Shelf life extension of beef retail cuts subjected to an advanced vacuum skin packaging system

Vacuum skin packaging (VSP) is a new and promising technology that includes the instantaneous heating of the upper packaging film immediately before its descent over the meat surface. In the present paper we evaluated this technology for the packaging of a wide variety of beef retail cuts and compared this with traditional vacuum packaging (TVP) performed in parallel. Shelf-life and quality evolution was estimated by analysing three spoilage bacterial groups, an ubiquitous psychrotrophic food pathogen, and three biochemical and physico-chemical attributes throughout 40 days of storage at 4 °C. Statistically-significant lower microbial counts were obtained for all microbial parameters and meat types. The VSP lot exhibited lower pH. This, however, involved a lower water holding capacity and a higher degree of firmness, the latter indicating a limited tenderisation process in the VSP batch. Extended aging times in the carcasses were studied to improving the tenderness of VSP samples. The extension of the aging process prior to VSP may be useful for improving the tenderness of certain meat types and to improve the sensory quality of meat cuts processed under this system.     

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.     

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.     

Effect of acid resistance of Escherichia coli O157:H7 on efficacy of buffered lactic acid to decontaminate chilled beef tissue and effect of modified atmosphere packaging on survival of Escherichia coli O157:H7 on red meat.

The present study examined the effect of pH-independent acid resistance of Escherichia coli O157:H7 on efficacy of buffered lactic acid to decontaminate chilled beef tissue. A varied level of acid resistance was observed among the 14 strains tested. Eight strains were categorized as acid resistant, four strains as acid sensitive, and two strains demonstrated acid-inducible acid resistance. The survival of an acid-resistant (II/45/4) and acid-sensitive (IX/8/16) E. coli O157:H7 strain on chilled beef tissue treated with 1 and 2% buffered lactic acid, sterile water, or no treatment (control) was followed. A gradual reduction of E. coli O157:H7 was noticed during the 10 days of storage at 4 degrees C for each of the treatments. Decontamination with 1 and 2% buffered lactic acid did not appreciably affect the pathogen. Differences in the pH-independent acid resistance of the strains had no effect on the efficacy of decontamination. The effect of modified atmosphere packaging (MAP) on survival of E. coli O157:H7 in red meat was also studied. MAP (40% CO2/60% N2) or vacuum did not significantly influence survival of E. coli O157:H7 on inoculated sliced beef (retail cuts) meat compared to packing in air. The relative small outgrowth of lactic acid bacteria during storage under vacuum for 28 days did not affect survival of E. coli O157:H7. Neither lactic acid decontamination nor vacuum or MAP packaging could enhance reduction of E. coli O157:H7 on beef, thus underlining the need for preventive measures to control the public health risk of E. coli O157:H7.     

Modification of in-pack conditions to extend the storage life of vacuum packaged lamb

High pH (>5·9) lamb loins from a research abattoir were subjected to differing packaging treatments to determine whether package modification could reliably extend the storage life of chilled lamb cuts beyond that attained by cuts vacuum-packaged in film of low gas permeability, as in current commercial practice. Treatments applied were carbon dioxide flushing or addition of a citrate buffer (pH 4·8), a 5% lactic acid solution or a Lactobacillus inoculum (plastic packs only) and packaging in a plastic film of moderately low oxygen permeability (140 cc/m(2)/24 h at 25°C and 90% relative humidity) or in a foil laminate of immeasurably low oxygen permeability. After 12 weeks' storage at -0.5°C, the cuts packaged in the plastic film were spoiled by off-odours produced by enterobacteria, except for inoculated cuts, which, instead, had developed unacceptable dairy flavours. In contrast, cuts packaged in foil laminate developed floras of lactobacilli that had not caused spoilage after 12 weeks, and meat colour was much improved by the exclusion of oxygen. Loin cuts from a commercial packaging operation were packaged in a shrinkable plastic film of low oxygen permeability (30 to 40 cc/m(2)/24 h at 25°C and 90% relative humidity), in foil laminate, or in foil laminate after the addition of 5% lactic acid solution. For the first 6 weeks, cuts were stored in a commercial chiller nominally operating at 0°C; subsequently, they were held in a laboratory chiller at -0.5°C. Some cuts packaged in the shrinkable plastic were spoiled after 9 weeks' storage and all were spoiled at 12 weeks, because of off-flavours produced by enterobacteria. All cuts packaged in the foil laminate were very acceptable at 9 weeks but most were spoiled by off-flavours at 12 weeks. Most cuts treated with lactic acid and packaged in foil laminate were unspoiled after 12 weeks. The packaging requirements indicated to be necessary for reliable extension of the storage life of vacuum packaged lamb are discussed.     

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.     

Centralized packaging of retail meat cuts: a review.

