Microbiological and organoleptic qualities of vacuum-packaged ground beef prepared from pasteurized manufacturing beef

Manufacturing beef was pasteurized by immersion in water of 85 degrees C for 60 s, or was not pasteurized before being coarsely ground. The coarsely ground beef was vacuum-packaged and stored at 2 degrees C for up to 6 weeks. Before storage and at weekly intervals, three packs of pasteurized and three of unpasteurized beef were opened. The meat from each pack was finely ground and displayed in two overwrapped packs at 4 degrees C for 3 days after storage for up to 3 weeks, or for 2 days after longer storage times. Samples for microbiological analysis were obtained at the times of preparation of display packs and at the end of display. Displayed meat was assessed daily for colour, discolouration and retail acceptability, and for odour intensity and acceptability at the end of display. Before storage, the numbers of total aerobic bacteria, presumptive pseudomonads and presumptive Brochothrix thermosphacta recovered from pasteurized meat were >1 log unit less than the corresponding numbers recovered from unpasteurized meat, but the numbers of presumptive lactic acid bacteria and presumptive enterobacteria were <1 log unit less from pasteurized than from unpasteurized meat. After all periods of storage and display, the numbers of bacteria recovered from pasteurized and unpasteurized meat at each time were mostly similar. The colour of pasteurized meat was perceived as being paler than that of unpasteurized meat, but discolouration and retail acceptability of pasteurized and unpasteurized meat were perceived as similar at most times. The odours of displayed, pasteurized and unpasteurized meat were perceived to be similar at all times that odours were assessed. The findings indicate that pasteurizing of manufacturing beef to improve the microbiological safety of ground beef would not unacceptability degrade the appearance of the ground product, but that the storage life of ground beef would not be greatly extended by the treatment.     

The display of retail packs of ground beef after their storage in master packages under various atmospheres

Batches of coarsely ground beef trimmings were each divided into four portions. One portion from each batch was vacuum packaged, then stored at -1·5°C. The other portions were finely ground and distributed in retail packs. The retail packs were master packaged under atmospheres of N(2), CO(2) or O(2) + CO(2) (2:1, v/v), then stored at 2°C. The product was assessed after storage times of up to 32 days. For each assessment, a vacuum pack and a master pack of each type, each containing products from the same batch, were withdrawn from storage. The vacuum packaged product was finely ground and distributed into retail packs. The newly prepared retail packs and those from the master packs were displayed in a retail cabinet in which air temperatures averaged 4 ± 2°C. The appearance of the displayed product from each storage packaging was assessed twice daily until it was judged to be unacceptable. At the beginning and end of the display, the product in each pack was assessed for discoloration and off-odours, the chemical states of the muscle pigment at the exposed surface were estimated, and the surface microflora was characterized. The appearance of the product displayed after storage in a vacuum pack, for times up to 32 days, became unacceptable within 48 h. A product stored in any of the master packs for 1 day appeared unacceptable after 6 h of display. The display life of products stored under N(2) or CO(2) was similar to that of the vacuum packaged products when storage times were between 2 and 24 days but the display life was shorter when the storage times were 28 or 32 days. The display life of products stored under O(2) + CO(2) was similar to that of the vacuum packaged product when storage times were 2, 4 or 6 days, but the appearance of products stored under O(2) + CO(2) for 8 days or longer was unacceptable when master packs were opened. Apart from those latter packs, a product was not discoloured when storage packs were opened. However, all products were discoloured, and the metmyoglobin fractions of the surface pigments had increased, when the product was withdrawn from display. The products in all storage packagings developed flora dominated by lactic acid bacteria. The spoiage flora on products stored in vacuum pack or under O(2) + CO(2) did not attain the maximum numbers of 10(7)/g during either storage or display. Those maximum numbers were attained on products stored under N(2) and CO(2) after 16 and 28 days storage respectively. Some products stored under N(2) for 16 days or longer developed moderate or strong off-odours during display that were ascribable to microbial action. Other products developed only slight, non-microbial off-odours during display. Retail-ready packs or ground beef master-packaged under an oxygen-depleted atmosphere could then have a useful storage life of about 30 days in commercial circumstances.     

