The effects of atmospheric pressure cold plasma treatment on microbiological, physical-chemical and sensory characteristics of vacuum packaged beef loin.

Effects on vacuum packaged and non-packaged beef longissimus samples exposed to atmospheric cold plasma (ACP) generated at different powers were studied over a 10day period of vacuum-, and a subsequent 3day period of aerobic storage. Exposure of non-covered beef samples under high power ACP conditions resulted in increased a*, b*, Chroma and Hue values, but ACP treatment of packaged loins did not impact colour (L*, a*, b*, Chroma, Hue), lipid peroxidation, sarcoplasmic protein denaturation, nitrate/nitrite uptake, or myoglobin isoform distribution. Colour values measured after 3days of aerobic storage following unpackaging (i.e. 20days post-mortem) were similar and all compliant with consumer acceptability standards. Exposure to ACP of the polyamide-polyethylene packaging film inoculated with Staphylococcus aureus, Listeria monocytogenes and two Escherichia coli strains resulted in >2 log reduction without affecting the integrity of the packaging matrix. Results indicate that ACP can reduce microbial numbers on surfaces of beef packages without affecting characteristics of the packaged beef.

Effectiveness of a polyamide film releasing lactic acid on the growth of E. coli O157:H7, Enterobacteriaceae and Total Aerobic Count on vacuum-packed beef.

The suitability of a polyamide 6 monolayer film containing lactic acid for use as an antimicrobial package for fresh beef cuts was studied. The release of lactic acid in an aqueous environment was immediate (within 1h) and was from approx. 55 µg lactic acid/cm(2) film at 0-8°C to approx. 67 µg lactic acid/cm(2) film at 12-20°C. Beef was contaminated with an Escherichia coli O157:H7 isolate with known minimum inhibitory concentration against lactic acid (0.09% v/v), then wrapped with the lactic-acid polyamide film and vacuum packaged. During storage at 12°C, the numbers of E. coli were 1 log unit lower than that of a control (untreated polyamide film) and decreased by an additional 1 log during storage for 14 days.

Application of Classification and Regression Tree (CART) analysis on the microflora of minced meat for classification according to Reg. (EC) 2073/2005.

In a retrospective study on the microbiology of minced meat from small food businesses supplying directly to the consumer, the relative contribution of meat supplier, meat species and outlet where meat was minced was assessed by "Classification and Regression Tree" (CART) analysis. Samples (n=888) originated from 129 outlets of a single supermarket chain. Sampling units were 4-5 packs (pork, beef, and mixed pork-beef). Total aerobic counts (TACs) were 5.3±1.0 log CFU/g. In 75.6% of samples, E. coli were <1 log CFU/g. The proportion of "unsatisfactory" sample sets [as defined in Reg. (EC) 2073/2005] were 31.3 and 4.5% for TAC and E. coli, respectively. For classification according to TACs, the outlet where meat was minced and the "meat supplier" were the most important predictors. For E. coli, "outlet" was the most important predictor, but the limit of detection of 1 log CFU/g was not discriminative enough to allow further conclusions.

Carcass and meat quality traits of wild boar (Sus scrofa s. L.) with 2n=36 karyotype compared to those of phenotypically similar crossbreeds (2n=37 and 2n=38) raised under the same farming conditions 2 Fatty acid profile and cholesterol.

The aim of this study was to compare European wild boar (Sus scrofa) with chromosomal number 2n=36 to phenotypically similar animals with 2n=37 and 2n=38 chromosomes (crossbreeds) with respect to fatty acid (FA) profile and cholesterol content. According to gender and genetic group (2n=36, 2n=37, and 2n=38; seven animals each), the FA profile in longissimusdorsi (LD), semimembranosus (SM) muscles, and back fat was measured. Cholesterol content of LD and SM muscles was also analysed. The animals were fed and reared under the same conditions until slaughter at the age of nine months. FA profiles of LD, SM, and back fat were measured by GC and cholesterol with HPTLC. SM muscle of wild boar group (2n=36) showed a higher proportion of PUFAs and lower C16:0 and C18:0 than that of crossbreeds. No differences in the FA profiles of LD and cholesterol content of LD and SM muscles among karyotypes were found.

Enumeration of Enterobacteriaceae in various foods with a new automated most-probable-number method compared with petrifilm and international organization for standardization procedures.

