1583 Journal o f Food Protection, Vol. 77, No. 9, 2014, Pages 1583-1587 doi: 10.4315/0362-028X.JFP-14-092
Research Note
Chemical Additive To Enhance Antimicrobial Efficacy of Chlorine and Control Cross-Contamination during Immersion Chill of Broiler Carcasses1 B. T. SCHAMBACH,1J M. E. BERRANG,1* M. A. HARRISON,2 AND R. J. MEINERSMANN1 'U.S. Department o f Agriculture, Agricultural Research Service, Russell Research Center, Athens, Georgia 30605; and 2University o f Georgia, Food Science and Technology Department, Athens, Georgia 30602, USA MS 14-092: Received 25 February 2014/Accepted 2 May 2014
A BSTR A CT Immersion chilling of broiler carcasses can be a site for cross-contamination between the occasional highly contaminated carcass and those that are co-chilled. Chlorine is often used as an antimicrobial but can be overcome by organic material. A proprietary chlorine stabilizer (T-128) based on phosphoric acid-propylene glycol was tested as a chill tank additive in experiments simulating commercial broiler chilling. In bench-scale experiments, 0.5% T-128 was compared with plain water (control), 50 ppm of chlorine, and the combination of 0.5% T-128 with 50 ppm of chlorine to control transfer of Salmonella and Campylobacter from inoculated wing drummettes to co-chilled uninoculated drummettes. Both chlorine and T-128 lessened cross-contamination with Salmonella (P < 0.05); T-128 and T-128 with chlorine were significantly more effective (P < 0.05) than the control or plain chlorine for control of Campylobacter. T-128 treatments were noted to have a pH of less than 4.0; an additional experiment demonstrated that the antimicrobial effect of T-128 was not due merely to a lower pH. In commercial broiler chilling, a pH close to 6.0 is preferred to maximize chlorine effectiveness, while maintaining water-holding capacity of the meat. In a set of pilot-scale experiments with T-128, a near-ideal pH of 6.3 was achieved by using tap water instead of the distilled water used in bench-scale experiments. Pilot-scale chill tanks were used to compare the combination of 0.5% T-128 and 50 ppm of chlorine with 50 ppm of plain chlorine for control of cross-contamination between whole carcasses inoculated with Salmonella and Campylobacter and co-chilled uninoculated carcasses. The T-128 treatment resulted in significantly less cross contamination by either direct contact or water transfer with both organisms compared with plain chlorine treatment. T-128 may have use in commercial broiler processing to enhance the effectiveness of chlorine in processing water.
The U.S. Department of Agriculture, Food Safety Inspection Service (USDA-FSIS) reported for the third quarter of 2010 that an average of 7.4% of commercially processed, postchill chicken carcasses were positive for detectable levels of Salmonella (11). As of July 2011, the USDA-FSIS implemented new performance standards for the poultry industry for Salmonella and, for the first time, for Campylobacter (11). The new USDA performance standard for broiler carcasses sets limits for Salmonella at 7.5% positive and for thermophilic Campylobacter spp. at 10.4% (3). Control of carcass-to-carcass cross-contamina tion during broiler chilling is an important step in the effort to meet these requirements. In the United States, most broiler processors use cold water immersion for carcass chilling. Chlorine has been the * Author for correspondence. Tel: 706 546 3551; Fax: 706 546 3066; E-mail: [email protected]. f Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. f Present address: Coca Cola Co., 1 Coca Cola Plaza, Atlanta, GA 30313, USA.
traditional antimicrobial agent used to control bacterial contamination in chill tanks, allowable at levels up to 0.005% by volume (10). Despite a USDA requirement for 2.3 to 2.6 liters of fresh chill water per carcass (6), high organic loads occur and have been shown to reduce the antimicrobial effectiveness of chlorine (5). A chlorine stabilizer, to lessen the effect of high organic loads associated with incoming carcasses, would be useful to maintain efficacy of chlorine during broiler chilling. A proprietary phosphoric acid—propylene glycol formula for the stabilization of chlorine in solution, T-128 (Smartwash Solutions, Salinas, CA), was found to stabilize chlorine in the presence of high organic loads, increasing efficacy against Escherichia coli and Salmonella spp. in lettuce washing applications (7). Although T-128 alone provided only limited antimicrobial effect, when it was combined with chlorine, a significant reduction in pathogen survival was detected, even in the presence of a high concentration of organic matter (7). The exact mechanism by which the addition of T-128, a blend of phosphoric acid and propylene glycol, to a properly chlorinated system improves the efficacy of the wash solution against bacterial survival has not yet been
1584
SCHAMBACH ET AL.
determined. However, results of produce washing suggest that there is a relationship between T-128 and chlorine that causes a decrease in cross-contamination of fresh-cut lettuce with human pathogens (7). It is possible that T-128 could be useful to stabilize chlorine and control cross-contamination during broiler carcass chilling, thereby aiding the poultry industry in their ongoing efforts to meet regulatory standards and reduce levels of human pathogens in the food chain. The objective of the current study was to determine the effectiveness of T-128, with and without chlorine, at reducing cross contamination of broiler parts and carcasses with inoculated Campylobacter and Salmonella during immersion chill. This study will provide the poultry processing industry with information relative to an intervention strategy for preven tion and control of carcass cross-contamination with pathogenic bacteria. MATERIALS AND METHODS Overview and experimental design. For all experiments, the concentration of T-128 was set at 0.5% based on preliminary efficacy trials (data not shown). This study included three experiments. Experiment 1 was designed to test the potential o f T-128 to lessen cross contamination with Campylobacter and Salmonella during a bench-scale chill tank simulation with 50 ppm o f chlorine. In this experiment, two broiler wing dmmmettes were co-chilled in small containers. One drummette was inoculated and the other was not. A fter the simulated chill was complete, the level of inoculated bacteria detected in the chill water and on the uninoculated drummette was measured. Experim ent 2 was designed to determine whether the efficacy of T-128 was solely due to the lowered pH of the chlorinated chill water. In this experiment, T-128 was compared with the acidic component of T-128 (H3PO4) in pH-matched bench-scale chill tank simulations using an inoculated and uninoculated drummette design similar to the first experiment. Experiment 3 was conducted at a larger pilot plant scale and was intended to compare T-128 with 50 ppm of chlorine to 50 ppm of chlorine alone using whole broiler carcasses in a chill system much closer to commercial conditions than was achieved during the bench-scale experiments. Cultures and inoculation. Antimicrobial-resistant marker strains of Salmonella and Campylobacter (both originally isolated from chicken) were used to inoculate drummettes or carcasses. Salmonella enterica Typhimurium inocula were resistant to nalidixic acid; Campylobacter coli inocula were resistant to gentamicin. By incorporating the respective antimicrobial (200 ppm) into the appropriate medium, we were able to recover our inocula without interference from other naturally occurring bacteria. No resistant bacteria were found on any uninoculated drummettes or carcasses tested during preliminary trials to confirm the utility of the marker strains. Both cultures were maintained as frozen stock, and inocula were prepared as cell suspensions in PBS from 24-h plates, as described in the section “ Sampling and culturing.” Optical density was measured (Thermo Fisher Scientific, Waltham, MA), and the number per ml was confirmed by plate count, as described in “ Sampling and culturing.” Drummettes or carcasses were inoculated with 10 pi of cell suspension containing approximately 106 cells o f each inoculum. The cell suspension was spread with a sterile plastic inoculating loop over approximately 4 cm2 of the
J. Food Prot., Vol. 77, No. 9
skin and was allowed to dry for 10 min before starting the immersion chill process.