Consumer acceptance of display packs of beef stored under N2 or CO2 in master packs

Display-packaged samples of beef steak and of ground beef were delivered to the homes of 120 panelists. Each panelist received a set of samples of each meat. Each set consisted of one sample freshly prepared for retail display from vacuum-packaged product, one retail-packaged and then stored in a master pack under N₂ and one retail-packaged and the stored under CO₂. The samples in each set were prepared from the same strip loin or batch of coarsely ground beef and had been stored for between 21 and 23 days at 2°C. The panelists completed questionnaires on the attributes of the meats while they were packaged, when they were unpackaged for cooking, and when they were eaten. The responses to each question were tabulated, and the probability of the χ² statistics was calculated for each table.There were no significant differences in the general acceptability of the steaks from the three storage treatments. Significant numbers of panelists judged that ground beef prepared from vacuum-packaged product was of better colour and had less exudate, but was of poorer eating quality than the product from master packs. However, the majority of panelists did not distinguish between ground beef from the three storage treatments. The consumer responses indicate that controlled-atmosphere master packaging of display packs may offer a means of preserving display-ready beef for times that would allow wide distribution of the product through current commercial systems.     

Prevention of Transient Discoloration of Beef

Oxygen absorbent technology in conjunction with controlled atmosphere packaging(CAP) was used to prevent transient discoloration in master‐packaged beef steaks. Two types of commercial O₂ scavengers were used in the study. The master packs were stored at 1± 0.5 °C. The steaks from master packs were presented in a display‐case for visual evaluation. Reflectance spectra from each steak‐surface were obtained to estimate metmyoglobin content. Steaks packaged without O₂ scavengers showed more discoloration, and had significantly higher proportions of metmyoglobin when compared to steaks with O₂ scavengers, after most storage intervals (p < 0.05). Prevention of metmyoglobin formation was influenced by the number but not the type of O₂ scavenger employed (p > 0.05). Keywords: oxygen scavengers, centralized meat operations, transient discoloration     

Oxymyoglobin formation in meat and poultry

Display-packaged samples of beef steak and of ground beef were delivered to the homes of 120 panelists. Each panelist received a set of samples of each meat. Each set consisted of one sample freshly prepared for retail display from vacuum-packaged product, one retail-packaged and then stored in a master pack under N₂ and one retail-packaged and the stored under CO₂. The samples in each set were prepared from the same strip loin or batch of coarsely ground beef and had been stored for between 21 and 23 days at 2°C. The panelists completed questionnaires on the attributes of the meats while they were packaged, when they were unpackaged for cooking, and when they were eaten. The responses to each question were tabulated, and the probability of the χ² statistics was calculated for each table.

There were no significant differences in the general acceptability of the steaks from the three storage treatments. Significant numbers of panelists judged that ground beef prepared from vacuum-packaged product was of better colour and had less exudate, but was of poorer eating quality than the product from master packs. However, the majority of panelists did not distinguish between ground beef from the three storage treatments. The consumer responses indicate that controlled-atmosphere master packaging of display packs may offer a means of preserving display-ready beef for times that would allow wide distribution of the product through current commercial systems.     

The chilled storage life and retail display performance of vacuum and carbon dioxide packed hot deboned beef striploins

Two cooling regimes that complied with the New Zealand meat hygiene requirement that hot deboned meat be chilled to +7 °C or less within 24 hr of leaving the slaughter floor were evaluated for the production of chilled table meats. Electrically stimulated hot deboned bull beef half striploins were either vacuum or carbon dioxide packed before being cooled in accordance with either Regime 1 (cool at +5 °C for 24 hr, transfer to chiller operating at −1.0 ± 0.5 °C) or Regime 2 (cool at +5 °C for 24 hr, hold at 5 °C for 6 days, transfer to chiller operating at −1.0 ± 0.5 °C). Striploins were removed from −1.0 °C storage 8, 28, 42, 56, 70, 84 and 98 days after slaughter and subjected to microbiological, tenderness, sensory and retail display performance evaluations.

Both Regimes 1 and 2 produced meat of acceptable mean tenderness, 8 kgF (MIRINZ Tenderometer) in either vacuum or carbon dioxide packs within 28 and 8 days of slaughter, respectively. However, 70 days after slaughter the first signs of over-ageing became apparent. Steaks from Regimes 1 and 2 maintained acceptable visual appearance during retail display at 5 °C for 48 hr and 24 hr, respectively. After these times, the product was judged by the panel to be unacceptable because of its dull dark lean tissue and grey to green discoloration of the fat. Poor colour stability during retail display was mirrored by deterioration of sensory attributes, particularly aroma which is indicative of incipient spoilage. While carbon dioxide packaging in combination with Regime 1 offered an initial microbiological advantage over vacuum packaging, this advantage was not, however, carried over into retail display.

