Crab-meat-isolated psychrophilic spore forming bacteria inactivation by electron beam ionizing radiation.

The present work was performed to evaluate the potential of electron beam ionizing radiation for the inactivation of three psychrophilic spore forming bacteria (Bacillus mycoides, Bacillus weihenstephanensis and Psychrobacillus psychrodurans) isolated from ready-to-eat brown crab (Cancer pagurus). Inactivation curves for the three spores were performed in both types of crab meat, brown and white. Also the effect of pH and water activity (aw) on the lethal efficacy of ionizing radiation, for the three different psychrophilic spore forming bacteria, was evaluated. The effects of pH, aw and their possible interactions were assessed in citrate-phosphate buffers of different pH, ranging between 7 and 4, and aw, ranging from <0.99 to 0.80. A reduction of aw increased the spores resistance between >0.99 and 0.90, while an aw reduction from 0.90 to 0.80 had a minor impact on their resistance. In contrast to aw, the effect of pH showed a greater variability depending on the spore species. While pH did not affect the resistance of B. weihenstephanensis at any aw, B. mycoides showed slightly higher resistance at pH 5.5 at aw of 0.90 and 0.80. pH showed a significant effect on the resistance of P. psychrodurans. For the two types of crab meat, slightly differences were observed in 6D values. B. weihenstephanensis was the most resistant, requiring 7.3-7.6 kGy to inactivate 6 Log10-cycles of this spore forming bacterium, while for B. mycoides and P. psychrodurans 6.1-6.3 and 5.4-5.3 kGy respectively were necessary to reach the same inactivation level in crab meat. An agreement between spore resistance in crab meats and lab media, with similar characteristics in pH and aw, was also observed. The results obtained in this research demonstrated the potential for ionizing radiation to achieve an appropriate inactivation level of spores naturally present in brown crab with the application of doses lower than 10 kGy.

Isolation & identification of bacteria for the treatment of brown crab (Cancer pagurus) waste to produce chitinous material.

AIMS: To isolate bacteria from soil for microbial pretreatment of brown crab (Cancer pagurus) shell waste and the production of chitin. METHODS AND RESULTS: Isolates were screened for protease enzymes and acid production in order to facilitate the removal of protein and calcium carbonate fractions from brown crab shell to yield a chitinous material. Selected isolates were applied in various combinations in successive, two-step fermentations with brown crab shell waste. These isolates were identified as: Exiguobacterium spp. (GenBank accession number: KP050496), Bacillus cereus (GenBank accession number: KP050499), B. subtilis (GenBank accession number: KP050498), Bacillus licheniformis (GenBank accession number: KP050497), Pseudomonas migulae (GenBank accession number: KP050501), Pseudomonas spp. (GenBank accession number: KP050500), Pseudomonas spp. (GenBank accession number: KP050502), Arthrobacter luteolus (GenBank accession number: KP050503), Lactobacillus spp. (GenBank accession number: KP072000) and Enterococcus spp. (GenBank accession number: KP071999). CONCLUSIONS: Successive two-step fermentations with isolates in certain combinations resulted in a demineralization of >94% and the extraction of a crude chitin fraction from brown crab processing waste. The highest demineralization, 98·9% was achieved when isolates identified as B. cereus and Pseudomonas spp. were used in combination. The transfer of fermentations to a larger scale requires further research for optimization. SIGNIFICANCE AND IMPACT OF THE STUDY: The successful application of these isolates in successive two-step fermentation of brown crab shell waste to extract chitin means with further research into optimization and scale up, this chitin extraction process may be applied on an industrial scale and provide further commercial value from brown crab shell waste.

Sustainable co-location solutions for offshore wind farms and fisheries need to account for socio-ecological trade-offs.

