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Bacterial Contamination and Shelf Life of Freshly Eviscerated Broilers as Influenced by Holding Time in Slush Ice*
Bacterial Contamination and Shelf Life of Freshly Eviscerated Broilers as Influenced by Holding Time in Slush Ice* DANIEL FROMM
Poultry Science Department, North Carolina Agricultural Experiment Station, Raleigh, North Carolina
T
HE body heat of freshly eviscerated broilers is usually removed by submerging the carcass in a mixture of crushed ice and water. Currently the practice of many processors is to hold carcasses in slush ice for various periods ranging from approximately 1 to 24 hours after carcass temperature has been lowered to 40°F. Gunderson et al. (1954) found that storing poultry carcasses in chill tanks beyond the cooling period caused an increase in surface bacterial contamination. Lockhead and Landerkin (1935) and Ziegler et al. (1954) found that deterioration of fresh dressed poultry is essentially surface spoilage due to bacterial growth. Similar findings were reported by Gunderson et al. (1954). In view of the lack of sufficient information relative to the effects of holding eviscerated broilers in chill tanks for prolonged periods of time, the present study was undertaken to determine carcass bacterial contamination and shelf life as influenced by holding time in slush ice. EXPERIMENTAL
Carcasses weighing approximately 2 | pounds were processed in a commercial poultry processing plant in Raleigh, North Carolina. Approximate weights were determined on the processing line by an * Published with the approval of the Director of Research as Research Paper No. 805 of the Journal Series.
automatic weighing device. Carcasses were packed ice free in wirebound, wooden boxes and transported (approximately 20 minutes) to the College Poultry Science laboratories for treatment. Giblets were removed from 80 freshly eviscerated carcasses and the carcasses halved with a band-type meat saw. Thirtytwo half carcasses were individually packed in 8"X5|"X1" boat-type paper trays, placed on metal racks in a 35°F. chill room and covered and sealed with moisture-proof, transparent and heat sealing (MTS) cellophane after pectoral muscles were cooled to 40°F. The remaining half-carcasses were distributed at random in each of four 20"X27" sanitized galvanized cans and covered with crushed ice and water. Chlorinated tap water was used in the cooling medium. Slush ice and half-carcasses were air agitated. Half-carcasses were held in the cooling tanks for 1, 3, 5, or 24 hours. Carcass temperatures were determined with a Brown recording potentiometer. Thermocouple leads were placed in the pectoral muscles of carcasses as they were removed from the eviscerating line and of half-carcasses during the cooling operation. After 1, 3, 5 or 24 hours in slush ice each half-carcass was packed in an 8"X5|"X1" boat-type paper tray and covered and sealed with MTS cellophane. All packaged half-carcasses were held at 35°F. until analyzed.
1006
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
(Received for publication April 8, 1957)
BACTERIAL CONTAMINATION OF ICE CHILLED BROILERS
RESULTS AND DISCUSSION
The data presented in Table 1 show the washing effect of slush ice and the rate of chlorine dissipation in the wash water.
TABLE 1.—Bacterial counts per ml. and the residual chlorine in parts per million of neater used to chill half-carcasses1 Bacterial counts per ml. Water before treatment Water after carcasses held: 1 hour 3 hours S hours 24 hours 1
Residual CI2 in p.p.m.
80
2.10
3600 4600 4600 1400
0.35 0.01 — —
These data represent the means of 2 trials.
