Interest in Aeromonas hydrophila as a food-borne and human pathogen is increasing. Isolation media from the clinical laboratory were evaluated for food use and either did not give quantitative recovery of A. hydrophila or did not permit ready differentiation of A. hydrophila from the background microflora. A new medium was developed which permitted quantitative recovery of A. hydrophila from foods. The medium consisted of phenol red agar base (Difco Laboratories), soluble starch (10gliter), and ampicillin (10 mg/liter). All foods surveyed contained A. hydrophila. Foods sampled included red ieats, chicken, raw milk, and seafood (fish, shrimp, scallops, crab, and oysters). The count of A. hydrophila at the time of purchase ranged from 1 x 102/g (lower limit of detection) to 5 x 105/g. In most instances, the count of A. hydrophila increased during 1 week of storage at 5°C. The starch-ampicillin agar developed permitted rapid quantitative recovery ofA. hydrophila from foods in the presence of very large numbers of competing microflora.
The benefits and concerns about treating foods with ionizing radiation are reviewed. Radioactivity cannot be induced in foods by treatment with gamma rays from 137Cs or 60Co, X-ray sources of 5 MeV or lower energy, or electrons of 10 MeV or lower energy. The evidence supports the safety and eficacy of using ionizing radiation for insect disinfestation of grains; dried spices, vegetables and fruits; and fresh fruit. Species and dose dependent phytotoxic and vitamin changes may occur in some fruits at greater doses than currently approved by the US. Food and Drug Administration. Irradiation can inactivate protozoan or helminth parasites and signijicantly decrease the probability of viable food-borne bacterial pathogens in fish, poultry, and red meats. The titers of amino acids, fatty acids, and vitamins of chicken meat sterilized by thermal, electron-beam, or gamma radiation are presented. On the whole, the data support the safety and eficacy of the process.
Longissimus dorsi from beef, pork, and lamb and turkey breast and leg meats were inoculated with Escherichia coli 0157:H7, Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus, and the gamma radiation resistance of the pathogens were determined under identical conditions. At 5°C the respective radiation D-values of E. coli 0157:H7 and L. monocytogenes did not vary with the suspending meat. The Dvalue for a mixture of Salmonella spp. was significantly lower on pork than on beef, lamb, turkey breast, and turkey leg meats. The D-value for S. aureus was significantly lower on lamb and mechanically deboned chicken meat than on the other meats. All values were, nevertheless, within expected ranges.
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