THE EFFECTS OF FROZEN STORAGE AND PROTECTIVE STORAGE WRAP ON THE RETAIL CASE-LIFE OF PORK LOIN CHOPS

Loin chops from 60 pork carcass sides were utilized to evaluate the influences of frozen storage and protective storage wrap upon factors contributing to the retail case-life of thawed chops. The composite results of this study indicated that pork loin chops could be frozen and stored for 168 days or less at ?30° C and have a retail case-life of at least 6 days, under the conditions employed in the present study. The possible exception is an amount of drip in the packages of chops stored in certain protective wraps which may be unacceptable when displayed for prolonged periods.     

Colour stability of thawed lamb chops. II. Chops from loins frozen for long periods

Colour stability was examined during simulated retail display of thawed chops cut from loins after frozen storage. When loins had been stored for 30 weeks at –20°C, the thawed chops had a 2-day display life. If chops were stored at –20°C for an additional 8 weeks before thawing, display life decreased to 1 day. When loins were thawed, then cut into chops, a display life of 4 days was obtained. Thawed chops from loins stored for 60 weeks behaved similarly. The experiment showed no adverse trend with increased frozen storage, except for increased drip, and indicates definite commercial possibilities for chops cut from loins stored frozen.     

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.     

Colour stability of thawed lamb chops. I. Effect of short-term frozen storage

The colour stability of thawed lamb chops was examined, by colour panel and colorimeter, under simulated retail display conditions. Chops held frozen at –20°C for 1 week had a display life of 3 days when thawed, compared with 2 days for fresh chops. When the frozen storage was increased to 8 weeks the display life was reduced to 1 day. When the whole loin was stored frozen for 8 weeks, chops cut from it and thawed had a 2-day display life. By comparison, vacuum-packed chops stored at –1.5°C for 8 weeks had a 3-day display life. The relationship between Hunter colour values and panel scores is discussed.     

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.     

The display life of retail packaged pork chops after their storage in master packs under atmospheres of N(2), CO(2) or O(2) + CO(2)

Commercial, bone-in pork loins were divided into four portions. One portion of each loin was vacuum packaged, then stored at -1.5 °C. The other portions were each divided into three chops, which were retail packaged. 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 pork was assessed after storage for up to 42 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 portion was cut into three chops, which were retail packaged. The chops from all packagings were displayed in a retail cabinet which maintained average air temperatures between 3 and 6 °C. The chops were assessed twice daily until they were judged to be of undesirable appearance. After storage for 1 or 2 days, the chops from all master packs appeared less desirable than the freshly cut chops. After all longer storage times, chops from N(2) and CO(2) atmospheres appeared as desirable as freshly cut chops, as did chops from O(2) + CO(2) that were stored for up to 16 days. However, chops stored under O(2) + CO(2) for 21 days appeared undesirable. Chops stored under N(2) or O(2) + CO(2) developed spoilage odours, after storage for 28 or 21 days, respectively. Bacteria were more numerous on the fat than on the muscle tissue. The numbers of bacteria were 10(7) cfu cm(-2) on the fat surfaces of chops stored under vacuum or N(2) for 42 days. The numbers of bacteria were 10(6) cfu cm(-2) on the fat surfaces of chops stored under CO(2) for 42 days or under O(2) + CO(2) for 21 days. At those times, only lactobacilli were isolated from chops stored under CO(2), but small or large fractions of enterobacteria were present in the flora on chops stored under vacuum or N(2), respectively, while the flora on chops stored under O(2) + CO(2) contained large fractions of Brochothrix thermosphacta and Gram negative, strictly aerobic, spoilage bacteria. After all storage times, chops cut from vacuum packaged portions remained of desirable appearance when displayed for 48 hr or longer. Chops stored under N(2) or CO(2) for between 2 and 35 days, or under O(2) + CO(2) for between 4 and 12 days, retained a desirable appearance during display for the same times as the freshly cut chops. Off-odours were apparent in chops after their display following storage under vacuum or CO(2) for 21 days, or under N(2) or O(2) + CO(2) for 12 days. The numbers of bacteria on the fat surfaces of chops spoiled by off-odours were ≥ 10(5) cfu cm(-2). The flora on chops removed from display were generally enriched for B. thermosphacta, enterobacteria and/or Gram negative aerobes as compared with the flora on the chops when they were removed from the storage packs. Those data indicate that the storage life of master packaged, display ready pork will probably be severely limited by the poor hygienic condition of commercial products, to little more than 1 week for product stored under N(2) or O(2) + CO(2) or < 3 weeks for product stored under CO(2).     