The spatial expansion of offshore wind farms (OWFs) is key for the transition to a carbon free energy sector. In the North Sea, the sprawl of OWFs is regulated by marine spatial planning (MSP) and results in an increasing loss of space for other sectors such as fisheries. Understanding fisheries benefits of OWFs and mitigating the loss of fishing grounds is key for co-location solutions in MSP. For the German exclusive economic zone (EEZ) of the North Sea we conducted a novel socio-ecological assessment of fisheries benefits which combines exploring potential spill-over from an OWF with an experimental brown crab (Cancer pagurus) pot fishery and an economic viability analysis of such a fishery. We arrayed a total of 205 baited pots along transects from an OWF located near the island of Helgoland. After a soaking time of 24 h we retrieved the pots and measured the carapace width (mm), weight (g), and sex of each individual crab. To conclude on cumulative spill-over potentials from all OWFs in the German EEZ and drivers of passive gear fisheries we analysed vessel monitoring system (VMS)-data and computed random forest regressions. Local spill-over mechanisms occurred up to distances of 300 to 500 m to the nearest turbines and revealed an increasing attraction of pot fishing activities to particular OWFs. This corresponds to the observation of constantly increasing fishing effort targeting brown crab likely due to both a growing international demand and stable resource populations at suitable habitats, including OWFs. Our break-even scenarios showed that beam trawlers have the capacities to conduct during summer an opportunistic but economically viable pot fishery. We argue that particularly in the North Sea, where space becomes limited, integrated assessments of the wider environmental and socio-economic effects of planning are crucial for a sustainable co-location of OWFs and fisheries.

High-Pressure Processing for the Production of Added-Value Claw Meat from Edible Crab (Cancer pagurus).

High-pressure processing (HPP) in a large-scale industrial unit was explored as a means for producing added-value claw meat products from edible crab (Cancer pagurus). Quality attributes were comparatively evaluated on the meat extracted from pressurized (300 MPa/2 min, 300 MPa/4 min, 500 MPa/2 min) or cooked (92 °C/15 min) chelipeds (i.e., the limb bearing the claw), before and after a thermal in-pack pasteurization (F9010 = 10). Satisfactory meat detachment from the shell was achieved due to HPP-induced cold protein denaturation. Compared to cooked or cooked-pasteurized counterparts, pressurized claws showed significantly higher yield (p < 0.05), which was possibly related to higher intra-myofibrillar water as evidenced by relaxometry data, together with lower volatile nitrogen levels. The polyunsaturated fatty acids content was unaffected, whereas the inactivation of total viable psychrotrophic and mesophilic bacteria increased with treatment pressure and time (1.1-1.9 log10 CFU g-1). Notably, pressurization at 300 MPa for 4 min resulted in meat with no discolorations and, after pasteurization, with high color similarity (ΔE* = 1.2-1.9) to conventionally thermally processed samples. Following further investigations into eating quality and microbiological stability, these HPP conditions could be exploited for producing uncooked ready-to-heat or pasteurized ready-to-eat claw meat products from edible crab.

Elemental content of brown crab (Cancer pagurus) - Is it safe for human consumption? A recent case study from Mausund, Norway.

The brown crab (Cancer pagurus; the edible crab) is consumed worldwide and greatly appreciated for the essential elements (e.g., Zn, Se) that it contains. However, alongside these, it contains toxic elements that can pose serious risks for human health. For the brown meat parts of the brown crab, which contain considerable Cd concentrations, official legal limits of exposure are still lacking by regulatory bodies, rendering its consumption a potential food safety threat. In this study, a survey was conducted during 2016-2018 in a major Mid-Norway commercial crab fishing area of Mausund in Frøya municipality, Norway, where brown crab media samples were collected to assess the occurrence and profile of select elements, including toxic elements (Cd, Pb, Hg, Sr, As). A yearly median concentration ranging from 6.75 (2016) to 14.0 (2017) mg Cd/kg dry weight (est.: 2.11 (2016) to 4.37 (2017) mg Cd/kg wet weight) indicated high Cd concentrations, which were alarming when compared to the maximum allowed concentration of 0.5 mg/kg wet weight set by the E.U. for raw white crab meat. Human exposures were assessed by estimating intakes of elements per 100 g serving portion of dry edible media (white/brown meat), and the tolerable upper intake levels (ULs) (as specified by the United States National Academy of Sciences) were exceeded for Fe, Cu, Ni, Se, Ca, Mg and P. The median Se and Cd estimated human dietary intakes (EDIs) (from brown crab) were 8.21-8.59 and 9.64-20.0 µg/kg body weight, respectively. The human intake dose (ID) of Cd (from brown crab) reached the order of a few tens of milligrams (mg). In addition, 33% of brown crab samples were found to be suitable for human consumption when the Se:Cd concentration ratio was applied and a stoichiometric excess of Se over Cd was indicated.

An assessment of the application of ultrasound in the processing of ready-to-eat whole brown crab (Cancer pagurus).

