Improvements in Poultry Slaughterhouse Hygiene as a Result of Cleaning Before Cooling

Improvements in Poultry Slaughterhouse Hygiene as a Result of Cleaning Before Cooling

Improvements in Poultry Slaughterhouse Hygiene as a Result of Cleaning Before Cooling R. W. A. W. MULDER AND C. H . VEERKAMP Spelderholt Institute fo...

273KB Sizes 0 Downloads 0 Views

Improvements in Poultry Slaughterhouse Hygiene as a Result of Cleaning Before Cooling R. W. A. W. MULDER AND C. H . VEERKAMP

Spelderholt Institute for Poultry Research, Beekbergen, The Netherlands (Received for publication December 3, !973)

ABSTRACT A new method of defeathering, simultaneous scalding and plucking improves the hygiene in poultry slaughterhouses. Results of experiments with this system are given. Defeathering followed by spray cleaning before and after evisceration lowered the total number of microorganisms, especially the amount of Enterobacteriaceae. The ultimate effect on the end-product is described.



LTHOUGH live poultry is contaminated with microorganisms (from the feathers, skin and intestinal tract), the slaughtered endproduct has a comparatively low bacterial count, because the carcasses are cleaned during processing. As, however, many authors have shown that poultry and poultry products can be potential sources of Salmonellae infection, public health authorities are greatly concerned about the sanitary conditions and procedures during processing of poultry. These procedures include scalding, plucking, evisceration and cooling. Up to now, focus has been on cooling only. Several objections have been brought forward against the equipment normally used. 1. The water, especially the water in the first section of the chillers, becomes contaminated with microorganisms, resulting in an increase in total amount of Enterobacteriaceae particularly at the beginning of the day. 2. Cross-contamination may take place. 3. Water picked up by carcasses during cooling, which is technologically unavoidable is not of "drinking water" quality. Though it is quite true, that the criticism mentioned is valid, it is all due to abuse of the method. To overcome these objections against immersion-chillers, both improve-

ments of the existing method (immersionchilling) and alternative methods (spraychilling, air-chilling) have been suggested and investigated. A third possibility to overcome the immersion-chiller draw-backs, is through improvement of the pre-chilling operations, as these may have a definite bearing on the sanitary conditions during chilling and on the endproduct. In this paper the results of: 1. simultaneous scalding and plucking, 2. spray-cleaning before evisceration, 3. spray-cleaning before cooling, are described. The results on the microbiological quality of the carcasses directly after immersion- and spray-cooling are given. Also the effect on the endproduct is considered. EXPERIMENTAL The broilers used for the cleaning experiments weighed about 1000 g. (dressed). All experiments were carried out in the pilot slaughterhouse plant of the Spelderholt Institute for Poultry Research. The simultaneous scalding and plucking procedure is described by Veerkamp and Hofmans (1973). The broilers are plucked mechanically and scalded with hot water (65° C.) sprayed simultaneously with nozzles. The capacity of the plucker used was 3000 broilers per hour. The spray-cleaning experiments before and


Downloaded from at New York University on December 14, 2014

POULTRY SCIENCE 53: 1690-1694, 1974



The cleaning effect is measured by the reduction of the bacteriological counts.

IogN0 (Mulder and Veerkamp, 1973), in which N 0 = initial count and N = count after a given procedure. This R c value is given in the tables, together with the experimental results. A value of R c = 0.20 means a reduction in bacteriological counts of one log cycle from 5 to 4.0. The same R c is found when the reduction of counts is from 3 to 2.4. If R c = 0.10 a good reduction of the bacteriological counts is obtained.

TABLE 1.—Bacteriological examinations of the

water from a broiler processing scald tank

Time of sampling

Total count log N / m l .

0700 0830 1000 1130 1330 1500 1615

2.48 4.04 4.04 4.45 4.68 3.87 4.32

crease in bacterial counts is found at the beginning of the day (Table 1). After a few hours a stationary phase is reached and the counts remain on this level throughout the day, so the possible cross-contamination of pathogen bacteria is constant during the day. Another disadvantage is described by Tarver and May (1963) and by Lillard (1973). The broilers are said to inspire this heavily contaminated water in their struggle for life and this provides another source of contamination of the broiler carcasses. Simultaneous scalding and plucking instead of the usual scalding and plucking equipment has advantages in this respect. Steam heating of the water holds the temperature at 65° C. and the water is recycled. Table 2 gives the results of this process from the bacteriological point of view. Measurements were done on the total count and the TABLE 2.—Bacteriological examinations of

broilers after scalding and plucking


RESULTS AND DISCUSSION The scalding tank as used in nearly all poultry slaughterhouses has several drawbacks. In the Netherlands the water in the scalding-tank for sub-scald products is usually 60° C , at which temperature the bacteria are not killed, so that the bacterial load increases with each scalded broiler. An in-

Enterobacteriaceae log N / m l . 1 1.38 2.34 2.78 2.38 2.43 2.70

Number of samples

Total count log N/g.

