Kimberly D. Ingram

Tracking spoilage bacteria in commercial poultry processing and refrigerated storage of poultry carcasses

Four trials were conducted to examine the effect of commercial processing and refrigerated storage on spoilage bacteria in the native microflora of broiler carcasses. Prescalded, picked, eviscerated, and chilled carcasses were obtained from a commercial processing facility, and psychrotrophs in the bacterial flora were enumerated on Iron Agar, Pseudomonas Agar, and STAA Agar. The size of the population of spoilage bacteria on processed carcasses stored at 4 degrees C for 7, 10, or 14 days was also determined. Bacterial isolates were identified and dendrograms of the fatty acid profiles of the isolates were prepared to determine the degree of relatedness of the isolates. Findings indicated that although some processing steps increased the level of carcass contamination by selected bacteria, the number of spoilage bacteria recovered from processed carcasses was significantly (P< or = 0.05) less than the number of bacteria recovered from carcasses entering the processing line. Acinetobacter and Aeromonas spp. were the primary isolates recovered from carcasses taken from the processing line. During refrigerated storage, there was a significant (P < or =0.05) increase in the population of bacteria on the carcasses, and Pseudomonas spp. were the predominant bacteria recovered from these carcasses. Dendrograms of the fatty acid profiles of the isolates indicated that bacterial cross-contamination of carcasses occurs during all stages of processing and that some bacteria can survive processing and proliferate on carcasses during refrigerated storage. Furthermore, cross-contamination was detected between carcasses processed on different days at the same facility. Findings indicate that although poultry processing decreases carcass contamination by psychrotrophic spoilage bacteria, significant levels of bacterial cross-contamination occur during processing, and bacteria that survive processing may multiply on the carcasses during refrigerated storage.

Effect of dry air or immersion chilling on recovery of bacteria from broiler carcasses.

A study was conducted to investigate the effect of chilling method (air or immersion) on concentration and prevalence of Escherichia coli, coliforms, Campylobacter, and Salmonella recovered from broiler chicken carcasses. For each of four replications, 60 broilers were inoculated orally and intracloacally with 1 ml of a suspension containing Campylobacter at approximately 10(8) cells per ml. After 1 day, broilers were inoculated with 1 ml of a suspension containing Salmonella at approximately 10(8) cells per ml. Broilers were processed, and carcasses were cooled with dry air (3.5 m/s at -1.1 degrees C for 150 min) or by immersion chilling in ice water (0.6 degrees C for 50 min). Concentrations of E. coli, coliforms, Campylobacter, and Salmonella recovered from prechill carcasses averaged 3.5, 3.7, 3.4, and 1.4 log CFU/ml of rinse, respectively. Overall, both chilling methods significantly reduced bacterial concentrations on the carcasses, and no difference in concentrations of bacteria was observed between the two chilling methods (P < 0.05). Both chilling methods reduced E. coli and coliforms by 0.9 to 1.0 log CFU/ml. Air and immersion chilling reduced Campylobacter by 1.4 and 1.0 log CFU/ml and reduced Salmonella by 1.0 and 0.6 log CFU/ml, respectively. Chilling method had no effect on the prevalence of Campylobacter and Salmonella recovered from carcasses. These results demonstrate that air- and immersion-chilled carcasses without chemical intervention are microbiologically comparable, and a 90% reduction in concentrations of E. coli, coliforms, and Campylobacter can be obtained by chilling.

Use of Oleic Acid To Reduce the Population of the Bacterial Flora of Poultry Skin