Poor colour and sensory stability during retail display suggest that chilled table cuts derived from hot deboned bull beef are more suited to the Hotel-Restaurant-Institutional (HRI) trade than supermarket retailing. To serve the HRI, vacuum packed hot deboned bull beef primal cuts processed by Regime 1 appear to be the combination of choice. This combination would enable commercial processors to produce quality table beef with a chilled storage life of up to 70 days.     

Temperatures and ages of packs of beef displayed at stores in Canada

The surface temperatures and ages of 1703 retail packs of chilled, raw beef in cut or ground forms on display in a case at each of 41 Canadian retail stores were determined. For each case, data were collected from packs at pre-selected positions in the case. Data for a position were not collected if a pack of beef was not present there. Data were collected at a different time on each of 3 days, with each store being visited within l h after opening and l h before closing and between 12:00 and 14:00 h, without regard to the operation of the case defrosting cycle. The median temperatures of pack surfaces were <4?°C, between 4 and 7?°C, and >7?°C at 24, 16 and one stores, respectively. The maximum temperatures were <4?°C, between 4 and 7?°C and >7?°C at 3, 18, and 20 stores, respectively. The median ages were 0 day, 1 day, and 2 or 3 days at 19, 17 and 5 stores, respectively. The maximum ages were ?2 days, between 2 and 4 days, and >4 days at 21, 14 and six stores, respectively. Temperatures were generally lower at the backs than at the fronts of cases, on upper than on bottom shelves, and within than on the tops of stacks of packs. Temperatures were apparently not affected by the positions of packs along the lengths of cases, and did not differ at different times of day.     

RETAIL APPEARANCE OF ELECTRICALLY STIMULATED BEEF

Top round steaks (adductor) and ground beef from the top round were obtained from both sides of ten U.S. Choice carcasses. Left sides were electrically stimulated (ES) with 17 impulses (1.8 set duration, 1.8 set interval) of 550 volts of alternating current at 5 amps. Steaks and ground beef from top rounds from nonstimulated right sides served as control (CON) samples. Steaks and ground beef were displayed under simulated retail conditions for 4 and 3 days, respectively. Steaks were weighed prior to and at the termination of the display interval to determine percentage weight loss. Samples for microbiological evaluation were obtained prior to and at the termination of the display interval. No significant differences were observed for muscle color, surface discoloration or overall appearance for samples of ground beef at any retail display interval. With one exception, muscle color was brighter and surface discoloration was reduced for round steaks from ES sides. Few significant differences in overall appearance were observed between ES and CON samples during the display period. No significant differences between ES and CON samples were observed for bacterial counts either initially or at the termination of the display period for either steaks or ground beef samples. Percentage weight loss was not significantly different between ES and CON steaks. These data suggest that electrical stimulation may enhance, and certainly does not detract from, the appearance of round steaks displayed under retail market conditions.     

The storage life of beef and pork packaged in an atmosphere with low carbon monoxide and high carbon dioxide

Ground beef, beef loin steaks and pork chops were packaged in modified atmospheres of 0.4% CO/60% CO(2)/40% N(2) and 70% O(2)/30% CO(2). In addition ground beef was packaged in clipped chub packs, beef loin steaks were vacuum packaged, and pork chops were packaged in an atmosphere of 60% CO(2)/40% N(2) with each pack containing an O(2) absorber. The packs were stored in the dark at 4 or 8°C for up to 21 days. Meat in 0.4% CO/60% CO(2)/40% N(2) had a stable bright red colour that lasted beyond the time of spoilage. The storage lives in this gas mixture at 4°C, as limited by off-odours, were 11, 14 and 21 days for ground beef, beef loin steaks and pork chops, respectively. The 70% O(2)/30% CO(2) atmosphere resulted in an initially bright red to red colour of the meat, but the colour was unstable and off-odours developed rapidly. The off-odours probably were caused by Brochothrix thermosphacta, which grew in all meat types, or by pseudomonads in ground beef. Meat stored in chub packs, vacuum packs or 60% CO(2)/40% N(2) with an O(2) absorber developed off-odours and microflora similar to those of meat in 0.4% CO/60% CO(2)/40% N(2), but with less acceptable appearances. These results show that a low CO/high CO(2) atmosphere is effective for preserving retail-ready meat. ?     

