Kinetics of drosopterin release as indicator pigment for heat-induced color changes of brown shrimp (Crangon crangon).

Heat-induced color changes of crustaceans are commonly described as the release of astaxanthin. In this study on Crangon crangon, it was found that astaxanthin plays a minor role in the (dis)coloration. By LC-HRMS, two polar, process dependent pigments were found. One pigment was identified as riboflavin and one as drosopterin (level-2 certainty). Thermal treatments had highest effect on drosopterin concentration changes and were chosen as indicator for a kinetic study of heat-induced color changes. The kinetic data fitted a consecutive step model (r2 = 0.971), including a first step in which drosopterin was released (kd,85°C = 0.95 ±â€¯0.09 min-1; Ead = 105 ±â€¯4 kJ/mol) and a second step where drosopterin is degraded (kb,85°C = 0.02 ±â€¯0.002 min-1; Eab = 190 ±â€¯15 kJ/mol). The kinetic model shows that shrimp should be heated at lower temperatures (<80 °C) than the heating temperatures used by fishermen (86-101 °C), creating opportunities for quality optimization. Therefore, this study delivers essential information needed in a comprehensive quality optimization study of the cooked brown shrimp.

Generation of a comprehensive panel of crustacean allergens from the North Sea Shrimp Crangon crangon.

BACKGROUND: Published data on crustacean allergens are incomplete. The identification of tropomyosin (TM), arginine kinase (AK), sarcoplasmic Ca-binding protein (SCP) and myosin light chain (MLC) as shrimp allergens are all important contributions but additional allergens are required for the development of a complete set of reagents for component resolved diagnosis and the exploration of novel vaccination strategies. METHODS: The North Sea shrimp (Crangon crangon), which is frequently consumed in Europe, served as a model organism in this study. TM and AK were directly cloned from mRNA based on sequence homology and produced as recombinant proteins. Additional IgE-reactive proteins were isolated by preparative SDS-PAGE and identified by mass spectrometry and corresponding cDNAs were cloned and expressed in E. coli. The relevance of the 6 cloned crustacean allergens was confirmed with sera of 31 shrimp-allergic subjects, 12 of which had a positive double-blind, placebo-controlled food challenge (DBPCFC) to shrimp and 19 a convincing history of food allergy to shrimp, including 5 cases of anaphylaxis. Quantitative IgE measurements were performed by ImmunoCAP. RESULTS: Six recombinant crustacean proteins: TM, AK, SCP, a novel MLC, troponin C (TnC), and triosephosphate isomerase (TIM) bound IgE in ImmunoCAP analysis. Specific IgE to at least one of these single shrimp allergens was detected in 90% of the study population, thus the in vitro diagnostic sensitivity was comparable to that of shrimp extract (97%). In 75% of the subjects, the combined technical sensitivity was similar to or greater with single shrimp allergens than with natural shrimp extract. CONCLUSIONS: We identified six IgE-binding proteins from C. crangon, three of which have not before been described as allergens in crustaceans. This extensive panel of shrimp allergens forms a valuable asset for future efforts towards the identification of clinically relevant biomarkers and as a basis to approach patient-tailored immunotherapeutic strategies.

Effect of food matrix and pH on the volatilization of bases (TVB) in packed north Atlantic gray shrimp (Crangon crangon): volatile bases in MAP fishery products.

The total volatile basic nitrogen fraction (TVB-N) is often used as a quality parameter in the fish industry to assess spoilage. This parameter often leads to discussions between producers and retailers when it comes to defining clear limits of acceptability for modified atmosphere (MA) packed fish and fishery products. Suggested product limits (mg N/100 g fish) do not always correlate with the presence of off-odors. Gray shrimp are an economic valuable, very perishable niche product, where the TVB-N fraction plays an important role considering its shelf life. This research focuses on the effect of a shrimp matrix and its pH on the volatilization of these formed bases, revealing the relationship between concentrations in the fishery product and the concentrations of these bases present in the headspace of the packed product. Especially, the pH of the product, which is lowered when fishery products are packed under a carbon dioxide enriched atmosphere, appeared to have an immense effect on the volatilization of these bases. The effect of the fish matrix itself is established by means of calculated equilibration constants (dimensionless) being 2.13×10(-4)±0.38×10(-4) for trimethylamine, 6.34×10(-5)±1.71×10(-5) for dimethylamine, and 2.58×10(-5)±0.49×10(-5) for ammonia. Comparison of these constants with the equilibration constants of an aqueous solution indicated the retention of these bases in the product. This article provides not only the important insights for the interpretation of TVB-N values in modified atmosphere packaged gray shrimp but also the methodology to extend these findings to other fish and fishery products.

Bioaccumulation of the new antifoulant medetomidine in marine organisms.