Centralized packaging of retail meat cuts is growing more popular because of its economies and potential to maintain quality, enhance safety, and extend the shelf life of fresh meat. Requirements for optimizing shelf life of centrally prepared retail cuts for periods up to 15 weeks are slightly different from those needed to extend the shelf life of fresh, chilled meat. Chilled meat primarily deteriorate at the cut or uncut muscle surface. In long-term storage, primal cuts are placed in an atmosphere saturated with carbon dioxide and containing very low residual oxygen. These cuts are held at -1.5+/-0.5 degrees C. When the meat is removed, it is fabricated into retail or food service cuts. New fresh surfaces are created in the process, revitalizing the meat's appearance. After being prepared for retail display, the meat normally has four more days of shelf life. Depending on the meat species, shelf life is usually limited by development of undesirable organoleptic changes, usually defects in color, which are independent of microbial presence. The microbes consist of a lactic acid bacterial population that maximizes under storage conditions at about 10(8) CFU/cm2 well before shelf life ends. Circumstances are different with centralized distribution of retail-ready fresh meat. The wholesale storage period following initial packaging of the retail cuts is about 20 to 30 days. Prepared products must withstand retail display for up to 2 days without further manipulation of package contents. Retail packages are simply moved from their storage container (usually a unit or overwrap containing a modified atmosphere) to retail display, where desirable meat color develops upon exposure to air. Three gas atmospheres have some potential to satisfy storage needs for centralized distribution of retail-ready packages: 100% CO2, 100% N2, or 70% N2 + 30% CO2. Shelf life is limited by undesirable changes in surfaces exposed at initial packaging, caused by growth of psychrotrophic bacteria. If 100% CO2 is used, these are all lactic acid bacteria (LAB). Therefore, initial bacterial numbers on the meat and storage temperature become critical to success. The most attractive storage option is 100% CO2 used at - 1.5 +/-0.5 degrees C. This review presents the reason for that recommendation, along with basic concepts of meat chemistry, a discussion of modified atmosphere packaging, meat microbiology, and current results with simulated centralized packaging of retail-ready meats.     

Effectiveness of gelatine and chitosan spray coating for extending shelf life of vacuum-packaged beef

The effects of applying gelatine (10%) and chitosan (1%) as spray coatings to extend the shelf life of vacuum-packaged beef was studied and compared against uncoated vacuum-packaged beef for up to 21 days. The impact of edible coatings on the water-holding properties of vacuum-packaged beef was investigated by LF-NMR together with physicochemical, microbiological and sensorial assessments. Chitosan coating significantly reduced lipid oxidation by ~30% to 36% and inhibited the growth of lactic acid bacteriaby ~ 1–2 log cfu compared to purge collected from uncoated and gelatine coated samples. It did not negatively affect the meat pH, tenderness and colour, and exhibited significantly higher sensorial acceptance compared to beef coated with gelatine. Both coatings were not effective in reducing purge loss in vacuum-packaged meat as the storage time increased. This study suggests that chitosan spray coating could be easily adapted to industrial plant settings as an antioxidant and antimicrobial application before carrying out meat vacuum packaging operation.     

Postpackage pasteurization of ready-to-eat deli meats by submersion heating for reduction of Listeria monocytogenes

A mixed cocktail of four strains of Listeria monocytogenes was resuspended in product purge and added to a variety of ready-to-eat (RTE) meat products, including turkey, ham, and roast beef. All products were vacuum sealed in shrink-wrap packaging bags, massaged to ensure inoculum distribution, and processed by submersion heating in a precision-controlled steam-injected water bath. Products were run in pairs at various time-temperature combinations in either duplicate or triplicate replications. On various L. monocytogenes-inoculated RTE deli meats, we were able to achieve 2- to 4-log cycle reductions when processed at 195 degrees F (90.6 degrees C), 200 degrees F (93.3 degrees C), or 205 degrees F (96.1 degrees C) when heated from 2 to 10 min. High-level inoculation with L. monocytogenes (approximately 10(7) CFU/ml) ensured that cells infiltrated the least processed surface areas, such as surface cuts, folds, grooves, and skin. D- and z-value determinations were made for the Listeria cocktail resuspended in product purge of each of the three meat categories. However, reduction of L. monocytogenes in product challenge studies showed much less reduction than was observed during the decimal reduction assays and was attributed to a combination of surface phenomena, including surface imperfections, that may shield bacteria from the heat and the migration of chilled purge to the product surface. The current data indicate that minimal heating regimens of 2 min at 195 to 205 degrees F can readily provide 2-log reductions in most RTE deli meats we processed and suggest that this process may be an effective microbial intervention against L. monocytogenes on RTE deli-style meats.     

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.     

