Bacteriological quality assurance (BQA) of mechanically deboned meat (MDM)

Adequacy of bacteriological quality assurance during the commercial production of mechanically deboned meat (MDM) was assessed. Lax standards of hygiene during production were observed, resulting in high numbers of Staphylococcus aureus, viz. 10⁴ to 10⁵ cfu g⁻¹, and severe contamination with Enterobacteriaceae: 10⁵ to 10⁶ cfu g⁻¹. These data indicate that measures of hygiene observed during boning of carcasses and during collection, storage and transport of bones or poultry parts should be markedly tightened, while conditions of refrigerated storage of raw materials and MDM should be improved. Use of bones of poor sensory quality (discoloration, abnormal smell) generally resulted in MDM of inferior bacteriological quality.

Phage typing, biotyping and assessment of enterotoxin production was carried out with 136 St. aureus cultures, isolates from mechanically deboned pork produced at one plant. Fifty-five per cent of the isolates was not typable, 28% was typable with human phages, 8% with bovine phages. The majority of the strains could not be explicitly assigned to any Meyer and/or Hájek and Mar álek types. Applying the simplified system of Devriese to eighteen strains isolated in our investigation, ten were found to belong to the poultry ecovar, one to the bovine ecovar, while seven strains were non-host specific. None of the isolates produced enterotoxins A–E.

Microbiological inspection of end products is recommended as part of an integrated quality assurance system. The following reference values for the final product (maximal colony counts to be expected under GMP conditions expressed as 95th percentile) were calculated: Pig MDM: log₁₀ mesophilic colony count 6·8 and log₁₀ cfu mesophilic Enterobacteriaceae g⁻¹ 4·8; Poultry MDM: log₁₀ mesophilic colony count 6·6 and log₁₀ cfu mesophilic Enterobacteriaceae g⁻¹ 4·7.     

Microbial contamination of carcasses and equipment from an Iberian pig slaughterhouse

The microbial contamination of carcasses and equipment has been studied in an industrial slaughterhouse of Iberian pigs. Samples of the surface of carcasses were taken at different stages of the process and aerobic plate count at 37 degrees C (APC), Enterobacteriaceae-count (E-count) and Escherichia coli-count (EC-count) were determined. It was demonstrated that in scalding and singeing the APC decreased (P < 0.01), while in the dehairing it increased (P < 0.01). The E-count and EC-count decreased in the scalding but increased in the evisceration (P < 0.001). The implementation of good manufacturing practices (GMP) in the stages of closure of the anus and evisceration significantly decreased the EC-count. It changed from 61.1% in carcasses without GMP that had counts higher than 1 log CFU/cm2 to only 7.4% in GMP carcasses. A final wash of the carcasses with potable water at high pressure (the only decontaminating treatment permitted in the European Union) was tested and failed to decrease the counts. It was also demonstrated that cleaning and disinfection of the dehairing and scraping machines is not effective.     

Microbiological effects of acid decontamination of pork carcasses at various locations in processing

The microbiological effect of hot (55° C), 1% (v/v) lactic acid sprayed on the surface of pork carcasses (n = 36) immediately after dehairing, after evisceration (immediately before chilling) or at both locations in slaughter/ processing was determined. Mean aerobic plate counts (APCs) of all acid-treated carcass surfaces were numerically lower than those of control carcasses: however, in most cases these reductions were not statistically significant (P>0·05). All samples tested for the presence of Salmonella and Listeria were negative. No significant differences in sensory characteristics or microbiological counts were evident for acid-treated and control carcass loins that were vacuum packaged and stored 0–14 days post-fabrication. Mean pH value and scores of sensory attributes such as lean color, surface discoloration, fat color, overall appearance and off-odor of chops from acid-treated carcasses were not significantly and/or consistently different from chops of comparable control carcasses. The role of bacterial attachment to pork skin and its effect on the decontaminating efficiency of lactic acid are discussed.     

