Determination of organochlorine pesticides in shrimp by gas chromatography–mass spectrometry using a modified QuEChERS approach

Pacific white shrimp (Litopenaeus vannamei) collected during dry and rainy seasons from three different states in Malaysia were analyzed for nine organochlorine pesticides (OCPs) (α-HCH, β-HCH, γ-HCH, δ-HCH, trans-chlordane, cis-chlordane, p,p′-DDE, p,p′-DDD and p,p′-DDT) using QuEChERS sample preparation method and GC–MS SIM with split/splitless injection mode. The efficiency of combination of primary and secondary amine (PSA) and octadecyl (C18) at 25 mg of PSA and 25 mg of C18 per mL of shrimp extract as the clean-up sorbent to remove matrix interferences was evaluated. By combining PSA and C18, matrix interferences such as gamma-tocopherol and cholesterol were not able to be eliminated. Good separation and high recoveries which ranged from 90 to 105% with associated RSD < 15% were obtained for all OCPs at 3–75 ng/g. No significant difference in recoveries due to seasonal variation for studied OCPs, except for α-HCH, β-HCH, δ-HCH and p,p′-DDT were obtained. The limits of detection and quantification ranged from 0.3 to 4.5 ng/g and 3 to 15 ng/g, respectively. The linearity for matrix matched standard calibrations was >0.99.     

Prevalence and antimicrobial susceptibility of Vibrio species related to food safety isolated from shrimp cultured at inland ponds in Thailand

Inland farming of marine shrimp species is a relatively recent development, in response to increasing demand for the products. This study aimed to investigate the prevalence and antimicrobial resistance of potentially pathogenic Vibrio species in shrimps cultured at inland ponds with low salinity in Thailand. Of 16 shrimp samples (white-leg shrimps and black-tiger shrimps) from ponds with water temperatures from 29 to 32 °C, and salinities from 1 to 5 parts per trillion, 15 contained Vibrio cholerae (densities: 62–252,000 MPN/g). Vibrio parahaemolyticus was present in six samples (370–6,300,000 MPN/g), and Vibrio vulnificus was present in two samples (16–1300 MPN/g). V. parahaemolyticus has higher affinity for non-native white-leg shrimp than for native black-tiger shrimp. The minimum inhibitory concentrations were then measured for 12 common antimicrobial agents. Resistance to ampicillin and oxytetracycline (8% and 2% of the isolates) was documented in V. cholerae isolates, resistance to ampicillin and oxytetracycline (72% and 3%) was found in V. parahaemolyticus isolates, and resistance to nalidixic acid (20%) was detected in V. vulnificus isolates. β-lactamase and tetracycline resistance genes were detected in the resistant Vibrio isolates. The oxytetracycline-resistance phenotype was eliminated by plasmid curing, suggesting that the resistance was related to R-plasmids. Our results show that shrimps cultured even in low salinity ponds are potentially contaminated with pathogenic Vibrio species, and that shrimp are a vehicle for transfer of species with antimicrobial resistance genes to the public.     

Chitosan coatings enriched with active shrimp waste for shrimp preservation

An active coating solution composed of chitosan (Ch) and a shrimp protein-lipid concentrate (PCc), both obtained from Litopenaeus vannamei processing wastes, was applied to preserve shrimp during chilled storage. The addition of PCc increased the antioxidant capacity of the Ch coating, yielding a lower-viscosity mixture which, however, was viscous enough to adhere to the shrimp while maintaining its activity. The shrimp storage trial showed that the Ch coatings, especially when enriched with PCc (Ch-PCc), delayed microbial growth, mainly by extending the lag phase. Pseudomonas spp. appeared to be the predominant bacteria in the microbiota. H₂S-producing organisms and luminescent colonies were especially sensitive to this active coating, with inhibition greater than 4 and 2 log cycle respectively, while the growth of lactic acid bacteria was not favored. The Ch-PCc coating delayed the onset of melanosis and did not confer any sensorially detectable color, taste or odor. It therefore shows promise as a means to improve the quality of shrimp during cold storage.     

