Dar seafood ppp standard
Table 1.5: Potential food safety hazards along the crustacean supply chain
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Table 1.5: Potential food safety hazards along the crustacean supply chain
Prawns are also potentially exposed to a range of indigenous microbial contaminants from the water environment, including A. hydrophila, V. parahaemolyticus, V. vulnificus, V. cholerae, Salmonella spp. and L. monocytogenes [3,7]. Vibrios are known to utilise the chitinous exoskeleton of crustacea as points of attachment and to metabolise it as a carbon/energy source [3,8]. V. parahaemolyticus, V. vulnificus and V. cholerae are considered part of the indigenous microflora of estuarine prawns [9]. V. cholerae O1 and O139 and Salmonella spp. derived from faecal contamination may become established as environmental contaminants in waters from which prawns are harvested and have the potential to contaminate free-living prawns prior to catch. Noroviruses and hepatitis A may also be present. Prawns inhabiting estuarine environments may be exposed to a greater number of potential sources of microbial or chemical contamination, due to their proximity to shore, land animals, human dwellings, and the introduction of chemical and faecal pollutants [3]. After harvest, prawns caught on commercial vessels can be processed in a variety of ways. While on board, they may be boxed as green (uncooked) product and chilled or frozen on board. In some operations, catch is cooked on board vessels, and subsequently stored in either brine or ice. Dipping of prawns in metabisulphite to inhibit formation of blackspot can present a risk to asthmatics due to formation of sulphur dioxide. The processing of prawns on board vessels presents considerable potential for further contamination. Raw product may come into contact with chemical or microbial contaminants through contact with water, surfaces or containers. Pathogens of concern include V. cholerae, V. parahaemolyticus, E. coli, Campylobacter, Shigella, Yersinia and Salmonella spp. and L. monocytogenes. Human handling also introduces potential for contamination by enteric pathogens such as Salmonella, S. aureus, hepatitis A virus and noroviruses. Prawns that undergo a cooking step are effectively rendered pathogen free, as any micro-organisms present will be inactivated, assuming that the product is heated at sufficient temperature and time. However, cooking will not remove or inactivate chemical hazards already present in the product, such as arsenic, mercury and other chemical residues. Cross contamination between raw and processed crustaceans during processing, transport and storage, particularly on board vessels, is recognised as an area of particular concern [3,7], potentially reintroducing environmental microbial hazards. Cooling water and brine/ice used for storage of prawns are also recognised as potential sources of recontamination. Cooked crustacea may also be contaminated by food handlers, introducing enteric pathogens. Use of low temperatures during transport and storage (of both raw and cooked product), as well as during processing, will reduce the opportunities for growth of most microbial contaminants if temperatures are rigorously maintained below 5C. However, some pathogens are able to proliferate at temperatures close to this: V. cholerae will grow at 8C, V. parahaemolyticus can grow at 5C [1], and L. monocytogenes is able to grow at temperatures as low as –0.4C [19,20,21]. Once frozen, no further microbial growth can occur, and many pathogens will decline in number with prolonged frozen storage [3]. However, survival rates in frozen crustacea are variable. Time/temperature abuse of thawed product can provide opportunity for growth of any bacterial pathogens that have survived freezing. In some situations, periods of several days may elapse between cooking of prawns and consumption. This time delay provides potential opportunities for outgrowth and further contamination with microbial pathogens, particularly L. monocytogenes. Frequently, consumption of pre-cooked prawns does not include another cooking step, or only one of insufficient time and/or temperature to inactivate these microbial contaminants. Cooked crustacea such as prawns are frequently added to cold dishes which receive only warming, and which are then potentially subject to time/temperature abuse. This may allow bacterial growth and toxin production by contaminating S. aureus. Toxin production may also be enhanced if the seafood is part of a dish with a starch component [7]. This general pattern of processing and consumption represents an area of primary concern to the health and safety of the prawn-consuming public. Yüklə 2,7 Mb. Dostları ilə paylaş:
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