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This Article Abstract Full Text (PDF) All Versions of this Article: jas.2007-0394v1 86/4/972    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hamling, A. E. Articles by Calkins, C. R. Search for Related Content PubMed PubMed Citation Articles by Hamling, A. E. Articles by Calkins, C. R.

Effects of dark storage and retail display on beef chuck and round muscles enhanced with ammonium hydroxide, salt, and carbon monoxide^1,2

Animal Science Department, University of Nebraska, Lincoln 68583

	Abstract

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
The objective of this study was to determine the retail shelf stability of beef chuck and round muscles enhanced with ammonium hydroxide, salt, and carbon monoxide. A split plot design was used for each of 3 muscles [triceps brachii (TB), biceps femoris (BF), and rectus femoris (RF)] with 2 treatments (0 and 20% pump), 3 dark storage periods (1, 2, and 3 wk), and 3 replications in the whole plot and retail display period as the split plot. There were a total of 12 subprimals per treatment per dark storage period (n = 72 each). Individual steaks were cut to a thickness of 2.54 cm and packaged in a modified-atmosphere package (MAP). The TB was packaged in a high-oxygen MAP (80% oxygen, 20% carbon dioxide). The BF and RF were packaged in a low-oxygen MAP (100% carbon dioxide). At the completion of each dark storage period, steaks were subjected to 7 d of simulated retail display. Steaks were used for objective and subjective color measurements, total plate counts, and determination of retail purge and oxidation. For all muscles, total plate counts were always numerically greater in injected steaks. Triceps brachii steaks held in dark storage for 3 wk and displayed at retail for 4 or more days all exceeded 10⁷ log of cfu/cm² for aerobic plate count. Biceps femoris and RF steaks packaged in a low-oxygen MAP had much lower bacterial counts, with levels below 4.2 log of cfu/cm², even after 7 d of retail display. Oxidation values for the TB were extremely high (ranging from 12.3 to 26.6), whereas the BF and RF had values that were much lower (1.0 mg of malonaldehyde/kg of muscle), likely due to the oxidation occurring in a high-oxygen MAP for the TB. Enhanced TB steaks proved to have greater color stability (less discoloration) than nonenhanced TB steaks. In addition, the BF and RF (low-oxygen MAP) steaks had better color stability (more stable redness values) than TB (high-oxygen MAP) steaks, although TB steaks initially exhibited a brighter red color. Retail display life was enhanced by packaging in 100% carbon dioxide, and enhanced steaks exhibited greater color stability in retail display than control steaks.

Key Words: enhancement • modified-atmosphere packaging • retail display • shelf life

	INTRODUCTION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Enhancement of meat pH with a solution containing ammonium hydroxide, carbon oxide, and salt has been shown to improve consumer palatability ratings (Everts et al., 2006; Nath et al., 2006). Little is known about the effect of this enhancement system (patent pending for Freezing Machines Inc., Dakota Dune, SD) on color and microbial stability of beef.

The presence of carbon monoxide in the enhancement solution could be expected to increase color stability and maintain red color because low levels of carbon monoxide in modified-atmosphere packages (MAP) often cause this effect in fresh beef (Luno et al., 2000; Jayasingh et al., 2001; John et al., 2005; Grobbel, 2007). Grobbel (2007) found injection-enhanced steaks packaged in a low-oxygen MAP discolored at a slower rate and to a lesser extent than steaks packaged without carbon monoxide. However, the enhancement system did not include pH adjustment from ammonium hydroxide.

Hand et al. (2006) reported lower levels of inoculated Escherichia coli O157:H7 on pH-enhanced round steaks after 0 or 2 d of anaerobic storage but higher levels after 14, 28, or 56 d of anaerobic storage. Under aerobic conditions, lower levels of inoculated E. coli O157:H7 were observed. These results raise some questions about the microbial stabililty of pH-adjusted meat.

Luno et al. (2000) reported that MAP of fresh beef in an atmosphere containing 1% carbon monoxide in conjunction with 24% oxygen reduced total aerobic population numbers when compared with MAP with no carbon monoxide and 70% oxygen. There was no effect on lactic acid bacteria.

The objectives of this study were to evaluate the color and microbial stability of beef chuck and round muscles enhanced with ammonium hydroxide, salt, and carbon monoxide.

	MATERIALS AND METHODS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Experimental Design

The 3 muscles (n = 72 for each muscle) studied were the triceps brachii (TB), biceps femoris (BF), and rectus femoris (RF). Subprimals were randomly assigned to treatment (0 or 20% pump level) and dark storage period (1, 2, and 3 wk). There were 3 replications.

