Influence of Injection, Packaging, and Storage Conditions on the Quality of Beef and Bison Steaks

The combined effects of injection, packaging (modified atmosphere packaging [MAP] with 70% O₂/ 30% CO₂ and vacuum packaging [VP]), storage temperature (‐1 °C and +4 °C), and storage time on the color, microbial and oxidative stability of beef and bison longissimus lumborum (LL) steaks were investigated. Beef LL steaks in MAP retained their bright red color longer than bison steaks. Bison steaks developed higher 2‐Thiobarbituric acid reactive substances (TBARS) during storage, and this might have influenced the resulting rapid loss of redness from the bloomed meat. Storage at ‐1 °C in MAP provided greater color stability and a longer storage life for both meat species studied. Injection of salt/phosphate had a beneficial effect on the color stability of steaks during retail display; however, this positive effect was more pronounced for bison steaks compared with those of beef. Steaks stored overnight under MAP before retail display maintained the highest a* values for up to 5 d compared with those stored under vacuum. MAP‐OV steaks generally maintained the highest OMB content for up to 5 d during retail display compared with those stored under vacuum. Nevertheless, OMB levels were significantly (P < 0.05) lower in bison steaks compared with those of beef irrespective of packaging treatments. Injected steaks and those stored at ‐1 °C had significantly (P < 0.05) higher OMB levels compared with non‐injected counterparts and those stored at +4 °C, respectively. MAP is an excellent option for short‐term storage due to its positive effects on meat color, but for longer storage, VP may be necessary. Storing meat under vacuum and then placing it under MAP just before retail display might be another option to increase shelf life.     

Microflora and Color of Ground Beef in Gas Exchange Modified Atmosphere Packaging with Abusive Display Temperatures

Gas exchange modified atmosphere packaging (GEMAP) with display gas of 80% O²:20% CO₂ retarded microbial growth and improved color stability of ground beef patties compared with vacuum packaging (VP) followed by air‐permeable polyvinylchloride (PVC) overwrapping during 3 d of retail display. Predominant microorganisms for GEMAP were Pseudomonas, Yersinia, Aeromonas, and Enterobacter and for VP‐PVC were Pseudomonas, Brochothrix, Aeromonas, Enterobacter, Moraxella, and Lactobacillus. Lower levels of pathogens were isolated in GEMAP samples with 7 °C than 15 °C display temperature. Patties were darker (lower L*) with those with 15 °C than with 7 °C display and redder (higher a*) in GEMAP than VP‐PVC. Good manufacturing practices should be followed with MAP meat to reduce the risk of pathogenic microbial growth.     

Mild protein oxidation enhanced hydration and myofibril swelling capacity of fresh ground pork muscle packaged in high oxygen atmosphere

Abstract: This study investigated the influence of an oxygen‐enriched modified atmosphere packaging (HiOx: 80% O₂/20% CO₂) in comparison with air‐permeable polyvinylchloride (PVC) wrapping and partial vacuum (VP: 60%) packaging on the ability of myofibrils to imbibe water during retail display of fresh ground pork at 2 to 4 °C. Both HiOx and PVC muscles after 4 d showed maximum myofibril swelling and A‐band dissolution when isolated myofibrils were subjected to a graded series of salt solutions (0.2→0.4 M NaCl with 10‐mM sodium pyrophosphate, pH 6.2), while VP samples exhibited no remarkable change. Protein carbonyl content increased substantially from day 0 to 4 in all muscle samples. For HiOx, muscle hydration capacity increased linearly (P < 0.05) during storage up to 14 d, corresponding to protein carbonyl production. No significant changes in hydration properties were noted in VP muscle samples, which also maintained lower levels of protein oxidation, during storage up to 21 d. These results indicated that packaging in modified atmosphere with high levels of oxygen could result in increased protein oxidation but enhanced hydration capacity of fresh meat. Practical Application: Packaging of fresh meat, including ground pork, under an oxygen‐enriched atmosphere condition is widely used in the industry to preserve red color of meat. Results from the present study indicate that high oxygen packaging has a discordant effect on fresh ground pork: it enhances hydration but decreases water‐binding, and this seems to be caused by increased swelling of muscle fibers due to mild protein oxidation. Hence, it is advisable to employ a water‐binding agent in this type of packaging system so as to retain the moisture in stored fresh pork products while maintaining the color stability.     