Effect of Co2 or vacuum packaging on normal and high pH meat shelf-life

In order to extend meat shelf-life, normal-pH and high-pH beef steaks were packaged under vacuum or in 100% C 0 2 atmosphere. Microbiological, colour (L*, a*, b*)
and reflectance (R630-R580 values) characteristics were measured.
After packaging under vacuum, Enterobacteriaceae, Brochothrix thermosphacta and Pseudomonas numbers were 10- to 100-fold greater on high-pH meat than on
normal-pH meat.
Packaging under C 0 2 improved the shelf-life of meat, particularly that of high-pH meat up to 42 days. For both high- and normal-pH meats, the bacterial flora was
composed only of lactic acid bacteria. Normal-pH meat in C 0 2 atmosphere and vacuum packaging had a purple colour. After C02-pack opening the meat colour
became bright red and R630- R580 measurements were high, whereas after opening of vacuum packaging R630-R580 decreased rapidly with increasing aerobic exposure.
High-pH meat became paler with increasing storage time in C02. Simultaneously R630-R580 values increased and the pH fell. In addition it lost less exudate and
oxidized less in air than the normal-pH meat under the same conditions.     

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.     

Combined effects of packaging atmosphere and lactic acid on growth and survival of Listeria monocytogenes in crayfish tail meat 4 degrees C.

The effect of lactic acid on growth and survival of Listeria monocytogenes in crayfish tail meat stored under refrigeration and various gas environments was investigated. Frozen crayfish tail meat was thawed overnight, autoclaved, cooled, and inoculated with approximately 4 log colony-forming units (CFU) of a mixed-strain (Scott A and F5027) L. monocytogenes culture per gram of meat. Inoculated samples were blended with 0, 0.5, 1.0, 1.5, or 2.0% lactic acid and packaged under air, vacuum, or modified atmosphere (74.8% CO2, 10.4% O2, and 14.8% N2) and stored at 4 degrees C for 20 days. Results demonstrated that modified atmosphere packaging inhibited the growth of L. monocytogenes more than air and vacuum packaging at 0 and 1% lactic acid. Microbial counts declined steadily in crayfish tail meat treated with 2% lactic acid, with no differences among the packaging atmospheres. The lag phase was extended by 8 days in samples treated with 1% lactic acid and modified atmosphere compared to that in air or vacuum packaging. Overall, the combination of lactic acid and modified atmosphere had the greatest potential to prevent growth of L. monocytogeines.     

Use of biodegradable films for fresh cut beef steaks packaging

A comparative study on the use of biodegradable films for fresh cut meat packaging is presented. Beef steaks were packaged using three different films: polyvinyl chloride (PVC), which is actually used to package this food product, a biodegradable polymeric film composed of starch and polyester and a biodegradable film composed of a mixture of three biodegradable polyesters. The packaged beef steaks were stored at 4 and 15 °C to simulate actual storage conditions and thermal abuse, respectively. Colour, total viable counts as well as spoilage microorganism counts were monitored over a period of 6 days. No substantial differences were observed among the beef steaks packaged using the three investigated films, suggesting that biodegradable films, such as those used in this investigation, could be advantageously used to replace PVC films in packaging of fresh processed meat, reducing in this way the environmental impact of polymeric films.     

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.     

Influence of packaging method and length of chilled storage on microflora, tenderness and colour stability of venison loins

Sections of venison loins (LD) weighing approximately 300 g from 12 red deer (Cervus elaphus) were packaged using four packaging methods: (a) vacuum packaging, (b) CO₂ flushed using a nylon containment film (CO₂-Nylon), (c) CO₂ flushed using an ultra-high barrier containment film (CO₂-UHB), and (d) CO₂ flushed using an aluminium foil laminate containment film (CO₂-Foil) and stored for 1, 6, 12 and 18 weeks at 0°C. Meat pH values were lower in all CO₂ flushed meat packages (P<0·05) than in vacuum packaged meat. Lactic acid bacteria and total anaerobic counts increased over storage time in all packages regardless of treatment up to values of log₁₀ 7·8 and 7·6 g⁻¹, respectively. Tenderness tended to increase as meat was stored for up to 18 weeks. Colour scores taken during simulated retail display indicated that colour deteriorated more rapidly when meat was stored for 12 and 18 weeks than for 1 and 6 weeks. Vacuum packaging and gas flushing (CO₂-Foil) resulted in higher initial colour scores than venison packaged in the CO₂-Nylon or CO₂-UHB materials. Venison stored for 18 weeks also exhibited a higher proportion of packages containing off odours, lower flavour desirability and flavour intensity scores as well as higher off flavour scores than meat stored for shorter times. The implications of these effects are discussed. Although there were few significant differences in microbial growth and sensory characteristics due to packaging method or containment film, vacuum packaging appeared to be the most economic and produced meat of better colour stability.     

