20⁵0℃及p H3.0⁶.5范围内稳定;氯化钠、焦磷酸钠对重组CAT L活性的抑制作用呈现剂量依赖关系,而各浓度蔗糖、山梨醇则对其活性无明显作用。本研究成功克隆、表达和纯化了建鲤CAT L,并阐明了热、p H及鱼糜生产和冻藏中常用添加剂对该酶稳定性的不同影响。      

Effect of frozen storage on thermal stability of sarcoplasmic protein and myofibrillar protein from common carp (Cyprinus carpio) muscle

Thermal stability of sarcoplasmic protein and myofibrillar protein extracted from fresh and frozen common carp was comparatively studied. Total sulphydryl content (SH) in sarcoplasmic protein solution from 5‐month frozen carp decreased by 19.43% compared with fresh sample. The SDS‐PAGE patterns showed that all the bands of sarcoplasmic protein from frozen‐stored samples were almost invisible at 80 °C. Myofibrillar protein from fresh sample exhibited lower turbidity and surface hydrophobicity and higher Ca²⁺‐ATPase activity and SH content than frozen‐stored sample when heated from 20 to 80 °C. The Ca²⁺‐ATPase activity from fresh (M0), 2 (M2)‐ and 5 (M5)‐month frozen‐stored carp was completely lost at 48, 46 and 46 °C, respectively. When heated to 80 °C, the SH content of myofibrillar solutions in M0, M2 and M5 decreased by 26%, 60% and 70%, respectively. Sarcoplasmic and myofibrillar proteins from frozen carp were more susceptible to aggregate during heating treatment.     

Effect of carp (Cyprinus carpio) oil incorporation on water vapour permeability,mechanical properties and transparency of chitosan films

The effect of carp oil incorporation on properties of chitosan films was evaluated. Chitosan and carp oil were obtained from shrimp wastes and viscera respectively. Tests were performed with different values of chitosan: oil ratios, agitation rates, homogenisation times and pH. The optimum conditions for stability of the film–forming dispersions were of 20,000 rpm at 10 min, and 10:1 ratio of chitosan:oil. The highest values of tensile strength and elongation percentage (%E) of films were obtained at pH 3.5. The addition of carp oil in the chitosan films (10:1 ratio) showed an increase in the resistance to diffusion of water vapour (1.7 g mm m^?2 day^?1 kPa^?1) in relation to pure chitosan films (4.1 g mm m^?2 day^?1 kPa^?1). However, pure chitosan films showed better mechanical properties (38 MPa and%E 18%) and transparency than films of chitosan:oil (20.4 MPa and 8.8%).     

A mechanistic model for the uptake of waterborne strontium in the common carp (Cyprinus carpio L.)

The release of radioactive strontium to the environment is of concern due to the strong accumulation of this calcium resembling element in the bone and other tissues. To predict the effects of changes in environmental conditions on the uptake of Sr2+ and Ca2+ by freshwater fish, a Michaelis-Menten type model is introduced that accounts for the effects of chemical speciation, hydrogen ion activity, and metal ion competition. The uptake kinetics were characterized in vivo from short-term exposure experiments using the common carp (Cyprinus carpio) as the model organism. Fish were exposed to a wide range of waterborne Sr2+ (0.2-10,000 microM) and Ca2+ (10-10,000 microM) concentrations and water pH (5.0-8.5). Strontium uptake by the whole body of fish increased with increasing Sr2+ activity, displaying saturation kinetics, but decreased significantly with increasing Ca2+ and H+ activities in the water. Likewise, calcium uptake by the fish decreased with increasing Sr2+ and H+ activities in the water. The model fitted to the pooled data explains 97.5% of the variation in Sr2+ uptake and 86% in Ca2+ uptake over the wide range of exposure conditions and reveals that Sr2+ and Ca2+ inhibit each other completely competitively, while H+ inhibits the uptake of both metal ions in a partially noncompetitive way. This model can be used as a mechanistic tool to predict the uptake of these metals in carp under variable conditions.     

Effects of E‐beam irradiation and vacuum packaging on biogenic amines formation in common carp (Cyprinus carpio) fillets

The effects of vacuum packaging followed by E‐beam irradiation treatment on the shelf life of common carp (Cyprinus carpio) fillets were studied by measuring biogenic amines and sensory analysis. Samples were irradiated at doses of 0.10, 0.50, 1.0 and 2.0 kGy. Putrescine, cadaverine, histamine and tyramine showed very good correspondence with the irradiation dose and the time of storage. Spermine, spermidine, tryptamine and phenylethylamine did not show statistically significant changes with the time of storage. According to the sensory assessment and biogenic amines index (BAI), the shelf life of unirradiated common carp fillets was found to be approximately seven days. The 1 and 2 kGy irradiation doses extended the shelf life of samples up to 66 and 77 days, respectively. High values of correlation coefficients (r < ?0.86) between BAI and sensory evaluation indicated that BAI could be considered as a quality indicator of common carp fillets.