Role of peroxyacetic acid, octanoic acid, malic acid, and potassium lactate on the microbiological and instrumental color characteristics of ground beef

Abstract: This study evaluated the effects of peroxyacetic acid (PAA), malic acid (MA), octanoic acid (OA), and potassium lactate (KL) followed by mixing with trisodium phosphate (TSP) and an ultra‐chilled CO₂ snow shower on microbial counts of Escherichia coli (EC), coliform (CF), aerobic plate count (APC), and Salmonella Typhimurium (ST) on inoculated beef trimmings and the instrumental color attributes of the resultant ground beef. Beef trimmings inoculated with EC and ST were treated with either 0.02% PAA; 2% MA; 0.04% OA; or 2% KL, followed by mixing with 10% TSP and rapid chilling with CO₂ snow shower. Treated trimmings were then ground, packaged, displayed under simulated retail conditions, and sampled on days 1, 2, 3, 5, and 7 for microbial counts and instrumental color characteristics. PAA, MA, OA, and KL reduced (P < 0.05) the microbial counts of EC, CF, APC, and ST during display. Among treatments, OA was most effective on EC, CF, ST, and APC during retail display. Chilling beef trimmings with CO₂ improved instrumental color characteristics of the produced ground beef but made little difference in reducing microbial counts during display. During retail display, ground beef produced from beef trimmings treated with antimicrobials tended to maintain redness, myoglobin redox form stability (630 nm/580 nm), and overall instrumental color characteristics. Practical Application: This research provides a practical and cost‐effective decontamination technology for beef processors that can be immediately implemented in the ground beef production chain. Using antimicrobial intervention coupled with rapid chilling could benefit the meat industry by preserving the quality attributes of ground beef during retail display under aerobic packaging environment.     

Type of packaging affects the colour stability of vitamin E enriched beef

Colour stability is a very important parameter for meat retail display, as appearance of the product is the deciding factor for consumers at time of purchase. This study investigated the possibility of extending appearance shelf-life through the combined use of packaging method (overwrapping - OVER, modified atmosphere - MAP, vacuum skin packaging - VSP and a combination of modified atmosphere and vacuum skin packaging - MAPVSP) and antioxidants (vitamin E enriched beef). Retail attributes (appearance, lean colour, % surface discolouration), as well as colour space analysis of images for red, green and blue parameters were measured over 18days. MAPVSP provided the most desirable retail appearance during the first 4days of retail display, while VSP-HB had the best colour stability. Overall, packaging type was more influential than α-tocopherol levels on meat colour stability, although α-tocopherol levels (>4μgg(-1) meat) had a protective effect when using high oxygen packaging methods.     

The retail display life of steaks prepared from chill stored vacuum and carbon dioxide-packed sub-primal beef cuts

Chilled striploins and cube rolls from ten Australian steers (grain-fed for 150 days) were trimmed of external fat and cut transversely into portions approximately 10 cm thick, each weighing between 750 and 1000 g. These 'retailer-ready' cuts were each wrapped in drip saver pads and slid inside a plastic sleeve before being individually placed into a clear plastic high oxygen barrier film, metallized film or conventional vacuum bag. Cuts in clear plastic and metallized film packs were packaged in an oxygen-free saturated carbon dioxide atmosphere (CO(2)-CAP), those in vacuum bags were conventionally vacuum-packed. All packs were returned to the chiller for further cooling. After 24 hr, half the clear plastic and metallized CO(2)-CAP packs were carbon dioxide master-packed in groups of eight. Retailer-ready cuts in both clear plastic and metallized film single unit and master-packed CO(2)-CAP packs were air freighted to New Zealand and sea freighted to Japan for assessment. The control vacuum packs were all consigned to New Zealand. Assessments in both countries after 39-89 days storage at between 0 °C and -1.0 °C indicated that fat colour stability limited the retail display life of steaks cut from meat in these retailer-ready packs to approximately 48 hr. In this regard, meat from single unit CO(2)-CAP, master pack CO(2)-CAP and vacuum packs performed similarly. Lean meat colour and sensory attributes remained acceptable for up to 48 hr after displayed product was rejected because of grey-green fat discoloration. The microbiological status of retailer-ready cuts removed from CO(2)-CAP packs after 89 days chilled storage was superior to that of cuts from vacuum packs. Clear plastic and metallized film CO(2)-CAP packs performed comparably.     