Physical, Sensory and Microbiological Characteristics of Lamb Retail Cuts Vacuum Packaged in High Oxygen-Barrier Film

Lamb chops and steaks from fresh (F) or vacuum packaged (VP) racks, loins and legs were packaged in polyvinyl chloride (PVC) film or vacuum packaged in high oxygen-barrier (HOB) film. Use of previously vacuum packaged (PVP) cuts did not affect overall appearance of rib or loin chops during subsequent retail display but HOB film-packaged leg steaks from PVP cuts had lower overall appearance scores than did leg steaks from F cuts. Prior VP storage negatively affected flavor desirability and odor at the conclusion of retail display (4 days in PVC or 10 or 15 days in HOB film). Pseudomonas spp. were a dominant part of the microflora of PVC-wrapped chops while L. cellobiosus was a dominant part of the microflora of HOB-wrapped chops.     

SODIUM LACTATE EFFECTS ON THE STABILITY OF FRESH AND CURED PORK LONGISSIMUS

Boneless pork loins sliced into 1.9 cm fresh chops were dipped to retain 0, 1.5 or 3% sodium lactate (SL) and packaged in polyvinylchloride (PVC) or vacuum-packaged (VP), Color of fresh chops was monitored visually and objectively. Boneless pork loins were cured by injection with 0, 1.5 or 3% SL, or were dipped after slicing to retain 0, 1.5 or 3% SL. Cure for the dipped loins contained no SL. Color and aerobic plate count (APC) of vacuum-packaged chops were evaluated over 70 days of retail storage (4C). Visual color was darker (P < 0.05) and L* values were lower (P < 0.05) for 3% SL-dipped fresh chops. Fresh chops containing 1.5 and 3% SL had higher a* values than controls. Surface discoloration of 3% SL fresh chops was lower (P < 0.05) than control chops. Cured injected chops (3% SL) had lower (P < 0.05) L* values than dipped chops or injected controls. L*, a* and b* values of cured dipped chops (3% SL) were not different (P > 0.05) from controls. No consistent trends were found in APC of cured chops. Injection of SL prior to cooking darkened the color of cured pork loin chops.     

The effect of pH on shelf-life of pork during aging and simulated retail display

The pork industry uses pH to differentiate product of varying quality; thus, the effect of pH on shelf-life is important as time during transport is extended. The objective was to develop regression equations to predict shelf-life over a range of ultimate pH (5.42–6.26). Shelf-life was evaluated after vacuum aging pork loin sections 0, 7, 14, 21, or 28 d and during 3 d of simulated retail display (4.5 °C) for pork loin chops. Correlation coefficients indicated a strong relationship between pH and quality measurements. Regression analysis with Aging Day and pH was able to explain 87% of the variation in aerobic plate counts for pork. After 28 d of vacuum aging, loin sections from the upper end of the pH distribution had about a 3 log(1000X) greater aerobic plate count than did the lower end pH product. An increase in pH resulted in pork with lower L*, a*, b* and R₆₃₀ − R₅₈₀ values and as Aging Day increased, instrumental measurements of color increased slightly. Although higher pH is associated with improved pork quality, higher pH and longer aging periods will result in increased microbial proliferation and decreased shelf-life. Thus, an intermediate pH may provide the most desirable combination of quality and shelf-life when extensive aging is used.     