The mean bacterial count of the slush ice before half-carcasses were added was 80 per ml. After the addition of half-carcasses to the coolant, the numbers of bacteria per ml. increased by 45 times within an hour. Presumably these bacteria orginated from the half-carcasses as shown in Figure 2 by the drop in bacterial numbers between air cooled half-carcasses and half carcasses held in slush ice for 1 hour. The mean residual chlorine concentration of the slush ice prior to the addition of half-carcasses was 2.10 p.p.m. (Table 1). The residual chlorine in its initial concentration probably had some bactericidal action when half-carcasses were added to the chill tanks. Three hours after amalgamation of slush ice and half-carcasses the concentration of residual chlorine was 0.01 p.p.m. and the bacterial count per ml. of coolant had increased slightly above slush ice used for cooling half-carcasses for 1 hour. Due to the absence of residual chlorine in slush ice after 5 hours, the decrease in bacteria per ml. of slush ice used to chill half-carcasses for 5 hours to that used for 24 hours cannot be attributed to the bactericidal action of chlorine. Figure 1 shows the relationship between length of time half-carcasses were held in slush ice and bacterial numbers on the half-carcasses during various periods of subsequent storage at 35° F. in the chill
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
Since chlorinated tap water was used in the slush ice, the rate of chlorine dissipation was determined with an amperometric titrater (Wallace and Tiernan) in order to estimate the effect of residual chlorine on bacterial numbers in the coolant and on the half-carcasses. Four half-carcasses within each treatment were analyzed for bacterial numbers immediately after the halving operation and at 3-day intervals until odor or slime developed. One square inch of the pectoral tract under the wing of each of the 4 halfcarcasses was swabbed. Each swab was placed in a 150X16 mm. test tube containing 5 ml. sterile physiological saline solution. Each test tube was violently slapped against the palm of the hand 25 times. Serial dilutions were made and samples plated on heart infusion agar (Difco). Plates were incubated at 30°C. for 48 hours and the mean number of bacteria per square inch of carcass determined. Samples of slush ice in each tank were analyzed for bacterial numbers before and after the half-carcasses were chilled. Serial dilutions were made and samples plated on heart infusion agar (Difco). Plates were incubated at 30°C. for 48 hours and the mean number of bacteria per milliliter determined. Shelf life was determined by smell and sight. Ten designated packaged halfcarcasses within each treatment were analyzed twice each day until signs of spoilage were evident and the mean days of shelf life determined. This experiment was replicated in its entirety and the data were pooled in the statistical analyses.
1007
1008
D. FROMM
6
9
AGE IN DAYS FIG. 1. The relationship between number of hours half-carcasses were held in slush ice and the mean bacterial counts per square inch of carcasses after various storage periods.
aoo 2
room. Statistical analysis showed that the significant factor affecting halfcarcass bacterial numbers was the length of time half-carcasses were held in slush ice. The trend indicates that the bacterial flora decreased in numbers'as half-carcasses were held longer in slush ice. The influence of the slush ice chilling time on bacterial counts was present during the various days of storage. This is evident by the way the rates of increase in bacterial numbers for each treatment essentially parallel each other during the storage periods. The relationships between length of time carcasses were held in slush ice, the mean bacterial count per square inch of
HOURS IN SLUSH ICE
FIG. 2. The relationships between number of hours half-carcasses were kept in slush ice and the mean total bacterial counts per square inch of carcass skin and shelf life in days.1 • Hours in slush ice and shelf life r = +0.534 (insignificant). Hours in slush ice and bacterial numbers r = —0.535 (insignificant). Shelf life and bacterial numbers r = -0.997 (P=0.01).
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
3
half-carcasses and the mean shelf life of half-carcasses held at 35°F. is presented in Figure 2. Each bacterial count represents the geometric mean for the 4 analysis periods within each treatment. Bacterial numbers decreased as holding time in slush ice was increased. The sharpest decline in numbers occurred between air chilled half-carcasses and half-carcasses held in slush ice for 1 hour. Bacterial numbers declined 258,000 between air chilled half-carcasses and half-carcasses held in slush ice for 1 hour. The decrease in bacterial numbers was 18,000 between groups held for 1 hour and 3 hours in slush ice. After the decline in bacterial numbers between the 1 and 3 hour groups, the rate of reduction in bacterial numbers increased between groups held 3 and 5 hours in coolant. The difference in mean bacterial numbers per square inch of half-carcass between groups held for 3 hours and 5 hours in slush ice was 61,000. The rate of decline in bacterial numbers leveled off between groups held for 5 and 24 hours.
BACTERIAL CONTAMINATION OF ICE CHILLED BROILERS
1009
FIG. 3. Cooling rates of air-chilled (35°F.) and slush ice chilled half-carcasses.
