Arginine aminopeptidase from white shrimp (Litopenaeus vannamei) muscle: purification and characterization

Aminopeptidases act on N-terminal of proteins and peptides produce free amino acids making an impact on the final flavor of foods. An arginine aminopeptidase (RAP) which preferred to hydrolyze basic amino acids from N-termini of peptides and proteins was purified to homogeneity from white shrimp (Litopenaeus vannamei) muscle. The molecular mass of RAP was estimated as 100 kDa on SDS-PAGE. Peptide mass fingerprinting analysis obtained 95 amino acid residues which was 100 and 77.9 % identical to puromycin-sensitive aminopeptidases from insect and zebrafish, respectively. Optimum pH and temperature of the RAP were 7.0 and 30 °C. RAP rapidly hydrolyzed fluorogenic substrates l-arginine 4-methylcoumaryl-7-amide (Arg-MCA) and Lys-MCA with K _m values of 2.7 and 4.9 μM, respectively. The enzyme can be strongly inhibited by puromycin, bestatin, and 1,10-phenanthroline and partially inhibited by ethylenediaminetetraacetic acid (EDTA) and ethylene glycol-bis (2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA). Moreover, the competitive inhibition of puromycin for RAP was confirmed, and K _i value was calculated as 0.07 nM. Metal ions of Zn²⁺ and Mn²⁺ significantly reactivated the inactive apoenzyme activity dialyzed by EDTA. All these results indicated that the purified enzyme is a metalloaminopeptidase which would possibly contribute to flavor development in shrimp muscle.     

Autolysis of Pacific white shrimp (Litopenaeus vannamei) meat: characterization and the effects of protein additives

ABSTRACT:  Autolytic activity of Pacific white shrimp ( Litopenaeus vannamei ) mince in the absence and in the presence of 2.5%NaCl was investigated. Pacific white shrimp mince exhibited the maximum autolytic activity at 35 and 40 °C in the absence and in the presence of 2.5%NaCl, respectively, as evidenced by the highest TCA-soluble peptide content and the greatest disappearance of myosin heavy chain (MHC). The autolysis was more pronounced in the acidic pH values, followed by alkaline pH ranges. Pepstatin A showed the highest inhibition toward autolysis in the acidic condition, revealing that aspartic proteinase was dominant in shrimp muscle. Nevertheless, soybean trypsin inhibitor effectively inhibited the autolysis at neutral and alkaline pH values, suggesting that serine proteinase was present in shrimp mince but contributed to autolysis at a lower extent in shrimp meat. Autolysis in shrimp meat could be inhibited partially by all protein additives, including bovine plasma protein (BPP), egg white (EW), and whey protein concentrate (WPC). The inhibition of autolysis increased when the level of protein additives increased with the concomitant increase in band intensity of MHC retained. WPC and BPP in the range of 2% to 3% exhibited the highest inhibition toward autolysis of shrimp mince.     

Effect of cinnamaldehyde on melanosis and spoilage of Pacific white shrimp (Litopenaeus vannamei) during storage

BACKGROUND: Shrimp is a very perishable product and postmortem changes occur rapidly. Sulfiting agents were once and are still widely used as a preservative in the shrimp industry. However, the application of sulfite in shrimp may pose a risk to human health. Thus development of a natural preservative as a sulfite alternative to extend the shelf life of Pacific white shrimp is urgently needed. RESULTS: The effects of cinnamaldehyde essential oil (1 and 5 g kg^?1) on the shelf life of Pacific white shrimp stored at 4 °C were investigated. As the concentration of cinnamaldehyde increased, residual polyphenoloxidase (PPO) enzyme activity decreased. Kinetic analysis showed that cinnamaldehyde was a noncompetitive inhibitor for the oxidation of L ‐DOPA (L ‐3,4‐dihydroxyphenylalanine) by PPO of Pacific white shrimp. Based on this study, shrimp treated with 5 g kg^?1 cinnamaldehyde possessed the lowest aerobic plate count, total volatile basic nitrogen, and pH values in all treatments after 10 days of storage. According to the results of L*, cinnamaldehyde showed inhibitory activity toward the formation of melanosis. CONCLUSION: Treatment with cinnamaldehyde could improve the sensory properties and extend the shelf life of Pacific white shrimp to 8 days. Therefore, cinnamaldehyde could be used as a promising natural preservative for inhibiting melanosis and preventing the growth of microbes during the chilled storage of Pacific white shrimp. Copyright © 2012 Society of Chemical Industry     

Formula optimization for melanosis-inhibitors of Pacific white shrimp (Litopenaeus vannamei) by response surface methodology

Food Science and Biotechnology - Melanosis is major problem of crustaceans during their rigor mortis storage. This study for the first time was designed to optimize the formula of...     

