Effects of Selected Psychrophilic Bacteria on the Flavor of Chicken Breast Meat1,2

1256

T. E. CHAPMAN AND D. MIHAI

to egg production. World's Poultry Sci. J. S: 29. Lifschitz, E., O. German, E. A. Favret and F. Manso, 1967. Difference in water ingestion associated with sex in poultry. Poultry Sci. 46: 1021-1023. Lumijarvi, D. H., and F. W. Hill, 1968. Influence of sexual maturity and laying condition on water turnover in fowl. Poultry Sci. 47 : 1689. Ohmart, R. D., T. E. Chapman and L. Z. McFarland, 1970. Water turnover in roadrunners under different environmental conditions. Auk,

87: 787-793. Osbaldiston, G. W., 1969. Water and electrolyte balance studies of birds showing "wet droppings." Brit. Vet. J. 12S: 653-663. Richmond, C. R., W. H. Langham and T. T. Trujillo, 1962. Comparative metabolism of tritiated water by mammals. J. Cell. Comp. Physiol. 59: 45-53. Romanoff, A. L. and A. J. Romanoff, 1949. The Avian Egg. John Wiley and Sons, Inc., New York.

Department

M. G. MAST 3 AND J. F. STEPHENS of Poultry Science, Ohio Agricultural Research and Development Columbus, Ohio 43210

Center,

(Received for publication November 5, 1971)

ABSTRACT To determine the effects of psychrophilic microorganisms on flavor of chicken breast meat, aseptically procured samples were inoculated with an Alcaligenes sp., a Flavobacterium sp., or Pseudomonas putrefaciens, and stored at 3°C. for periods of time up to 14 days. Following storage at 3 C C, the samples were analyzed for total bacterial numbers. The meat was then heat-treated and the pH of each sample was determined. Broth samples from the meat were presented to a taste panel for flavor evaluation. Both triangle and ranking tests were utilized. The number of bacteria increased from the initial inoculum of 104 per gram of chicken breast tissue to 1.72 X 108 (Flavobacterium sp.), 1.61 X 1010 (Alcaligenes sp.), and 3.40 X 1010 per gram (P. putrefaciens) after 14 days of storage at 3°C. Uninoculated chicken breast meat maintained a pH of 6.33 throughout a storage period of 14 days. Samples of chicken breast meat which were inoculated with either the Alcaligenes sp. or P. putrefaciens increased in pH to 8.9 and 7.95 respectively, after 14 days of storage at 3°C. The broth extracted from "fresh" chicken meat, i.e., uninoculated and heat-treated immediately after thawing, was judged by taste panelists to be superior in flavor to the broth of all other uninoculated and inoculated meat samples. The broth extract from uninoculated chicken meat was usually judged to be superior in flavor to broth from inoculated meat samples stored for similar periods of time. However, samples inoculated with P. putrefaciens and stored for 3 or 7 days were preferred to uninoculated samples stored for corresponding periods of time. POULTRY SCIENCE 51: 1256-1265, 1972

in poultry meat is primarily SPOILAGE due to the growth of certain psychrophilic microorganisms, especially Pseudo1

Ohio Agricultural Research and Development Center Journal Article No. 100-71. 2 A portion of the thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree. 3 Present address: Department of Poultry Science, The Pennsylvania State University, University Park, Pennsylvania 16802.

monas and Achromobacter species. Spoilage of the meat, indicated by changes in odor and slime formation, occurs as the microbial level reaches 106 to 107 cells per square centimeter (Lochhead and Landerkin, 1935; Walker and Ayres, 1956) or approximately 107 cells per gram (Essary et al., 1958; Mailman et al., 1958; Meyer et al., 1959). Carlin et al. (1957) reported that as the number of microorganisms increased on

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Effects of Selected Psychrophilic Bacteria on the Flavor of Chicken Breast Meat1'2