The effects of postmortem product handling and aging time on beef palatability

The effects of postmortem handling and aging time were investigated on the palatability attributes of beef at weekly intervals up to four weeks using both an experienced laboratory panel and a highly trained, flavour/texture profile panel. The presence of bone in intact meat cuts reduced both cooking times and cooking losses, irrespective of postmortem handling treatment. Bone-in (intact), vacuum packaged meat cuts were more tender initially and overall and had less perceived connective tissue and lower shear force values than conventionally aged controls and controlled atmosphere, boneless, display-ready cuts. Boneless, vacuum packaged cuts also were more tender overall than controlled atmosphere, boneless, display-ready cuts. Both bone-in (intact) and boneless, vacuum packaged cuts were rated higher in juiciness and flavour desirability than conventionally aged controls and controlled atmosphere, boneless, display-ready cuts. Bone-in (intact), vacuum packaged cuts were also perceived to have a more intense beef flavour than cuts receiving any other postmortem handling treatment. Consequently, both bone-in (intact) and boneless vacuum packaged cuts were rated higher in overall palatability than conventionally aged controls and controlled atmosphere, boneless, display-ready cuts. However, detailed flavour and texture profile analysis indicated steaks could be aged for up to four weeks without influencing the overall quality of the flavour or texture, irrespective of postmortem handling treatment. Both initial and overall tenderness improved progressively and Warner–Bratzler shear force values and the amount of perceived connective tissue decreased progressively as postmortem storage was extended. In addition, both flavour intensity and desirability increased progressively with the extension of postmortem aging. Consequently, postmortem aging appeared to be beneficial to all palatability attributes, except juiciness. Therefore, steaks can be aged for up to four weeks to obtain substantial improvements in overall texture, without adversely affecting overall flavour quality, irrespective of postmortem handling treatment.     

Storage Changes of Fresh and Pasteurized Blue Crab Meat in Different Types of Packaging

We investigated pasteurization and storage of blue crabmeat in steel cans, aluminum cans, plastic cans, nonbarrier pouches, and barrier pouches. Fresh meat was packed in copolymer polyethylene/polypro-pylene cups, Saran® over-wrapped or vacuum skin packaged polystyrene trays, and nonbarrier pouches. Meat pasteurized in plastic and aluminum cans had better sensory and microbiological quality and longer shelf life than meat packed in steel cans. Oxygen-barrier pouches had the lowest quality and shortest shelf life. Nonbarrier pouches had product with quality similar to meat in steel cans, but with an extended shelf life. No packaging materials improved the microbiological shelf life of freshly cooked meat. Vacuum skin packaging resulted in improved sensory qualities of freshly cooked and picked meat.     

黑木耳多糖/壳聚糖可食性复合膜的制备及对鲜牛肉的保鲜效果

为了开发具有优良保鲜效果的可食性复合膜,以黑木耳多糖（Auricularia auricular polysaccharide,AAP）和壳聚糖（chitosan,CS）为原料,通过测定复合膜理化指标、结构和抗氧化性,并将不同材料真空包装的冷鲜牛肉于4 ℃条件下贮藏10 d进行保鲜实验,研究不同AAP添加量对AAP/CS可食性复合膜理化性质和冷鲜牛肉保鲜效果的影响。结果表明：AAP的添加可增加AAP/CS复合膜的厚度、密度、溶解度、溶胀度、抗拉强度和1,1-二苯基-2-三硝基苯肼自由基清除率,并降低复合膜的水蒸气透过率和透明度;通过分析复合膜的傅里叶变换红外光谱,初步推测复合膜液中AAP和CS之间发生了相互作用。与市售聚对苯二甲酸乙二酯/聚乙烯复合真空包装组及CS膜包装组相比,AAP/CS复合膜包装组牛肉感官得分和pH值更高,菌落总数和硫代巴比妥酸反应物值更低。因此,AAP/CS可食性复合膜有望在食品抑菌保鲜等方面发挥积极作用。     

Packaging conditions for extended storage of chilled dark, firm, dry beef

Normal-pH (5·5-5·7) and high-pH (> 6·0) beef cuts of 500g were vacuum packaged in polyvinylidene chloride (PVDC), metalized polyester or aluminium foil laminates, or in foil laminate packs inflated with 1 litre of CO(2). During storage at + 1°C. vacuum packaged cuts developed spoilage floras of lactobacilli and enterobacteria; cuts stored under CO(2) developed floras of lactobacilli alone. Floras on all high-pH vacuum packaged cuts approached maximum numbers after 6 weeks' storage. At this time, cuts in PVDC laminate showed early symptoms of spoilage, but such symptoms did not develop in other vacuum packaged high-pH cuts until 9 or more weeks. Similarly, normal-pH cuts in PVDC film showed spoilage symptoms at 12 weeks, but such symptoms did not develop in other vacuum packaged normal-pH cuts until 15 weeks. Both normal- and high-pH cuts packaged under CO(2) were unspoiled at 15 weeks.