Effect of low-temperature preservation on quality changes in Pacific white shrimp,Litopenaeus vannamei: a review

Shrimp has been widely accepted as an excellent resource for white meat due to its high-protein and low-fat content, especially low cholesterol. However, shrimps are highly perishable during preservation and retailing procedures due to the activities of enzymatic proteolysis, lipid oxidation, and microbial degradation. With increasing knowledge of and demands for safety, nutrition, and freshness of shrimp products, energy efficient, quality, maintained, and sustainable preservation technologies are needed. Low-temperature preservation, a practical processing method for improving the shelf life of food products, is widely used in the aquatic industry. This review focuses on the effects of low-temperature preservation on the quality changes in Litopenaeus vannamei. It considers physicochemical properties, sensory evaluation, melanosis assessment, and microbiological analysis. The perspectives of non-protein-based techniques on quality analysis of shrimps during preservation are also discussed. © 2019 Society of Chemical Industry     

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

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

不同贮藏条件下南美白对虾中生物胺的变化

利用超声辅助固相分散萃取结合反相高效液相色谱法测定在常温(25℃)和冷藏(4℃)条件下南美白对虾中生物胺的变化,并分析生物胺与pH、总挥发性盐基氮(total volatile basic nitrogen,TVB-N)、硫代巴比妥酸(thiobarbituric acid,TBA)值和菌落总数(total viabl...     

Impact of pulsed electric field pretreatment on yield and quality of lipid extracted from cephalothorax of Pacific white shrimp (Litopenaeus vannamei) by ultrasound-assisted process

Pacific white shrimp cephalothorax was subjected to pulsed electric field (PEF) pretreatment at different electric field strengths (4, 8, 12 and 16 kV cm⁻¹) and pulse numbers (120, 160, 200 and 240) to enhance the extraction yield of lipids. PEF-treated samples were subsequently subjected to lipid extraction using ultrasound-assisted extraction (UAE) process at ultrasound amplitude of 80% for 25 min in continuous mode. PEF-pretreated samples subjected to UAE rendered the highest lipid yield (30.34 g 100 g⁻¹ solids). PEF pretreatment resulted in reduced lipid oxidation as evidenced by the decreases in peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Lipids from PEF-pretreated samples extracted using UAE had higher content of PUFAs and carotenoids, including astaxanthin, astaxanthin monoester, astaxanthin diester, canthaxanthin and β-carotene. Overall, PEF pretreatment helped in enhancing the extraction yield of lipids and carotenoids from shrimp cephalothorax and reduce lipid oxidation to some extent.     

膨化制粒和环模制粒工艺对饲料制粒加工质量和凡纳滨对虾生长性能的影响

本次研究比较了膨化制粒和环模制粒工艺对饲料制粒加工质量和凡纳滨对虾生长性能、饲料利用、肝胰腺和肠道组织学的影响。设计鱼粉质量分数为20%的基础饲料,分别采用环模制粒和膨化制粒的方式,生产硬颗粒饲料和沉性膨化颗粒饲料,在检测饲料制粒加工质量指标后,饲喂初重为7.72 g的凡纳滨对虾6周。和硬颗粒饲料相比,沉性膨化颗粒饲料的容重、耐久性指数和淀粉糊化度显著增加（P<0.05）,硬度和含粉率显著降低（P<0.05）, 但二者在溶失率上没有显著差异（P>0.05）。经过6周养殖后,沉性膨化颗粒饲料组的饲料系数显著低于硬颗粒饲料组（P<0.05）,虾体增重率在数值上高于硬颗粒饲料组（P>0.05）;二者在摄食量、成活率、含肉率、全虾组成和肝胰腺消化酶、糖代谢相关酶活性方面均无显著差异（P>0.05）;在肝胰腺和肠道组织学方面,摄食沉性膨化颗粒饲料和硬颗粒饲料的凡纳滨对虾均表现为组织结构清晰完整,未见明显的损伤。综上,沉性膨化颗粒饲料较硬颗粒饲料具有更优的加工性能和更高的饲料利用效率（更低的饲料系数）,二者对于凡纳滨对虾肝胰腺消化酶、糖代谢相关酶活性和肝胰腺、肠道组织学方面具有基本一致的影响。     

Purification of a lipase from the hepatopancreas of oil sardine (Sardinella longiceps linnaeus) and its characteristics and properties

Lipase has been purified from the hepatopancreas of oil sardine (Sardinella longiceps) by defatting, water extraction, ammonium sulphate fractionation and chromatography on DEAE Sephadex and Sephadex G-100. The preparation was homogeneous on polyacrylamide disc gel electrophoresis and on gel filtration through Sephacryl S-200. The enzyme showed a molecular weight of 54000±57000 with 6.1% of carbohydrate. The pH and temperature optima of purified sardine lipase were 8 and 37°C respectively. Sardine lipase remained stable up to 45°C (15 min) and in the pH range 5 to 9.5. The K_m values obtained for the substrates tributyrin and triacetin were 4 × 10^?2 and 30 × 10^?2, respectively. The effect of halogens and various metal ions on sardine lipase activity, substrate specificity, amino acid and carbohydrate composition are also reported.     