Effect of dietary α-tocopherol supplementation on color and lipid stability in pork

Myoglobin and lipid oxidation are major causes of quality deterioration in fresh pork. A process to enhance color and lipid stability would prove valuable to the pork industry given the current trend of centralized packaging and distribution to retail markets. Our objective was to determine the effects of dietary α-tocopherol (α-Toc) supplementation on color and lipid stability in ground pork, and loin chops stored in modified atmosphere packaging (MAP). Yorkshire crossbred pigs (n=20) were randomized into two groups and fed diets containing 48 (CON) or 170 mg α-Toc acetate/kg feed (VIT-E) for 6 weeks before slaughter. Plasma α-Toc concentration was measured weekly. Post-slaughter, Boston butt shoulders were ground, formed into patties with or without 1.5% salt, and stored fresh at 4°C for 0, 2, 4, or 6 days, and frozen at −20°C for 45 or 90 days. Pork loin chops were packaged aerobically and stored at 4°C for 0, 2, 4 or 6 days, or in MAP at 4°C for 7, 10 or 13 days prior to Hunter L*,a*,b* and TBARS analyses. α-Toc concentration of longissimus dorsi, psoas major, biceps femoris, semimembranosus and semitendinosus muscles was determined. Plasma α-Toc was greater (P<0.05) in VIT-E animals compared with CON and α-Toc concentrations were greater (P<0.05) in all VIT-E muscles compared with CON. TBARS values of both fresh and salted patties were less in VIT-E than in CON meat following 6 days at 4°C; VIT-E TBARS of salted patties were less (P<0.05) after 45 days at −20°C compared with CON. α-Toc supplementation did not influence (P>0.05) color of aerobically packaged or MAP chops, or of fresh or salted pork patties. α-Toc supplementation reduced TBARS formation in fresh and salted pork but had no significant impact on color.     

EFFECTS OF NISIN AND MODIFIED ATMOSPHERE PACKAGING (MAP) ON THE QUALITY OF EMULSION‐TYPE SAUSAGE

ABSTRACT

The aim of this work was to study the effects of nisin (30 ppm) and modified atmosphere packaging (MAP) on the chemical, microbial and sensory properties of emulsion‐type sausage stored under two different atmospheres (%CO₂/%N₂/%CO/%O₂): 39.5/60/0.5/0 and 39.5/20/0.5/40. The samples were stored at 3 ± 1C for 42 days. Microbial count, values of pH, CIE L*, a* and b* color parameters, lipid oxidation, production of nitrosomyoglobin and sensory properties were assessed throughout the storage period. The data showed that nisin was able to reduce the growth of mesophilic, psychrotrophic and lactic acid bacteria. In addition, the MAP did not show any significant effects on microbial growth. However, free O₂ MAP, in combination with nisin, reduced the growth of yeast and mold. MAP could produce a stabilized red color and minimize the oxidative reactions in the samples. Packaging conditions had no significant effect on pH and sensory properties.

PRACTICAL APPLICATIONS

The results of this study confirmed that nisin can reduce the growth rate of lactic acid bacteria, psychrotrophic and mesophilic bacteria in emulsion‐type sausage, and free O₂ MAP, in combination with nisin, inhibits the growth of yeast and mold. The use of 30 ppm nisin, in combination with MAP containing 39.5% CO₂ and 0.5% CO gases, can lead to better quality preservation of the emulsion‐type sausages stored at low temperature and can extend their shelf life.     

Effect of Heat Treatment and Selected Antimicrobials on the Shelf-life and Safety of Cooked, Vacuum-Packaged, Refrigerated Pork Chops

The shelf-life of refrigerated (2–4°C) pork chops inoculated with Clostridium sporogenes PA3679 and Staphylococcus aureus Z88 was examined in products sliced from loins cooked to 66°C (150°F), dipped in 5% polyphosphate blend, 2.5% potassium sorbate or 2% acetic acid solutions, vacuum-packaged and stored at 2–4°C. The effect of a second in-the-bag cooking step to 66°C (150°F) after vacuum packaging was also studied. Pork chops not reheated after packaging showed incipient spoilage after 15 days at 2–4°C, depending on surface treatment. The second cooking increased the shelf-life of refrigerated product to more than 60 days and reduced counts of inoculated cultures to undetectable levels. However, on exposure of the chops to simulated mishandling (24–25°C), clostridial growth was detected in all samples except those dipped in polyphosphate or acetic acid solutions.     