MICROBIOLOGICAL CONDITIONS OF SHEEP CARCASSES DURING THE SLAUGHTERING PROCESS

This study was undertaken to determine the microbiological quality of sheep carcasses during different stages in the slaughtering process. A total of eleven carcasses were selected at random in an abattoir. The samples were taken by excision from four different sites; leg, brisket, shoulder and neck. The samples were collected from the same carcasses at four different stages in the slaughtering process; after dressing, after evisceration, after washing and chilling. The aerobic mesophilic bacteria, coliforms and Enterobacteriaceae recovered from each sample were enumerated. Chilling reduced the aerobic mesophilic and coliform counts of carcasses, significantly. Levels of carcass microbial load after chilling were 1.69, 0.11 and 0.11 log cfu/cm² for aerobic mesophilic counts, coliform counts and Enterobacteriaceae counts, respectively. According to data obtained in the present study, chilling of carcasses was the most important step in improving the hygienic quality of carcasses. Processing stages changed significantly both aerobic mesophilic and coliform counts of neck, therefore, among different sites of carcass, neck should be the only critical site for microbiological sampling for sheep carcasses.     

Isolation,characterisation and identification of lactic acid bacteria from bushera: a Ugandan traditional fermented beverage

One hundred and thirteen strains of lactic acid bacteria (LAB) were selected from 351 isolates from 15 samples of traditionally fermented household bushera from Uganda and also from laboratory-prepared bushera. Isolates were phenotypically characterised by their ability to ferment 49 carbohydrates using API 50 CHL kits and additional biochemical tests. Coliforms, yeasts and LAB were enumerated in bushera. The pH, volatile organic compounds and organic acids were also determined.

The LAB counts in household bushera varied between 7.1 and 9.4 log cfu ml⁻¹. The coliform counts varied between <1 and 5.2 log cfu ml⁻¹. The pH of bushera ranged from 3.7 to 4.5. Ethanol (max, 0.27%) was the major volatile organic compound while lactic acid (max, 0.52%) was identified as the dominant organic acid in household bushera.

The initial numbers of LAB and coliforms in laboratory-fermented bushera were similar; however, the LAB numbers increased faster during the first 24 h. LAB counts increased from 5.5 to 9.0 log cfu ml⁻¹ during the laboratory fermentation. Coliform counts increased from 5.9 to 7.8 log cfu ml⁻¹ at 24 h, but after 48 h, counts were less 4 log cfu ml⁻¹. Yeasts increased from 4.3 to 7.7 log cfu ml⁻¹ at 48 h, but thereafter decreased slightly. The pH declined from 7.0 to around 4.0. Lactic acid and ethanol increased from zero to 0.75% and 0.20%, respectively.

Lactic acid bacteria isolated from household bushera belonged to Lactobacillus, Streptococcus and Enterococcus genera. Tentatively, Lactobacillus isolates were identified as Lactobacillus plantarum, L. paracasei subsp. paracasei, L. fermentum, L. brevis and L. delbrueckii subsp. delbrueckii. Streptococcus thermophilus strains were also identified in household bushera. LAB isolated from bushera produced in the laboratory belonged to five genera (Lactococcus, Leuconostoc, Lactobacillus, Weissella and Enterococcus. Eight isolates were able to produce acid from starch and were identified as Lactococcus lactis subsp. lactis (four strains), Leuconostoc mesenteroides subsp. mesenteroides (one strain), Leuconostoc mesenteroides subsp. dextranicum (one strain), Weissella confusa (one strain) and L. plantarum (one strain).     

Salmonella in slaughter pigs: prevalence, serotypes and critical control points during slaughter in two slaughterhouses

The purpose of this study was to show the distribution of Salmonella in slaughtered pigs and the environment of the slaughterhouse. 1114 samples of slaughtered pigs (six different samples for Salmonella isolation and one serum sample for ELISA on antibodies per pig) and 477 samples of the slaughterhouse environment were collected in two slaughterhouses on two sampling days per slaughterhouse. Salmonella was isolated from one or more samples of 47% of the pigs. The highest prevalence of Salmonella was observed in rectal content samples (25.6%), whereas the lowest prevalence of Salmonella was observed on the carcasses (1.4%). The prevalence of Salmonella in other samples was: 19.6% in tonsils, 9.3% on livers, 9.3% on tongues, and 9.3% in mesenterial lymphnodes. The prevalence of Salmonella in environmental samples was high in the drain water samples in both slaughterhouses (61%) and on the carcass splitter in one slaughterhouse (33%). Salmonella typhimurium was the most frequently isolated serotype in pig samples and environmental samples in both slaughterhouses: 43% of the Salmonella isolates from pigs and 33% of the Salmonella isolates from the environment was S. typhimurium.