The mean difference between these cooling groups was 68,000 bacteria per square inch of half-carcass. Correlation coefficients for relationships between hours held in slush ice and bacterial numbers, and shelf life and bacterial numbers are presented in Figure 2. There was a direct insignificant correlation between hours in slush ice and shelf life. The inverse correlation between hours in slush ice and bacterial numbers was insignificant. The coefficient for shelf life and bacterial numbers was inverse and significant at the 1% level. The difference in bacterial numbers per square inch of half-carcass between air chilled and slush ice chilled poultrywas caused by contrasting cooling rates (Figure 3) and the washing effect of the slush ice (Table 1). Figure 3 illustrates the cooling rates of the half-carcasses in a 35°F. chill room and slush ice. The pectoral muscles were chilled to 40°F. in 4 hours when held in a 35°F. chill room and in | hour when chilled in air agitated slush ice. This difference in cooling time would permit more bacterial growth for
SUMMARY
Surface bacterial contamination and shelf life were determined for 2\ pound eviscerated broilers held 1, 3, 5 and 24 hours in slush ice. Bacterial contamination and shelf life were also determined for carcasses air chilled at 35°F. The results of this study showed that: 1. There was an inverse relationship between bacterial numbers on the carcasses and length of time carcases were held in slush ice. 2. Carcass shelf life and bacterial numbers on the carcass were inversely related. 3. Shelf life was directly proportional to the number of hours, from 0 to 24, that carcasses were held in slush ice. REFERENCES Gunderson, M. F., H. W. McFadden and T. S. Kyle, 1954. The Bacteriology of Commercial Poultry Processing. The Burgess Publishing Co., Minneapolis, Minn. Lockhead, A. G., and G. B. Landerkin, 1935. Bacteriological studies on dressed poultry. Can. J. Agr. Sci. 15:765-770. Ziegler, F., J. V. Spencer and W. J. Stadleman, 1954. A rapid method for determining spoilage in fresh poultry meat. Poultry Sci. 23: 1253-1255.
FEBRUARY 24—NATIONAL FOOD CONFERENCE, WASHINGTON, D.C. AUGUST 5-8—POULTRY SCIENCE ASSOCIATION, ANNUAL MEETING, CORNELL UNIVERSITY, ITHACA, N.Y.
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
some period on air chilled half-carcasses than slush ice chilled half-carcasses. The inverse relationship between the numbers of bacteria per ml. of coolant (Table 1) and the numbers of bacteria per square inch of half-carcass skin(Figure 1) for half-carcasses held 1, 3, 5 or 24 hours in slush ice may be attributed to the unfavorable environment for mesophilic or thermophilic bacteria which are normally found in and on live poultry.
Poultry Science Department, North Carolina Agricultural Experiment Station, Raleigh, North Carolina
T
HE body heat of freshly eviscerated broilers is usually removed by submerging the carcass in a mixture of crushed ice and water. Currently the practice of many processors is to hold carcasses in slush ice for various periods ranging from approximately 1 to 24 hours after carcass temperature has been lowered to 40°F. Gunderson et al. (1954) found that storing poultry carcasses in chill tanks beyond the cooling period caused an increase in surface bacterial contamination. Lockhead and Landerkin (1935) and Ziegler et al. (1954) found that deterioration of fresh dressed poultry is essentially surface spoilage due to bacterial growth. Similar findings were reported by Gunderson et al. (1954). In view of the lack of sufficient information relative to the effects of holding eviscerated broilers in chill tanks for prolonged periods of time, the present study was undertaken to determine carcass bacterial contamination and shelf life as influenced by holding time in slush ice. EXPERIMENTAL
Carcasses weighing approximately 2 | pounds were processed in a commercial poultry processing plant in Raleigh, North Carolina. Approximate weights were determined on the processing line by an * Published with the approval of the Director of Research as Research Paper No. 805 of the Journal Series.
automatic weighing device. Carcasses were packed ice free in wirebound, wooden boxes and transported (approximately 20 minutes) to the College Poultry Science laboratories for treatment. Giblets were removed from 80 freshly eviscerated carcasses and the carcasses halved with a band-type meat saw. Thirtytwo half carcasses were individually packed in 8"X5|"X1" boat-type paper trays, placed on metal racks in a 35°F. chill room and covered and sealed with moisture-proof, transparent and heat sealing (MTS) cellophane after pectoral muscles were cooled to 40°F. The remaining half-carcasses were distributed at random in each of four 20"X27" sanitized galvanized cans and covered with crushed ice and water. Chlorinated tap water was used in the cooling medium. Slush ice and half-carcasses were air agitated. Half-carcasses were held in the cooling tanks for 1, 3, 5, or 24 hours. Carcass temperatures were determined with a Brown recording potentiometer. Thermocouple leads were placed in the pectoral muscles of carcasses as they were removed from the eviscerating line and of half-carcasses during the cooling operation. After 1, 3, 5 or 24 hours in slush ice each half-carcass was packed in an 8"X5|"X1" boat-type paper tray and covered and sealed with MTS cellophane. All packaged half-carcasses were held at 35°F. until analyzed.