Raw Meat Materials

No approval was obtained from the Institutional Animal Care and Use Committee because samples were obtained from a federally inspected slaughtering facility.

Vacuum-packaged subprimals containing the TB, BF, and RF muscles (72 clod hearts, NAMP #114E; 72 sirloin caps, NAMP #184D; and 72 peeled knuckles, NAMP #167A, respectivly; NAMP, 2007) from USDA Choice beef carcasses were obtained from Tyson Foods in Dakota City, Nebraska. Subprimals (2 to 3 d postmortem) were randomly assigned to 1 of 2 pump levels and 1 of 3 dark storage periods. For each muscle, there were 24 subprimals per each of 3 replications (12 per pump level, 4 per dark storage period). Preparation of the samples took place at the Beef Products Inc. facility (Dakota City, NE) on 3 dates, with 1 subprimal type tested on each date.

Injection of Samples

All operations occurred in a cool room (<10°C). For each replication, 12 subprimals assigned to the 0% pump level (CON, control) were unpackaged and cut. Subprimals (12) assigned to the 20% pump level (PUMP) were unpackaged and an initial weight was taken. Subprimals were injected with a solution containing 1% sodium chloride and sufficient ammonium hydroxide to bring the pH of the brine to 11.4. The solution also contained carbon monoxide, which was formulated so that a 20% pump would result in less than 0.4% CO in the finished product. This is patented technology from Freezing Machines Inc. (US Patents 7,022,361 and 7,094,435). Subprimals were injected to the target pump level using an 88-needle Fomaco injector (model #FGM-88SW, Koge, Denmark). Once injected, subprimals were weighed to determine the actual pump level. The second and third replications followed in the same manner. Actual pump levels achieved were 19.1, 19.5, and 19.6% for RF, TB, and BF, respectively.

Cutting Procedures

After a final weight was recorded and the pump level was determined, 3 to 4 steaks from each subprimal were cut parallel to the cut surface to a thickness of 2.54 cm. The TB was cut ventral to dorsal, the BF was cut dorsal to ventral, and the RF was cut proximal to distal. Steaks were then trimmed of excess fat and muscles, leaving the muscle of interest (TB, BF, and RF) intact.

Packaging Procedures

Individual TB steaks were placed in 3.81-cm-deep trays (#10 tray, Jamestown Plastics, Brockton, NY) containing an absorbent pad (PL-75, Sealed Air Corp., Duncan, SC). A Ross Jr. A-10 model packaging machine (Midland, VA) was used with premixed gas (80% oxygen, 20% carbon dioxide) to package the steaks. The trays were sealed with Cryovac lid 1050 film (Duncan, SC), sorted into boxes, and sent to the cold storage facility (–2°C) at Beef Products, Inc. (Dakota City, NE). On the following day, the boxes were shipped approximately 3 h in a refrigerated truck to the Loeffel Meat Laboratory at the University of Nebraska.

Pairs of BF steaks and individual RF steaks were placed in 0.635-cm-deep trays (#10 tray, Jamestown Plastics) containing an absorbent pad (PL-75, Sealed Air Corp.) and packaged in a low-oxygen MAP (100% carbon dioxide) on a Ross Jr. A-10 model packaging machine (Midland, VA). The trays were sealed with Cryovac lid 1050 film (Duncan, SC), sorted into boxes, and sent to the cold storage facility (–2°C) at Beef Products Inc. (Dakota City, NE). On the following day, the boxes were shipped approximately 3 h in a refrigerated truck to the Loeffel Meat Laboratory at the University of Nebraska.

Dark Storage

Subprimals were randomly assigned to 1 of 3 dark storage periods (1, 2, or 3 wk). Samples remained in their MAP and boxes for the assigned dark storage period. Boxes remained in the Loeffel Meat Laboratory cooler (4°C) for their assigned storage period before retail display.

Retail Display

Two Tyler retail display cases (model LNSC5, Tyler Refrigeration Corporation, Niles, MI) were used for retail display. Three 2-bulb (3000K Universal Fluorescent, Philips F32T8/ADV830/ALTO, Somerset, NJ) fixtures covered the whole display area to an intensity of 1,614 lx for 24 h/d. To minimize potential effects of variation in temperature throughout the retail display case, samples were randomly shifted around every day. The retail display cases were placed in a dark room and the only lighting came from the fluorescent lighting. The retail display cases operated at <4°C. On one occasion, during display of the RF steaks, a malfunction was discovered. One retail display case approached 10°C for less than a single day. Subsequent color data from those samples were deleted from the data set.