Chill parameters, experiment 1. Fresh drummettes were purchased at retail and were preheated to an internal temperature of 42°C to simulate a warm carcass. Two drummettes were placed in each container, one inoculated as described above and the other left uninoculated. Bench-scale chilling was conducted in large beakers (15-cm inside diameter), each with two drummettes, water, and ice in a 1:2:4 ratio by weight. Chill water included additives according to the following four treatments: (i) control, distilled water; (ii) chlorine, 50 ppm o f chlorine (Clorox germicidal bleach [Clorox Professional Products Co., Oakland, CA], 6.15% sodium hypo chlorite) in distilled water; (iii) T-128, 0.5% T-128 (Smartwash Solutions LLC, Salinas, CA) in distilled water; and (iv) combination, 50 ppm of chlorine and 0.5% T-128 in distilled water. Filled beakers were covered and then were placed in an orbital shaking incubator (Labline Instruments, Rockville, MD) at 130 rpm for 45 min at 25°C. Measurements were made at 0 and 45 min of chill time for water temperature, pH (pHTestr 30, Eutech Instruments, Vernon Hills, IL), and free and total chlorine levels (Pocket Colorimeter II, Hach Company, Loveland, CO). Duplicate chill vessels were used for each treatment in each of 10 replications, for a sample size of 20 per treatment. Chill parameters, experiment 2. Experiment 2 was a benchscale chill study conducted as described in experiment 1 except for chill water additives tested. Two treatments were included: (i) 50 ppm o f chlorine and 0.5% T-128 in distilled water and (ii) 50 ppm of chlorine and 0.01% H3PO4 (Fisher Scientific, Fair Lawn, NJ) in distilled water. In this study, pH was matched for both treatments at approximately 3.5; temperature, pH, and chlorine levels were confirmed initially and after 45 min of chill time, as described above for experiment 1. Duplicate chill vessels were used for each treatment in each of 10 replications, for a sample size o f 20 per treatment. Chill parameters, experiment 3. Experiment 3 was conducted in two pilot-scale four-section paddle chill tanks. Sections were separated such that broiler carcasses could not move from section to section, but paddles were perforated, allowing water to move freely throughout each tank. Each tank was filled with approximately 75 liters o f water and 40 kg of ice. Treatments were as follows: (i) one tank was filled with water containing 50 ppm o f chlorine and (ii) the second tank was filled with water containing 50 ppm o f chlorine with 0.5% T-128. Unchilled carcasses (48) were collected from a commercial processing plant and brought to the lbatoratory within 30 min. Carcasses were placed into each tank, six per section. In two noncontiguous sections o f each tank, three o f the carcasses were inoculated on the breast skin as described above for drummettes, and three were left uninoculated. Each of the intervening sections was filled with six uninoculated broiler carcasses. All carcasses were marked with colored pull ties to indicate inoculation status and section within the chill tank. W ater temperature, pH, and chlorine level were tested initially and after 45 min o f chill time as described above. Three replications were conducted. Sampling and culturing. After completion of the chill process, drummettes or carcasses were subjected to rinse sampling. Drummettes were placed in a sterile bag (Whirl-Pak, Nasco, Fort Atkinson, WI) and were rinsed (shaken by hand) for 60 s in 30 ml of sterile PBS. Carcasses were placed into clean plastic bags and rinsed for 60 s by mechanized shaker in 100 ml o f sterile distilled
J. Food Prot., Vol. 77, No. 9
1585
ANTIMICROBIAL CHILL TANK ADDITIVE
TABLE 1. Populations o f Salmonella and Campylobacter recovered from drummette rinses and chill water after 45-min immersion chill treatmentsa Organism Salmonella
Campylobacter
Treatment* Control Chlorine T-128 T-128 + chlorine Control Chlorine T-128 T-128 + chlorine
Inoculated drummette 2.70 2.32 2.43 2.0 3.03 2.79 2.55 2.65
± ± ± ± ± ± ± +
0.38 0.37 0.38 0.38 0.48 0.48 0.48 0.48
a
x
a
x
a
x x x x x
a
x
a a a a
Uninoculated drummette 2.25 1.68 2.0 1.1 2.79 1.32 0.89 0.74
± ± ± ± ± ± ± ±
0.42 0.42 0.42 0.42 0.40 0.40 0.41 0.41
a
y y
ab
a
y
b
y
a b b
x
y y
B y
Chill water 3.23 2.47 2.62 1.57 3.75 1.86 0.86 0.59
+ ± ± ± + ± + ±
0.49 a 0.50 a b 0.50 a 0.49 b 0.40 a 0.41 b 0.41 c 0.41 c
a Populations are expressed as log CFU per milliliter + 95% confidence interval. Immersion chill treatments were 50 ppm of chlorine, 0.50% T-128, or a combined solution (n = 20 per treatment). Each drummette was inoculated with approximately 6.0 log CFU each of Salmonella and Campylobacter. Values within columns and sample type with different capital letters (a to c) are significantly different by Tukey’s honestly significant difference at P < 0.05. Values for drummette rinses within rows with different lowercase letters (x and y) represent significantly different mean numbers of each organism by Student’s t test at P < 0.05. h Mean initial conditions: control, pH 6.97, 0.00 ppm of free chlorine; chlorine, pH 7.34, 51.9 ppm of free chlorine; T-128, pH 2.99, 0.00 ppm of free chlorine; T-128 + chlorine, pH 3.59, 50.5 ppm of free chlorine. water with the addition of 0.6 g of sodium thiosulfate (J.T. Baker, Phillipsburg, NJ). Chill water was also collected from each chill vessel. All rinsate and water samples were held on ice until serial dilutions were prepared and were plated for enumeration of Salmonella and Campylobacter, within 30 min. Salmonella were enumerated on brilliant green sulfa agar (Acumedia, Lansing, MI) with 200 ppm of nalidixic acid (Sigma-Aldrich, St. Louis, MO) incubated aerobically at 35°C for 24 h. Campylobacter were enumerated on Campy-Cefex agar (9) with 200 ppm of gentamicin (Sigma-Aldrich) and were incubated in resealable bags flushed with 5% 0 2, 10% C 0 2, 85% N 2 at 42°C for 48 h. As an enrichment, 1 ml of each whole carcass rinsate was added to 9 ml of buffered peptone water (Acumedia) incubated at 35°C for 24 h and Campylobacter enrichment broth (Med-Ox, Lafayette, LA) incubated microaerobically at 42°C for 48 h. In the case of a negative set of plates at the zero dilution, the respective enrichment broth was plated for a definitive result.