Enterobacteriaceae fog N / g .







40 40 20

4.64 6.03 5.43

2.45 3.78 3.80

Pilot plant Simultaneous scalding and plucking normal scalding and plucking Industrial A B C

Downloaded from at New York University on December 14, 2014

after the evisceration procedure were carried out in the equipment as described by Veerkamp et al. (1972). In these experiments 1 liter water per broiler was used for the cleaning. Immersion-chilling was also carried out in a pilot-plant unit, using 1 liter water per broiler. The bacteriological counts of the broiler skin samples were obtained with the use of the skin-crush method (Veerkamp et al., 1972). Plate count agar (OXOID) was used for the total count. Incubation time was 48 hr. at 30° C. The Enterobacteriaceae were estimated on Violet Red Bile Glucose Agar (OXOID). The double poured plates were incubated for 18-24 hrs. at 37° C. The water was sampled by the usual techniques. The counts are given as logarithmic averages and expressed as microorganisms per gram or per ml.



TABLE 3.—Spray cleaning of the broiler carcasses after plucking

After plucking initial counts

After spray cleaning


No. of samples

Total count log N / g .

1 2 3 4

10 10 10 10

4.12 3.87 4.84 3.65

1 2 3 4

10 10 10 10

3.49 3.24 4.01 3.33

after plucking after evisceration spray cleaning after evisceration


2.41 2.34 2.84 2.28 0.15 0.16 0.17 0.09

2.19 1.93 2.28 1.90

0.09 0.18 0.20 0.17

cleaning of the broiler carcasses after evisceration

Experiment 1 2 1 2

No. of samples 10 10 10 10

Total count log N / g . 4.12 4.84 4.35 4.21

1 2

10 10

3.44 3.47




Enterobacteriaceae log N / g . 2.41 2.84 3.65 2.82


0.21 0.18

2.36 2.38

0.35 0.16

after plucking spray cleaning


< 100

evisceration and spray cleaning

Enterobacteriaceae count of the broiler skin. As can be seen from the table, this new process has the best effect with respect to the total count and can also reduce the number of Enterobacteriaceae to a very low level. The cross-contamination as described by van Schothorst et al. (1972) with a normal plucker is absent from these experiments (Notermans, 1973). This process makes possible a total count of 3.37 on the broiler skin, whereas this is now 5.43 (middle value found in 3 slaughterhouses) in a normal poultry slaughterhouse. After the simultaneous scalding and plucking, it is possible to improve the bacteriological quality of broiler carcasses by spraycleaning. The results of four series of experi-

ments are given in Table 3. As by the simultaneous scalding and plucking here, there also is a decrease in the amount of Enterobacteriaceae. For comparison with these results with uneviscerated broilers, the results of spray cleaning of eviscerated broilers are given in Table 4. It is clear that spray cleaning of the uneviscerated broilers has the advantage of improving the bacteriological quality of the skin at an early point in the processing line. Although the bacteriological counts on the spray cleaned uneviscerated broilers were very low, there can be a further reduction by spray cleaning after evisceration. One series of experiments with spray cleaning after plucking and spray cleaning after evisceration gave the following results:

Downloaded from at New York University on December 14, 2014

TABLE 4I.—Spray


Enterobacteriaceae log N / g .



TABLE 5.—Cleaning of the broiler carcasses by immersion cleaning Enterobacteriaceae log N / g .

No. of samples

Total count log N / g .

after scalding and plucking



after scalding and plucking + immersion in 1 litre water






after evisceration









Drip Total count log N / m l .

Enterobactenaceae log N / m l .












No. of samples

Skin total count log N / g .

Enterobacte naceae log N / g .