Assignment of Steaks

After the dark storage period, samples were placed in the retail display cases. The first steak from each sample was used for determination of total plate count, retail purge, and oxidation on d 0 of retail display and was not placed in the retail display case. Steak 2 was placed in retail display and removed on d 4 for determination of total plate counts and retail purge. Steak 3 from each sample received color measurements and discoloration scores on d 0 to 7. On d 7 of retail display, the steaks were removed and used for total plate counts, retail purge, and oxidation for d 7 of retail display.

Color Measurements

L*, a*, and b* measurements were taken every day of retail display on steaks displayed for 7 d by a Hunter Lab Mini Scan XE Plus (Model 45/0-L, Reston, VA) hand-held colorimeter. The colorimeter was fitted with a 2.54-cm port and was standardized using a black tile and a white tile (X = 78.5, Y = 83.2, and Z = 88.7). Color measurements for L*, a*, and b* were taken with the colorimeter using illuminant A and 10° standard observer. Three measurements were taken across the whole steak and an average was recorded. The measurements were taken through the packaging film. To avoid getting purge on the surface of the steak, trays containing the TB steaks were tipped to the side, such that purge remained on one edge of the package and the meat touched the packaging film so that color measurements could be made.

Discoloration scores were assigned by an experienced panelist (a graduate student trained to do so and who had been involved with previous color research) to steaks under retail display for 7 d. Discoloration scores ranged from 1 to 11 (0, 1 to 10, 11 to 20, 21 to 30, 31 to 40, 41 to 50, 51 to 60, 61 to 70, 71 to 80, 81 to 90, and 91 to 100%). Scores for discoloration were determined immediately after the color measurements were taken with the colorimeter.

Total Plate Counts

Steaks pulled on d 0, 4, and 7 of retail display were sampled for total plate counts. A 6.45-cm² area was swabbed in 3 directions with a BD BBL CultureSwab (BD Biosciences, Sparks, MD). Swabs were then sent to the microbiology lab in Food Science at the University of Nebraska. Aerobic plate counts (TB steaks) were obtained using the pour plate method. Swabs were vortexed for 10 to 15 s in 10 mL of sterile PBS in 16 x 125-mL tubes for the first 10¹ dilution. Serial dilutions were then made from this solution. Initially, samples were plated at dilutions of 1:10, 1:100, and 1:1,000 (vol/vol) and plated on plate count agar (Difco, Becton Dickinson and Company, Sparks, MD). Dilutions were increased if necessary for the next sampling period. Plates for aerobic plate counts were incubated at 32 ± 1°C for 48 h. Plates for anaerobic plate counts (BF and RF steaks) were plated on plate count agar and incubated at 32 ± 1°C for 48 h in rectangular jars (Mitsubishi Gas Chemical, New York, NY) containing Anaero-packs (Mitsubishi Gas Chemical Company Inc., Tokyo, Japan) for anaerobic atmosphere generation.

Results were reported as the number of log₁₀ colony forming units per square centimeter (cfu/cm²).

Retail Purge

Purge was determined on steaks pulled on d 0, 4, and 7 of retail display. The entire package (steak included) was weighed for a primary weight. The steak was removed, the surface blotted with a paper towel, and the steak was weighed to determine the weight. These weights were used, in addition to the weight of a package, film, and unused absorbent pad (tare weight), to calculate the amount of purge incurred during the retail display.

The percentage purge was calculated by the following equation: [primary weight – steak weight – tare weight)/(primary weight – tare weight)] x 100.

Oxidation

The thiobarbituric acid assay (TBA) of Ahn et al. (1998) was used, with the modifications of Buege and Aust (1978).

Thiobarbituric acid values were determined for steaks pulled after 0 and 7 d of retail display. Fourteen milliliters of double-distilled water was added to a 5-g sample randomly obtained from steak powdered in liquid nitrogen and 1.0 mL of butylated hydroxyanisole [10% (vol/vol) stock solution dissolved in 90% ethanol]. The mixture was homogenized and then centrifuged at 2,000 x g for 5 min. Two milliliters of TBA/TCA was added to 1 mL of homogenate, vortexed, and then incubated in a 70°C water bath for 30 min to develop color. Samples were then allowed to cool in a cold water bath (13°C) for 10 min before centrifuging at 3,000 x g for 15 min. Duplicate aliquots of 200 µL were transferred to a 96-well plate. Absorbance was read at 540 nm on a Dynatech Laboratories MR5000 plate reader (Chantilly, VA) and analyzed by BioLinx assay management software (Dynatech Laboratories).

