The microbial quality of raw fillets of aquacultured catfish, salmon, tilapia, and trout was evaluated. A total of 272 fillets from nine local and nine Internet retail markets were tested. Mean values were 5.7 log CFU/g for total aerobic mesophiles, 6.3 log CFU/g for psychrotrophs, and 1.9 log most probable number (MPN) per gram for coliforms. Differences in these microbial levels between the two kinds of markets and among the four types of fish were not significant (P > 0.05), except that Internet trout fillets had about 0.8-log higher aerobic mesophiles than did trout fillets purchased locally. Although Escherichia coli was detected in 1.4, 1.5, and 5.9% of trout, salmon, and tilapia, respectively, no sample had > or = 1.0 log MPN/g. However, E. coli was found in 13.2% of catfish, with an average of 1.7 log MPN/g. About 27% of all fillets had Listeria spp., and a positive correlation between the prevalence of Listeria spp. and Listeria monocytogenes was observed. Internet fillets had a higher prevalence of both Listeria spp. and L. monocytogenes than did those fillets purchased locally. L. monocytogenes was present in 23.5% of catfish but in only 5.7, 10.3, and 10.6% of trout, tilapia, and salmon, respectively. Salmonella and E. coli O157 were not found in any sample. A follow-up investigation using catfish operation as a model revealed that gut waste exposed during evisceration is a potential source of coliforms and Listeria spp.

Chlorine dioxide (ClO2) is an antimicrobial agent recognized for its disinfectant properties. In this study, the sanitizing effects of ClO2 solutions against Salmonella enterica and Erwinia carotovora in water, on tomato surfaces, and between loads of tomatoes were evaluated. In water, ClO2 at 5, 10, and 20 ppm caused a > or = 5-log reduction of S. enterica within 6, 4, and 2 s, respectively. Higher lethality was observed with E. carotovora; a 5-log reduction was achieved after only 2 s with 10 ppm ClO2. On fruit surfaces, however, the sanitizing effects were compromised. A full minute of contact with ClO2 at 20 and 10 ppm was required to achieve a 5-log reduction in S. enterica and E. carotovora counts, respectively, on freshly spot-inoculated tomatoes. On inoculated fruit surfaces, populations decreased > 3 log CFU/cm2 during desiccation at 24 +/- 1 degrees C for 24 h. Populations of air-dried Salmonella and Erwinia were not significantly reduced (P > 0.05) by ClO2 at < or = 20 ppm after 1 min. Either wet or dry inoculum of these two pathogens could contaminate immersion water, which in turn can cross-contaminate a subsequent load of clean fruit and water. ClO2 at 5 ppm used for immersion effectively prevented cross-contamination. Pathogen contamination during fruit handling is best prevented with an effective disinfectant. Once a load of fruit is contaminated with pathogens, even a proven disinfectant such as ClO2 cannot completely eliminate such contaminants, particularly when they are in a dehydrated state on fruit.

No abstract

This study compared the microbiological quality of frozen “edamame” to other varieties of frozen beans sold in Virginia. Furthermore, the reduction of microorganisms during experimental edamame processing was investigated. Commercial frozen in‐pod and shelled edamame had aerobic mesophiles at 3.4 and 3.1 log cfu/g, yeasts and molds at 2.3 and 2.1 log cfu/g, and some contained low levels of Escherichia coli and enterotoxigenic Bacillus spp. Salmonellae were not found; however, 5% edamame and 4% frozen beans in general were positive for Listeria monocytogenes. Rinsing and shelling raw edamame caused a 1–2 log reduction of total aerobic mesophile, yeast and mold, and coliform counts. No naturally occurring yeast, mold or coliform was detected after blanching edamame at 98C for≥30 s. Blanching for 60 s eliminated approximately 6 log cfu/g of inoculated E. coli and Listeria from in‐pod edamame. Adequate processing ensures the microbial quality and safety of frozen edamame. PRACTICAL APPLICATIONS Frozen “edamame” has the potential to be produced with microbial quality acceptable for direct consumption. However, current products may contain harmful bacteria such as Escherichia coli and Listeria monocytogenes; thus, thorough reheating is required for consumer safety. Strict sanitation and effective blanching practices are critical in assuring microbial quality and safety of frozen edamame. Data reported for the first time from this current study could be used to inform frozen edamame producers and consumers of the potentially associated microbial hazards and adequate means for food protection.

This study evaluated the microbial quality of ground beef and ground beef patties sold at local (Virginia) and Internet (U.S.) retail markets. A total of 152 ground beef products, consisting of locally purchased raw ground beef (LRG) and frozen beef patties (LFP) and Internet-procured frozen ground beef (IFG) and frozen beef patties (IFP), were tested. Results showed that LFP had significantly lower levels of aerobic mesophiles, psychrotrophs, and coliforms than LRG, IFG, and IFP. Furthermore, IFG had greater numbers of Escherichia coli than LRG and LFP. No sample was contaminated with E. coli 0157: H7, but one duplicate set of summer LFP samples contained Salmonella. Listeria spp. were present in 25 and 29% of samples from local and Internet markets, respectively. About 5.0, 11.1, 10.5, and 7.9% of LRG, LFP, IFG, and IFP samples were contaminated with L. monocytogenes. This study identified differences in microbial quality between local and Internet products. Careful handling and thorough cooking of ground beef products, regardless of market source, are recommended to prevent foodborne illness.