10 10

3.45 3.57

1.46 1.67



10 10

1st experiment after plucking after thawing 2nd experiment after thawing (5 min. in chiller) after thawing (15 min. in chiller) after thawing (30 min. in chiller)

number of broilers total count Enterobacteriaceae

10 2.53 < 1.00

Processed in the manner, as indicated above, the broilers will have a maximum bacteriological count (total count) of 3.00 before they enter the immersion-chiller. Simultaneous scalding and plucking and cleaning of the carcasses before evisceration have a vast effect on the counts on the broiler skin. It is possible to maintain this low bacteriological count by spray cleaning or by immersion in water (Table 5) in the subsequent process. Also the bacteriological quality of the endproduct could be improved. The ultimate effect of these methods (simultaneous scalding and plucking, spray cleaning before and spray cleaning and im-

mersion in water after evisceration) is measured on the endproduct after thawing. The bacteriological counts were estimated on the broiler-skin and on the dripwater after 24 hrs. thawing at +7° C. (storage 14 days at -18° C ) . The dripwater is important owing to the cross-contamination with Salmonellae after thawing. Table 6 shows the results for thawed broilers processed with the new system of simultaneous scalding and plucking and cleaning after evisceration. From the first part of Table 6, the low counts on the skin of the broilers, are evident. The second part with broilers, immersion-chilled for 5, 15 and 30 minutes also gives very good bacteriological counts on the skin and in the dripwater. The bacteriological counts on industrially processed broilers are given in Table 7. It showed, as compared with the data of Table

Downloaded from at New York University on December 14, 2014

TABLE 6.—Bacteriological counts on experimental processed broilers after thawing



TABLE 7.—Bacteriological counts on industrially processed broilers after thawing

Plant A Plant B Plant C Plant D Plant D Drip plant D

No. of samples

Total count log N / g . or ml.

Enterobacteriaceae log N / g . or ml.

20 25 10 10 10 10

5.27 5.16 5.08 5.97 5.68 5.09

3.13 3.01 4.03 2.74 2.71 2.49

REFERENCES Lillard, H. S., 1973. Contamination of blood system and edible parts of poultry with Clostridium perfringens during water scalding. J. Food Sci. 38: 151-154. Mulder, R. W. A. W., and C. H. Veerkamp, 1973. Microbiological aspects of the water-cooling of poultry. Lebensm.—Wiss. U. Technol. 6 (in press). Notermans, S., 1973. Unpublished data. Tarver, F. R., and K. N. May (1963). The effect of bleed time prior to scald and refrigerated storage upon bacterial counts in the axillary diverticula of the interclavicular air sac of chickens. Food Technol. 17: 198-200. Van Schothorst, M., S. Notermans and E. H. Kampelmacher, 1972. Einige hygienische Aspekte der Gefliigelschlachtung. Fleischwirtschaft, 52: 749752. Veerkamp, C. H., and G. J. P. Hofmans, 1973. Simultaneous scalding and plucking Poultry International, 12 (Feb.): 16 Veerkamp, C. H., R. W. A. W. Mulder and A. R. Gerrits, 1972. Kiihlung and Reinigung von Schlachtgeflugel. Fleischwirtschaft, 52: 612-621.

NEWS AND NOTES (Continued from page 1680) is told in a 12-minute presentation which emphasizes the role Federal-State graders play in assuring top quality eggs for the market place. A.M.S. administers the voluntary national grading service for shell eggs. The film provides the consumer with information on egg grades and sizes, and is intended for use by home economists, extension specialists, and other consumer educators. "Egg Grades—A Matter of Quality" is available for sale from the Motion Picture Service, Office of

Communication, U.S. Department of Agriculture, Washington, D.C. 20250. Prints are $67.00 each. The film can be borrowed from Cooperative Extension Libraries at Land Grant Universities in 50 States and Puerto Rico. State film libraries that lend U.S.D.A. motion pictures are: Arkansas—Audio-Visual Aids, Arkansas State Teachers College, Conway, AR 72032; Agricultural Extension Service, P.O. Box 391, Little Rock, AR 72203; Colorado—Bureau of Audio-Visual In-

(Continued on page 1724)

Downloaded from at New York University on December 14, 2014

6, that the different procedures give big differences in the results of the bacteriological experiments. The total counts of bacteria of industrial processed broilers estimated after thawing is 5.43; the Enterobacteriaceae count 3.12. For the dripwater lower values are found with the new processing steps These counts are: total count 3.74 and Enterobacteriaceae 1.73. In the dripwater as compared with Table 7 there are also found much lower counts. As it can be seen from these experiments, there is an enormous effect of the simultaneous scalding and plucking followed by spray cleaning before and after evisceration on the endproduct. The simultaneous scalding and plucking is not yet tested under practical conditions in

the poultry slaughterhouse. So, the effect of this procedure cannot be measured in the poultry slaughterhouse at the moment. But from the results above, it is evident that broilers must be produced as bacteriologically clean as possible, at the beginning of the processing line, thereby preventing any possibility of cross-contamination with pathogenic bacteria.