Increase in retail display of frozen lamb chops with increased loin storage time before cutting into chops

There is a steady deterioration of the colour of lamb chops during frozen storage. Storing meat in carcass form or as primals before cutting and packaging minimizes the exposure of the meat surfaces to deteriorating environmental effects. This experiment examines the effects of storage conditions (form, time and temperature) on the display life of frozen chops. Loins were removed from recently frozen carcasses and stored for 0, 10, 20 or 30 weeks at temperatures of -5°C, -10°C and -20°C. Chops were cut from the stored loins, packaged in oxygen permeable film, stored in the dark at -20°C for 0,4,8 or 12 weeks and then displayed at -20°C under continuous lighting. The retail display life of the chops was assessed by an experienced colour panel. The most rapid colour deterioration occurred in chops cut from unstored frozen loins and held for 12 weeks prior to display (display life of less than 1 day). Chops cut from loins stored for 30 weeks at -20°C, and then held for 12 weeks prior to display had a display life of 23 days. Both increased loin storage temperature and an increased duration of chop storage before display decreased the retial display life. This study indicates that frozen storage of cut chops for as little as 4 weeks reduces the display life by almost 80% so that whole carcasses or loins rather than cut chops should be shipped to distant markets. unstored frozen loins and held for 12 weeks prior to display (display life of less.     

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.     

MICROBIOLOGY OF BEEF SHELL FROZEN WITH LIQUID NITROGEN

SUMMARY— The effect of freezing primal cuts of beef with liquid nitrogen on the subsequent microbiological quality of their retail cuts was studied. Cryovac-packaged loins were shell frozen by spraying with liquid nitrogen and held for 2 or 3 days at room temperature (25–27°C) in insulated styrofoam boxes. Frozen packaged loins were also aged at 2°C for 21 days and at 22°C for 3 days before being cut into steaks. Steaks from each treated loin and steaks from fresh loins (controls) were packaged and stored in a display case at about 5°C. Examination was made of the loins and packaged steaks during storage to determine total anaerobes, fluorescent Pseudomonas , coliforms, enterococci, Clostridium perfringens , and incidence of Salmonellae and coagulase-positive staphylococci. Initial contamination on steaks increased with loins aged for a long time at low temperatures. Aging of loins at 22°C for 3 days promoted multiplication of C. perfringens and resulted in the steaks having the highest occurrence of coagulase positive Staphylococcus . Recovery of Salmonella from the steaks was more closely related to the source and level of contamination of the fresh meat than to time and temperature of holding of the wholesale cuts. These findings have application to shell freezing of beef with liquid nitrogen for air transport and to possible commercial aging practices.     

Effects of modified gas atmosphere packaging on pork loin colour, display life and drip loss

Boneless loins from both sides of 20 pig carcasses were divided into five sections each and assigned equally to five packaging treatments: 100 % CO(2); 50 % CO(2)/50 % N(2); 25 % CO(2)/ 75 % N(2); 25 % CO(2)/65 % N(2)/10 % O(2) and vacuum. Loin sections were packaged in bags of low O(2) permeability, then stored in darkness at 1 °C for up to 22 days. Retail chops were cut from the sections and displayed in oxygen-permeable film under light at 3 °C for 3 additional days. The O(2) concentrations in packages with nominally anoxic atmospheres were 0.1-0.4 %. Sections stored in 25 % CO(2)/65 % N(2)/10 % O(2) had more surface greying and greening, stronger off-odour and psychrotropic counts after storage were more than one log(10) higher compared to sections from the other four treatments. Displayed chops from sections stored in 25 % CO(2)/65 % N(2)/10 % O(2) also had greying/greening at an outer layer of the chops. Off-odour of chops was most pronounced for treatments with 10 % O(2) and vacuum. Drip loss from loin sections was highest for those in 100 % CO(2) (4.2 %) and lowest for those in vacuum (3.2 %). In conclusion, storage in CO(2) or CO (2)N (2) atmospheres benefitted the overall shelf life of pork.     

The microbiology and storage stability of vacuum packed lamb

Lamb joints (shoulders, loins and legs) stored in vacuum packs at 0–1°C remained unspoiled for 6 weeks, but since the aerobic storage life at 5°C (retail shelf life) of lamb after holding in vacuum packs at 0–1°C for 6 weeks was only 2 days, vacuum storage should be limited to a maximum of 4 weeks in practice. Brochothrix thermosphacta , Moraxella spp, and Moraxella-like organisms were predominant on aerobically spoiled lamb and the preservative effect of vacuum packing resulted from the inhibitory effects of the high carbon dioxide (>20%) and low oxygen concentrations (<1%) which developed in the packs. Brochothrix thermosphacta was not completely inhibited, however, and with lactic acid bacteria was the possible cause of cheesy/sour odours which terminated vacuum packed storage life.     