Albacore tuna (Thunnus alalunga) spleen trypsin partitioning in an aqueous two-phase system and its hydrolytic pattern on Pacific white shrimp (Litopenaeus vannamei) shells

Partitioning behaviors of trypsin from the spleen of albacore tuna (Thunnus alalunga) in an aqueous two-phase system (ATPS) were investigated. Partitioning behaviors of proteins were influenced by polyethylene glycol (PEG) molecular mass and concentration, types and concentration of salts, NaCl concentration, and temperature. Trypsin was preferentially partitioned into the PEG-rich top phase. The best ATPS conditions for trypsin partitioning from albacore tuna spleen were 15% PEG 4000–15% NaH₂PO₄ at 40°C without the addition of NaCl, which increased the purity by 5.54-fold with the recovered activity of 71.92%. Based on SDS-PAGE, the enzyme after ATPS separation was near homogeneity and the result of SDS-substrate gel electrophoresis revealed that the band intensity of enzyme in ATPS fraction increased, indicating the enhanced specific activity of splenic extract. The study further investigated the effect of fractionated trypsin on the hydrolysis of Pacific white shrimp (Litopenaeus vannamei) shells. Electrophoretic study revealed that trypsin after ATPS separation was a potential enzyme for extraction of carotenoprotein from Pacific white shrimp shell waste. Therefore, ATPS was an effective method for purification and recovery of trypsin from the spleen of albacore tuna and it could be used as an alternative cheap proteinase for the extraction of carotenoprotein from shrimp shells.     

Effect of severing skeletal muscle at different stage of rigor on the quality of pacific white shrimp (Litopenaeus vannamei)

Effect of severing skeletal muscle (by beheading) at different stages of rigor on the quality of pacific white shrimp (Litopenaeus vannamei) during ice storage was assessed by physical, chemical, and sensory evaluation. Shrimps were divided into three lots, one lot (T₁) beheaded immediately after killing, 2nd (T₂), and 3rd (T₃) lots were beheaded after 5 h and 35 h post‐mortem corresponding to pre‐rigor, in‐rigor, and post‐rigor stages, respectively. There was an increase in the moisture content in all the treatments during the storage. PV, TVB‐N, and TMA‐N values also increased with the storage time, though the values of all these parameters were well within the acceptable limits. Total protein, Sarcoplasmic protein, NPN, and water holding capacity showed a decreasing trend in all the treatments. Hardness, springiness, cohesiveness and chewiness values did not differ significantly (p ≤ .05) between the treatments. L* value showed a decreasing trend throughout the study. Information provided in this study can serve as baseline for postharvest preservative treatments of crustacea products.

Practical applications

This work examined the effect of the time of beheading on the quality of shrimps in ice storage. No work ever looked at the possibility of whether the quality of shrimp varies if its skeletal muscle is severed (by beheading) during pre‐rigor, on‐rigor, and post‐rigor stages. The ice storage studies of three lots demonstrated similar deterioration of quality, without significant differences among the lots. This strongly suggests that the transportation of the whole shrimps to a processing factory at a distant site provides no comparative advantage in terms of quality.     

Effect of pyrophosphate and 4-hexylresorcinol pretreatment on quality of refrigerated white shrimp (Litopenaeus vannamei) kept under modified atmosphere packaging

ABSTRACT:  The effect of pretreatment with pyrophosphate and 4-hexylresorcinol in combination with modified atmosphere packaging (MAP) (80% CO₂, 10% O₂, 10% N₂, or 80% CO₂, 20% N₂) on the quality of white shrimp during storage at 4 °C was investigated. Shrimp pretreated with 2% pyrophosphate and 0.25% 4-hexylresorcinol and stored under MAP showed the lower microbiological and chemical deteriorations as evidenced by delayed microbial growth as well as lower trimethylamine (TMA) and total volatile base nitrogen (TVB) production ( P < 0.05). Additionally, the growth of coliforms was inhibited effectively. White shrimp pretreated with 4-hexylresorcinol had the lower melanosis throughout the storage compared with those without treatment ( P < 0.05). This was associated with the lowered polyphenol oxidase (PPO) activity in shrimp treated with 4-hexylresorcinol. Therefore, the effective retardation of microbiological and chemical deterioration of white shrimp stored under MAP with the decrease in melanosis could be achieved by pretreatment of the shrimp with pyrophosphate and 4-hexylresorcinol. Furthermore, decapitation could be another means to lower the microbial load and melanosis in white shrimp, particularly those stored under MAP.