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Effects of Packaging Systems on the Natural Microflora and Acceptability of Chicken Breast Meat

N. Charles^*, S. K. Williams^,*,1 and G. E. Rodrick

^* Department of Animal Sciences and Department of Food Science and Human Nutrition, University of Florida, Gainesville 32611

¹ Corresponding author: Williams{at}Animal.ufl.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION REFERENCES

 
The effect of 3 packaging systems on the spoilage microflora, objective color, and sensory characteristics of fresh commercial broiler chicken breast meat was investigated. Fresh skinless and boneless chicken broiler breasts were purchased from a local poultry processing plant and packaged in either (1) a conventional Styrofoam tray with polyvinyl chloride overwrap and absorbent pad, (2) a Styrofoam tray with polyvinyl chloride overwrap minus absorbent pad, or (3) a Fresh-R-Pax (FRP) container equipped with an absorbent liner-gel system. All packages were heat sealed and stored at 1.2 ± 1°C for 8 d. At each sampling period (0, 2, 4, 6, and 8 d), packages from each treatment were analyzed for Pseudomonas spp., psychrotrophic organisms, objective color, and sensory characteristics. In general, Pseudomonas spp. and psychrotrophic counts increased as storage time increased for all packaging systems. Color and overall appearance were similar (P >0.05) for all packaging systems. Although not significant, the off-odor scores for breast meat packaged in FRP were higher (P >0.05) after 6 and 8 d when compared with the breast meat packaged in a Styrofoam tray with polyvinyl chloride overwrap with or without an absorbent pad. Although the absorbent pad did not control microbial growth, it maintained aesthetic appeal by absorbing all visible moisture released from the meat during storage.

Key Words: packaging • spoilage bacteria • Pseudomonas spp. • psychrotroph • chicken meat

	INTRODUCTION

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Packaging systems protect the product, maintain a state of freshness throughout the merchandising cycle, and add appeal to the product (Rust, 1977). The 2 most commonly used packaging systems in today’s retail markets include the conventional Styrofoam tray (with or without an absorbent pad liner and overwrapped with a polyvinyl chloride film) and vacuum-packaged or skin-packed systems. The case-ready packaging system is increasing in popularity for fresh retail muscle foods. A fourth system, the Fresh-R-Pax (FRP) super-absorbent tray, is currently being marketed as an improved alternative for raw meat and poultry to control excessive purge during storage and shipment. Fresh-R-Pax is composed of 2 different compartments. Compartment 1, the upper section, is a plastic tray lined with an absorbent film that allows the exudate, purge, or both to flow from the meat through to compartment 2. Compartment 2 contains an absorbent material that is composed of a noncross-linked, gel-forming polymer (sodium carboxymethyl cellulose), at least 1 clay (attapulgite), and a trivalent cation (aluminum sulfate). Fluids from the meat product pass through the fabric that separates the 2 compartments into the base of the tray where the absorbent material traps and gels the meat exudate, purge, or both. The manufacturer reported that the system might also extend shelf life in poultry and meat products (Maxwell Chase Technologies LLC, 2005).

Researchers have reported that the primary population of bacteria found on spoiled refrigerated meat and poultry is psychrotrophic organisms, especially Pseudomonas spp. (Russell et al., 1996). Barnes and Thornley (1966) reported that the bacteria on broiler meat immediately after processing were Micrococci (50%), gram-positive rods (14%), Flavobacteria (14%), Enterobacteriaceae (8%), Pseudomonas (2%), Acinetobacter (7%), and unidentified organisms (5%). Of these genera, only Pseudomonas and Acinetobacter grew well at refrigeration temperature. After the samples were stored at 1°C for 10 to 11 d, the bacterial flora changed to predominantly psychrotrophs, including 90% Pseudomonas spp. (Pseudomonas and Shewanella), 7% Acinetobacter, and 3% Enterobacteriaceae. The objective of this study was to compare the storage stability of commercial broiler breast meat stored in the conventional tray pack system (with and without an absorbent pad) with that stored in the Fresh-R-Pak system.