PSYCHROPHILIC BACTERIA AND FLAVOR

chickens reared under germfree or gnotobiotic conditions. However, Lonsdale et al. (1969) reported that more chicken flavor may be present in chickens reared in a germfree environment. The objective of the present study was to determine the effects of the growth of three psychrophilic microorganisms (a Flavobacterium species, an Alcaligenes species, and Pseudomonas putrejaciens) on the flavor of aseptically procured chicken breast meat held in storage at 3°C. for periods up to 14 days. In order to more accurately determine changes which may occur in chickens in market channels, meat from conventionally reared broilers was used inthis study. MATERIALS AND METHODS

The breast tissue used in this study was procured from 61 broiler-type chickens. The following information about these birds was supplied by the owner (a commercial feed manufacturer). Age Sex Feed

7 weeks and 6 days male and female commercial broiler crumbles, 22% protein, and commercial broiler pellets, 20% protein Medication coccidiostat (Amprolium— 0.0125% of the diet) Average live weight.. .1.828 kilograms Feed conversion 2.014

Procurement and samples. The birds were slaughtered by an automatic in-line killing machine, bled, and scalded. After passing through the automatic feather remover, the feet were removed at the hocks and the carcasses dropped from the shackles onto a platform. A worker then hung the carcasses on shackles leading to the eviscerating line. It was at this point that the birds for this study were selected. Only carcasses with excellent fleshing and free of breast blisters and/or cuts and bruises were selected. These carcasses were then transferred to a laboratory adjacent to the processing plant for removal of the breast tissue.

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breast and thigh meat during storage at 2°C, the flavor scores also decreased. Felstehausen et al. (1963) investigated the effects of Escherichia coli, Proteus vulgaris, and three species of Pseudomonas when added to precooked poultry products which were subsequently held in frozen storage. A four-hour time lapse between inoculation and freezing proved to be a critical period since changes in flavor could be detected after that time. The length of time in frozen storage was a significant factor only for samples inoculated with Pseudomonas fluorescens; flavor scores of these samples decreased as storage time increased. Griffiths and Lea (1969) detected no change in the flavor of poultry meat inoculated with two different strains of Pseudomonas and held at 1°C. for five days; however, when stored longer, the odor of the raw meat was adversely affected. Adamcic and Clark (1970) observed that a faint but distinct off-odor was produced as strains of Achromobacter and Pseudomonas reached levels of 108 cells per sq. cm. on chicken skin. The nature of this odor was not reported; however, Thomas et al. (1971) speculated that it was probably caused by carbonyl compounds. Williams (1960) described a process whereby red meats can be tenderized and the flavor enhanced by inoculating the surface with Pseudomonas and/or Achromobacter organisms. When used separately, the organisms produced different flavors in the meat and when used in combination a "deeper, richer flavor" was produced. However, Griffiths and Lea (1969) were unsuccessful in attempts to produce such favorable changes using this process on chicken meat. Harris et al. (1968) found that meat from chickens reared under conventional conditions had a stronger and more characteristic chicken flavor than did meat from

1257

12S8

M. G. MAST AND J. F. STEPHENS

petri plates (20 X 140 mm.) and held at 3°C. for periods of 3, 7, and 14 days. Microorganisms. Three cultures of psychrophilic microorganisms were used in this study. Two of the organisms, an Alcaligenes species and a Flavobacterium species, were isolated from a broiler carcass which showed signs of spoilage. The third organism, Pseudomonas putrefaciens No. 465, was obtained from the culture laboratory of the Department of Microbiology, The Ohio State University, Columbus, Ohio.