Statistical analysis. All counts of CFUs were log trans formed. Geometric means were calculated and used for statistical analyses (Statistica 7, StatSoft, Tulsa, OK). Data from experiments 1 and 2 were subjected to general linear models, and means were separated using Tukey’s honestly significant difference test. In experiment 1, further comparisons were made by Student’s t test between bacterial numbers recovered from inoculated and uninoculated drummettes within the same chill vessel. Significance level for experiments 1 and 2 was assigned at P < 0.05. In the pilot-scale study, experiment 3, the numbers recovered by direct plating were low; and, in some cases, the marker strains were only detected on carcass rinses after enrichment. For this reason we elected to report the data as positive or negative. Comparison according to treatment was conducted using a chi-square test for independence, with significance assigned at P < 0.01. RESULTS
Results from experiment 1, in which inoculated and uninoculated wing drummettes were co-chilled in 50 ppm of chlorine, 0.5% T-128, or a combination of both chemicals, are presented in Table 1. Chill tank chemical treatment had no significant effect on the numbers of Salmonella or Campylobacter detected on inoculated drummettes. Ap proximately 6.0 log of each was placed on the drummettes,
and 2.0 to 3.0 log of each was recovered. However, chemical treatment did significantly (P < 0.05) affect the cross-contamination of the uninoculated companion drumm ette. All uninoculated drummettes had significantly less Salmonella than their inoculated companion drummettes (P < 0.05). Those chilled with the combination of both 50 ppm of chlorine and T-128 fared the best, with significantly (JP < 0.05) fewer Salmonella recovered than with the control or plain T-128. Uninoculated drummettes chilled in plain water had similar numbers of Campylobacter as inoculated compan ions. However, all other treatments significantly (P < 0.05) lessened the amount of Campylobacter detected on uninoculated drummettes. Results of culturing the chill water itself supported the findings on drummettes; chemical additives, especially T-128, significantly lessened the number of Campylobacter detected per ml of chill water (P < 0.05). Experiment 2 was conducted to determine whether T-128 efficacy was solely due to a decrease in pH. Results from the comparison of pH-matched chill treatments with T-128 compared with H 3 PO 4 (the acidic component of T128) are presented in Table 2. For both Salmonella and Campylobacter, significantly fewer organisms were detect ed on uninoculated dmmmettes when chilled with T-128 with chlorine as opposed to H 3 P 0 4 with chlorine (P < 0.05). In the case of Campylobacter, significantly fewer were found per ml of chill water. Interestingly, no difference in the number of Salmonella per ml of chill water was detected according to chemical used. Results from the pilot-scale chilling experiment (ex periment 3), in which 50 ppm of chlorine was compared with 50 ppm of chlorine with the addition of 0.50% T-128, are presented in Table 3. In this experiment, the numbers recovered per ml of carcass rinse was low, sometimes below the level of detection without enrichment. Therefore, the data are presented as positive or negative. The addition of T-128 significantly lowered the prevalence of Campylobacter on inoculated carcasses (JP < 0.01). Furthermore, the prevalence of Salmonella and Campylobacter on uninoculated
1586
J. Food Prot., Vol. 77, No. 9
SCHAMBACH ET AL.
TABLE 2. Populations « /Salmonella and Campylobacter recovered from drummette rinses and chill water after 45-min immersion chill treatment in chlorine with additivesa Organism Salmonella Campylobacter
Additive* H3PO4 T-128 H3 PO.4 T-128
Inoculated drummette 2.50 2.35 2.79 2.23
± ± ± ±
0.14 0.17 0.18 0.22
Uninoculated drummette 2 .1 2
a
±
0 .2 2
1.56 ± 0.28 2.07 + 0.19 0.75 ± 0.36
a a a
Chill water 2.84 2.58 2.72 1.0
a b a b
± ± + ±
0.08 0.17 0.10 0.33
a a a b
a Populations are expressed as log CFU per milliliter + 95% confidence interval. Immersion chill treatments were 50 ppm of chlorine with either 0.50% T-128 or a pH-matched 0.01% H3 PO4 solution (n = 20). Each drummette was inoculated with approximately 6.0 log CFU each of Salmonella and Campylobacter. Values within a column and organism with different letters are significantly different by Tukey’s honestly significant difference at P < 0.05. * Mean initial chill conditions: H3 PO4 , pH 3.42, 50.5 ppm of free chlorine; T-128, pH 3.55, 50.6 ppm of free chlorine.