An automated most-probable-number (MPN) system (TEMPO, bioMérieux, Marcy l'Etoile, France) for enumeration of Enterobacteriaceae (EB) was compared with methods involving violet red bile glucose agar (VRBG) (International Organization for Standardization [ISO] method 21528-2) (ISO-VRBG) and Petrifilm (PF-EB). The MPN partitioning (three different volumes with 16 replicates of each) is done automatically in a disposable card. Bacterial growth is indicated by acid production from sugars, lowering the pH of the medium, and quenching the fluorescence of 4-methylumbelliferone. After incubation, the number of nonfluorescent wells is read in a separate device, and the MPN is calculated automatically. A total of 411 naturally contaminated foods were tested, and 190 were in the detection range for all methods. For these results, the mean (+/- standard deviation) counts were 2.540 +/- 1.026, 2.547 +/- 0.995, and 2.456 +/- 1.014 log CFU/g for the ISO-VRBG, PF-EB, and automated MPN methods, respectively. Mean differences were -0.084 +/- 0.460 log units for the automated MPN results compared with the ISO-VRBG and 0.007 +/- 0.450 for the PF-EB results compared with the ISO-VRBG results. The automated MPN method tends to yield lower numbers and the PF-EB method tends to yield higher numbers than does the ISO-VRBG method (difference not significant; Kruskal-Wallis test, P = 0.102). Thus, the average difference was highest between the automated MPN method and the PF-EB method (-0.091 +/- 0.512 log units). Differences between the automated MPN and ISO-VRBG results of > 1 log unit were detected in 3.4% of all samples. For 3.9% of the samples, one comparison yielded differences of < 1 log CFU/g and the other yielded > 1 but < 2 log CFU/g, which means that the differences are possibly > 1 log CFU/g. For the ISO-VRBG method, confirmation of isolates was necessary to avoid a bias due to the presence of oxidase-positive glucose-fermenting colonies. The automated MPN system yielded results comparable to those of the confirmed Enterobacteriaceae ISO-VRBG method but required only 24 h of analysis time.

Influence of storage conditions and shotshell wounding on the hygienic condition of hunted, uneviscerated pheasant (Phasianus colchicus).

The effects of shot wounds on the hygienic conditions of pheasants (particularly those in the body cavity) were studied. Slaughtered (n = 33) and hunted pheasants (31 specimens with, and 33 specimens without shots in the body cavity) were stored uneviscerated at 0 and 4 degrees C. Specimens were taken at d 0, 3, 7, and 14. Hunted pheasants differed from slaughtered pheasants with respect to muscular hemorrhages and blood and fecal matter in the body cavity but also with regard to the presence of Escherichia coli in breast and thigh muscles. In addition, a higher thigh muscle pH (P < 0.05) was noted in hunted pheasants, with no significant (P > 0.05) increase observed during storage. Concentrations of biogenic amines in muscle tissue remained below the determination limit of 1 mg/kg for 90% of samples analyzed, with the maximum concentration for the remaining 10% of samples reaching 5.7 mg/kg, indicating a low incidence of contaminant bacteria. The observed changes in pH values and levels of biogenic amines failed to correlate with the presence or absence of shot lesions in the body cavity or abdominal region. Total aerobic counts increased significantly during storage, but the absolute numbers were consistently below 10(6) log(10) cfu/g. Although E. coli were <1 log(10) cfu/g in muscles of hunted pheasants on d 3 at 4 degrees C, counts of up to 3.7 log(10) cfu/g on d 7 at 4 degrees C indicated a loss of hygienic quality. Therefore, it is recommended that hunted, uneviscerated pheasants be stored 3 d at 4 degrees C, but not longer than 7 d after the hunt.

Energy supply patterns for finishing steers: Feed conversion efficiency, components of bodyweight gain and meat quality.