Microbial analyses and preparation of extracts for taste panel studies. At the end of 0, 3, 7, or 14 days of storage, samples of tissue were mixed with four volumes of sterile, demineralized, double-distilled water, placed in a sterile blendor jar, and blended for 2 minutes (single speed WarPreparation of tissue for storage studies. ing Blendor, 15,000 r.p.m.). Approximately 12 hours before the tissue was to be processed, it was removed from the Five ml. of this homogenate were added — 36°C. freezer and placed in a freezer held aseptically to 5 ml. of 0.5% saline. Total at — 12°C. This kept the tissue frozen but plate counts were made according to methmade it easier to macerate. ods outlined by A.P.H.A. (1960). TrypTissue samples were removed from their tone Glucose Extract Agar (Difco) was containers, cut with a sterile knife into nar- used as a medium for the plate counts. Colrow strips, and ground in a food chopper. onies were counted after the plates had been The holes in the chopper plate had a diam- incubated at 20°C. for 48 hours. eter of 4.5 mm. This operation was perThe homogenate in the blendor jar was formed at 3°C. under a hood, the interior dispensed into pint glass jars, heat-treated of which had been sanitized and subjected (121°C. for 15 minutes at 15 p.s.i.), and to UV light for 24 hours. All utensils and then stored at 3°C. until needed for taste equipment were autoclaved prior to use. panel analyses. The pH of the homogenate The chopped tissue was collected, mixed was measured with a Corning Model 12 pH thoroughly, and held in a large container meter following the heat treatment. Aqueous extracts of the heat-treated macovered with aluminum foil. The tissue was then divided into appropriate amounts and terial were prepared by blending the mateeither treated as a control (no microorga- rial, then removing the solid portion by nisms added) or enough microorganisms of centrifugation and nitration. The extracts a known strain were added to provide a to- were heated to 90°C, and then cooled to tal of 10* microorganisms per gram. Inocu- 60°C. in a water bath before being sublated samples, along with corresponding jected to organoleptic evaluation. Samples uninoculated samples, were placed in glass of this extract were pipetted into one-ounce

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The carcasses were placed in tap water containing approximately 2% Wescodyne (West Chemical Products, Inc., Long Island, N.Y.) and thoroughly washed by scrubbing with a brush. The carcasses were then rinsed in tap water, drained, and placed in 70% ethanol for IS seconds. Each carcass was then secured to a stainless steel tray, the ethanol ignited, and allowed to bum off completely. The tray with the cleaned carcass was immediately placed under a microbiology hood where the breast tissue was aseptically removed, placed in a numbered, sterile container, and weighed. The average weight per container with two breast halves was 173.5 grams, for a total of 10,586.5 grams. The samples were stored at — 36°C. until used.

PSYCHROPHILIC BACTERIA AND FLAVOR

paper cups for immediate evaluation by a taste panel.

Test design. Since the main purpose of these studies was to determine if microorganisms had an effect on flavor, aqueous extracts from uninoculated samples were used for comparisons in the triangle tests. Inoculated and uninoculated samples of tissue were held for 0, 3, 7, and 14 days at 3°C. Seven triangle test comparisons were made for samples inoculated with each of the three bacterial species. Samples inoculated with bacteria and stored at 0, 3, 7, and 14 days were compared to fresh (not stored at 3°C.) uninoculated samples. Uninoculated samples stored for 3, 7, and 14 days were also compared with the inoculated samples stored for corresponding periods. Samples from the four storage periods were also presented to the panelists to be ranked according to flavor preference. Interpretation of taste panel results. The results of the triangle tests were analyzed by comparing the number of correct responses by the panel with the number of correct responses that theoretically would result from chance alone. In the triangle test the chance probabilitiy is 33.3%. Significance in the results was determined by comparing the number of correct responses obtained in the tests with figures given in

prepared tables (A.S.T.M., 1968). In addition to identifying the odd sample in the triangle tests, panelists were also instructed to indicate the degree of difference between the samples (slight, moderate, much, extreme) and to indicate which sample they preferred (odd or duplicate). Responses in this part of the test were considered valid and analyzed only if the panelists correctly identified the odd sample. Results of the ranking test were analyzed by the method of Fisher and Yates as described by Larmond (1967). The ranks were transformed into scores (mean deviations, obtained from a table). When four samples are ranked, the scores are: First, 1.03; second, 0.30; third, - 0 . 3 0 ; and fourth, - 1 . 0 3 . These scores were analyzed by analysis of variance. If a significant F-ratio was found, Duncan's multiple range test (Duncan, 1955) was used to determine which means were different from the others. RESULTS AND DISCUSSION