carcasses, whether they were physically touching the inoculated carcasses or were only exposed by the shared chill tank water, was significantly lower in the chill tank with chlorine and T-128 (P < 0.01). DISCUSSION Compared to controls, chlorine and T-128 each individually reduced cross-contamination with Salmonella and, to an even greater extent, Campylobacter. This is in agreement with earlier reports that showed that chlorinated chilling has limited efficacy against Salmonella on chicken skin (8, 13, 14) and that Campylobacter can be more sensitive to the effects of chlorine (4, 14). When used in concert, chlorine with T-128 resulted in significantly better control of cross-contamination with Salmonella and Cam pylobacter than either chemical alone. This may be due to a multihurdle effect (16), or perhaps T-128, and the coincident low pH, results in better efficacy of the chlorine (1). The exact mechanism of interaction between T-128 and chlorine has not yet been determined; a similar enhancement of chlorine efficacy was reported on fresh-cut produce (7). Chlorine is most effective in the hypochlorous acid form; acidification of the chill system can be helpful to maintain a high percentage of active chlorine. Organic acids have been successfully used to improve the antimicrobial effect of immersion chilling (2, 12). We wanted to test
whether the low pH of T-128 alone was responsible for the effect in initial studies or whether some other interaction between T-128 and chlorine was occurring. When compared to the same pH produced by H 3PO4 (the acidic component of T-128), T-128 outperformed the acid alone. This suggests that T-128 may indeed stabilize or enhance chlorine more than would be expected by simple pH control. Although an acid pH can be beneficial for microbial control, a very low pH may be detrimental to product quality and yield. The water-holding capacity of poultry meat is related to pH. When the pH of broiler meat drops below 5.8, water holding capacity drops greatly; this could adversely affect yield and further processing (15). Therefore, a balanced chill system with a high percentage of active chlorine, maintained at a pH of 6.0 to 7.0 and including multiple antimicrobial hurdles, balances pathogen control with production require ments. Certainly the mean pH of 3.59 encountered in our bench-scale experiments would be problematic from a production standpoint. When used with municipal tap water, the T-128-treated pilot-scale chill tank had a more moderate mean pH of 6.3. This was likely a result of tap water having a higher mineral content than the distilled water used in benchscale experiments. Even with the higher pH, in pilot-scale experiments, T-128 continued to show good effectiveness by significantly (P < 0.01) lessening cross-contamination with Salmonella and Campylobacter. This suggests that T-128 has potential for use as a commercial processing aid for control of
TABLE 3. Detection of Salmonella or Campylobacter on inoculated and co-chilled uninoculated broiler carcasses treated with chlorine or chlorine and T-128a No. of positive carcasses/no. sampled (% positive) Organism Salmonella Campylobacter
Chill treatment* Chlorine Chlorine + T-128 Chlorine Chlorine + T-128
Inoculated 17/18 17/18 18/18 8/18
(94) a (94) A (1 0 0 ) a (44) b
Uninoculated companion 15/18 6/18 10/18 3/18
(83) (33) (55) (17)
A b a b
Uninoculated separated 12/36 3/36 9/36 0/36
(33) A (0.8) b (25) a (0) b
a Carcasses were treated with 50 ppm of chlorine or 50 ppm of chlorine and 0.50% T-128. Inoculated carcasses were inoculated with approximately 6.0 log CFU each of Salmonella and Campylobacter (n = 18). Uninoculated companion carcasses were chilled in the same compartment as inoculated carcasses (n = 18); uninoculated separated carcasses were chilled in compartments separate from inoculated carcasses but open to chill water transfer (n = 36). Values within a column and organism with different letters are different (P < 0 .0 1 ) by chi-square test for independence. * Mean initial conditions: chlorine, pH 7.75, 55.6 ppm of free chlorine; chlorine + T-128, pH 6.31, 48.0 ppm of free chlorine.
J. Food Prot., Vol. 77, No. 9
cross-contamination with human pathogens during immer sion chilling, even at a pH that should not negatively affect product yield or meat quality. Commercial-scale field trials are currently under consideration.
ANTIMICROBIAL CHILL TANK ADDITIVE
7.
8.
ACKNOWLEDGMENTS The authors acknowledge expert technical assistance provided by Eric Adams and Steven Knapp. Funding was provided by the USDA, Agricultural Research Service Bacterial Epidemiology and Antimicrobial Resistance Research Unit and by Smartwash Solutions.
REFERENCES 1.
2.
3.
4.
5.
6.
Berrang, M. E., W. R. Windham, and R. J. Meinersmann. 2011. Campylobacter, Salmonella and E. coli on broiler carcasses subjected to a high pH scald and low pH post-pick chlorine dip. Poult. Sci. 90: 896-900. Fabrizio, K. A., R. R. Sharma, A. Demirci, and C. N. Cutter. 2002. Comparison of electrolyzed oxidizing water with various antimicro bial interventions to reduce Salmonella species on poultry. Poult. Sci. 81:1598-1605. Hansen, M. 2010. Comments of Consumers Union on United States Department of Agriculture (USDA) Food Safety Inspection Service (FSIS) notice on new performance standards for Salmonella and Campylobacter in young chicken and turkey slaughter establish ments; new compliance guides. Docket no. FSIS-20090-0034. Consumers Union, Yonkers, NY. Li, Y., H. Yang, and B. L. Swem. 2002. Effect of high-temperature inside-outside spray on survival of Campylobacter jejuni attached to prechill chicken carcasses. Poult. Sci. 81:1371-1377. Lillard, H. S. 1979. Levels of chlorine and chlorine dioxide of equivalent bactericidal effect in poultry processing water. J. Food Sci. 44:1594-1597. Northcutt, J. K., D. Smith, R. I. Huezo, and K. D. Ingram. 2008. Microbiology of broiler carcasses and chemistry of chiller water as affected by water reuse. Poult. Sci. 87:1458-1463.
9.
10.
11.
12.
13.
14.
15.
16.
1587
Nou, X., Y. Luo, L. Hollar, Y. Yang, H. Feng, P. Millner, and D. Shelton. 2011. Chlorine stabilizer T-128 enhances efficacy of chlorine against cross-contamination by E. coli 0157:H7 and Salmonella in fresh-cut lettuce processing. J. Food Sci. 76:M218M224. Parveen, S., M. Taabodi, J. G. Schwarz, T. P. Oscar, J. Harter-Dennis, and D. G. White. 2007. Prevalence and antimicrobial resistance of Salmonella recovered from processed poultry. J. Food Prot. 70: 2466-2472. Stem, N. J„ B. Wojton, and K. Kwiatek. 1992. A differentialselective medium and dry ice-generated atmosphere for recovery of Campylobacter jejuni. J. Food Prot. 55:515-517. U.S. Department of Agriculture, Food Safety and Inspection Service. 2003. Use of chlorine to treat poultry chiller water. FSIS notice 45-03. Available at: http://www.fsis.usda.gov/OPPDE/rdad/FSISNotices/45-03. htm. Accessed 5 July 2012. U.S. Department of Agriculture, Food Safety and Inspection Service. 2010. Compliance guideline for controlling Salmonella and Cam pylobacter in poultry, 3rd ed. Available at: http://www.fsis.usda.gov/ PDF/Compliance_Guide_Controling_Salmonella_Campylobacter_ Poultry_0510.pdf. Accessed 17 February 2013. Van der Marel, G. M., J. G. Van Logtestijn, and A. A. D. Mossel. 1988. Bacteriological quality of broiler carcasses as affected by inplant lactic acid decontamination. Int. J. Food Microbiol. 6:31^12. Yang, H., Y. Li, C. L. Griffis, and A. L. Waldroup. 2002. A probability model for cross-contamination by Campylobacter jejuni and Salmonella Typhimurium in poultry chilling process. Appl. Eng. Agric. 18:717-724. Yang, H., Y. Li, and M. G. Johnson. 2001. Survival and death of Salmonella Typhimurium and Campylobacter jejuni in processing water and on chicken skin during poultry scalding and chilling. J. Food Prot. 64:770-776. Young. J. F., A. H. Karlsson, and P. Henckel. 2004. Water-holding capacity in chicken breast muscle is enhanced by pyruvate and reduced by creatine supplements. Poult. Sci. 83:400-405. Zhao, T., and M. P. Doyle. 2006. Reduction of Campylobacter jejuni on chicken wings by chemical treatments. J. Food Prot. 69:762-767.