	MATERIALS AND METHODS

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Preparation and Storage of Samples

Fresh boneless and skinless broiler chicken breast meat, cut into halves longitudinally, was purchased from a local poultry processing plant. The meat was packed in plastic bags, stored in ice chests containing frozen cold packs, and transported to the meat research laboratory. The breast meat was divided into 3 groups containing equal number of breast halves. The breasts were packaged (2 halves per tray) in either (1) a conventional 16S Styrofoam tray (Cryovac Inc., Graceville, SC) with polyvinyl chloride overwrap and an absorbent pad (PAD), (2) a Styrofoam tray with polyvinyl chloride overwrap (catalog no. RMF 61 HY, Borden Chemical, Columbus, OH; 64-gauge film; oxygen transmission rate: 1,400 cc/m² per 24 h per 22.8°C; water vapor transmission rate: 32 g/24 h per 37.8°C) minus the absorbent pad (STY), or (3) FRP (Maxwell Chase Technologies LLC, Atlanta, GA) equipped with an absorbent liner-gel system. The original FRP tray manufactured by Maxwell Chase Technologies LLC had the dimensions 25.4 x 30.48 x 7.62 cm. In this study, the top portion of the container was incised with sterile scissors to reduce the height of the container to 1.27 cm, which was the height of the 16S Styrofoam tray. All packages were heat sealed and stored at 1.2 ± 1°C for 8 d. At each sampling period (0, 2, 4, 6, and 8 d), 3 packages from each treatment were analyzed for total Pseudomonas spp. and psychrotrophic organisms, 2 packages for objective color, and 1 package for sensory characteristics (off-odor and overall appearance). Three trials were conducted.

Microbiological Analyses

Three packages per treatment were analyzed on each sampling day. The surface of each package was wiped with alcohol swabs before opening. The breast meat was aseptically placed into a stomacher bag and weighed. The appropriate quantity of sterile 0.1% peptone water was added to achieve a 1:10 dilution, and the bag was agitated for approximately 60 s. The appropriate serial dilutions were prepared, and 1.0-mL aliquots were plated onto 3M (St. Paul, MN) Petrifilm for total psychrotrophic organisms, and 0.1-mL aliquots were plated onto prehardened bacto Pseudomonas isolation agar (Difco, catalog no. DF 0927-17-1, Fisher Scientific, Atlanta, GA) for Pseudomonas spp. Petrifilm for psychrotrophic counts was incubated for 10 d at 7°C. Pseudomonas plates were incubated at 37°C for 48 h then counted on a Quebec colony counter. All analyses were performed in duplicate.

Color Analysis

Reflectance spectra were recorded for each package using a CR-100 Minolta chroma meter (Minolta Corp., Ramsey, NJ). Two packages per treatment were analyzed on each sampling day. The chroma meter was calibrated using the standard white reflector plate. A sheet of the overwrap film was placed over the surface of the reflector plate to ensure accuracy when measuring the meat enclosed in the packaging material. Total lightness (L*), redness (a*), and yellowness (b*) values were recorded for each sample. Two measurements were recorded for each breast meat sample (i.e., 4 measurements per package). One measurement was taken approximately 1 cm from the center of the breast and the other was approximately 1.27 to 2.54 cm from the edge of each sample.

Sensory Analysis

Two packages of chicken breasts per treatment were evaluated for odor and overall appearance by an untrained sensory panel. The panelists were instructed to record the appearance of the sample using an 8-point scale where 8 = extremely desirable, 7 = very desirable, 6 = desirable, 5 = slightly desirable, 4 = slightly undesirable, 3 = undesirable, 2 = very undesirable, and 1 = extremely undesirable. Panelists were also instructed to sniff the sample and record off-odor using a 6-point scale where 6 = none detected, 5 = barely detected, 4 = slight odor, 3 = moderate odor, 2 = strong odor, and 1 = extreme odor.

Statistical Analysis

A total of 135 samples (i.e., 3 treatments x 3 packages x 3 trials x 5 d of storage) was analyzed for psychrotrophic and Pseudomonas organisms, 90 samples (i.e., 3 treatments x 2 packages x 3 replications x 5 d of storage) for color, and 36 samples (i.e., 3 treatments x 1 package x 3 replications x 4 storage days) were analyzed for sensory characteristics (off-odor and overall appearance). Differences were determined between main effects (treatment and storage day) using SAS GLM procedure (SAS Institute, 1996). Duncan’s multiple range test was used to compare treatment means when required.