The effect of oleic acid on native bacterial flora of poultry skin was examined. Skin from commercial broiler carcasses was washed once or twice in solutions of 0, 2, 4, 6, 8, or 10% (wt/vol) oleic acid and rinsed in peptone water. Aerobic bacteria, Enterobacteriaceae, Campylobacter, and enterococci in the rinsates were enumerated. Significantly fewer aerobic bacteria, Enterobacteriaceae, Campylobacter, and enterococci were recovered from rinsates of skin washed in oleic acid than from control samples. Additionally, fewer bacteria were recovered from rinsates of skin washed in higher concentrations of oleic acid than from skin washed in lower concentrations of the fatty acid. In most cases, there was no significant difference in the number of bacteria recovered from rinsates of skin washed once or twice in solutions of oleic acid. Washing skin samples twice in 10% solutions of oleic acid significantly reduced the number of aerobic bacteria, Enterobacteriaceae, Campylobacter, and enterococci that remained attached to the skin. Campylobacter sp., Enterococcus faecalis, and Listeria monocytogenes isolates possessed the least resistance to the antibacterial activity of oleic acid in vitro, while Escherichia coli and Pseudomonas aeruginosa showed higher resistance. Enterobacter cloacae, Staphylococcus lentus, and Salmonella Typhimurium had the greatest resistance to the antibacterial activity of oleic acid. Findings indicate that oleic acid reduces the number of bacteria on the skin of processed broilers and that the fatty acid is bactericidal to several spoilage and pathogenic bacteria associated with poultry.

Coliform, Escherichia coli, and Salmonellae Concentrations in a Multiple-Tank, Counterflow Poultry Scalder

Scald water samples from a commercial broiler processing plant were tested for coliforms, Escherichia coli, and salmonellae to evaluate the numbers of suspended bacteria in a multiple-tank, counterflow scalder. Water samples were taken from each of three tanks on 8 different days after 6-week-old broilers had been processed for 8 h. Coliforms and E. coli were counted using Petrifilm, and the most probable number (MPN) of salmonellae was determined both in water samples and in rinses of defeathered carcasses that were removed from the processing line immediately after taking the water samples. Mean coliform concentrations in tanks 1, 2, and 3 (the last tank that carcasses pass through before being defeathered) were 3.4, 2.0, and 1.2 log10(CFU/ml), respectively. E. coli concentrations followed the same pattern with means of 3.2, 1.5, and 0.8 in tanks 1, 2, and 3, respectively, with significant differences (P < 0.02) in the concentrations of both coliforms and E. coli between the tanks. Sixteen of 24 scald-water samples were positive for salmonellae with a geometric mean of 10.9 MPN/100 ml in the positive samples. Salmonellae were isolated from seven of eight water samples from both tanks 1 and 2, but in only two of eight water samples from tank 3, the last tank that carcasses pass through. It appears that most bacteria removed from carcasses during scalding are washed off during the early part of scalding.

Microbicidal Activity of Tripotassium Phosphate and Fatty Acids toward Spoilage and Pathogenic Bacteria Associated with Poultry

The ability of solutions of tripotassium phosphate (TPP) and fatty acids (lauric and myristic acids) to reduce populations of spoilage and pathogenic microorganisms associated with processed poultry was examined. In vitro studies were conducted with cultures of bacteria (Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Typhimurium, and Staphylococcus aureus) and yeasts (Candida ernobii and Yarrowia lipolytica). Cultures of the bacteria and yeasts were suspended in solutions of TPP or mixtures of TPP with lauric or myristic acid and mixed for 5 min. Viable numbers (log CFU per milliliter) in the suspensions were enumerated on microbiological agar. Results indicated that TPP solutions are highly bactericidal toward gram-negative bacteria and that mixtures of TPP and fatty acids are highly microbicidal toward gram-negative bacteria, gram-positive bacteria, and yeasts. The microbicidal activity of mixtures of TPP and fatty acids toward the native bacterial flora of skin of processed broiler carcasses was also examined. Skin samples were washed in mixtures of TPP and fatty acid, and the populations of total aerobic bacteria, campylobacters, enterococci, E. coli, lactic acid bacteria, pseudomonads, staphylococci, and yeasts in the skin rinsates were enumerated on the appropriate microbiological media. Results indicated that washing the skin in mixtures of TPP and fatty acids produced significant reductions in the number of aerobic bacteria, campylobacters, E. coli, pseudomonads, and yeasts recovered from skin rinsates, but there was no significant reduction in the populations of enterococci, lactic acid bacteria, or staphylococci. These findings indicate that mixtures of TPP and fatty acids possess microbicidal activity against several microorganisms associated with processed poultry and that these solutions could be useful as microbicides to reduce the populations of some bacteria and yeasts associated with some poultry processing operations.