Factors influencing frozen display life of lamb chops and steaks: Effect of packaging and temperature

Frozen lamb loin and rib chops and leg steaks were wrapped in film of high oxygen permeability or vacuum packaged in film of low oxygen permeability and stored in the dark at -10, -20 or -35°C for periods from 0-20 weeks. After storage, the wrapped cuts were displayed in an open-top cabinet operating at -20°C under continuous fluorescent lighting (Philips Deluxe 32°). Cuts were evaluated by a trained colour panel to determine acceptable display life, and chop lean colour was evaluated using a Hunter colorimeter. Cuts wrapped in oxygen permeable film had better colour retention during storage and display. Storage of the frozen chops reduced the display life, with the largest effect occurring during the first 4-5 weeks' storage. Cuts stored at -10°C had no display life after 10 weeks' storage, whereas cuts stored at -20 and -35°C had some acceptable display life even after the longest storage period tested. Rib chops in general had better colour stability than loin chops.     

Effects of Packaging and Processing Procedures on the Quality and Shelf Life of Fresh Pork Loins

Thirty crossbred hogs were slaughtered and the longissimus muscle from the left side was removed and divided into two equal sections within 20 min postmortem (HP) and those from the right side were removed and divided 24 hr postmortem(CP). One-half of the muscle from each side was wrapped in parchment paper (PP) and the other half was vacuum packaged (VP) and loin sections were assigned to storage intervals of 0, 7, 14, 21, or 28 days. At the end of each storage period, loins were evaluated for moisture loss, bacterial levels, off-odor, sensory properties and retail case display. VP and HP treatments had reduced moisture loss (P<0.05). Off-odor scores were higher (P<0.05) for PP wrapped loins on day 14. Few palatability differences were observed with packaging and processing treatments. Vacuum packaging had positive effects on the storage and retail display characteristics of fresh pork.     

Retail Shelf-Life of Pork Dipped in Organic Acid before Modified Atmosphere or Vacuum Packaging

Modified atmosphere packaging (MAP) is increasingly popular for meat, but raw, chilled pork in vacuum or anoxic environments has a purple color. The retail shelf‐life of pork chops dipped in 500 ppm ascorbic acid, 250 ppm citric acid, or no acid dip and stored at 1 °C before simulated retail display in MAP with gas exchange or air‐permeable packaging after vacuum pouch storage was determined. The 80% N₂:20% CO₂ in MAP was exchanged with 80% O₂:20% CO₂, and chops were removed from vacuum packages and overwrapped with permeable film (VP‐PVC) on the 7th day before simulated retail display at 4 °C. Shelf‐life traits were determined at 1, 7, 8, 10, 12, and 14 d postpackaging. The pH values changed with time, but returned to post‐dipped, prepackaged levels at the end of simulated retail storage. Weight loss of chops increased (P < 0.05) in VP‐PVC compared with MAP. The a* values increased (P < 0.05) and L* and b* values decreased during simulated retail display, with higher L*, a*, and b* color values for chops in MAP than VP‐PVC. Log numbers of psychrotrophic microorganisms were higher (P < 0.05) on VP‐PVC samples than for chops in MAP on days 12 and 14. Psychrotrophic counts on ascorbic acid‐treated samples were decreased compared with citric acid or no dipping on pork during simulated retail display. Pork chops in MAP with gas exchange had lighter and redder color, increased weight retention, decreased psychrotrophic counts, and increased lipid oxidation compared with conventional vacuum and overwrap packaging systems.     

Fate of inoculated Escherichia coli O157:H7, cultured under different conditions, on fresh and decontaminated beef transitioned from vacuum to aerobic packaging