Continued inhibitory effect of carbon dioxide packaging on Listeria monocytogenes and other microorganisms on normal pH beef during abusive retail display

Beef steaks of normal pH (5.3–5.5) were inoculated with Listeria monocytogenes , individually packaged in saturated carbon dioxide atmosphere packaging (SCAP) for <3 h or 5 or 8 weeks or in vacuum packaging (VP) for <3 h, and stored at −1.5°C. After each storage period, 27 individually packaged steaks were removed from their storage packs, overwrapped and placed on retail display under conditions simulating gross temperature abuse (12.25°C). Other steaks were removed from their storage packs and rinsed to remove L. monocytogenes cells, which were re-inoculated onto freshly cut beef steaks to simulate cross-contamination. These crosscontaminated steaks were overwrapped and also subjected to abusive display. Meat pH did not change significantly during storage or retail display. During the retail display of steaks previously stored in SCAP, the lag phase of aerobic bacteria and lactic acid bacteria was longer after prolonged storage compared to short (<3 h) exposure to carbon dioxide. For the same samples, L. monocytogenes failed to grow during retail display or grew only slightly after a prolonged lag phase (>75 h), even after only brief exposure time (<3 h) to carbon dioxide. In contrast, with cross-contaminated steaks, when the inocula had been exposed to SCAP or VP for a short time (<3 h) the L. monocytogenes lag phase was shorter (<20 h). Inocula from steaks stored in SCAP for 5 or 8 weeks did not grow on the cross-contaminated steaks. It is concluded that exposure of both the beef substrate and the L. monocytogenes inoculum to carbon dioxide during prolonged chilled storage does not increase the risk of growth of L. monocytogenes when that meat is subsequently placed on retail display, nor is there a large risk of growth of L. monocytogenes where cross-contamination from SCAP stored raw beef to fresh raw beef occurs prior to retail display.     

Effects of meat pH and the initial numbers of spores of Clostridium estertheticum on the development of blown pack spoilage of vacuum‐packaged beef

To understand how the initial numbers of Clostridium estertheticum spores on, and the concentration of glucose in meat affect the development of blown pack spoilage, beef of pH ≤5.6 and of pH ≥5.8 was inoculated with the spores at various numbers, vacuum‐packaged and stored at 2 °C. For beef of pH ≤5.6, the volumes of packs inoculated with ≤10 spores did not change; and packs inoculated with ≥30 spores started swelling after 35 days, and the rate of volume increase increased with increasing number of inoculated spores. For beef of pH ≥5.8, packs inoculated 0, three or ten spores slackened, and packs inoculated with ≥30 spores became swollen at the end of storage, but to a much lesser degree than the corresponding packs of beef of pH ≤5.6. Glucose was reduced by 21 mm and depleted in the rinse fluids from swollen packs of beef of pH ≤5.6 and of pH ≥5.8, respectively.     

The influence of storage temperature and storage time on color stability,retail properties and case-life of retail-ready beef