Enumeration and Identification of Yeasts Associated with Commercial Poultry Processing and Spoilage of Refrigerated Broiler Carcasses

Yeasts associated with broiler carcasses taken from various stages of commercial poultry processing operations and broiler carcasses stored at refrigerated temperatures were enumerated and identified. Whole carcass rinses were performed to recover yeasts from carcasses taken from a processing facility and processed carcasses stored at 4 degrees C for up to 14 days. Yeasts in the carcass rinsates were enumerated on acidified potato dextrose agar and identified with the MIDI Sherlock Microbial Identification System. Dendrograms of fatty acid profiles of yeast were prepared to determine the degree of relatedness of the yeast isolates. Findings indicated that as the carcasses are moved through the processing line, significant decreases in the number of yeasts associated with broiler carcasses usually occur, and the composition of the yeast flora of the carcasses is altered. Significant (P < 0.05) increases in the yeast population of the carcasses generally occur during storage at 4 degrees C, however. Furthermore, it was determined that the same strain of yeast may be recovered from different carcasses at different points in the processing line and that the same strain of yeast may be isolated from carcasses processed on different days in the same processing facility.

Use of MIDI-fatty acid methyl ester analysis to monitor the transmission of Campylobacter during commercial poultry processing.

The presence of Campylobacter spp. on broiler carcasses and in scald water taken from a commercial poultry processing facility was monitored on a monthly basis from January through June. Campylobacter agar, Blaser, was used to enumerate Campylobacter in water samples from a multiple-tank scalder; on prescalded, picked, eviscerated, and chilled carcasses; and on processed carcasses stored at 4 degrees C for 7 or 14 days. The MIDI Sherlock microbial identification system was used to identify Campylobacter-like isolates based on the fatty acid methyl ester profile of the bacteria. The dendrogram program of the Sherlock microbial identification system was used to compare the fatty acid methyl ester profiles of the bacteria and determine the degree of relatedness between the isolates. Findings indicated that no Campylobacter were recovered from carcasses or scald tank water samples collected in January or February, but the pathogen was recovered from samples collected in March, April, May, and June. Processing generally produced a significant (P < 0.05) decrease in the number of Campylobacter recovered from broiler carcasses, and the number of Campylobacter recovered from refrigerated carcasses generally decreased during storage. Significantly (P < 0.05) fewer Campylobacter were recovered from the final tank of the multiple-tank scald system than from the first tank. MIDI similarity index values ranged from 0.104 to 0.928 based on MIDI-fatty acid methyl ester analysis of Campylobacterjejuni and Campylobacter coli isolates. Dendrograms of the fatty acid methyl ester profile of the isolates indicated that poultry flocks may introduce several strains of C. jejuni and C. coli into processing plants. Different populations of the pathogen may be carried into the processing plant by successive broiler flocks, and the same Campylobacter strain may be recovered from different poultry processing operations. However, Campylobacter apparently is unable to colonize equipment in the processing facility and contaminate broilers from flocks processed at later dates in the facility.

Partitioning of external and internal bacteria carried by broiler chickens before processing