The objective was to determine the effect of pre-slaughter growth rate on feed efficiency, components of body growth and on the tenderness of longissimus muscle from steers reared to a common age and carcass weight. Sixty Friesian steers were group-housed and offered grass silage ad libitum and 3.5kg concentrates per animal daily for 5 months and then 5kg concentrates and 1kg grass hay for 1month before the experiment began. The animals were then weighed and in a randomised block were assigned to one of 5 groups, for slaughter at the beginning of the experiment or to be offered concentrates and hay (900 and 100g/kg total diet, respectively) to achieve target growths of: 0.72kg/day continuously for 17 weeks, 0.36kg/day for the first 8 weeks and 1.08kg/day for the final 8 weeks (low-high), 1.08kg/day for the first 8 weeks and 0.36 for the final 8 weeks (high-low) or 0.36kg/day for the first 2 weeks, 0.72kg/day during weeks 4 and 14 and 1.08kg/day for the final 2 weeks (pulse). One week was allowed for transition to the different dietary allowances within each energy supply pattern. The mean age at the beginning and end of the study was 18 and 22.5 months, respectively. After slaughter, the weight of the carcass and kidney+channel fat depot were recorded, the pistola hind quarter was dissected into fat, lean and bone and the tenderness of the m. longissimus thoracis et lumborum (LTM) muscle was measured instrumentally and using a trained taste panel after 2, 7 or 14 days ageing. The pattern of energy supply did not affect carcass weight, fat score or kidney+channel fat weight. The pistola hind quarter from animals offered the low-high energy pattern had a similar composition to the continuously-fed animals but contained more muscle than that from animals offered high-low or pulse energy patterns. After 14 days ageing, LTM from the continuously-fed animals was more tender than that from animals offered the other energy supply patterns but shear force did not differ between supply patterns. The data do not support the hypothesis that pre-slaughter growth rate increases tenderness but suggest that energy supply pattern can influence body composition of finishing cattle.

Salmonella diagnosis in pig production: methodological problems in monitoring the prevalence in pigs and pork.

Salmonellosis is an important foodborne infection in industrialized and developing countries. Especially for human Salmonellosis caused by Salmonella enterica serovar Typhimurium, pigs and pork are the major sources of infection. Mitigation and control strategies that result from surveillance programs attempt to reduce or even eradicate Salmonella in pork to lower consumers' risks. The methodology for Salmonella screening in pigs is generally based on antibody detection at slaughter with meat juice as the sample matrix. The instructions to most commercial enzyme-linked immunosorbent assay (ELISA) kits for the detection of Salmonella antibodies state that their product is suitable for antibody detection in meat juice and sera. In the present study, we show that it is essential to recalculate the percent optical density (OD%) data obtained from meat juice by the ELISA (IDEXX HerdCheck swine Salmonella) by the following regression equation: OD%sera = -70.5587 + 128.1490/ {1 + exp[(-18.8969 - OD%meatjuice)/27.6032]}(1.1771), r = 0.87, to compare results with those obtained from sera. By this regression equation, we were able to compare the Salmonella antibody levels (classified as <10, 10 to <20, 20 to <40, and > or =40 OD%) for sows, growers, and slaughter pigs. We identified significantly higher numbers of growers with lower OD% levels than for sows and slaughter pigs. Without a recalculation of the meat juice results, the higher fraction of samples with low OD% values led to an underestimation of the actual seroprevalence.

Enumeration of total aerobic bacteria and Escherichia coli in minced meat and on carcass surface samples with an automated most-probable-number method compared with colony count protocols.

An automated most-probable-number (MPN) system for the enumeration of total bacterial flora and Escherichia coli was compared with plate count agar and tryptone-bile-glucuronide (TBX) and ColiID (in-house method) agar methodology. The MPN partitioning of sample aliquots was done automatically on a disposable card containing 48 wells of 3 different volumes, i.e., 16 replicates per volume. Bacterial growth was detected by the formation of fluorescent 4-methylumbilliferone. After incubation, the number of fluorescent wells was read with a separate device, and the MPN was calculated automatically. A total of 180 naturally contaminated samples were tested (pig and cattle carcass surfaces, n = 63; frozen minced meat, n = 62; and refrigerated minced meat, n = 55). Plate count agar results and MPN were highly correlated (r = 0.99), with log MPN = -0.25 + 1.05 x log CFU (plate count agar) (n = 163; range, 2.2 to 7.5 log CFU/g or cm2). Only a few discrepancies were recorded. In two samples (1.1%), the differences were > or = 1.0 log; in three samples (1.7%), the differences were > or = 0.5 log. For E. coli, regression analysis was done for all three methods for 80 minced meat samples, which were above the limit of detection (1.0 log CFU/g): log MPN = 0.18 + 0.98 x log CFU (TBX), r = 0.96, and log MPN = -0.02 + 0.99 x log CFU (ColiID), r = 0.99 (range, 1.0 to 4.2 log CFU/g). Four discrepant results were recorded, with differences of > 0.5 but < 1.0 log unit. These results suggest that the automated MPN method described is a suitable and labor-saving alternative to colony count techniques for total bacterial flora and E. coli determination in minced meat or on carcass surfaces.

Modified-atmosphere storage under subatmospheric pressure and beef quality: I. Microbiological effects.