Steaks from three different muscles were either vacuum or carbon dioxide packed and stored for up to 24 weeks at three different storage temperatures (−1.5, 2, or 5 °C). Following storage, they were displayed for up to 30 h. CIE color coordinates, the oxidative states of myoglobin and pH were measured and muscle color, surface discoloration, retail appearance, and odor were evaluated prior to storage and during display (0, 1, 2, 4, 6, 24 and 30 h), and/or immediately prior to and following display. Prior to display, pH was negatively related to duration of storage, and samples stored at −1.5 °C had the highest and samples stored at 5 °C, had the lowest pH. Perception of muscle color was influenced by duration of storage and display, but lower storage temperatures appeared to produce a stabilizing effect. Both lightness of muscle color and deoxymyoglobin content were apparently not influenced by storage temperature or duration of storage or display. Both oxymyoglobin (OMB) and redness, as defined by CIE a* values, were lost progressively during storage and display, but this loss was progressively lower as storage temperature decreased. Yellowness of muscle color, as defined by CIE b* values, generally decreased as storage was prolonged, and this decrease was observed more quickly at higher storage temperatures. Surprisingly, b* values were not related to duration of display. Both surface discoloration and metmyoglobin (MMB) content increased progressively during storage and display. Samples stored at 5 °C displayed the most surface discoloration, while samples stored at −1.5 °C contained the least MMB and displayed the least surface discoloration. Retail appearance deteriorated progressively during storage in all samples stored at 2 and 5 °C and in samples stored at −1.5 °C, which were displayed for at least 24 h. Retail appearance also deteriorated progressively during display in samples stored at −1.5 and 2 °C for three weeks or longer and in samples stored at 5 °C for 0 to 15 and 24 weeks. In unstored samples, samples to be stored at −1.5 °C generally received the lowest retail appearance scores, but after prolonged storage and display, samples stored at −1.5 °C received higher retail appearance scores than samples stored at 5 °C, particularly when samples were stored for 12 weeks or longer and displayed for 1 h or more. Odor deteriorated progressively during storage when measured both prior to display and after 30 h of display. In samples stored for three weeks or longer, samples stored at −1.5 °C generally received the lowest odor scores and were perceived to have the least prevalent off-odors. Samples stored at −1.5 °C maintained a retail case-life of 30 h, when stored for up to 17 weeks, while samples stored at 2 and 5 °C maintained a retail case-life of 30 h, when stored for only eight and seven weeks, respectively. Consequently, storage life can be more than doubled by storage at subzero temperatures (−1.5 °C).     

Shelf life of case-ready beef steaks (Semitendinosus muscle) stored in oxygen-depleted master bag system with oxygen scavengers and CO2/N2 modified atmosphere packaging

This study aims to evaluate the stability of beef from Semitendinosus muscle packaged in oxygen permeable wrapped-tray units and stored in a master bag system, with and without oxygen scavengers. Changes in the atmosphere composition, microbiological indexes, myoglobin forms and color parameters were monitored during the storage in master bag, blooming and display life. The presence of scavengers reduced rapidly the oxygen concentration and maintained it at values not detectable instrumentally. Within few days of storage in master bags, the resolution of the transient discoloration was completed and the meat quality was maintained over the anoxic storage. After the removal from master bags meat bloomed completely reaching OxyMb level and Chroma values higher than those on fresh meat at t₀. During 48 h of display life at 4 °C, quality attributes had a decay slower than samples stored traditionally in air. Without scavengers the oxygen caused the irreversible discoloration within 7 days, due to the formation of metmyoglobin on the surface.     

Carbon dioxide flavour taint in modified atmosphere packed beef steaks

The objective of this study was to investigate the effects of carbon dioxide (CO₂) concentration (100mlCO₂/100 ml pack gas, 50mlO₂:20mlCO₂:30mlN₂/100 ml pack gas, 70mlO₂:30mlCO₂/100 ml pack gas and 80mlO₂:20mlCO₂/100 ml pack gas) on the sensory quality of modified atmosphere packed (MAP) beef steaks (M. longissimus thorasis). Steaks were stored at 4 °C for 15 days and tested for CO₂ off flavour, lipid oxidation flavour, juiciness and tenderness (up to day 12) of the resulting cooked meat as well as pH, colour, drip loss, and cooking loss. One steak from each of the experimental treatments was taken immediately from the respective MA packs and cooked before serving straight to panellists. A second steak from each of the pack was treated similarly, but left in ambient air for 30 min to let dissolved CO₂ dissipate from the meat prior to cooking and serving. The 50mlO₂:20mlCO₂:30mlN₂/100 ml pack gas treatment displayed a significantly (P ≤ 0.05) and negative correlation to CO₂ flavour which was even more pronounced for samples where the CO₂ was allowed to dissipate (Dis, P ≤ 0.001). Thus this packaging gas combination could be used to optimise the sensory quality of MAP steak. Additionally opening retail MAP packs up to 30 min prior to cooking has a benefit towards the perceived sensory quality of the cooked product.     

Effect of Freezing Temperature on Weight Loss and Quality Characteristics of Beef Liver, Kidney, Heart, and Tongue

Temperature at which variety meats were frozen (—126°C, -34°C, - 18°C, -8°C) had little effect on weight loss, color, appearance, odor or tenderness of beef liver, kidney, heart and tongue, before, during or after thawing and retail display. Freezing of variety meats at -34°C, as opposed to -126°C: (a) appeared to minimize weight losses associated with thawing, retail display and/or application of pressure; (b) did not materially affect color of meat surfaces during retail display; (c) might improve overall appearance enough to increase retail caselife; and (d) did not affect off-odor incidence or tenderness of variety meats.     