Broiler chickens from the loading dock of a commercial processing plant were sampled to determine the incidence and counts of coliforms, Escherichia coli, and pathogenic bacteria. Feathers were removed by hand from ten 6-week-old chickens from each of seven different flocks and rinsed in 400 ml of 0.1% peptone water. Heads and feet were removed and rinsed, and the picked carcass was also rinsed, each in 200 ml. The ceca, colon, and crop were aseptically removed and stomached separately in 100 ml of peptone water. Campylobacter was present in six of the seven flocks. Salmonella was isolated from 50 of the 70 carcasses, with at least 2 positive carcasses in each flock, and five-tube most-probable-number (MPN) assays were performed on positive samples. Significantly (P < 0.05) more coliforms and E. coli were found in the ceca than in the feathers, which in turn carried more than the other samples, but total external and internal counts were roughly equivalent. Counts of Campylobacter were higher in the ceca and colon than in the other samples. Salmonella was isolated in external samples from 46 of the 50 positive carcasses compared with 26 positive internal samples or 17 positives in the ceca alone. The total MPN of Salmonella was approximately equivalent in all samples, indicating that contamination was distributed through all external and internal sampling locations. Salmonella-positive samples did not carry higher counts of coliforms or E. coli, and there were no significant correlations between the indicators and pathogens in any sample. Campylobacter numbers in the ceca were correlated with Campylobacter numbers in the feathers and colon, but Salmonella numbers in those samples were not correlated. The pattern of bacterial contamination before processing is complex and highly variable.

Antimicrobial Activity of Potassium Hydroxide and Lauric Acid against Microorganisms Associated with Poultry Processing

The antimicrobial activity of solutions of potassium hydroxide (KOH) and mixtures of KOH and lauric acid against microorganisms associated with poultry processing was determined. In vitro tests were performed by enumerating viable microorganisms recovered from bacterial cultures suspended in peptone water (control) and in solutions of 0.1% KOH or mixtures of 0.1% KOH and 0.25 or 0.50% lauric acid. Additional studies were conducted to identify changes in the native microbial flora of poultry skin washed in distilled water, KOH, or KOH-lauric acid. Although results of in vitro studies indicated that significantly fewer bacteria (P < or = 0.05) were recovered from cultures suspended in KOH than from cultures suspended in peptone water, there were also significantly fewer bacteria recovered from cultures suspended in KOH-lauric acid than from cultures suspended in KOH. Results of experiments with broiler skin indicated that although rinsates of skin washed in 1.0% KOH solutions contained significantly fewer total aerobic bacteria and enterococci than did skin washed in water, significantly fewer of these microorganisms were generally recovered from rinsates of skin washed in mixtures of 1.0% KOH and 0.5, 1.0, 1.5, or 2.0% lauric acid than from skin washed in KOH alone. Washing of broiler skin in solutions of 0.25 to 1.00% KOH or mixtures containing these concentrations of KOH and two parts lauric acid (wt/vol) also significantly reduced the populations of bacteria and yeasts in the native flora of broiler skin. Enterococci, lactic acid bacteria, and staphylococci in the native flora of the skin had the highest level of resistance to the bactericidal activity of KOH-lauric acid. These findings indicate that the antimicrobial activity of KOH-lauric acid is significantly greater than that of KOH alone in vitro and on poultry skin. Thus, KOH-lauric acid may be useful for reducing the level of microbial contamination associated with poultry processing.

Bactericidal activity of tripotassium phosphate and potassium oleate on the native flora of poultry skin

Abstract The ability of solutions of tripotassium phosphate (K 3 PO 4 ) and potassium oleate to reduce the population of the native bacterial flora of poultry skin was examined. Skin from commercial broiler carcasses was washed in solutions of K 3 PO 4 , potassium oleate, or K 3 PO 4 and oleic acid then rinsed in peptone-water. Aerobic bacteria, Enterobacteriaceae, Campylobacter , and enterococci in the rinsates and the washed skin were enumerated on the appropriate bacteriological media. Washing skin in solutions of K 3 PO 4 significantly reduced the number of Enterobacteriaceae and Campylobacter recovered from rinsates of poultry skin, but did not effect the number of aerobic bacteria and enterococci recovered. Washing poultry skin in mixtures containing both K 3 PO 4 and potassium oleate significantly reduced the number of aerobic bacteria, Enterobacteriaceae, Campylobacter , and enterococci recovered in samples of skin rinsates and in blended suspensions of skin. In vitro inhibition studies showed that K 3 PO 4 is primarily bactericidal towards Gram-negative bacteria, while potassium oleate is bactericidal toward Gram-positive bacteria. Findings indicate that mixtures of phosphates and fatty acids are effective bactericides that can reduce the number of bacteria found on poultry skin.