1006
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
(Received for publication April 8, 1957)
BACTERIAL CONTAMINATION OF ICE CHILLED BROILERS
RESULTS AND DISCUSSION
The data presented in Table 1 show the washing effect of slush ice and the rate of chlorine dissipation in the wash water.
TABLE 1.—Bacterial counts per ml. and the residual chlorine in parts per million of neater used to chill half-carcasses1 Bacterial counts per ml. Water before treatment Water after carcasses held: 1 hour 3 hours S hours 24 hours 1
Residual CI2 in p.p.m.
80
2.10
3600 4600 4600 1400
0.35 0.01 — —
These data represent the means of 2 trials.
The mean bacterial count of the slush ice before half-carcasses were added was 80 per ml. After the addition of half-carcasses to the coolant, the numbers of bacteria per ml. increased by 45 times within an hour. Presumably these bacteria orginated from the half-carcasses as shown in Figure 2 by the drop in bacterial numbers between air cooled half-carcasses and half carcasses held in slush ice for 1 hour. The mean residual chlorine concentration of the slush ice prior to the addition of half-carcasses was 2.10 p.p.m. (Table 1). The residual chlorine in its initial concentration probably had some bactericidal action when half-carcasses were added to the chill tanks. Three hours after amalgamation of slush ice and half-carcasses the concentration of residual chlorine was 0.01 p.p.m. and the bacterial count per ml. of coolant had increased slightly above slush ice used for cooling half-carcasses for 1 hour. Due to the absence of residual chlorine in slush ice after 5 hours, the decrease in bacteria per ml. of slush ice used to chill half-carcasses for 5 hours to that used for 24 hours cannot be attributed to the bactericidal action of chlorine. Figure 1 shows the relationship between length of time half-carcasses were held in slush ice and bacterial numbers on the half-carcasses during various periods of subsequent storage at 35° F. in the chill
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
Since chlorinated tap water was used in the slush ice, the rate of chlorine dissipation was determined with an amperometric titrater (Wallace and Tiernan) in order to estimate the effect of residual chlorine on bacterial numbers in the coolant and on the half-carcasses. Four half-carcasses within each treatment were analyzed for bacterial numbers immediately after the halving operation and at 3-day intervals until odor or slime developed. One square inch of the pectoral tract under the wing of each of the 4 halfcarcasses was swabbed. Each swab was placed in a 150X16 mm. test tube containing 5 ml. sterile physiological saline solution. Each test tube was violently slapped against the palm of the hand 25 times. Serial dilutions were made and samples plated on heart infusion agar (Difco). Plates were incubated at 30°C. for 48 hours and the mean number of bacteria per square inch of carcass determined. Samples of slush ice in each tank were analyzed for bacterial numbers before and after the half-carcasses were chilled. Serial dilutions were made and samples plated on heart infusion agar (Difco). Plates were incubated at 30°C. for 48 hours and the mean number of bacteria per milliliter determined. Shelf life was determined by smell and sight. Ten designated packaged halfcarcasses within each treatment were analyzed twice each day until signs of spoilage were evident and the mean days of shelf life determined. This experiment was replicated in its entirety and the data were pooled in the statistical analyses.
1007
1008
D. FROMM
6
9
AGE IN DAYS FIG. 1. The relationship between number of hours half-carcasses were held in slush ice and the mean bacterial counts per square inch of carcasses after various storage periods.
aoo 2
room. Statistical analysis showed that the significant factor affecting halfcarcass bacterial numbers was the length of time half-carcasses were held in slush ice. The trend indicates that the bacterial flora decreased in numbers'as half-carcasses were held longer in slush ice. The influence of the slush ice chilling time on bacterial counts was present during the various days of storage. This is evident by the way the rates of increase in bacterial numbers for each treatment essentially parallel each other during the storage periods. The relationships between length of time carcasses were held in slush ice, the mean bacterial count per square inch of
HOURS IN SLUSH ICE
FIG. 2. The relationships between number of hours half-carcasses were kept in slush ice and the mean total bacterial counts per square inch of carcass skin and shelf life in days.1 • Hours in slush ice and shelf life r = +0.534 (insignificant). Hours in slush ice and bacterial numbers r = —0.535 (insignificant). Shelf life and bacterial numbers r = -0.997 (P=0.01).