The results of this study show that Salmonella prevalences in pigs differ a lot, depending on which part of the pig is sampled. Not all different samples of the pig will become available for human consumption, but collecting more than one sample per pig showed that Salmonella can be found in almost the whole pig. The result of surface samples of carcass and liver gives information about hygiene during the slaughter process; the result of tonsils, lymphnodes and rectal contents, combined with the serological result, gives information about infection of the pig before the slaughter process (on the farm, during transport or in lairage).

It can be concluded that results of Salmonella isolation of slaughter pigs should always be carefully interpreted, depending on the type of sample that has been collected.     

Microbiological contamination of pig carcasses at different stages of slaughter in two European Union-approved abattoirs

At sequential steps of slaughter (scalding, dehairing, singeing, polishing, trimming, washing, and chilling), 200 pig carcasses from two abattoirs were examined for total viable bacteria count (TVC) and the presence of Enterobacteriaceae and coagulase-positive Staphylococcus (CPS) by the wet-dry double-swab technique at the neck, belly, back, and ham. Before scalding, mean TVCs ranged from 5.0 to 6.0 log CFU cm(-2), and Enterobacteriaceae and CPS were detected on all carcasses. At abattoir A, mean TVCs and the percentage of Enterobacteriaceae-positive carcasses were reduced (P < 0.05) after scalding (1.9 log CFU cm(-2) and 12%, respectively), singeing (1.9 log CFU cm(-2) and 66%, respectively), and blast chilling (2.3 log CFU cm(-2) and 17%, respectively) and increased (P < 0.05) after dehairing (3.4 log CFU cm(-2) and 100%, respectively) and polishing (2.9 log CFU cm(-2)). The proportion of CPS-positive samples decreased to < or = 10% after scalding and remained at this level. At abattoir B, mean TVCs and the percentages of Enterobacteriaceae- and CPS-positive carcasses were reduced (P < 0.05) after scalding (2.4 log CFU cm(-2) and 29 and 20%, respectively), polishing (3.7 log CFU cm(-2)), and chilling (2.6 log CFU cm(-2) and 55 and 77%, respectively) and increased (P < 0.05) after the combined dehairing-singeing (4.7 log CFU cm(-2) and 97 and 100%, respectively). Among sites, the neck tended to yield higher levels of contamination from trimming to chilling at both abattoirs (P < 0.05). Consequently, scalding, singeing, and chilling may be integrated in a hazard analysis critical control point (HACCP) system for pig slaughter. As indicated by the higher levels of contamination on carcasses after dehairing-singeing and the following stages at abattoir B, each abattoir should develop its own baseline data and should customize HACCP systems to match process- and site-specific circumstances.     

The microbiology of sheep carcasses processed in a modern Indian abattoir

A study has been conducted on the microbiology of sheep carcasses processed in a modern abattoir. The data revealed that careful handling at the different stages of processing of sheep reduced the level of microbial contamination of carcasses. Processing steps such as evisceration and washing did not increase the microbial counts on the carcass surface. Sources of microbial contamination in the abattoir were examined. It was observed that skin, floor washings, intestinal contents and gambrels were the major sources of microbial contamination. Seasonality did not have any effect on the microbial contamination of carcasses. The study revealed that total plate counts in 86·6% of the carcasses ranged between 3·0–4·9log/cm². The counts of coliforms, staphylococci, enterococci and psychrotrophs were low. Pathogens such as Salmonella were not detected. The microbial counts were well within the generally acceptable levels. These findings demonstrated hygienic handling of carcasses. Shoulder and neck are the critical points for microbiological sampling as these sites showed higher microbial counts. Micrococcus and Staphylococcus predominated among microorganisms associated with carcasses. It was noted that differences occurred in microbial types of carcasses processed in tropical and temperate climates. The data generated in a model facility procided useful information for improving meat handling practices.     