Bacteriology and pH of samples. All of the control samples were bacteria-free at each time period (0, 3, 7, and 14 days) in the first two trials. In the third trial, 17 microorganisms per gram of tissue (average of three replicates) were present after three and seven days of storage at 3°C, and 7 microorganisms per gram were detected after 14 days of storage. Figure 1 illustrates the growth curves of the three species used in this study (a Flavobacterium species, an Alcaligenes species and Pseudomonas putrefaciens) in raw chicken breast meat following its inoculation with approximately 104 cells per gram. No attempt was made to determine the shapes of the growth curves beyond 14 days. Under similar conditions, Mast and Mountney (1970) found that the maximum stationary phase of the growth curve

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Taste panel. The taste panel was composed of nine women ranging in age from 25 to 39 years. All of the panelists were married and had small children, none had full-time employment outside the home, and all were non-smokers. Two training sessions were held to introduce the panelists to taste panel operations and proper methods of evaluating samples by triangle and ranking tests (Larmond, 1967).

1259

1260 H

M. G. MAST AND J. F. STEPHENS

r

o Cofitrol (no inoculum)

o-

o Alcaligenes species

oo

I

-o

Flavobacterium species

o Pseudomonas putrefaciens

•

0 L 0

' 3

1 7 Days in Storage

°< 14

FIG. 1. Growth of microorganisms in raw chicken breast meat stored at 3°C.

was reached after ten days when chicken meat was stored at 5°C. The growth of certain microorganisms in meat can alter the pH, which in turn may influence the flavor of the meat. Figure 2 illustrates the changes in pH caused by the three species of microorganisms used in this study. The pH of the uninoculated meat and meat inoculated with the Flavobacterium species remained constant at pH 6.33 and 6.20, respectively, throughout the 14day storage period. As indicated previously, the studies were not continued beyond 14 days; had they been, the number of cells might have increased with a subsequent change in pH of the meat. No dramatic changes in the pH of meat inoculated with the other two organisms (Alcaligenes sp. and P. putrefaciens) was evident until the number of cells exceeded 108-109 per gram. Major changes in the pH occurred between the seventh and fourteenth days in chicken meat inoculated with either the Alcaligenes species or P. putrefaciens. The pH of meat inoculated with the Alcaligenes

y

//

>

•

.

-O

*-•• o — _ »- —„

.

0

_ _

3

Control (no inoculum) Alcaligenes species Flavobacterium species Pseudomonas putrefaciens

7 Days in S t o r a g e

14

FIG. 2. pH of cooked chicken breast meat inoculated with microorganisms and stored at 3°C.

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2 .

o

species increased from 6.32 at seven days (1.48 X 109 bacteria per gram present) to 9.3 at fourteen days (1.61 X 1010 bacteria per gram). P. putrefaciens caused the pH of the meat to increase from 6.12 at seven days (1.13 X 10s bacteria per gram present) to 7.95 after 14 days (3.40 X 1010 bacteria per gram). As the meat samples were being processed for the bacteriological tests, they were routinely checked for odor. The meat inoculated with the Flavobacterium species maintained the odor of "good" chicken throughout the storage period. The meat containing the Alcaligenes species had a good aroma after three days storage, a very slight off-odor after seven days of storage and a very strong "sweet, ammonia-like" odor after 14 days of storage. The meat inoculated with P. putrefaciens retained a good odor through seven days, but had a putrid, repulsive odor after 14 days of storage at 3°C. Results similar to those found in this study were reported by Adamcic and Clark (1970). They observed that changes in the pH of chicken skin and off-odors occurred concurrently as levels of psychrotolerant

1261

PSYCHROPHILIC BACTERIA AND FLAVOR

Senory evaluation of samples by a test panel. The results of the triangle test comparisons of uninoculated meat and meat inoculated with the Flavobactenum species are presented in Table 1. Data pertaining to bacteriology and pH values of these samples are included in this table to facilitate discussion of the taste panel results. The number of correct identifications required for significance at various levels in a triangle test with 26 judgments was deter-

mined to be: 14 correct answers at P < 0.05; 15 correct answers at P < 0.01 level, and 17 correct answers at P < 0.001. In this series of comparisons, a significant difference was found only when the Control14 (uninoculated meat stored for 14 days at 3°C.) was compared with the Flavo-14 (meat inoculated with the Flavobactenum species stored for 14 days at 3 ° C ) . Although statistically significant differences were not present in six of the seven comparisons, most of the panelists preferred the flavor of the uninoculated meat to that of the meat inoculated with the Flavobactenum species. The results of the ranking tests for the samples inoculated with the Flavobacterium species are presented in Table 2. The panelists most preferred the seven-day sample and least preferred the three-day sample. However, there was no significant difference (P < 0.05) among any of the sample preference means, indicating that the Flavobactenum species did not greatly influence the flavor of the chicken meat under the conditions employed. The results of the comparisons of unin-