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
3
half-carcasses and the mean shelf life of half-carcasses held at 35°F. is presented in Figure 2. Each bacterial count represents the geometric mean for the 4 analysis periods within each treatment. Bacterial numbers decreased as holding time in slush ice was increased. The sharpest decline in numbers occurred between air chilled half-carcasses and half-carcasses held in slush ice for 1 hour. Bacterial numbers declined 258,000 between air chilled half-carcasses and half-carcasses held in slush ice for 1 hour. The decrease in bacterial numbers was 18,000 between groups held for 1 hour and 3 hours in slush ice. After the decline in bacterial numbers between the 1 and 3 hour groups, the rate of reduction in bacterial numbers increased between groups held 3 and 5 hours in coolant. The difference in mean bacterial numbers per square inch of half-carcass between groups held for 3 hours and 5 hours in slush ice was 61,000. The rate of decline in bacterial numbers leveled off between groups held for 5 and 24 hours.
BACTERIAL CONTAMINATION OF ICE CHILLED BROILERS
1009
FIG. 3. Cooling rates of air-chilled (35°F.) and slush ice chilled half-carcasses.
The mean difference between these cooling groups was 68,000 bacteria per square inch of half-carcass. Correlation coefficients for relationships between hours held in slush ice and bacterial numbers, and shelf life and bacterial numbers are presented in Figure 2. There was a direct insignificant correlation between hours in slush ice and shelf life. The inverse correlation between hours in slush ice and bacterial numbers was insignificant. The coefficient for shelf life and bacterial numbers was inverse and significant at the 1% level. The difference in bacterial numbers per square inch of half-carcass between air chilled and slush ice chilled poultrywas caused by contrasting cooling rates (Figure 3) and the washing effect of the slush ice (Table 1). Figure 3 illustrates the cooling rates of the half-carcasses in a 35°F. chill room and slush ice. The pectoral muscles were chilled to 40°F. in 4 hours when held in a 35°F. chill room and in | hour when chilled in air agitated slush ice. This difference in cooling time would permit more bacterial growth for
SUMMARY
Surface bacterial contamination and shelf life were determined for 2\ pound eviscerated broilers held 1, 3, 5 and 24 hours in slush ice. Bacterial contamination and shelf life were also determined for carcasses air chilled at 35°F. The results of this study showed that: 1. There was an inverse relationship between bacterial numbers on the carcasses and length of time carcases were held in slush ice. 2. Carcass shelf life and bacterial numbers on the carcass were inversely related. 3. Shelf life was directly proportional to the number of hours, from 0 to 24, that carcasses were held in slush ice. REFERENCES Gunderson, M. F., H. W. McFadden and T. S. Kyle, 1954. The Bacteriology of Commercial Poultry Processing. The Burgess Publishing Co., Minneapolis, Minn. Lockhead, A. G., and G. B. Landerkin, 1935. Bacteriological studies on dressed poultry. Can. J. Agr. Sci. 15:765-770. Ziegler, F., J. V. Spencer and W. J. Stadleman, 1954. A rapid method for determining spoilage in fresh poultry meat. Poultry Sci. 23: 1253-1255.
FEBRUARY 24—NATIONAL FOOD CONFERENCE, WASHINGTON, D.C. AUGUST 5-8—POULTRY SCIENCE ASSOCIATION, ANNUAL MEETING, CORNELL UNIVERSITY, ITHACA, N.Y.
Downloaded from http://ps.oxfordjournals.org/ at University of Massachusetts Medical School on April 10, 2015
some period on air chilled half-carcasses than slush ice chilled half-carcasses. The inverse relationship between the numbers of bacteria per ml. of coolant (Table 1) and the numbers of bacteria per square inch of half-carcass skin(Figure 1) for half-carcasses held 1, 3, 5 or 24 hours in slush ice may be attributed to the unfavorable environment for mesophilic or thermophilic bacteria which are normally found in and on live poultry.