Washing whole and cut produce by dipping or submerging in chlorinated water has a sanitizing effect, although reduction in microbial populations is minimal and is usually less than 100-fold. A study was undertaken to evaluate the efficacy of a spray application of chlorine in killing Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, yeasts and molds, and total aerobic mesophilic microorganisms on whole apples, tomatoes, and lettuce leaves. Inoculated produce was treated (sprayed and then soaked) with water (control) or solutions containing 200 or 2,000 ppm of chlorine for 0, 1, 3, 5, or 10 min, rinsed with sterile water, and analyzed for populations (CFU/cm2) of target microorganisms. Compared to the control treatment, further reductions in numbers of pathogens of 0.35 to 2.30 log CFU/cm2 were achieved by treatment with chlorine. Chlorine was generally more effective at 2,000 ppm than at 200 ppm. Inactivation of microorganisms occurred essentially within 1 min after application of chlorine. These reductions are significant relative to populations of pathogenic microorganisms that may be present on produce. Spray application of chlorine to raw produce at food service or household levels may be a suitable, and more convenient, alternative to treatment by dipping or submersion.

Colonization of the ceca and contamination on carcasses of chickens by Campylobacter spp. was investigated. Samples were taken on the farm and after transport and holding. In the first set of experiments, 20 chickens, obtained from each of 10 broiler farms, were collected from houses containing 6- to 7-wk-old birds. Half of the birds were slaughtered at the farm; the other half were transported (10 birds per chicken coop) to a holding facility and killed within 16 to 18 h. The levels of Campylobacter spp. on the carcass and in the ceca were assessed. Ceca from birds in 9 of the 10 farms sampled were positive for Campylobacter spp. Colonization levels ranged from 10(4.11) to 10(7.28) cfu Campylobacter spp./g cecal matter, except on one farm, where the organism was not isolated. The mean count on the farm was 10(5.44) cfu Campylobacter spp./g cecal material, and after transport the mean was 10(6.15) cfu/g. Significant increases (P = .0085) in levels of Campylobacter spp. on the chicken carcasses occurred after transport. Levels of Campylobacter spp. enumerated from unprocessed chicken carcasses after transport averaged 10(7.11) per carcass, up from an average of 10(3.66) cfu per carcass of the farm. To further verify this observation, field trials were conducted to assess levels on carcasses before and after commercial transport. Employing five farms and 200 6-wk-old chickens, the above observations were confirmed: prior to transport 12.1% of the chickens harbored an average of 10(2.71) cfu per carcass, but after transport 56.0% of the chicken exteriors harbored an average of 10(5.15) cfu per carcass. The results of this study indicate that transport and holding prior to processing contributes to the Campylobacter spp. of > 10(4) cfu normally found on processed poultry carcasses.

The survival of unheated and heat-stressed (52؇C, 30 min) cells of Escherichia coli O157:H7 inoculated into tryptic soy broth (TSB) adjusted to various pHs (6.0, 5.4, and 4.8) with lactic acid and various water activities (a w s) (0.99, 0.95, and 0.90) with NaCl and incubated at 5, 20, 30, and 37؇C was studied. The performance of tryptic soy agar (TSA), modified sorbitol MacConkey agar (MSMA), and modified eosin methylene blue agar in supporting colony development of incubated cells was determined. Unheated cells of E. coli O157:H7 grew to population densities of 10 8 to 10 9 CFU ml ؊1 in TSB (pHs 6.0 and 5.4) at an a w of 0.99. Regardless of the pH and a w of TSB, survival of E. coli O157:H7 was better at 5؇C than at 20 or 30؇C. At 30؇C, inactivation or inhibition of growth was enhanced by reduction of the a w and pH. A decrease in the a w (0.99 to 0.90) of TSB in which the cells were heated at 52؇C for 30 min resulted in a 1.5-log 10 reduction in the number of E. coli O157:H7 cells recovered on TSA; pH did not significantly affect the viability of cells. Recovery was significantly reduced on MSMA when cells were heated in TSB with reduced pH or a w for an increased length of time. With the exception of TSB (a w , 0.90) incubated at 37؇C, heat-stressed cells survived for 24 h in recovery broth. TSB (a w , 0.99) at pH 6.0 or 5.4 supported growth of E. coli O157:H7 cells at 20 or 37؇C, but higher numbers of heated cells survived at 5 or 20؇C than at 37؇C. The ability of unheated and heat-stressed E. coli O157:H7 cells to survive or grow as affected by the a w of processed salami was investigated. Decreases of about 1 to 2 log 10 CFU g ؊1 occurred soon after inoculation of salami (pHs 4.86 and 4.63 at a w s of 0.95 and 0.90, respectively). Regardless of the physiological condition of the cells before inoculation into processed salami at an a w of either 0.95 or 0.90, decreases in populations occurred during storage at 5 or 20؇C for 32 days. If present at <100 CFU g ؊1 , E. coli O157:H7 would unlikely survive storage at 5؇C for 32 days. However, contamination of salami with E. coli O157:H7 at 10 4 to 10 5 CFU g ؊1 after processing would pose a health risk to consumers for more than 32 days if storage were at 5؇C. Regardless of the treatment conditions, performance of the media tested for the recovery of E. coli O157:H7 cells followed the order TSA > modified eosin methylene blue agar > MSMA.