TABLE 1.—Triangle tests: Comparison of uninoculated meat and meat inoculated with a Flavobacterium species

Log No. of bacteria per gram of inoculated sample pH of inoculated samplesb Correct identifications/No. of judgments" Difference Slight Moderate Much Extreme Preference Control Flavobacterium

C-0 C-3 C-0 vs. vs. vs. Flavo-7 Flavo-14 Flavo-3

C-7 C-14 vs. vs. Flavo-7 Flavo-14

C-O vs. Flavo-0

C-0 vs. Flavo-3

4.07 6.17

4.31 6.18

5.81 6.18

8.24 6.20

4.31 6.18

5.81 6.18

8.24 6.20

13/26 10 2 1

13/26 10 3

12/26 10 2

7/26 4 3

11/26 7 3 1

10/26 7 3

15/26** 9 5 1

11 2

9 4

9 3

5 2

7 4

5 5

11 4

a C = uninoculated sample; Flavo = sample inoculated with a Flavobacterium species. Numbers 0,3, 7, and 14 represent number of days of storage at 3°C. b pH of all control (uninoculated) samples was 6.33. Number of bacteria per gram in C-0 was 0; in C-3 14 represent number of days of storage at 3°C. and C-7, logio 0.4; in C-14, logio 0.3. 0 Two asterisks indicate significance at 1.0% level.

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bacteria approached 108 per gram. One strain of bacteria which they studied, a non-pigmented Pseudomonas, strain 47, caused the pH in the chicken skin to ultimately increase to approximately 7.9S, which is the same maximum pH obtained in the current study when P. putrefaciens grew in chicken breast meat. In the current studies the Alcaligenes species and P. putrefaciens caused changes to occur in chicken breast meat which elevated the pH and created off-odors. The off-odors presumably resulted from the formation of ammonia and other decomposition products as the microorganisms grew in the meat.

1262

M. G. MAST AND J. F. STEPHENS

TABLE 2.—Sample means1 from taste panel

ranking tests Inoculum Control (uninoculated) Alcaligenes species Flavobaclerium species Pseudomanas putrefaciens

Days of Storage at 3°C. 0 0.208" 0.488" 0.102" 0.238"

3

7

14

-0.309 b 0.076" 0.025" 0.522" —0.115b -0.895° -0.215" 0.261" -0.148"b 0.243" 0.521" - 1 . 0 0 1

oculated meat with meat inoculated with an Alcaligenes species are summarized in Table 3. As the storage time of the inoculated meat increased, the number of correct identifications by the panel also increased. The inoculated sample stored for 14 days was so noticably different from Control-0 that all panelists identified the sample correctly (i.e., 26/26). Twenty-one of 26 responses indicated that the difference between those two samples was either "much" or "extreme", and all but one response indicated preference for the flavor of the control sample. An error in recording prefer-

TABLE 3.—Triangle tests: Comparison of uninoctdaled meat and

meat inoculated with an Alcaligenes species

Log. No. bacteria per gram of inoculated sample pH of inoculated samples b Correct identifications/No. of judgments" Difference Slight Moderate Much Extreme Preference Control Alcaligenes