This study evaluated the behavior of Escherichia coli O157:H7 during aerobic storage, after storage in vacuum packages, on beef inoculated with cultures prepared (35 degrees C, 24 h) in tryptic soy broth without dextrose (TSB), nonacid hot water carcass decontamination runoff fluids (washings; pH 6.0; WASH), cells from biofilms formed on stainless steel coupons in WASH (WETB), or WETB dried (25 degrees C, 12 h) before harvesting of cells (DRYB). These inocula were applied to fresh beef pieces (40 cm2), which were then left untreated or treated by immersion in hot water (75 degrees C) followed by 2% lactic acid (55 degrees C; hot water/lactic acid [HW/LA]), for 30 s each. Inoculated samples were vacuum packaged and stored at 0 (30, 60, or 90 days), 4 (7 or 14 days), or 12 degrees C (4 or 8 days) and subsequently transferred to retail packages for aerobic storage at 7 degrees C for 5 days. Populations of E. coli O157:H117, regardless of inoculum type, remained generally unchanged (P > 0.05) after aerobic storage (7 degrees C, 5 days) of untreated or HW/LA-treated beef samples previously stored in vacuum packages at 0 or 4 degrees C. However, reductions in E. coli O157:H7 levels were generally obtained when vacuum packaged, untreated beef samples previously stored at 12 degrees C were transitioned to aerobic conditions. Additionally, despite similar (P > 0.05) levels of E. coli O157:H7 cells of TSB, WASH, WETB, and DRYB origin on vacuum-packaged, untreated samples after 8 days of storage at 12 degrees C, subsequent aerobic storage resulted in larger (P < 0.05) reductions of cells of WETB and DRYB origin than for cells of TSB and WASH origin. For HW/LA-treated beef previously stored at 12 degrees C in vacuum packages, populations of E. coli O157:H7 remained largely unchanged after aerobic storage in retail packages. Results thus indicated that aerobic storage of beef (7 degees C, 5 days) previously stored in vacuum packages at 0 or 4 degrees C did not lead to E. coli O157:H7 population changes, whereas transition from vacuum packages stored under mildly abusive temperature (12 degrees C) to aerobic storage may have caused injury and death to the pathogen.     

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.     

Effect of modified atmospheres on microbiological, color and sensory properties of refrigerated pork

Pork loin samples were stored (4 °C) in nylon polyethylene plastic bags using different modified atmospheres packaging (MAP): vacuum, 100% CO₂ 99% CO₂ + 1% CO, 100% O₂ or 100% CO followed by vacuum. Throughout the storage period Pseudomonas growth was limited in loins packaged in all MAPs evaluated, except for 100% O₂. Psychrotrophs reached 10⁷ CFU g⁻¹ after 20 days of storage except for the loin samples in 100% O₂ MAP that present count above 10⁸ CFU g⁻¹. The 1% CO/99% CO₂ atmosphere was best for preserving the desirable pork loin color and the L* and a* values remained similar to the fresh meat values using this MAP. Pork loins in 99% CO₂/1% CO MAP obtained the highest consumer acceptance scores after 24 h of storage. These samples and those treated with CO and then vacuum packaged received the greatest acceptance scores even after 20 days of storage.     

包装方式和宰后不同时间包装对羊肉品质的影响

为探究包装方式和宰后不同时间包装对羊肉贮藏品质的影响,本研究对宰后1 h热分割羊肉和冷却成熟24 h后的分割羊肉分别进行热收缩包装、真空包装、贴体包装、50%（体积分数,下同）O2＋50% CO2气调包装,测定其在（2±2）℃贮藏过程中pH值、色泽、贮藏损失率、蒸煮损失率、离心损失率、剪切力、挥发性气味的变化。结果表明：与宰后24 h包装相比,宰后1 h包装羊肉pH值在贮藏14 d时更高,但其贮藏期间色泽较好,色泽稳定性更高,贮藏损失率更低。从整体来看,3 种真空处理（热收缩包装、真空包装、贴体包装）羊肉嫩度均优于气调包装羊肉,且宰后1 h包装时真空条件处理对羊肉嫩化效果最好,宰后24 h羊肉在贮藏前期气调包装对羊肉嫩化效果较好;而无论何时包装,热收缩包装和气调包装羊肉贮藏损失率均显著小于其他处理组（P＜0.05）,在贮藏前期色泽及稳定性较好,但贮藏后期色泽稳定性下降明显,气调包装羊肉在14 d时已部分发绿,贮藏21 d时挥发性气味变化显著。综上,宰后1 h包装有利于提高羊肉贮藏期间色泽及持水力,改善真空处理羊肉嫩度,宰后24 h包装可提高50% O2＋50% CO2气调包装羊肉贮藏前期的嫩度;其中热收缩包装和气调包装羊肉持水力高,贮藏前期色泽及稳定性好,真空包装、贴体包装羊肉品质变化相对稳定,适宜长期贮藏。     

Effect of Low Dose Irradiation of Pork Loins on the Microflora, Sensory Characteristics and Fat Stability

The effects of low dose (100 krad) irradiation on microflora, sensory characteristics, and development of oxidative rancidity of vacuum packaged pork loins was investigated after irradiation and during low temperature (4°C) storage up to 21 days. Irradiation reduced numbers of mesophiles, psychrotrophs, anaerobic bacteria (P<0.01), and staphylococci (P<0.05), with the effect on mesophiles and psychrotrophic spoilage organisms the greatest. Effect of irradiation on sensory characteristics of pork loin was minimal with no detectable differences between irradiated and nonirradiated pork after 14 days of storage. Irradiation of pork did not affect cooking loss or thiobarbituric acid values.     

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. ?