Longitudinal Dissemination of Salmonella enterica Clonal Groups through the Slaughter Process of Salmonella-Positive Pig Batches

This study was conducted to assess the dissemination of Salmonella clonal groups in slaughterhouses that received batches of Salmonella -positive pigs and used different routine processing procedures. Eight serial sampling sessions were conducted in three slaughterhouses (A, B, and C). Blood was collected randomly (n = 25) from each batch of pigs and processed for serology. Carcasses (n = 12) were identified and sampled after dehairing, after singeing, after evisceration, and before chilling. A section of cecum also was collected. Salmonella isolates were submitted to pulsed-field gel electrophoresis. The overall seroprevalence of Salmonella was 80.6% (316 of 392 samples), and cecal contents were positive for Salmonella in 23.8% (26 of 109) of the pigs sampled. Carcasses after dehairing had a significantly higher prevalence of Salmonella (P = 0.004) and the highest Salmonella levels (median ～ 0.26 log CFU/300 cm(2)). The singeing step significantly affected the Salmonella status of the carcasses (P = 0.001); however, the efficacy of singeing differed among slaughterhouses. In the prechilling step, 14.7% (16 of 109) of the carcasses were positive for Salmonella. Salmonella pulsotypes found on the prechill carcasses were also found in the lairage, in the cecal contents, and on carcasses after dehairing, suggesting that the main source of contamination was the slaughter process before singeing. Slaughterhouse C was the most likely (odds ration [OR] ～ 6.51) to have pigs carrying Salmonella in the gut, and slaughterhouse B was the most likely (OR ～ 14.66) to have contaminated carcasses at the prechilling step. These findings indicate that the procedures adopted in slaughterhouse B contributed to the spread of Salmonella strains. In contrast, in slaughterhouse C the Salmonella strains carried by the pigs or found in the lairage were not recovered from prechilled carcasses, validating the effectiveness of the slaughterhouse interventions. These results indicate that an effective slaughter process can help decrease the number of Salmonella-positive carcasses in slaughterhouses that receive Salmonella-positive pig batches.     

Methods to Detect the Occurrence of Various Indicator Bacteria on the Surface of Retail Poultry in Spain

ABSTRACT: Contamination levels (cfu/g and cfu/cm²) of indicator microorganisms in retail broiler chicken carcasses in León (Spain) were investigated. Counts (log₁₀ cfu/g) were 5.19, 3.04, 2.73, 3.38, and 3.16 for total aerobic counts ( TAC), Enterobacteriaceae , coliforms determined by the standard VRBA method (coliforms-VRBA), coliforms determined by the Hydrophobic Grid Membrane Filter method (coliforms-HGMF), and Escherichia coli (HGMF method), respectively. These values fit into the microbiological criteria for poultry meat consulted. A low correlation coefficient was found between TAC and Enterobacteriaceae counts (r = 0.308; P = 0.053) and between coliforms-VRBA and coliforms-HGMF counts ( r = 0.398; P = 0.048). The determination method had a significant influence on the coliform counts obtained. All broiler chicken carcasses harbored E. coli biotype I. E. coli biotype II was detected in 20% of the samples. The HGMF method was not completely specific for detecting E. coli since 11.25% of false positive colonies were found.     

The production and microbiological status of skin-on sheep carcasses

There is a demand by certain ethnic consumer groups in the United Kingdom for skin-on, singed carcasses, primarily from older sheep, but their production is illegal under current EU legislation. The aim of this study was to devise a protocol to produce carcasses having the desired ‘smoked’ colour and odour and an acceptable microbiology. A successful result could form the basis of a case to revise the legislation. Three key steps in the selected procedure were carcass singeing using specially designed gas burner equipment, pressure washing to clean the carcass and then evisceration. It was shown that a second heat application, termed ‘toasting’, if applied after evisceration, significantly (P < 0.001) reduced Enterobacteriaceae and TVC counts on carcasses before chilling. Microbiological quality was also improved when toasting was the final step, following carcass splitting and inspection. Carcasses produced in this way had significantly (P < 0.001) lower Enterobacteriaceae and TVC counts before chilling than conventionally dressed sheep carcasses produced in the same abattoir.     