Biofouling is a huge problem globally and new alternative antifoulants are presently being investigated. One candidate is medetomidine, a commonly used sedative in veterinary medicine, which has been shown to effectively prevent settlement of barnacles. The purpose of this study was to measure uptake, elimination and bioconcentration of medetomidine in Mytilus edulis, Abra nitida, Crangon crangon and periphyton communities to evaluate the risk of bioaccumulation in the marine environment. Bioconcentration factors (BCF) and bioaccumulation factors (BAF) were used to assess the bioaccumulation. The calculations of these factors were based on the distribution of the radiolabelled medetomidine. BCF for C. crangon was 2.8 while M. edulis had a BCF of 134 and the periphyton communities' BCF was 1195 l/kg fresh weight (FW). The concentration of medetomidine in the animals reached steady state after 24-48 h for all test systems except for A. nitida, which never stabilised enough to calculate a bioaccumulation factor (BAF). Elimination from the organism's tissues was rapid for three of the test systems with half-lives between 1 and 24 h. A. nitida had a half-life of 96-120 h. This study demonstrates that the bioconcentration and bioaccumulation of medetomidine differs between aquatic organisms and that microalgal communities in the form of periphyton have the highest bioconcentration factor of the organisms tested.

Bioaccumulation of trace metals in the brown shrimp Crangon crangon (Linnaeus, 1758) from the German Wadden Sea.

The objective of the present study is to evaluate the suitability of the brown shrimp Crangon crangon (Linnaeus, 1758) from the German Wadden Sea as a biomonitor for the trace metals Cd, Pb, Cu, and Zn and to analyse whether the two-compartment model sensu OECD could be used as a predictive tool to assess environmental quality. The tested decapods accumulated Cd and Pb upon exposure and it was possible to estimate significant model parameters of two-compartment models, while they did not respond to waterborn Cu and Zn. Kinetic BCFs at theoretical equilibrium were 860 for Cd and 750 for Pb. A tentative estimation showed the following sensitivity of C. crangon to an increase of soluble metal exposure: 0.4 microg Cd l(-1) and 0.9 microg Pb l(-1). Available information can be used to quantify a measure of agreement or disagreement between bioaccumulation in various decapods. This can be regarded as an important step in the calibration of biomonitors, which is necessary to assess the potential for bioaccumulation on different temporal and geographical scales.

Chitin purification from shrimp wastes by microbial deproteination and decalcification.

Chitin was purified from Penaeus monodon and Crangon crangon shells using a two-stage fermentation process with anaerobic deproteination followed by decalcification through homofermentative lactic acid fermentation. Deproteinating enrichment cultures from sewage sludge and ground meat (GM) were used with a proteolytic activity of 59 and 61 mg N l(-1) h(-1) with dried and 26 and 35 mg N l(-1) h(-1) with wet P. monodon shells. With 100 g wet cells of proteolytic bacteria per liter, protein removal was obtained in 42 h. An anaerobic spore-forming bacterium HP1 was isolated from enrichment GM. Its proteolytic activity was 76 U ml(-1) compared to 44 U ml(-1) of the consortium. Glucose was fermented with Lactobacillus casei MRS1 to lactic acid. At a pH of 3.6, calcium carbonate of the shells was solubilised. After deproteination and decalcification of P. monodon or C. crangon shells, the protein content was 5.8% or 6.7%, and the calcium content was 0.3% or 0.4%, respectively. The viscosity of the chitin from P. monodon and C. crangon was 45 and 135 mPa s, respectively, whereas purchased crab shell chitin (practical grade) had a viscosity of 21 mPa s, indicating a higher quality of biologically purified chitin.

Suitability of tryptophan radiation products as markers for the detection of gamma-irradiated protein rich food.

During gamma-irradiation (5 kGy) of aqueous tryptophan (Trp) solutions small amounts of 5-, 6-, and 7-hydroxytryptophan (OH-Trp) (0.04-0.08 Mol-%) are formed. Protein rich food like shrimps contain reasonable amounts of non-protein bound Trp (100 mg/kg). In order to detect the treatment of shrimps with gamma-irradiation a method for the determination of OH-Trp in gamma-irradiated shrimps was developed. After homogenization, squeezing of shrimp samples and protein precipitation, a two-step-SPE-clean up was performed using a C18-cartridge and a propylsulfonic acid cation-exchange SPE followed by HPLC analysis with electrochemical detection (750 mV). Results showed that 5-OH-Trp contents in shrimp samples increased with applied doses up to 3 kGy and then decreased with higher doses. Other OH-Trp isomers were not detectable in the irradiated shrimps. Similarly no formation of 4-, 6-, and 7-OH-Trp was detected in model solutions containing the same amino acid composition as in shrimps. This indicates a suppression of the reaction of OH-radicals with Trp by the 300 fold molar excess of other amino acids acting as well as radical scavengers. Therefore, non-physiological OH-Trp isomers formed from free Trp are not suitable as markers for the detection of gamma-irradiated protein-rich foodstuff.

Concentrations of Cd, Zn and Cu in sediments and brown shrimp (Crangon crangon L.) from the Severn Estuary and Bristol Channel, UK.

Cd, Zn and Cu levels were determined in sediments and Crangon crangon from 9 sites in the Severn Estuary/Bristol Channel during winter 1999. Metal levels in both shrimp and sediments varied significantly between sites and were related to proximity of input and/or sediment type. In the upper Estuary, Cd levels in shrimp were 100x higher than other reported values whereas sediment Cd contamination was comparable. It is suggested that high Cd levels in shrimp are due to the high inputs and enhanced bioavailability of metal during winter.