Effect of Trisodium Phosphate on Salmonellae Attached to Chicken Skin.

Processed carcasses from a commercial plant were inoculated with 108 or 102 colony forming units (CFU) of Salmonella typhimurium 14028. Inoculated carcasses were dipped in a 10% trisodium phosphate (TSP) solution for 15 min. Whole carcass rinses and skin homogenates were tested with and without a 2 L water rinse to remove residual TSP, using unbuffered or buffered peptone solutions. High pH values in test solutions resulting from TSP treatments could interfere with the efficient recovery of Salmonella . Salmonellae levels were reduced by 2 logs, but decreases in total aerobic counts were much smaller as a result of TSP treatments. Salmonellae were recovered from skin and carcasses inoculated with 108 or 102 CFU when a 2 L water rinse followed the TSP treatment, and buffered peptone was used for bacterial recovery.

Bactericidal Effect of Chlorine on Attached Salmonellae With and Without Sonification.

Broiler breast skin was immersed in a Salmonella typhimurium cell suspension for 0.25, 30, or 60 min, then i) shaken for 1 min or stirred for 30 min in a Cl2 solution with 0.5 ppm free residual Cl2 and ii) sonified for 15 or 30 min with or without chlorine (0.5 ppm free residual). Data showed that attached/entrapped salmonellae are not readily accessible to chlorine. Salmonellae were reduced by <1 log10 by chlorine. Sonification seemed to detach attached/entrapped cells thus reducing counts by 1 to 1.5 logs. Sonification of skin in a chlorine solution was the most effective treatment which reduced Salmonella counts by 2.44 to 3.93 logs.

The Impact of Commercial Processing Procedures on the Bacterial Contamination and Cross-Contamination of Broiler Carcasses.

Levels of aerobic bacteria, Enterobacteriaceae , and the incidence of Salmonella were determined at six sampling points in a commercial processing plant: (1) pre-scald (at bleed line); (2) post-scald; (3) post-pick (4) post-evisceration; (5) pre-chill (after the final washer); and, (6) post-chill. The level of aerobic bacteria and Enterobacteriaceae on broiler carcasses was reduced significantly by commercial processing procedures, but cross-contamination still occurred. There was no increase in Salmonella incidence on carcasses from the five sampling points starting with the kill line through the final washer. There was a significant increase in Salmonella incidence on carcasses exiting the immersion chiller, indicating that this may be the point of most significant cross-contamination in broiler processing plants.

Relationship of microbiological quality and oxidative stability of raw broiler meat during cold storage.

The purpose of this study was to determine whether 2-thiobarbituric acid (TBA) values could be used to predict microbiological spoilage of poultry meat. The TBA values of control and inoculated (cultured breast skin microflora, 10(5) cells/mL) chicken breast and leg meat were examined at 0, 2, 7, and 14 days storage in slightly adverse storage conditions (6 C) and at 26 and 20 days, respectively, when spoilage occurred (10(8) cfu/g). Psychrotrophic counts were also obtained on these sampling days for control and inoculated breast and leg meat. Microbiological counts were significantly different for control and inoculated samples on each of the sampling days. However, no significant differences between TBA values of control and inoculated samples were noted on any of the sampling days. No difference was observed between the TBA value of the inoculated product, which had reached spoilage levels (10(8) cfu/g), and the control product, which was not spoiled (less than 10(7) cfu/g). Therefore, the TBA test is not an accurate predictor of microbiological spoilage of poultry meat.

Incidence and Recovery of Salmonellae and Other Bacteria from Commercially Processed Poultry Carcasses at Selected Pre- and Post-Evisceration Steps.

This study was undertaken to determine whether bacteria are already attached to poultry skin when birds arrive at the processing plant. Multiple rinses were performed on breast skin and whole carcasses taken from five processing points in a commercial plant: Before scalding, after scalding, after picking, after the final washer, and from the exit end of the chiller. Aerobic bacteria and Enterobacteriaceae were recovered from carcasses in up to 40 consecutive whole carcass rinses with a difference of only about one log for Enterobacteriaceae , and 1 to 2 logs for aerobes from the first to the last rinse of carcasses taken from the beginning and the end of the processing line. Data from rinses prior to scalding indicated that bacteria were firmly attached to poultry carcasses when they first arrived in the plant. Not all bacteria were removed during processing; however, there were fewer aerobes and Enterobacteriaceae at progressive sampling points. Attached salmonellae were not always recovered in the first whole carcass rinse, but were sometimes recovered in 3rd, 5th, and 10th rinses. These data show that a single whole carcass rinse can result in false negative test results for salmonellae. Because of the small number of positive samples in this study, the probability of recovering salmonellae with a single whole carcass rinse could not be estimated accurately.