This study assesses the potential of incorporating ultrasound as a processing aid in the production of whole cooked brown crab (Cancer pagurus). The FDA recommended heat treatment to reduce Listeria monocytogenes by 6 log10 cycles in this product is a F707.5 of 2min. An equivalent F value was applied at 75°C in presence and absence of ultrasound in water alone or in water with 5% w/v NaCl added. Heat penetration, turbidity and conductivity of the cook water and also salt and moisture content of the crab meat (white and brown) were determined. Ultrasound assisted cooking allowed a reduction of the cooking time by up to 15% while still maintaining an F707.5 of 2min. Ultrasound also enhanced the rate and total amount of compounds released from the crab, which suggests that crabs cooked in the presence of ultrasound would be expected to be cleaner. Ultrasound also proved to be effective in reducing the salt content but hardly affected the final moisture content of the crab meat.

Application of ultrasound in combination with heat and pressure for the inactivation of spore forming bacteria isolated from edible crab (Cancer pagurus).

This research was performed to characterize the resistance of three different bacterial spore species isolated from pasteurized edible crab (Cancer pagurus) meat to heat treatments and to assess the potential of manosonication (MS) and manothermosonication (MTS) as an alternative for their inactivation. The spore-forming bacteria used in this study were Bacillus mycoides, Bacillus weihenstephanensis and Psychrobacillus psychrodurans. The thermal resistance of these three species was determined at different temperatures ranging from 80 to 110 °C and their resistance to ultrasound under pressure from 35 to 95 °C. Ginafit Excel tool was used to fit the Geeraerd's 'Log-linear + shoulder' and Bigelow & Easty's equations to the survival curves for heat and MS/MTS treatments. From the results obtained it can be concluded that the profile of the survival curves either for heat or for ultrasound treatments depended on the bacterial spore species. When shoulders were detected in the inactivation curves for heat they were also present in the curves for MS/MTS treatments, although the application of an ultrasonic field reduced the shoulder length. B. weihenstephanensis was found to be the most resistant species to heat, requiring 1.4 min to reduce 4log10 cycles at 107.5 °C (zT=7.1 °C) while B. mycoides was the most sensitive requiring 1.6 min at 95 °C (zT=9.1 °C). By contrast, B. mycoides was the most resistant to MS. The efficiency of the combination of ultrasonic waves under pressure with heat (MTS) for bacterial spore inactivation was directly correlated with the thermal resistance. Indeed, MTS showed a synergistic effect for the inactivation of the three spores. The highest percentage of synergism corresponded to the spore species with higher zT value (B. mycoides), but the highest temperature at which this synergism was detected corresponded to the most heat tolerant spore species (B. weihenstephanensis). This study revealed that MTS treatment is capable of inactivating spore-forming bacteria and that the inactivation efficiency of the combined treatment is correlated with the thermal resistance of the spore species.

Quantification of the indirect effects of scallop dredge fisheries on a brown crab fishery.

This study aimed to describe the characteristics of the by-catch of Cancer pagurus in king scallop dredges in the Isle of Man, and to determine the damage, immediate mortality and estimated mortality during fishing seasons associated with scallop dredges. Based on dredge surveys, spatial and seasonal variations were observed, with the highest number of crabs found off the west coast of the Isle of Man in the autumn when berried females crabs were most frequently caught. In general, female crabs comprised 84% of the catch. The damage levels of crabs was high with 45% of crabs recorded as crushed or dead or with severe damage, whilst 24% of crabs exhibited missing limbs. Estimates of the potential mortality associated with scallop dredging led to a lower and upper estimate of possible crab by-catch mortality of 15t and 24t respectively which represented 3.0-4.8% of the commercial landings of brown crab for the Isle of Man. Heaviest mortalities of crabs occurred in autumn to the west of the Isle of Man when female berried crabs move offshore into deeper water. The use of a temporary and spatially restricted scallop dredging closure could provide a simple solution to mitigate additional crab mortality in the event that scallop dredging increased beyond current levels in the future.

Pervaporation investigation of recovery of volatile compounds from brown crab boiling juice.

Pervaporation has been used to obtain aroma concentrates from brown crab boiling juice. The boiling juice and the obtained permeate have been analysed by Headspace Solid Phase Dynamic Extraction Gas Chromatography/Mass Spectrometry. The effect of feed temperature on the pervaporation performance of the membrane has been analysed. The permeate aroma profile, at 25 ℃ and 40 ℃, was different from that of the boiling juice. Enrichment factors for some of the volatile compounds were much lower than those obtained in model aqueous dilute solutions. Pervaporation performance can be significantly improved by modifying the permeant circuit to include two condensation stages.