Effects of distribution packaging method and storage time on the physical properties and retail display characteristics of pork

The sensory characteristics of pork chops from bone-in loins and Boston butts (n = 65 each) were affected little by primal loin and the butt packaging method (paper wrap, vacuum pack and gas flush) and storage time (7, 10 and 14 days) under industry conditions. However, loin chops fabricated from vacuum-packaged loins after 14 days of storage had less (P < 0·05) discoloration and two-toning than chops fabricated from other loins. All loin chops were placed in retail display and overwrapped with a polyvinyl chloride film after fabrication at each storage time. Vacuum-packed butts stored for 10 and 14 days produced chops with less discoloration and two-toning, and higher overall appearance scores (P < 0·05) compared to chops from paper-wrapped or gas-flushed cuts. Vacuum-packaging resulted in higher quality retail cuts than paper-wrapped or gas-flushed packaging. Thus, it is recommended that the pork industry and retail distribution system utilize vacuum-packaging as the primary method to store and ship fresh pork before retail sale.     

Application of Electronic Nose for Measuring Total Volatile Basic Nitrogen and Total Viable Counts in Packaged Pork During Refrigerated Storage

The objective of this study was to predict the total viable counts (TVC) and total volatile basic nitrogen (TVB‐N) in pork using an electronic nose (E‐nose), and to assess the freshness of chilled pork during storage using different packaging methods, including pallet packaging (PP), vacuum packaging (VP), and modified atmosphere packaging (MAP, 40% O₂/40% CO₂/20% N₂). Principal component analysis (PCA) was used to analyze the E‐nose signals, and the results showed that the relationships between the freshness of chilled pork and E‐nose signals could be distinguished in the loadings plots, and the freshness of chilled pork could be distributed along 2 first principal components. Multiple linear regression (MLR) was used to correlate TVC and TVB‐N to E‐nose signals. High F and R² values were obtained in the MLR output of TVB‐N (F = 32.1, 21.6, and 24.2 for PP [R² = 0.93], VP [R² = 0.94], and MAP [R² = 0.95], respectively) and TVC (F = 34.2, 46.4, and 7.8 for PP [R² = 0.98], VP [R² = 0.89], and MAP [R² = 0.85], respectively). The results of this study suggest that it is possible to use the E‐nose technology to predict TVB‐N and TVC for assessing the freshness of chilled pork during storage.     

The effect of protein oxidation on hydration and water-binding in pork packaged in an oxygen-enriched atmosphere

This study investigated the in situ oxidative process of myofibrillar proteins in boneless pork loin chops (Longissimus lumborum) packaged in an oxygen-enriched atmosphere (HiOx: 80% O₂/20% CO₂), an air-permeable polyvinylchloride (PVC) overwrap, or a partial vacuum (VP) throughout display at 2 °C for up to 14, 7, and 21 days, respectively. Samples stored in HiOx were susceptible to lipid (TBARS) and protein (carbonyls, sulfhydryls, and aggregation) oxidation, while samples in PVC and VP showed lesser oxidative changes. Water-holding capacity of raw muscle decreased (P < 0.05) when stored in HiOx but not in PVC and VP. Upon salt and phosphate brine marination, HiOx and PVC muscle samples had improved hydration capacity during display compared with non-stored control, but display generally decreased hydration of VP samples. The result was in agreement with myofibril structural changes. Despite the enhanced hydration, HiOx muscle was least capable of withholding moisture upon cooking.     