Factors Affecting the Persistence of Salmonella During the Processing of Poultry.

Bacteria, including Salmonella , have been shown to attach firmly to poultry skin and meat. Neither fimbriae, flagella, nor electrostatic attraction seem to play a significant role in the mechanism of attachment. Bacterial cells (95%) were shown to be initially entrapped in a water film on the skin, then to migrate to the skin with prolonged immersion in a bacterial cell suspension. Using electron microscopy it was shown that bacteria appear to be entrapped in ridges and crevices which become more pronounced in the skin and muscle following water immersion. This may make bacteria on carcasses inaccessible to bactericides. It was shown that bacteria are firmly attached to poultry skin before broilers arrive at the plant and that high numbers are still recovered after 40 consecutive whole carcass rinses of a single carcass. It was further shown that Salmonella are not always recovered in the first whole carcass rinse and that this method of sampling could result in false negative reports for Salmonella incidence.

Comparison of Sampling Methods and Implications for Bacterial Decontamination of Poultry Carcasses by Rinsing.

This study showed that the whole carcass rinse and the stomaching or blending of excised skin techniques for sampling broilers, as commonly used, result in the isolation of comparable numbers of aerobes and Enterobacteriaceae . However, these data also show that all three methods recover only a very small percentage of the total bacteria present on broiler carcasses. Large numbers of bacteria were still recovered from the fortieth rinse of a single carcass, indicating that increased rinsing after bacteria become firmly attached to the carcass will only result in a slight reduction of the total bacterial load present, and will not result in a meaningful improvement in bacterial quality of the carcass.

Effect of Acetic Acid on the Microbiological Quality of Scalded Picked and Unpicked Broiler Carcasses.

Reductions in the levels and incidence of salmonellae in poultry scald water by the addition of acetic acid have been reported previously. Hence, acid treatment of scald water may help control cross-contamination of carcasses in the scald tank. However, the effect of acid-treated scald water on microbial levels of scalded carcasses has not been addressed. This study confirmed reductions in levels of total aerobic bacteria and Enterobacteriaceae in scald water containing 0.2 and 0.5% acetic acid; salmonellae were not detected. No significant reductions occurred in levels and/or incidence of salmonellae, total aerobic bacteria and Enterobacteriaceae on unpicked carcasses sampled after scalding in 0.5% acetic acid-treated scald water or on picked carcasses that were acid scalded and sprayed with 0.5% acetic acid water during picking.

Transfer of Firmly Attached 32P- Salmonella typhimurium from Raw Poultry Skin to Other Surfaces.

Salmonellae adhere firmly to poultry skin during processing. Loosely attached bacteria cross-contaminate work surfaces. This study was undertaken to determine if firmly attached bacteria present a health hazard through transfer to work surfaces. Attached 32P-labeled S. typhimurium cells were serially rinsed with 2 to 4 L of Salmonella -free potable tap water or with sterile 0.85% NaCl. Rinsing removed 61 to 89% of attached labeled cells. However, after rinsing, 11 to 39% of cells remained attached, and of these, 3 to 10% were able to detach and transfer from skin to stainless steel surfaces. It was concluded that large rinse volumes may not remove all attached salmonellae from poultry skin surfaces and the potential for cross-contamination does exist.

Distribution of "Attached" Salmonella typhimurium Cells Between Poultry Skin and a Surface Film Following Water Immersion.

Poultry skin was immersed in a saline solution (0.85%) containing 108 Salmonella typhimurium /ml. After 0.25 min, 95% of the water uptake was in a surface film and 5% in the skin. After immersion for 30 and 60 min, a significant increase in total water uptake occurred at each immersion time. A significant increase in the surface film occurred after 30 min of immersion, but not from 30 to 60 min. After 0.25 min of immersion, 94% of bacterial cells was entrapped in the water film and 6% was on the skin. As immersion time increased, the percentage of bacteria in the surface film decreased, whereas the percentage on the skin increased. After 60 min of immersion, about 39% of bacterial cells was in the surface film and 61% was on the skin. These data indicate a possible transfer of water and bacteria from surface film to skin during prolonged water immersion. Preventing the formation of the surface film by altering surface tension may reduce carcass contamination during immersion processes.

Bacterial Cell Characteristics and Conditions Influencing Their Adhesion to Poultry Skin.