Copyright of Journal of Food Protection is the property of Allen Press Publishing Services Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
Research Note
Chemical Additive To Enhance Antimicrobial Efficacy of Chlorine and Control Cross-Contamination during Immersion Chill of Broiler Carcasses1 B. T. SCHAMBACH,1J M. E. BERRANG,1* M. A. HARRISON,2 AND R. J. MEINERSMANN1 'U.S. Department o f Agriculture, Agricultural Research Service, Russell Research Center, Athens, Georgia 30605; and 2University o f Georgia, Food Science and Technology Department, Athens, Georgia 30602, USA MS 14-092: Received 25 February 2014/Accepted 2 May 2014
A BSTR A CT Immersion chilling of broiler carcasses can be a site for cross-contamination between the occasional highly contaminated carcass and those that are co-chilled. Chlorine is often used as an antimicrobial but can be overcome by organic material. A proprietary chlorine stabilizer (T-128) based on phosphoric acid-propylene glycol was tested as a chill tank additive in experiments simulating commercial broiler chilling. In bench-scale experiments, 0.5% T-128 was compared with plain water (control), 50 ppm of chlorine, and the combination of 0.5% T-128 with 50 ppm of chlorine to control transfer of Salmonella and Campylobacter from inoculated wing drummettes to co-chilled uninoculated drummettes. Both chlorine and T-128 lessened cross-contamination with Salmonella (P < 0.05); T-128 and T-128 with chlorine were significantly more effective (P < 0.05) than the control or plain chlorine for control of Campylobacter. T-128 treatments were noted to have a pH of less than 4.0; an additional experiment demonstrated that the antimicrobial effect of T-128 was not due merely to a lower pH. In commercial broiler chilling, a pH close to 6.0 is preferred to maximize chlorine effectiveness, while maintaining water-holding capacity of the meat. In a set of pilot-scale experiments with T-128, a near-ideal pH of 6.3 was achieved by using tap water instead of the distilled water used in bench-scale experiments. Pilot-scale chill tanks were used to compare the combination of 0.5% T-128 and 50 ppm of chlorine with 50 ppm of plain chlorine for control of cross-contamination between whole carcasses inoculated with Salmonella and Campylobacter and co-chilled uninoculated carcasses. The T-128 treatment resulted in significantly less cross contamination by either direct contact or water transfer with both organisms compared with plain chlorine treatment. T-128 may have use in commercial broiler processing to enhance the effectiveness of chlorine in processing water.
The U.S. Department of Agriculture, Food Safety Inspection Service (USDA-FSIS) reported for the third quarter of 2010 that an average of 7.4% of commercially processed, postchill chicken carcasses were positive for detectable levels of Salmonella (11). As of July 2011, the USDA-FSIS implemented new performance standards for the poultry industry for Salmonella and, for the first time, for Campylobacter (11). The new USDA performance standard for broiler carcasses sets limits for Salmonella at 7.5% positive and for thermophilic Campylobacter spp. at 10.4% (3). Control of carcass-to-carcass cross-contamina tion during broiler chilling is an important step in the effort to meet these requirements. In the United States, most broiler processors use cold water immersion for carcass chilling. Chlorine has been the * Author for correspondence. Tel: 706 546 3551; Fax: 706 546 3066; E-mail: [email protected]. f Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. f Present address: Coca Cola Co., 1 Coca Cola Plaza, Atlanta, GA 30313, USA.
traditional antimicrobial agent used to control bacterial contamination in chill tanks, allowable at levels up to 0.005% by volume (10). Despite a USDA requirement for 2.3 to 2.6 liters of fresh chill water per carcass (6), high organic loads occur and have been shown to reduce the antimicrobial effectiveness of chlorine (5). A chlorine stabilizer, to lessen the effect of high organic loads associated with incoming carcasses, would be useful to maintain efficacy of chlorine during broiler chilling. A proprietary phosphoric acid—propylene glycol formula for the stabilization of chlorine in solution, T-128 (Smartwash Solutions, Salinas, CA), was found to stabilize chlorine in the presence of high organic loads, increasing efficacy against Escherichia coli and Salmonella spp. in lettuce washing applications (7). Although T-128 alone provided only limited antimicrobial effect, when it was combined with chlorine, a significant reduction in pathogen survival was detected, even in the presence of a high concentration of organic matter (7). The exact mechanism by which the addition of T-128, a blend of phosphoric acid and propylene glycol, to a properly chlorinated system improves the efficacy of the wash solution against bacterial survival has not yet been
1584
SCHAMBACH ET AL.
determined. However, results of produce washing suggest that there is a relationship between T-128 and chlorine that causes a decrease in cross-contamination of fresh-cut lettuce with human pathogens (7). It is possible that T-128 could be useful to stabilize chlorine and control cross-contamination during broiler carcass chilling, thereby aiding the poultry industry in their ongoing efforts to meet regulatory standards and reduce levels of human pathogens in the food chain. The objective of the current study was to determine the effectiveness of T-128, with and without chlorine, at reducing cross contamination of broiler parts and carcasses with inoculated Campylobacter and Salmonella during immersion chill. This study will provide the poultry processing industry with information relative to an intervention strategy for preven tion and control of carcass cross-contamination with pathogenic bacteria. MATERIALS AND METHODS Overview and experimental design. For all experiments, the concentration of T-128 was set at 0.5% based on preliminary efficacy trials (data not shown). This study included three experiments. Experiment 1 was designed to test the potential o f T-128 to lessen cross contamination with Campylobacter and Salmonella during a bench-scale chill tank simulation with 50 ppm o f chlorine. In this experiment, two broiler wing dmmmettes were co-chilled in small containers. One drummette was inoculated and the other was not. A fter the simulated chill was complete, the level of inoculated bacteria detected in the chill water and on the uninoculated drummette was measured. Experim ent 2 was designed to determine whether the efficacy of T-128 was solely due to the lowered pH of the chlorinated chill water. In this experiment, T-128 was compared with the acidic component of T-128 (H3PO4) in pH-matched bench-scale chill tank simulations using an inoculated and uninoculated drummette design similar to the first experiment. Experiment 3 was conducted at a larger pilot plant scale and was intended to compare T-128 with 50 ppm of chlorine to 50 ppm of chlorine alone using whole broiler carcasses in a chill system much closer to commercial conditions than was achieved during the bench-scale experiments. Cultures and inoculation. Antimicrobial-resistant marker strains of Salmonella and Campylobacter (both originally isolated from chicken) were used to inoculate drummettes or carcasses. Salmonella enterica Typhimurium inocula were resistant to nalidixic acid; Campylobacter coli inocula were resistant to gentamicin. By incorporating the respective antimicrobial (200 ppm) into the appropriate medium, we were able to recover our inocula without interference from other naturally occurring bacteria. No resistant bacteria were found on any uninoculated drummettes or carcasses tested during preliminary trials to confirm the utility of the marker strains. Both cultures were maintained as frozen stock, and inocula were prepared as cell suspensions in PBS from 24-h plates, as described in the section “ Sampling and culturing.” Optical density was measured (Thermo Fisher Scientific, Waltham, MA), and the number per ml was confirmed by plate count, as described in “ Sampling and culturing.” Drummettes or carcasses were inoculated with 10 pi of cell suspension containing approximately 106 cells o f each inoculum. The cell suspension was spread with a sterile plastic inoculating loop over approximately 4 cm2 of the
J. Food Prot., Vol. 77, No. 9
skin and was allowed to dry for 10 min before starting the immersion chill process.