Results were expressed as milligrams of malonaldehyde per kilogram of sample.

Statistical Analysis

The experimental design for total plate counts, TBA values, and retail purge was a split plot, with treatment and period of dark storage in the whole plot and day of retail display as the split plot. Replication was used as the block. Color data were analyzed as a repeated measures design, with treatment and period serving as the whole plot, retail display day as the repeated measure, and sample as the block. Treatments, dark storage periods, and retail display times were considered fixed effects and replication was considered a random effect.

Data were analyzed using the GLIMMIX procedure (SAS Inst. Inc., Cary, NC). When significance (P 0.05) was indicated by ANOVA, means separations were performed using the LSMEANS and DIFF functions of SAS.

	RESULTS AND DISCUSSION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Bacterial Counts

For the TB (high-oxygen MAP), CON steaks always had numerically lower counts aerobic plate counts than PUMP steaks (Table 1). There was a 3-way interaction between treatment, storage period, and retail display time for the TB. Total plate counts increased as retail display time and dark storage time increased. Dainty and Mackey (1992) found that bacterial spoilage occurs when the number of bacteria reaches 10⁷ logs of cfu/cm². The enhanced TB steaks did not reach the spoilage level until d 4 of retail display after 3 wk of dark storage (7.22 log₁₀ cfu/cm²). Thus, maximum storage for an enhanced steak in high-oxygen MAP, based on aerobic plate count, was between 21 and 25 d.

Retail Purge

For the TB (high-oxygen MAP), PUMP steaks had nearly twice as much retail purge (Table 4) as CON (9.06 to 4.89%). Also, the amount of purge increased as dark storage lengthened and retail display increased. Generally, there was no significant increase in retail purge between samples after 4 d of retail display and 7 d of retail display, regardless of dark storage time. This suggests that most of the retail purge has occurred by 4 d of retail display.

Because the TB were packaged in a high-oxygen MAP, one would expect oxidation (TBA) values to be much greater than the BF and RF. This was the case even though the 3 muscles were not statistically compared. The TB exhibited very high TBA values ranging from 12.31 to 26.61 mg of malonaldehyde/kg of muscle tissue (Table 7). All values were much greater than the baseline of 1.0 mg of malonaldehyde/kg of muscle tissue (Tarladgis et al., 1960), which indicates spoilage.

Triceps brachii steaks, regardless of dark storage period, gradually got darker as retail display time progressed until d 4 (Figure 1). The L* values then slightly increased (lighter color) until d 7. Enhanced TB steaks tended to be darker (lower L*) and were always redder (a*) than CON steaks at the same sampling time. Values for a* gradually decreased over the 7-d retail display period (Figure 2). Steaks (TB) in 1 wk of dark storage before retail display had the lowest discoloration scores up to d 3 (Figure 3). Between d 3 and 4 of retail display, there was a sharp increase for discoloration scores. Enhanced steaks almost always had less discoloration than their CON counterparts.

View larger version (10K): [in this window] [in a new window]   Figure 1. L* values for triceps brachii steaks in retail display as influenced by pumping and dark storage (1, 2, or 3 wk).

View larger version (11K): [in this window] [in a new window]   Figure 2. a* values for triceps brachii steaks in retail display as influenced by pumping and dark storage (1, 2, or 3 wk).

View larger version (10K): [in this window] [in a new window]   Figure 3. Discoloration of triceps brachii steaks in retail display as influenced by pumping and dark storage (1, 2, or 3 wk).

View larger version (6K): [in this window] [in a new window]   Figure 4. L* values for biceps femoris steaks in retail display as influenced by pumping.

View larger version (8K): [in this window] [in a new window]   Figure 5. L* values for biceps femoris steaks in retail display as influenced by dark storage.

View larger version (11K): [in this window] [in a new window]   Figure 6. a* values for biceps femoris steaks in retail display as influenced by pumping and dark storage (1, 2, or 3 wk).

View larger version (7K): [in this window] [in a new window]   Figure 7. L* values for rectus femoris steaks in retail display as influenced by dark storage.

View larger version (10K): [in this window] [in a new window]   Figure 8. a* values for rectus femoris steaks in retail display as influenced by pumping and dark storage (1, 2, or 3 wk).