Conflicting reports appear in the literature regarding attachment of flagellated and nonflagellated bacteria to poultry skin. The following parameters which may influence bacterial attachment were examined: (a) sample type and size; (b) skin from fully processed and scalded but uneviscerated broilers; (c) skin from hard- and soft-scalded broilers; and (d) potentially variable tap rinse and constant pressure spray wash (50 psi). Gram-positive and gram-negative, flagellated and nonflagellated bacteria were used in suspension fluids ( Salmonella typhimurium , Salmonella gallinarum , Proteus vulgaris , Pseudomonas fluoresces , Clostridium perfringens , Staphylococcus aureus and a nonflagellated species of Micrococcus ). Results showed that none of the variables tested affected the ability of bacteria to adhere to poultry skin in 0.25 min. All species tested adhered to skin, and there was a generally linear increase in rate of attachment with time (0.25 to 60 min) following exposure of poultry skin to suspending fluid. It was concluded that nonflagellated bacteria attach as readily as flagellated bacteria under the same controlled conditions.

Effect of Reduced Processing on Recovery of Foodborne Pathogens from Hot-Boned Broiler Meat and Skin.

Recovery of pathogens from breast meat, thigh meat and skin from scalded, defeathered but uneviscerated broiler carcasses with and without spray washing was compared to recovery from breast meat, thigh meat and skin from fully processed, chilled carcasses (controls). The incidence of coagulase-positive staphylococci was not significantly different on meat and skin from both uneviscerated carcasses with and without a spray washing compared to meat and skin from fully processed carcasses. The incidence of Clostridium perfringens was not significantly different on skin, breast and thigh meat for any of the sampling sources except that incidence on meat from control breasts was lower than on breast meat from uneviscerated carcasses without spray-washing; and incidence on meat from control thighs was lower than on meat from spray-washed, uneviscerated carcasses. Salmonella incidence was higher on both breast and thigh meat from fully processed control carcasses than from uneviscerated unwashed carcasses. When uneviscerated carcasses were spray-washed after defeathering, the incidence of Salmonella was not significantly different on breast meat, and significantly lower on thigh meat than on these meats from fully processed control carcasses. Skin from fully processed control carcasses had a higher incidence of Salmonella than did skin from uneviscerated, unwashed carcasses, but not skin from uneviscerated, spray-washed carcasses. Reducing the number of stages of processing significantly reduced the incidence of Salmonella but not of coagulase-positive staphylococci or Clostridium perfringens .

Comparison of Brands of Media for Isolating Bacteria from Poultry, Beef and Shrimp.

Five brands of media (BBL, Difco, Gibco, Oxoid and Scott) were evaluated for enumerating microorganisms by the aerobic plate count and by Enterobacteriaceae , Escherichia coli , and coliform counts, and for determining Salmonella incidence. Microbiological evaluations were done on raw chickens, raw beef and raw shrimp, except that Salmonella incidence was not determined on shrimp samples. There were statistically significant differences in total plate counts (with chicken, beef and shrimp), Enterobacteriaceae counts (with shrimp) coliforms (with chicken) and E. coli counts (with chicken) by the five brands of media, but these differences were too small to be of practical significance. It was concluded that no differences of practical significance were found among the five brands of media.

Effect of freezing on incidence and levels of Clostridium perfringens in mechanically deboned chicken meat.

Paucity of information about the effect of plant practices on microbiological condition of comminuted chicken meat prompted this investigation. Commercially deboned chicken backs and necks were analyzed for levels of aerobic organisms, incidence and levels of Clostridium perfringens vegetative cells and spores before and after 4-6 weeks at -23 degrees C. Initially vegetative cells were isolated more frequently than spores. Frozen storage significantly reduced incidence and levels of vegetative cells and spores but did not affect levels of aerobic organisms. After frozen storage (a common industrial practice), with good food handling practices, C. perfringens should pose no undue hazard when comminuted chicken meat is incorporated into other food products.

Aflatoxigenic isolates of Aspergillus flavus from pecans.

Of 120 isolates of the Aspergillus flavus group from pecans used in bakery products, 85 were shown to produce aflatoxin on yeast extract sucrose medium. Extracts from moldy sections of raw pecans obtained commercially at the retail level showed aflatoxin-like spots on thin-layer chromatography. Cooked (autoclaved) pecans inoculated with toxigenic isolates of A. flavus were also good substrates for aflatoxin production.

Country cured ham as a possible source of aflatoxin.

Of 10 fungi isolated from a heavily molded country cured ham, 4 were identified as toxigenic strains of Aspergillus flavus.