	RESULTS AND DISCUSSION

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Microbiological Analysis

In general, Pseudomonas and psychrotrophic counts increased as storage time increased for all treatments (Table 1). A significant increase (P < 0.05) in Pseudomonas spp. and psychrotrophic organisms occurred in the FRP and STY packaging after 6 d storage and after 4 d for the PAD packages. Psychrotrophic counts were significantly higher (P < 0.05) than the Pseudomonas spp. counts after 6 and 8 d for all packaging systems. The higher psychrotrophic counts could be attributed to the fact that psychrotrophic counts include Pseudomonas spp. plus other micro-organisms that grow at refrigeration temperatures (Barnes and Thornley, 1966). Pseudomonas counts remained less than 7 log₁₀ cfu/g for all packaging systems. In general, spoilage defects in meat become evident when the number of bacteria at the surface reaches 7 log₁₀ cfu/g (Jay, 1992). It has been determined that when microbial counts reach 8 log₁₀ cfu/g, decomposition of the muscle tissue begins and is evident by surface slime formation. Total psychrotrophic counts reached 7 log₁₀ and at least 8 log₁₀ cfu/mL after 6 and 8 d, respectively, for all breast meat samples in all packaging systems.

Overall appearance was similar (P >0.05) for all breast meat in all packaging systems (Table 2). Off-odor was "barely detected" (score of 5.37 to 5.83) in breast meat packaged in FRP through 6 d and "slightly detected" (score of 4.30) after 8 d. Although not significant, the off-odor scores for breast meat packaged in FRP were higher (P >0.05) after 6 and 8 d when compared with the breast meat packaged in STY and PAD. Panelists’ responses revealed that off-odor of breast meat packaged in STY and PAD packaging systems was "slightly detected" (score of 4.60 to 4.67) after 6 d and "moderately detected" (score of 3.20) after 8 d. The panelist responses demonstrated a positive correlation with the microbiological data recorded. Total psychrotrophic counts reached log 7 and at least log 8 cfu/g after 6 and 8 d, respectively, for all breast meat samples in all packaging systems, and the detection of off-odor in the breast meat was most evident after 6 and 8 d of storage.

Except for on d 0, L* values were similar for all breast meat packaged in all packaging systems (Table 3). The breast meat packaged in the PAD system had significantly higher (P < 0.05) a* values when compared with breast meat packaged in the STY and FRP systems on d 0. After d 0, all breast meat had similar (P >0.05) a* values. The b* values for all breast meat in all packaging systems were similar (P >0.05) during the 8-d storage period. All L*, a*, and b* values were similar to values previously reported (Fletcher, 1999; Fletcher et al., 2000; Petracci et al., 2004).

The data revealed similar results for all packaging systems. Although the absorbent pad did not control microbial growth, it maintained aesthetic appeal by absorbing all visible moisture released from the meat during storage. In this study, 5 mL or less of exudates, purge, or both were measured for breast meat in the STY system. The absorbent systems used in PAD and FRP packaging prevented the presence of visible exudate, purge, or both. Observations of the FRP system revealed that it might have advantage in foods in which excessive exudate, purge, or both are prevalent. The data also suggested that FPR might retard off-odor in fresh broiler breast meat during retail storage. These conditions would include shipment and storage of raw meat cuts (subprimal and retail) and poultry carcasses.

Received for publication September 19, 2005. Accepted for publication April 4, 2006.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION REFERENCES

 
Barnes, E. M., and M. J. Thornley. 1966. The spoilage flora of eviscerated chickens stored at different temperatures. J. Food Technol. 1:113–119.

Fletcher, D. L. 1999. Broiler breast meat color variation, pH, and texture. Poult. Sci. 78:1323–1327.[Abstract/Free Full Text]

Fletcher, D. L., M. Qiao, and D. P. Smith. 2000. The relationship of raw broiler breast meat color and pH to cooked meat color and pH. Poult. Sci. 79:784–788.[Abstract/Free Full Text]

Jay, J. M. 1992. Spoilage of fresh beef, pork, and related meats. Pages 201–205 in Modern Food Microbiology. 4th ed. Chapman and Hall, New York, NY.

Maxwell Chase Technologies, LLC. 2005. Fresh-R-Pax for fresh meats, poultry and seafood. http://www.maxwellchase.com/ProdMeatPoulSeafood.php Accessed September 13, 2005.

Petracci, M., M. Betti, M. Bianchi, and C. Cavani. 2004. Color variation and characterization of broiler breast meat during processing in Italy. Poult. Sci. 83:2086–2092.[Abstract/Free Full Text]

Russell, S. M., D. L. Fletcher, and N. A. Cox. 1996. Spoilage bacteria of fresh broiler chicken meat. Poult. Sci. 75:2041–2047.

Rust, R. 1977. "Packaging and Order Assembly." Sausage and Processed Meats Manufacturing. AMI Center for Continuing Education, Ames, Iowa.

SAS Institute. 1996. SAS User’s Guide. Version 6.12. SAS Institute Inc., Cary, NC.

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