Use of Carbon Monoxide Packaging for Improving the Shelf Life of Pork

ABSTRACT: Effects of carbon monoxide in modified-atmosphere packaging (MAP-CO) for pork were investigated. Eighty pork loins (40 injected, 40 uninjected) were used to evaluate color, microbial growth, rancidity, purge, and sensory quality of pork chops in 4 packaging environments (aerobic-overwrap, vacuum, MAP without CO, and MAP-CO). Treatments were evaluated during 36 d of refrigerated storage. Overall Hunter a values were significantly ( P < 0.001) greater in MAP-CO (11.25) than aerobic (6.93) packages. Sensory color values (100 point scale) were also greater for chops in MAP-CO (85.91) than aerobic (62.47) packages. However, MAP-CO did not reduce purge loss. Results showed that CO significantly improved color stability and sensory panel scores for both injected and noninjected pork chops.     

Static, Controlled (CO2) Atmosphere Packaging of Retail Ready Pork

Wrapped boneless pork loin roasts and slices were stored at 4°in bulk under constant CO₂ concentrations of 50% and 100% for 1 and 2 wks. Samples stored under 50% CO₂ for 2 wks could subsequently be displayed (aerobic) for 3 days without becoming unacceptable or for 6 days if previously held under 100% CO₂ for 14 days. Aerobic shelf-life at 4°of the latter samples equalled that of fresh pork chops under simulated retail display. Physicochemical characteristics during storage did not limit acceptability. Reusable master packs have application for distribution of retail ready cuts under controlled atmosphere packaging.     

Shelf-stability enhancement of precooked red claw crayfish (Cherax quadricarinatus) tails by modified CO2/O2/N2 gas packaging

Three types of packaging systems were compared for their influence on the storage stability (2 °C) of precooked and peeled red claw crayfish tails. Modified atmosphere packaging (MAP; with 80%CO₂/10%O₂/10%N₂) almost totally inhibited the growth of aerobic bacteria and coliforms when compared with aerobic polyvinylchloride packaging (PVCP) and vacuum packaging (VP). MAP also prevented a pH rise, purge loss, and texture toughening or softening of stored red claw when compared with PVCP or VP (P<0.05). Lipid oxidation was minimal in all three packaging systems. Thus, MAP offers an attractive means to preserve the shelf life of precooked red claw stored under refrigerated retail display conditions.     

Effects of microbial inhibitors and modified atmosphere packaging on growth of Listeria monocytogenes and Salmonella enterica Typhimurium and on quality attributes of injected pork chops and sliced cured ham

This study was designed to determine the inhibitory effects of modified atmosphere packaging (MAP), both alone and in combination with potassium lactate and sodium diacetate (PLSD), on selected pathogens common to pork products. Effects of the treatments on product quality also were assessed. The hypothesis was that high-CO2 MAP would increase the effectiveness of PLSD for inhibition of pork pathogens. Fresh chops from untreated pork loins and loins that were injected with PLSD were inoculated with Salmonella enterica Typhimurium, and slices of untreated hams and hams that were injected with PLSD were inoculated with Listeria monocytogenes. The samples were subjected to vacuum packaging (VP) or MAP with high concentrations (99.5 to 100%) of CO2. Pathogens were enumerated periodically during storage at 4 and 10 degrees C. Storage of pork chops at 4 degrees C slowed the growth of Salmonella Typhimurium, and there was little difference in pathogen numbers between VP and MAP samples. L. monocytogenes growth on ham slices at 4 degrees C was inhibited for up to 28 days by all of the treatments, but after 28 days, the VP-PLSD treatment had a greater inhibitory effect than did the other treatments. At 10 degrees C, the PLSD and MAP treatments each effectively inhibited the growth of the pathogens on pork chops and ham slices when compared with controls (VP). However, the results obtained with MAP plus PLSD at 10 degrees C were not different from those obtained with either MAP or PLSD alone. Therefore, the hypothesis was not supported; the high-CO2 atmosphere of the MAP did not increase the effectiveness of PLSD for inhibition of pathogens.     