The microflora was studied in beef stored in stainless steel containers kept under reduced pressure (20 to 30 kPa) in a modified atmosphere (70% N2 + 30% CO2 or pure CO2) at 3 to 4 degrees C and 0 to 1 degrees C at a headspace:meat volume ratio of 2:1. Samples were obtained at weekly intervals, 1 to 3 times. Total colony counts (TCC) for Pseudomonas spp. and Brochothrix thermosphacta were generally 1 to 2 log10 cfu greater than in the control group of vacuum-packaged beef cuts stored at the same temperatures. In containers with the 70% N2 + 30% CO2 atmosphere at 20 to 30 kPa and 3 to 4 degrees C, substantial growth of Pseudomonas sp. was observed (median of 6 log10 cfu/cm2 at d 21 of storage compared with 3 log10 cfu/cm2 for vacuum-packaged beef). Pseudomonas counts were lower when the container system was held at 0 to 1 degrees C, especially when combined with the pure CO2 atmosphere. As expected for CO2-enriched atmospheres, B. thermosphacta was the dominant spoilage bacterium, in the same log10 order as the TCC. Lowering the storage temperature and changing the atmosphere to pure CO2 resulted in a reduction of 1 log10 for TCC (median values after 2 wk of storage). Although pathogenic bacteria such as Campylobacter, Salmonella, and Listeria monocytogenes were not detected in any sample, further studies are necessary to evaluate potential growth risks. The results demonstrate that CO2-enriched and O2-depleted atmospheres under low pressure have a limited effect on reducing bacterial growth, probably because the antibacterial activity of CO2 is proportional to the effective concentration of this gas in the headspace. At pressures of 20 to 30 kPa, a headspace with pure CO2 would still contain only approximately 20 to 30% CO2.

Modified-atmosphere storage under subatmospheric pressure and beef quality: II. Color, drip, cooking loss, sarcomere length, and tenderness.

Beef has a requirement for refrigerated storage up to 14 d to achieve adequate aging and a tender product. To achieve this aging with little spoilage and no surface drying, vacuum packaging is attractive, because it is inherently simple and offers a clear indication to the packer when the process has failed or there is risk of spoilage. However, there is increasing pressure on the meat industry to limit the use of packaging materials in view of their cost and the cost involved in their recovery and recycling. The purpose of this report was to evaluate an alternative storage system in containers using modified atmospheres at reduced pressure (approximately 25 kPa). The quality of the meat for both container- and vacuum-packed treatments was measured during chilled storage for up to 3 wk. Storage time had the most significant effect on quality characteristics, irrespective of the packaging method. Storage in containers under a 70%N2:30%CO2 gas mixture gave characteristics similar to beef stored under vacuum. Storage in containers under 100% CO2 produced less drip loss than under 70%N2:30%CO2, but generally container storage produced 3 times as much drip loss as vacuum packaging. Shear force of the LM was unaffected by the type of packaging, and at d 2 after slaughter (i.e., before the storage trial was begun), sarcomere lengths of muscles intended for container storage were similar to those destined for vacuum storage. During the packaging treatment, the comparison between the storage systems was always done within 1 animal using one carcass-half for container storage and the other half for vacuum packaging; all bulls were shackled from the left hindleg during bleeding. The majority of the muscles from the left sides had lower shear force values than those from the right sides at the earlier storage times (2 and 9 d after slaughter) but had similar values after longer storage (16 and 23 d after slaughter). This is the first report that shackling beef carcasses from the left side can result in more tender meat in the LM from that side. The increased tenderness in the LM from the shackled side probably resulted from an early decrease in pH and an increase in calpain activity after mechanical strain of the muscles on the shackled side. This effect of shackling should be taken into account when designing systematic comparisons of tenderness in beef.

Ultrastructural changes during aging in M. longissimus thoracis from moose and reindeer.

Game meat is commonly consumed in Europe but few studies have examined the quality related parameters. In this study we examined the changes in ultrastructure at four times postmortem in M. longissimus from moose (Alces alces) and reindeer (Rangifer tarandus tarandus). The moose were slaughtered during a hunt and reindeer by Swedish standard practices for this semi-domestic animal. Ultrastructural changes occurring in all animals included separation of the sarcolemma from myofibrils, I band breaks, and cytoskeleton breaks; however both I band breaks and cytoskeletal breaks were less common in moose and reindeer than values reported for sheep and beef. Fiber area in the longissimus thoracis muscle was approximately 3270 µm(2) for moose and 1170 µm(2) for reindeer indicating that the tenderness of reindeer meat may be largely determined by fiber size.