The display life of retail-packaged beef steaks after their storage in master packs under various atmospheres

Beef strip loins were divided into four portions. One portion of each loin was vacuum-packaged and then stored at −1·5°C. The other portions were each divided into three steaks, which were retail-packaged. The retail packs were master-packaged under atmospheres of N₂, CO₂, or O₂ + CO₂ (2 : 1, v/v) and then stored at 2°C. Product was assessed after storage times of up to 60 days. At each assessment, a vacuum pack and a master pack of each type, each containing product from the same loin, were withdrawn from storage. The vacuum-packaged product was cut into three steaks, which were retail-packaged. The newly prepared retail packs and those from the master packs were displayed in a retail cabinet, at air temperatures that averaged between 3 and 5·7°C, and were assessed twice daily until the product was judged to be unacceptable. When first assessed, steaks cut from vacuum-packaged product were generally considered desirable, with little metmyoglobin in the surface pigment, although the edges of same steaks were discoloured. Steaks stored under N₂ or CO₂ for 4 days or less were only slightly desirable at best, with metmyoglobin forming relatively large fractions of the surface pigment. However, after storage under N₂ or CO₂ for 6 days or more, metmyoglobin fractions were low, and the steaks bloomed to a desirable red colour. Steaks stored under O₂ + CO₂ had lower metmyoglobin fractions, and were desirable after storage for up to 8 days. However, the fractions of metmyoglobin increased, and steaks were judged to be less desirable after longer storage times. Steaks stored under O₂ + CO₂ for 20 days were unacceptable. After storage, the numbers of bacteria on steaks from vacuum packs and N₂, CO₂, and O₂ + CO₂ atmospheres were, respectively, <10⁴, <10⁶, <10⁵, and <10⁴ CFU/cm². The flora from steaks stored under CO₂ were composed wholly of lactic acid bacteria. Other flora were dominated by lactic acid bacteria, but contained fractions of enterobacteria and/or Brochothrix thermosphacta.

The appearance of product from vacuum packs generally was unacceptable after 72 h of display. The display life of steaks stored under N₂ or CO₂ was shorter than that of the product from vacuum packs when product was stored for 2 days or less, or 46 days or more. After other storage times, the product from vacuum packs or master packs with N₂ or CO₂ atmospheres had a similar display life. The display life of product stored under O₂ + CO₂ was similar to that of product from vacuum packs or CO₂ or O₂ + CO₂ was similar to that of product from vacuum packs after storage times of 8 days or less but was shorter after storage times of 12 or 16 days. The flora on displayed product from vacuum packs or CO₂ or O₂ + CO₂. atmospheres did not attain the maximum number of 10⁷ CFU/cm². and the product did not develop off-odours of microbial origin. However, numbers of 10⁷ CFU/cm² were approached or attained during display of product stored under N₂ for 28 days or longer, and some of that product developed moderate off-odours. It then appears that, under temperature regimes that are common in commercial practice, retail-packaged strip-loin steaks with a display life of 2 days or longer can be obtained from master packs after storage periods of up to about 2, 4, or 7 weeks, respectively, with master-pack atmospheres of O₂ + COPin2 (2 : 1, v/v), N₂, or CO₂.     

Evaluation of microsatellites as a potential tool for product tracing of ground beef mixtures

Microsatellite genotyping was evaluated as a potential tool for DNA-based tracing of ground beef product. DNA from mixtures containing different numbers of individuals was analysed with a set of cattle microsatellite markers frequently used for parentage testing. As samples contained DNA from several animals, the microsatellite markers showed multiple peaks. The method could distinguish between mixtures containing equal amounts of meat from three different individuals, meat from three individuals mixed in different proportions, ground beef mixtures purchased in different cities, and different batches of ground beef patties. Limitations occurred when batches contained large numbers of individuals (>10) and different batches used meat from the same individuals. We conclude that DNA microsatellites may be useful for DNA traceability of ground beef mixtures prepared from less than 10 individuals, but where larger numbers of animals contribute to a mixture the method is not consistently accurate.