The effect of wholesale vacuum and 100% CO2 storage on the subsequent microbiological, colour and acceptability attributes of PVC-overwrapped pork loin chops

The shelf life of chops cut from pork loins, after either vacuum or 100% CO₂ storage (0, 7 or 14 days), was determined. The PVC-overwrapped chops were assessed, following a shelf life study of 0, 2, 5 or 7 days at 0 or 5°C, regarding quality attributes such as microbiological contamination levels, colour and acceptability. The study indicated that according to the psychrotrophic counts, the PVC-overwrapped retail chops, from the vacuum as well as the 100% CO₂ stored pork loins (0, 7 or 14 days), still attained a conventional shelf life of 3 days.

Lactic acid bacteria and pseudomonads largely represented the psychrotrophic counts. No clear pattern could be detected regarding the colour scores except that the samples displayed at 0°C tended to retain colour longer. These samples were also judged to be more acceptable, although the determination of acceptability was subjective.     

VACUUM PACKAGING OF LAMB. 1. Microbial Considerations

SUMMARY –Paired loins from 148 lamb carcasses were utilized to determine the subsequent case-life of chops from loins that had been stored in vacuum packages. Bacterial samples which were obtained from the surface of the longissimus muscle were used to evaluate the retail case-life of loin chops. Longer periods of storage in vacuum packages were associated with higher initial psychrotrophic counts for subsequent loin chops. Comparisons between vacuum packaged loins that were stored at 0°C vs. 7°C indicated that storage temperatures of 7°C were more favorable for psychrotrophic bacteria growth and thus resulted in decreased subsequent case-life for chops from these loins. 8 days appears to be a reasonable maximum period for the storage of loins in vacuum packages. Fresh chops that were fabricated 8 days postmortem and displayed immediately exhibited an advantage of 1½1/4 days of increased case-life in comparison to those chops from loins which were vacuum packaged 8 days postmortem, stored under vacuum for 8 days, fabricated and subsequently displayed. The average case-life of fresh chops was 3½1/2 days when stored in a retail case at 0°C. The results of the present study indicate that vacuum packaging of lamb loins may be feasible; however, unless low storage temperatures are maintained and the storage interval is short, the retail case-life of chops will be reduced.     

Survival and Growth of Listeria monocytogenes and Yersinia enterocolitica in Pork Chops Packaged under Modified Gas Atmospheres

Listeria monocytogenes Scott A, serotype 4b, and Yersinia enterocolitica from vacuum-packaged pork were inoculated onto fresh pork chops. Survival and growth were determined in different atmospheres at 4 °C during 35-days. Atmospheres were gas mixtures [20/0/80, 40/ 0/60, and 40/10/50 (CO₂/O₂/N₂)], vacuum and air. In air L. monocytogenes and Y. enterocolitica grew slower than psychrotrophic spoilage flora. In gas atmospheres, Y. enterocolitica grew at the same rate as psychrotrophic spoilage flora and L. monocytogenes grew more slowly. When 10% O₂ was included in the 40% CO₂ mixture, growth was reduced. Vacuum packaging was no more effective than gas mixtures in retarding growth. Modified atmospheres provide an environment in the package that would allow growth of Y. enterocolitica and potentially compromise safety of meat products.     

Color and Oxidative Rancidity of Gamma and Electron Beam-Irradiated Boneless Pork Chops

Color and oxidative rancidity were determined for chilled (3 ± 2°C) and frozen (?17 ± 3°C) boneless pork chops packaged in vacuum or air and irradiated to an absorbed dose of 0, 1.5 or 2.5 kGy (chilled) or 0, 2.5 or 3.85 kGy (frozen) of electron beam or cobalt⁶⁰ irradiation. Irradiation of vacuum-packaged chops produced redder, more stable (color and rancidity) product. More pronounced oxidative rancidity and less stable display color were noted for samples irradiated in aerobic packaging. Irradiation source had varying but limited effects on color and rancidity. Optimum packaging conditions can control color and rancidity changes in boneless chops, thereby enabling irradiation to be a useful intervention technology.