C-0" vs. Alc-0

C-0 vs. Alc-3

C-0 vs. Alc-7

C-0 vs. Alc-14

C-3 vs. Alc-3

C-7 vs. Alc-7

C-14 vs. Alc-14

4.07 6.10

5.38 6.13

9.17 6.32

10.21 8.93

5.38 6.13

9.17 6.32

10.21 8.93

13/26

15/26**

17/26*** 26/26*** 10/26

15/26**

23/26***

12 1

9 6

6 7 4

12 1

10 5

15 2

5 10 11 25 1

7 3

3 10 2

6 4

11 4

7 6 10 22 1

" C = uninoculated sample; Alc=sample inoculated with an Alcaligenes species. Numbers 0, 3, 7, and 14 represent number of days of storage at 3°C. b pH of all control (uninoculated) samples was 6.33. Number of bacteria per gram in C-0 was 0; in C-3 and C-7, logio 0.4; in C-14, logio 0.3. c Two asterisks indicate significance at 1.0% level; three asterisks indicate significance at 0 . 1 % level.

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1 Means in the same row (horizontal) having different superscripts are significantly different (P <0.01). Control values are the means of 78 scores; all other values are the means of 26 determinations. The samples were scored according to the method of Fisher and Yates as described in Larmond (1967), where the sample ranked first by the panelist is assigned the value of 1.03; second, 0.30; third, -0.30; and fourth, -1.03.

ence by one panelist is suspected in that instance. In comparisons between inoculated samples stored for 3, 7, or 14 days, and uninoculated samples stored for corresponding periods, a trend occurred which was similar to that found when inoculated samples were compared to "fresh" samples, i.e., as storage time increased, the panelists could more easily distinguish between the samples, and preference for the inoculated samples decreased as storage time increased. In the present study, the growth of the Alcaligenes species in chicken meat caused an elevation of the pH, ultimately to 8.9. Although Peterson (1957) found that the flavor and odor characteristics of chicken broth were unfavorably affected when the pH changed from 6.4 to 8.7, it cannot be concluded from the present study that the pH was or was not the predominant factor in creating differences in flavor between the samples. Other changes caused by the growth of the bacteria in the meat, such as the degradation of fat and protein, may also contribute to the differences in flavor.

1263

PSYCHROPHILIC BACTERIA AND FLAVOR

guish between the uninoculated samples stored for 0 days and the inoculated stored for either 0 or 3 days. A significant (P < 0.05) number of panelists were able to distinguish between the inoculated and uninoculated samples which had been stored for seven days at 3°C. At that time (seven days) the pH had not increased and 1.13 X 10s bacteria per gram were present. However, at 14 days, when the pH was 7.95 and the bacterial load was 3.40 X 1010 cells per gram, all of the panelists correctly identified the odd sample, and 22 of the 26 panelists considered the difference to be "much" or "extreme". All of the panelists preferred the control sample to the inoculated sample. In comparing Control-3 and Pseud-3 (inoculated with P. putrejaciens and stored at 3°C. for 3 days), 15 of the 26 panelists properly identified the odd sample. Eleven of the 15 indicated a preference for the inoculated sample instead of the control sample. This unexpected result was amplified in the comparison of Control-7 and Pseud7. Eighteen of the 21 panelists who cor-

TABLE 4.—Triangle tests: Comparison of uninoculated meat and meat inoculated with pseudomonas putrefaciens

Log No. bacteria per gram of inoculated sample pH of inoculated samplesb Correct identifications/No. of judgments 0 Difference Slight Moderate Much Extreme Preference Control P. putrefaciens

C-7 C-14 C-0 C-3 C-0 vs. vs. vs. vs. vs. Pseud-7 Pseud-14 Pseud-3 Pseud-7 Pseud-14

C-0> vs. Pseud-0

C-0 vs. Pseud-3

4.13 6.12

5.25 6.12

8.05 6.12

10.53 7.95

12/26

12/26

14/26*

26/26*** 15/26**

10 2

10 2

11 3

9 3

9 3

11 3

4 11 11 26 0

5.25 6.12

8.05 6.12

10.53 7.95

21/26*** 25/26***

13 2

17 4

4 11

3 18

4 9 12 24 1

* C = uninoculated sample; Pseud=sample inoculated with Pseudomonas putrefaciens. Numbers 0, 3, 7, and 14 represent number of days of storage at 3°C. b pH of all control (uninoculated) samples was 6.33. Number of bacteria per gram in C-0 was 0; in C-3 and C-7, log10 0.4; in C-14, logio 0.3. 0 One asterisk indicates significance at 5.0% level; two asterisks, 1.0%; three asterisks, 0.1%.