Chill parameters, experiment 1. Fresh drummettes were purchased at retail and were preheated to an internal temperature of 42°C to simulate a warm carcass. Two drummettes were placed in each container, one inoculated as described above and the other left uninoculated. Bench-scale chilling was conducted in large beakers (15-cm inside diameter), each with two drummettes, water, and ice in a 1:2:4 ratio by weight. Chill water included additives according to the following four treatments: (i) control, distilled water; (ii) chlorine, 50 ppm o f chlorine (Clorox germicidal bleach [Clorox Professional Products Co., Oakland, CA], 6.15% sodium hypo chlorite) in distilled water; (iii) T-128, 0.5% T-128 (Smartwash Solutions LLC, Salinas, CA) in distilled water; and (iv) combination, 50 ppm of chlorine and 0.5% T-128 in distilled water. Filled beakers were covered and then were placed in an orbital shaking incubator (Labline Instruments, Rockville, MD) at 130 rpm for 45 min at 25°C. Measurements were made at 0 and 45 min of chill time for water temperature, pH (pHTestr 30, Eutech Instruments, Vernon Hills, IL), and free and total chlorine levels (Pocket Colorimeter II, Hach Company, Loveland, CO). Duplicate chill vessels were used for each treatment in each of 10 replications, for a sample size of 20 per treatment. Chill parameters, experiment 2. Experiment 2 was a benchscale chill study conducted as described in experiment 1 except for chill water additives tested. Two treatments were included: (i) 50 ppm o f chlorine and 0.5% T-128 in distilled water and (ii) 50 ppm of chlorine and 0.01% H3PO4 (Fisher Scientific, Fair Lawn, NJ) in distilled water. In this study, pH was matched for both treatments at approximately 3.5; temperature, pH, and chlorine levels were confirmed initially and after 45 min of chill time, as described above for experiment 1. Duplicate chill vessels were used for each treatment in each of 10 replications, for a sample size o f 20 per treatment. Chill parameters, experiment 3. Experiment 3 was conducted in two pilot-scale four-section paddle chill tanks. Sections were separated such that broiler carcasses could not move from section to section, but paddles were perforated, allowing water to move freely throughout each tank. Each tank was filled with approximately 75 liters o f water and 40 kg of ice. Treatments were as follows: (i) one tank was filled with water containing 50 ppm o f chlorine and (ii) the second tank was filled with water containing 50 ppm o f chlorine with 0.5% T-128. Unchilled carcasses (48) were collected from a commercial processing plant and brought to the lbatoratory within 30 min. Carcasses were placed into each tank, six per section. In two noncontiguous sections o f each tank, three o f the carcasses were inoculated on the breast skin as described above for drummettes, and three were left uninoculated. Each of the intervening sections was filled with six uninoculated broiler carcasses. All carcasses were marked with colored pull ties to indicate inoculation status and section within the chill tank. W ater temperature, pH, and chlorine level were tested initially and after 45 min o f chill time as described above. Three replications were conducted. Sampling and culturing. After completion of the chill process, drummettes or carcasses were subjected to rinse sampling. Drummettes were placed in a sterile bag (Whirl-Pak, Nasco, Fort Atkinson, WI) and were rinsed (shaken by hand) for 60 s in 30 ml of sterile PBS. Carcasses were placed into clean plastic bags and rinsed for 60 s by mechanized shaker in 100 ml o f sterile distilled
J. Food Prot., Vol. 77, No. 9
1585
ANTIMICROBIAL CHILL TANK ADDITIVE
TABLE 1. Populations o f Salmonella and Campylobacter recovered from drummette rinses and chill water after 45-min immersion chill treatmentsa Organism Salmonella
Campylobacter
Treatment* Control Chlorine T-128 T-128 + chlorine Control Chlorine T-128 T-128 + chlorine
Inoculated drummette 2.70 2.32 2.43 2.0 3.03 2.79 2.55 2.65
± ± ± ± ± ± ± +
0.38 0.37 0.38 0.38 0.48 0.48 0.48 0.48
a
x
a
x
a
x x x x x
a
x
a a a a
Uninoculated drummette 2.25 1.68 2.0 1.1 2.79 1.32 0.89 0.74
± ± ± ± ± ± ± ±
0.42 0.42 0.42 0.42 0.40 0.40 0.41 0.41
a
y y
ab
a
y
b
y
a b b
x
y y
B y
Chill water 3.23 2.47 2.62 1.57 3.75 1.86 0.86 0.59
+ ± ± ± + ± + ±
0.49 a 0.50 a b 0.50 a 0.49 b 0.40 a 0.41 b 0.41 c 0.41 c
a Populations are expressed as log CFU per milliliter + 95% confidence interval. Immersion chill treatments were 50 ppm of chlorine, 0.50% T-128, or a combined solution (n = 20 per treatment). Each drummette was inoculated with approximately 6.0 log CFU each of Salmonella and Campylobacter. Values within columns and sample type with different capital letters (a to c) are significantly different by Tukey’s honestly significant difference at P < 0.05. Values for drummette rinses within rows with different lowercase letters (x and y) represent significantly different mean numbers of each organism by Student’s t test at P < 0.05. h Mean initial conditions: control, pH 6.97, 0.00 ppm of free chlorine; chlorine, pH 7.34, 51.9 ppm of free chlorine; T-128, pH 2.99, 0.00 ppm of free chlorine; T-128 + chlorine, pH 3.59, 50.5 ppm of free chlorine. water with the addition of 0.6 g of sodium thiosulfate (J.T. Baker, Phillipsburg, NJ). Chill water was also collected from each chill vessel. All rinsate and water samples were held on ice until serial dilutions were prepared and were plated for enumeration of Salmonella and Campylobacter, within 30 min. Salmonella were enumerated on brilliant green sulfa agar (Acumedia, Lansing, MI) with 200 ppm of nalidixic acid (Sigma-Aldrich, St. Louis, MO) incubated aerobically at 35°C for 24 h. Campylobacter were enumerated on Campy-Cefex agar (9) with 200 ppm of gentamicin (Sigma-Aldrich) and were incubated in resealable bags flushed with 5% 0 2, 10% C 0 2, 85% N 2 at 42°C for 48 h. As an enrichment, 1 ml of each whole carcass rinsate was added to 9 ml of buffered peptone water (Acumedia) incubated at 35°C for 24 h and Campylobacter enrichment broth (Med-Ox, Lafayette, LA) incubated microaerobically at 42°C for 48 h. In the case of a negative set of plates at the zero dilution, the respective enrichment broth was plated for a definitive result.