Biofiltration potential of macroalgae for ammonium removal in outdoor tank shrimp wastewater recirculation system

Shrimp wastewater usually contain high amount of nitrogen that causes eutrophication, a phenomenon of algae bloom. It is harmful for shrimp growth and needs to be addressed if the objective is to improve water quality and make it suitable for shrimp growth. This paper addresses ammonium removal in tiger shrimp wastewater by using two macroalgae species: Ulva lactuca (U. lactuca) and Gracilaria edulis (G. edulis). To achieve this, an outdoor macroalgae with shrimp integrated system was developed. This integration was completed in two shrimp growth periods; 60 days and 120 days. The mean growth rates of G. edulis and U. lactuca were found as 4.0% day⁻¹ and 3.6% day⁻¹, respectively. The mean ammonium removal rates for G. edulis and U. lactuca were found to be 70% and 45%, respectively. Thus, both species are suitable as biofilter and their valuable biomass has a great commercial value. The potential applications of the findings include improvement of shrimp wastewater quality which will ultimately enhance shrimp and macroalgae productivity to meet growing demands of the market.     

Some Ozone Applications in Seafood

The use of ozonized seawater to reduce and eliminate bacterial pathogens in mariculture facilities and to extend shelf life of marine food products is demonstrated. Consequent benefits of this treatment are also discussed. Laboratory and pilot experiments were conducted using ozone gas to reduce disease-producing Vibrio sp. bacteria at a shrimp (Litopenaeus vannameii) hatchery in Ecuador, South America. Pacific Ocean seawater was treated in a 1,540 L capacity fiberglass contact tower (5–7 min retention) with an ozone oxidant residual of 0.07 mg/L. Prior to ozone treatment, Vibrio determined by TCBS plating was too numerous to count, causing shrimp to die of disease (30 tanks of 13,000 L each). After treatment, Vibrio counts and shrimp disease were eliminated, ozonized seawater decreased the time required for normal molting of shrimp and the total growth cycle was reduced by three days versus control water. From June 1991 until September 1992, survival rates of larval shrimp were robust, routine antibiotic addition was reduced, and one additional growth cycle was realized. Ozonized ice (fresh water) was prepared in the Milford Laboratory CT, USA; Gloucester Food Tech Lab, MA, USA; and a field station (brine water) for sockeye salmon (Oncorhynchus nerka) in Homer, AK. USA. In these studies, squid (Loligo pealei) and commercially captured salmon demonstrated a reduction in spoilage and extension of shelf life of 3 to 5 days' time using ozonized ice. Bacteria associated with commercial ice-producing machines were reduced by 4 logs using ozone treatment. In addition, no flavor aberration was noted using ozonized ice.     

An Overview of Plastics Recycling

In 1980, plastic in the United States has overtaken steel on a volume basis as the dominant material. Though recycling of iron and steel goes back to the early years of United States history, plastics recycling is in its infancy. Today, plastics recycling is an urgent necessity as petrochemical raw materials, energy, and disposal become more costly.     

Recombinant tropomyosin from Penaeus aztecus (rPen a 1) for measurement of specific immunoglobulin E antibodies relevant in food allergy to crustaceans and other invertebrates

Immunoglobulin E (IgE)-mediated food allergy to crustaceans and mollusks is relatively common and affected individuals typically react to a range of different species. The only known major allergen of shrimp was first described over 20 years ago and later identified as the muscle protein tropomyosin. This protein may be useful as a defined and relevant diagnostic marker for allergic sensitization to invertebrate foods. In order to generate an assay reagent suitable for this purpose, tropomyosin from the shrimp Penaeus aztecus (Pen a 1) was produced as a recombinant protein in Escherichia coli and characterized with respect to IgE antibody binding properties in comparison to natural shrimp tropomyosin. Hexahistidine-tagged rPen a 1 accumulated as a predominantly soluble protein in the E. coli expression host and a two-step chromatographic procedure provided a high yield of pure and homogeneous protein. rPen a 1 displayed chromatographic and folding characteristics similar to those of purified natural shrimp tropomyosin. Serum preincubation with serial protein dilutions revealed similar capacity of recombinant and natural tropomyosin to compete with immobilized shrimp extract for IgE binding. rPen a 1 was further shown to extensively and specifically compete for IgE binding to extracts of other crustacean species, house dust mite and German cockroach.     

冰核活性菌体蛋白微冻保鲜虾体的应用研究

本文首次把具冰核活性的菌体蛋白碎片应用在基围虾的低温微冻保鲜保藏技术中，保藏过程中，通过对虾体内各物质的检测，来判断保藏虾体的品质及风味的变化。研究结果表明，微冻保鲜20d后，经感官检测、品质检测和风味检测，其虾体的新鲜度变化趋势有相关性，且虾体的保鲜效果好，保存期长等特点；另外能耗低、易于管理和操作。