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Several panelists commented that the broth from the meat inoculated with the Alcaligenes species and stored for 14 days, contained an "ammonia-like" aroma. This observation supports Bouthilet (1949) who found that as the pH of chicken broth approached 9.0, NH 3 and other amines were predominant. The results of the ranking tests of the samples inoculated with the Alcaligenes species are presented in Table 2. No significant difference in the flavor was found between samples stored for zero days and those stored for three days. The flavor of the meat stored for seven days was preferred to that of meat stored for 14 days, and both samples were significantly less desirable than samples stored for zero or three days. It can therefore be concluded that the growth of the Alcaligenes species in chicken breast meat caused changes which were detrimental to the flavor of the meat. The results of the comparisons between uninoculated meat and meat inoculated with P. putrejaciens are summarized in Table 4. The panelists were unable to distin-

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M. G. MAST AND J. F. STEPHENS

REFERENCES Adamcic, M., and D. S. Clark, 1970. Bacteria-induced biochemical changes in chicken skin stored at 5°C. J. Food Sci. 35:103-106. A.P.H.A., 1960. Standard Methods for the Examination of Dairy Products, American Public Health Association, New York. A.S.T.M, 1968. Manual on Sensory Testing Methods, Special Technical Publication 434, Ameri-

can Society for Testing and Materials, Philadelphia, Pa. Bouthilet, R. J., 1949. A note on the nature of a flavor constituent from poultry meat. Food Technol. 3:118. Carlin, A. F., B. E. HoU and H. W. Walker, 1957. Correlation between flavor and number of microorganisms associated with eviscerated chicken treated with chlortetracycline. Food Technol. 11:573-577. Duncan, D. B., 1955. Multiple range and multiple F tests. Biometrics, 1 1 : 1-42. Essary, E. O., W. E. C. Moore and C. Y. Kramer, 1958. Influence of scald temperature, chill times, and holding temperatures on the bacterial flora and shelf life of freshly chilled tray packed poultry. Food Technol. 12: 684-687. Felstehausen, V. C , D. M. Strong and J. H. Torrie, 1963. The influence of selected bacteria upon the flavor of a precooked poultry product. Food Technol. 17: 654-656. Griffiths, N. M., and C. H. Lea, 1969. Chemical and organoleptic changes in poultry meat resulting from the growth of psychrophilic spoilage bacteria at 1°C. 5. Effects on palatability. Br. Poultry Sci. 10: 243-246. Harris, N. D., D. H. Strong and M. L. Sunde, 1968. Intestinal flora and chicken flavor. J. Food Sci. 33 : 543. Larmond, E., 1967. Methods for Sensory Evaluation of Food, Publication 1284, Canada Department of Agriculture. Lochhead, A. G., and G. B. Landerkin, 1935. Bacteriological studies of dressed poultry. I. Preliminary investigation of bacterial action at chill temperatures. Sci. Agr. 15: 765-770. Lonsdale, M. L., M. Woodburn and W. J. Stadelman, 1969. Flavor comparisons in gnotobiotic and conventional broiler chickens. Poultry Sci. 48: 1261-1264. Mailman, W. L., L. E. Dawson, B. M. Sultzer and H. S. Wright, 1958. Studies on microbiological methods for predicting shelf life of dressed poultry. Food Technol. 12: 122-126. Mast, M. G., and G. J. Mountney, 1970. Growth patterns of selected psychrophilic microorganisms in cooked and uncooked aseptically procured turkey meat. J. Food Sci. 3 5 : 618-620. Meyer, R. C , A. R. Winter and H. Weiser, 1959. Edible protective coatings for extending the shelf life of fresh poultry meat. Food Technol. 13: 146-148. Thomas, C. P., P. S. Dimick and J. H. MacNeil, 1971. Sources of flavor in chicken skin. Food Technol. 25:407-413.