Statistical analysis. All counts of CFUs were log trans formed. Geometric means were calculated and used for statistical analyses (Statistica 7, StatSoft, Tulsa, OK). Data from experiments 1 and 2 were subjected to general linear models, and means were separated using Tukey’s honestly significant difference test. In experiment 1, further comparisons were made by Student’s t test between bacterial numbers recovered from inoculated and uninoculated drummettes within the same chill vessel. Significance level for experiments 1 and 2 was assigned at P < 0.05. In the pilot-scale study, experiment 3, the numbers recovered by direct plating were low; and, in some cases, the marker strains were only detected on carcass rinses after enrichment. For this reason we elected to report the data as positive or negative. Comparison according to treatment was conducted using a chi-square test for independence, with significance assigned at P < 0.01. RESULTS
Results from experiment 1, in which inoculated and uninoculated wing drummettes were co-chilled in 50 ppm of chlorine, 0.5% T-128, or a combination of both chemicals, are presented in Table 1. Chill tank chemical treatment had no significant effect on the numbers of Salmonella or Campylobacter detected on inoculated drummettes. Ap proximately 6.0 log of each was placed on the drummettes,
and 2.0 to 3.0 log of each was recovered. However, chemical treatment did significantly (P < 0.05) affect the cross-contamination of the uninoculated companion drumm ette. All uninoculated drummettes had significantly less Salmonella than their inoculated companion drummettes (P < 0.05). Those chilled with the combination of both 50 ppm of chlorine and T-128 fared the best, with significantly (JP < 0.05) fewer Salmonella recovered than with the control or plain T-128. Uninoculated drummettes chilled in plain water had similar numbers of Campylobacter as inoculated compan ions. However, all other treatments significantly (P < 0.05) lessened the amount of Campylobacter detected on uninoculated drummettes. Results of culturing the chill water itself supported the findings on drummettes; chemical additives, especially T-128, significantly lessened the number of Campylobacter detected per ml of chill water (P < 0.05). Experiment 2 was conducted to determine whether T-128 efficacy was solely due to a decrease in pH. Results from the comparison of pH-matched chill treatments with T-128 compared with H 3 PO 4 (the acidic component of T128) are presented in Table 2. For both Salmonella and Campylobacter, significantly fewer organisms were detect ed on uninoculated dmmmettes when chilled with T-128 with chlorine as opposed to H 3 P 0 4 with chlorine (P < 0.05). In the case of Campylobacter, significantly fewer were found per ml of chill water. Interestingly, no difference in the number of Salmonella per ml of chill water was detected according to chemical used. Results from the pilot-scale chilling experiment (ex periment 3), in which 50 ppm of chlorine was compared with 50 ppm of chlorine with the addition of 0.50% T-128, are presented in Table 3. In this experiment, the numbers recovered per ml of carcass rinse was low, sometimes below the level of detection without enrichment. Therefore, the data are presented as positive or negative. The addition of T-128 significantly lowered the prevalence of Campylobacter on inoculated carcasses (JP < 0.01). Furthermore, the prevalence of Salmonella and Campylobacter on uninoculated
1586
J. Food Prot., Vol. 77, No. 9
SCHAMBACH ET AL.
TABLE 2. Populations « /Salmonella and Campylobacter recovered from drummette rinses and chill water after 45-min immersion chill treatment in chlorine with additivesa Organism Salmonella Campylobacter
Additive* H3PO4 T-128 H3 PO.4 T-128
Inoculated drummette 2.50 2.35 2.79 2.23
± ± ± ±
0.14 0.17 0.18 0.22
Uninoculated drummette 2 .1 2
a
±
0 .2 2
1.56 ± 0.28 2.07 + 0.19 0.75 ± 0.36
a a a
Chill water 2.84 2.58 2.72 1.0
a b a b
± ± + ±
0.08 0.17 0.10 0.33
a a a b
a Populations are expressed as log CFU per milliliter + 95% confidence interval. Immersion chill treatments were 50 ppm of chlorine with either 0.50% T-128 or a pH-matched 0.01% H3 PO4 solution (n = 20). Each drummette was inoculated with approximately 6.0 log CFU each of Salmonella and Campylobacter. Values within a column and organism with different letters are significantly different by Tukey’s honestly significant difference at P < 0.05. * Mean initial chill conditions: H3 PO4 , pH 3.42, 50.5 ppm of free chlorine; T-128, pH 3.55, 50.6 ppm of free chlorine.