In summary, when packaged in a high-oxygen MAP, the enhanced steaks proved to have less discoloration and oxidation than the nonenhanced steaks. However, with the extended dark storage period and retail display time in this study, both the oxidation levels and bacterial counts made all steaks unacceptable at the end of the 3-wk dark storage and 7-d retail display period. When packaged in a low-oxygen MAP, enhanced steaks proved to have less discoloration and oxidation than nonenhanced steaks. Enhanced steaks always had greater bacterial counts than the nonenhanced steaks. Data suggest that enhancement of beef chuck and round muscles can improve and extend shelf life under low-oxygen packaging conditions.

	Footnotes

 
¹ A contribution of the University of Nebraska Agricultural Research Division, Lincoln, NE 68583.

² Funded by the Beef Checkoff.

³ Corresponding author: ccalkins1{at}unl.edu

Received for publication July 3, 2007. Accepted for publication January 4, 2008.

	LITERATURE CITED

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 


Ahn, D. U., D. G. Olsen, C. Jo, X. Chen, C. Wu, and J. I. Lee. 1998. Effect of muscle type, packaging, and irradiation on lipid oxidation, volatile production, and color in raw pork patties. Meat Sci. 49:27–39.[CrossRef]

Buege, J. A., and S. D. Aust. 1978. Microsomal lipid peroxidation. Methods Enzymol. 52:302–310.[Medline]

Dainty, R. H., and B. M. Mackey. 1992. The relationship between the phenotypic properties of bacteria from chilled-stored meat and spoilage processes. J. Appl. Bacteriol. Symp. Suppl. 21, 73:113–114.

Everts, A. J., A. K. R. Everts, C. D. Hand, T. M. Nath, D. M. Wolf, and R. J. Maddock. 2006. Effects of pH-enhancement on consumer ratings of various meat products. Page 24 in Proc. Recip. Meat Conf., Book of Abstracts, Am. Meat Sci. Assoc., Savoy, IL.

Grobbel, J. P. 2007. Effects of packaging atmospheres and injection enhancement on beef postmortem proteolysis, instrumental tenderness, sensory traits, and display color. PhD Diss. Kansas State University, Manhattan.

Hand, C. D., T. M. Nath, A. J. Everts, A. K. R. Everts, D. M. Wulf, D. R. Henning, and R. J. Maddock. 2006. Effects of pH enhancement on survivability and growth of E. coli on beef subprimals and steaks. Page 41 in Proc. Recip. Meat Conf., Book of Abstracts, Am. Meat Sci. Assoc., Savoy, IL.

Jayasingh, P., D. P. Cornforth, C. E. Carpenter, and D. Whittier. 2001. Evaluation of carbon monoxide treatment in modified atmosphere packaging or vacuum packaging to increase color stability of fresh beef. Meat Sci. 59:317–324.[CrossRef]

John, L., D. Cornforth, C. E. Carpenter, O. Sorheim, B. C. Pette, and D. R. Whittier. 2005. Color and thiobarbituric acid values of cooked top sirloin steaks packaged in modified atmospheres of 80% oxygen, or 0.4% carbon monoxide, or vacuum. Meat Sci. 69:441–449.[CrossRef]

Luno, M., P. Roncales, D. Djenane, and J. A. Beltran. 2000. Beef shelf life in low O₂ and high CO₂ atmospheres containing different low CO concentrations. Meat Sci. 55:413–419.[CrossRef]

NAMP. 2007. The Meat Buyers Guide. North Am. Meat Processors Assoc., Reston, VA.

Nath, T. M., C. D. Hand, A. J. Everts, A. K. R. Everts, D. M. Wulf, and R. J. Maddock. 2006. Trained and consumer evaluations of five different beef muscles with or without pH enhancement using ammonium hydroxide. Page 22–23 in Proc. Recip. Meat Conf., Book of Abstracts, Am. Meat Sci. Assoc., Savoy, IL.

Tarladgis, B. G., B. M. Watts, and M. T. Younathan. 1960. A distillation method for the quantitative determination of malonaldehyde in rancid foods. J. Am. Oil Chem. Soc. 37:44–48.[Medline]

This Article Abstract Full Text (PDF) All Versions of this Article: jas.2007-0394v1 86/4/972    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hamling, A. E. Articles by Calkins, C. R. Search for Related Content PubMed PubMed Citation Articles by Hamling, A. E. Articles by Calkins, C. R.