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rectly identified the odd sample preferred the sample inoculated with P. putrefaciens. However, this trend was reversed when Control-14 and Pseudo-14 were compared. Twenty-five of 26 panelists identified the odd sample, and 24 of these 25 preferred the control sample (Table 4). The results of the ranking test for the uninoculated control samples are summarized in Table 2. The fresh (i.e., no storage at 3°C.) chicken meat received the highest ranking by the taste panel, although not significantly higher than samples stored either 7 days or 14 days. The meat held at 3°C. for 3 days received a much lower rating than the other samples. This difference cannot be explained on the basis of bacterial counts (all samples were virtually free of bacteria) or pH (all samples remained constant at 6.33). It is possible that changes occurring in the early stages of storage created temporary off-flavors which were detectable by the sensory panel. In order to further investigate this difference (i.e., between Control-3 and the other Control samples), a triangle comparison test was conducted with Control-3 and Control-0. The panelists validly differentiated between these two samples (P < 0.05). Eleven of the 13 panelists who correctly identified the odd sample indicated that the differences between the samples was slight. Most of the panelists (8 of 13) did prefer the Control-0 to Control-3, further substantiating the results of the ranking test.

PSYCHROPHILIC BACTERIA AND FLAVOR Walker, H. W., and J. C. Ayres, 1956. Incidence and kinds of microorganisms associated with commercially dressed poultry. Appl. Microbiol. 4:345-349.

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Williams, B. E., 1960. Method of tenderizing and flavouring meat. Brit. Patent 882, 239. London: HMSO. From Gardner and Stewart, 1966. J. Appl. Bacteriol. 29: 365-374.

Performance of Broiler Breeders on Slats Versus Slat-Litter Floors*

(Received for publication November 8, 1971) ABSTRACT Factors considered in two experiments using the same strain, feed, housing and equipment were egg production, fertility, hatchability, mortality and cracked eggs. There were 120 hens and 12 males per pen with 4 groups on each treatment. Each bird had 1672 sq. cm. of floor space. Those on combination flooring had 40 percent of the floor space as litter. Hen day production was significantly higher (P < 0.01) for the birds on the combination floors. Percent fertility was higher in both experiments when combination floors were used but not significantly. There was no difference in hatchability due to treatment. Mortality was significantly higher in the second experiment for those birds on the combination type floors. In the first experiment, it was higher on the slatted floors but not significantly. The percentage of cracked eggs was low 2.3 and 2.9 for slatted and combination floors respectively on 1 experiment for which it was determined. POULTRY SCIENCE 51: 1265-1267, 1972

HE production of broiler hatching eggs has generally been practiced with the breeders on litter floors. The production of commercial or shell eggs has been carried out with hens on different floor types such as slat, wire and litter. Osborn et al. (1959) comparing performance of White Leghorn hens on slats versus litter reported results of 53.0 and 60.2% egg production; 2.4 and 7.2% mortality respectively for slat and litter floors. No report was given for fertility or hatchability even though males were in the pens. Yao (1959) reported lower egg production per hen (75 versus 90) on slat floors, versus littered floors, more mortality and lower body weight. He did obtain more eggs per square foot of floor space, (75 for slat versus 30 for litter). The hens had 1 square foot versus 3 square feet for slat and litter

T

* Published with the approval of the Director of the South Carolina Exp. Sta. as Technical Contribution No. 967.

floors respectively. This would indicate an economical use of floor space. Decrease in hatchability of eggs due to microorganisms was reported by Quarles et al. (1968) when Leghorn breeders were kept on litter instead of sloping wire floors. The pipped embryos, cull or normal chicks indicated that egg contamination and shell penetration, by coliform organisms, had occurred. Nordskog and Schierman (1965) reported that fertility on slat floors was as good as on litter floors after 10-12 days. Magruder and Nelson (1965) reported no differences in percentage of broken eggs, shell thickness or shell strength when using slats or litter as a floor. By allowing only 0.75 square feet on slats versus 2.0 square feet per bird on litter floors, the labor, in time, per bird per year was reduced from 35.3 to 19.7 minutes. Cooper and Barnett (1970) reported on the use of combination litter and slat

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J. B. COOPER AND B. D. BARNETT Poultry Science Department, Clemson, South Carolina 29631