carcasses, whether they were physically touching the inoculated carcasses or were only exposed by the shared chill tank water, was significantly lower in the chill tank with chlorine and T-128 (P < 0.01). DISCUSSION Compared to controls, chlorine and T-128 each individually reduced cross-contamination with Salmonella and, to an even greater extent, Campylobacter. This is in agreement with earlier reports that showed that chlorinated chilling has limited efficacy against Salmonella on chicken skin (8, 13, 14) and that Campylobacter can be more sensitive to the effects of chlorine (4, 14). When used in concert, chlorine with T-128 resulted in significantly better control of cross-contamination with Salmonella and Cam pylobacter than either chemical alone. This may be due to a multihurdle effect (16), or perhaps T-128, and the coincident low pH, results in better efficacy of the chlorine (1). The exact mechanism of interaction between T-128 and chlorine has not yet been determined; a similar enhancement of chlorine efficacy was reported on fresh-cut produce (7). Chlorine is most effective in the hypochlorous acid form; acidification of the chill system can be helpful to maintain a high percentage of active chlorine. Organic acids have been successfully used to improve the antimicrobial effect of immersion chilling (2, 12). We wanted to test
whether the low pH of T-128 alone was responsible for the effect in initial studies or whether some other interaction between T-128 and chlorine was occurring. When compared to the same pH produced by H 3PO4 (the acidic component of T-128), T-128 outperformed the acid alone. This suggests that T-128 may indeed stabilize or enhance chlorine more than would be expected by simple pH control. Although an acid pH can be beneficial for microbial control, a very low pH may be detrimental to product quality and yield. The water-holding capacity of poultry meat is related to pH. When the pH of broiler meat drops below 5.8, water holding capacity drops greatly; this could adversely affect yield and further processing (15). Therefore, a balanced chill system with a high percentage of active chlorine, maintained at a pH of 6.0 to 7.0 and including multiple antimicrobial hurdles, balances pathogen control with production require ments. Certainly the mean pH of 3.59 encountered in our bench-scale experiments would be problematic from a production standpoint. When used with municipal tap water, the T-128-treated pilot-scale chill tank had a more moderate mean pH of 6.3. This was likely a result of tap water having a higher mineral content than the distilled water used in benchscale experiments. Even with the higher pH, in pilot-scale experiments, T-128 continued to show good effectiveness by significantly (P < 0.01) lessening cross-contamination with Salmonella and Campylobacter. This suggests that T-128 has potential for use as a commercial processing aid for control of
TABLE 3. Detection of Salmonella or Campylobacter on inoculated and co-chilled uninoculated broiler carcasses treated with chlorine or chlorine and T-128a No. of positive carcasses/no. sampled (% positive) Organism Salmonella Campylobacter
Chill treatment* Chlorine Chlorine + T-128 Chlorine Chlorine + T-128
Inoculated 17/18 17/18 18/18 8/18
(94) a (94) A (1 0 0 ) a (44) b
Uninoculated companion 15/18 6/18 10/18 3/18
(83) (33) (55) (17)
A b a b
Uninoculated separated 12/36 3/36 9/36 0/36
(33) A (0.8) b (25) a (0) b
a Carcasses were treated with 50 ppm of chlorine or 50 ppm of chlorine and 0.50% T-128. Inoculated carcasses were inoculated with approximately 6.0 log CFU each of Salmonella and Campylobacter (n = 18). Uninoculated companion carcasses were chilled in the same compartment as inoculated carcasses (n = 18); uninoculated separated carcasses were chilled in compartments separate from inoculated carcasses but open to chill water transfer (n = 36). Values within a column and organism with different letters are different (P < 0 .0 1 ) by chi-square test for independence. * Mean initial conditions: chlorine, pH 7.75, 55.6 ppm of free chlorine; chlorine + T-128, pH 6.31, 48.0 ppm of free chlorine.
J. Food Prot., Vol. 77, No. 9
cross-contamination with human pathogens during immer sion chilling, even at a pH that should not negatively affect product yield or meat quality. Commercial-scale field trials are currently under consideration.
ANTIMICROBIAL CHILL TANK ADDITIVE
7.
8.
ACKNOWLEDGMENTS The authors acknowledge expert technical assistance provided by Eric Adams and Steven Knapp. Funding was provided by the USDA, Agricultural Research Service Bacterial Epidemiology and Antimicrobial Resistance Research Unit and by Smartwash Solutions.
REFERENCES 1.
2.
3.
4.
5.
6.
Berrang, M. E., W. R. Windham, and R. J. Meinersmann. 2011. Campylobacter, Salmonella and E. coli on broiler carcasses subjected to a high pH scald and low pH post-pick chlorine dip. Poult. Sci. 90: 896-900. Fabrizio, K. A., R. R. Sharma, A. Demirci, and C. N. Cutter. 2002. Comparison of electrolyzed oxidizing water with various antimicro bial interventions to reduce Salmonella species on poultry. Poult. Sci. 81:1598-1605. Hansen, M. 2010. Comments of Consumers Union on United States Department of Agriculture (USDA) Food Safety Inspection Service (FSIS) notice on new performance standards for Salmonella and Campylobacter in young chicken and turkey slaughter establish ments; new compliance guides. Docket no. FSIS-20090-0034. Consumers Union, Yonkers, NY. Li, Y., H. Yang, and B. L. Swem. 2002. Effect of high-temperature inside-outside spray on survival of Campylobacter jejuni attached to prechill chicken carcasses. Poult. Sci. 81:1371-1377. Lillard, H. S. 1979. Levels of chlorine and chlorine dioxide of equivalent bactericidal effect in poultry processing water. J. Food Sci. 44:1594-1597. Northcutt, J. K., D. Smith, R. I. Huezo, and K. D. Ingram. 2008. Microbiology of broiler carcasses and chemistry of chiller water as affected by water reuse. Poult. Sci. 87:1458-1463.
9.
10.
11.
12.
13.
14.
15.
16.
1587
Nou, X., Y. Luo, L. Hollar, Y. Yang, H. Feng, P. Millner, and D. Shelton. 2011. Chlorine stabilizer T-128 enhances efficacy of chlorine against cross-contamination by E. coli 0157:H7 and Salmonella in fresh-cut lettuce processing. J. Food Sci. 76:M218M224. Parveen, S., M. Taabodi, J. G. Schwarz, T. P. Oscar, J. Harter-Dennis, and D. G. White. 2007. Prevalence and antimicrobial resistance of Salmonella recovered from processed poultry. J. Food Prot. 70: 2466-2472. Stem, N. J„ B. Wojton, and K. Kwiatek. 1992. A differentialselective medium and dry ice-generated atmosphere for recovery of Campylobacter jejuni. J. Food Prot. 55:515-517. U.S. Department of Agriculture, Food Safety and Inspection Service. 2003. Use of chlorine to treat poultry chiller water. FSIS notice 45-03. Available at: http://www.fsis.usda.gov/OPPDE/rdad/FSISNotices/45-03. htm. Accessed 5 July 2012. U.S. Department of Agriculture, Food Safety and Inspection Service. 2010. Compliance guideline for controlling Salmonella and Cam pylobacter in poultry, 3rd ed. Available at: http://www.fsis.usda.gov/ PDF/Compliance_Guide_Controling_Salmonella_Campylobacter_ Poultry_0510.pdf. Accessed 17 February 2013. Van der Marel, G. M., J. G. Van Logtestijn, and A. A. D. Mossel. 1988. Bacteriological quality of broiler carcasses as affected by inplant lactic acid decontamination. Int. J. Food Microbiol. 6:31^12. Yang, H., Y. Li, C. L. Griffis, and A. L. Waldroup. 2002. A probability model for cross-contamination by Campylobacter jejuni and Salmonella Typhimurium in poultry chilling process. Appl. Eng. Agric. 18:717-724. Yang, H., Y. Li, and M. G. Johnson. 2001. Survival and death of Salmonella Typhimurium and Campylobacter jejuni in processing water and on chicken skin during poultry scalding and chilling. J. Food Prot. 64:770-776. Young. J. F., A. H. Karlsson, and P. Henckel. 2004. Water-holding capacity in chicken breast muscle is enhanced by pyruvate and reduced by creatine supplements. Poult. Sci. 83:400-405. Zhao, T., and M. P. Doyle. 2006. Reduction of Campylobacter jejuni on chicken wings by chemical treatments. J. Food Prot. 69:762-767.
Copyright of Journal of Food Protection is the property of Allen Press Publishing Services Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