Survival of pathogenic microorganisms in an egg-nog-like product containing 7% ethanol

A liquor consisting of whole egg, saccharose (25% w/v) and ethanol (7.0% w/v) was artificially contaminated with Salmonella enteritidis, S. typhimurium, Staphylococcus aureus (three different strains), Bacillus cereus and Listeria monocytogenes. After 3 weeks of incubation at 22°C the numbers of Salmonella, S. aureus and L. monocytogenes decreased more than 3 log₁₀ units. Under such conditions, however, the total number of microorganisms increased 3 log₁₀ units. At 4°C the decrease of pathogenic microorganisms was much slower and a decrease of 3 log₁₀ units was observed only after 7 weeks of incubation. Egg-nog, without ethanol, incubated at 22°C allowed growth of Salmonella and S. aureus, while the numbers of B. cereus spores remained unchanged. Vegetative cells of B. cereus as well as L. monocytogenes decreased in numbers. However, after prolonged incubation the numbers of L. monocytogenes increased significantly.     

The influence of RN genotype, including the new V199I allele, on the eating quality of pork loin

The eating quality of M. longissimus dorsi (LD) from RN⁻ homozygotes, RN⁻ heterozygotes and RN⁻ non-carriers was investigated in a Swedish Hampshire×Finnish Landrace pig population. The recently identified new allele (V199I, here denoted rn*) at the RN locus was also detected among the pigs selected and included in the sensory evaluation. The number of animals varied from 10 to 15 in the five genotype groups; RN⁻/RN⁻, RN⁻/rn+, RN⁻/rn*, rn+/rn+ and rn+/rn* (in total 59 pigs). In addition, one pig was determined to be rn*/rn* but was excluded from the analysis. The three genotypes in which the RN⁻ allele was represented (RN⁻/RN⁻, RN⁻/rn+ and RN⁻/rn*) had higher glycogen and lower protein contents as well as lower ultimate pH (measured 48 h post-mortem) in LD than the non-carriers (rn+/rn+ and rn+rn*). Of the sensory parameters evaluated (tenderness, chewing time, chewing residual, juiciness, meat flavour and acidity), the five RN genotypes only affected acidity significantly; the RN⁻ allele contributing to a more acid taste in LD. The influence of the rn* allele resembled that of rn+ on the sensory parameters. When the material was divided into three groups (homozygous, heterozygous and non-carriers of the RN⁻ allele) the juiciness was found to be significantly influenced by RN genotype, and LD from animals that were homozygous and heterozygous with respect to the RN⁻ allele exhibited a higher juiciness than LD from non-carriers. The RN⁻ allele also tended to contribute to greater tenderness, which was significantly higher in LD from heterozygous carriers than from non-carriers of the RN⁻ allele. A more rapid decline in pH (measured as pH at 45 min and 3 h post-mortem) contributed to a greater tenderness in LD (according to a trained panel and Warner-Bratzler shear force). In addition to the RN genotype, the decline in pH was influenced by carcass weight, which varied between 71 and 97 kg, and by stunning procedure, which changed during the course of the study from individual to group stunning with CO₂. The individual stunning procedure contributed to a lower pH in the initial post-mortem phase (pH₄₅), whereas a higher carcass weight and the RN⁻ allele lowered the pH in the mid-post-mortem region (pH_3h and pH_24h), significantly (P0.05). The pH continued to decline after 24 h post-mortem and the ultimate pH was not reached until 48 h post-mortem. The cooking loss, juiciness and acidity were related to the specific characteristics of the RN⁻ carriers, such as higher glycogen content, lower protein content and lower ultimate pH (pH_48h).     

Microbiological quality of freshly shot game in Germany

In the framework of a project on the hygiene status of freshly shot game 289 samples were microbiologically analysed: 127 samples from wild boars, 95 from roe deer and 67 from red deer. The microbiological parameters evaluated were the mesophilic aerobic count (APC), which showed mean log10-counts of 2.6 cfu/cm² for roe deer, 2.9 cfu/cm² for red deer and 3.2 cfu/cm² for wild boars and the numbers of Enterobacteriaceae, which gave mean log10-values of 2.1 cfu/cm² for all three species with differing ranges. The concentrations of coagulase positive staphylococci were >2.0 log10 cfu/cm² between 3.2 and 6.3%, according to species. Listeria was found in 14 samples and three samples gave a positive result for Campylobacter. Salmonella was not found in any of the samples analysed.     

MICROBIAL CHANGES ON FRESHLY SLAUGHTERED PORK CARCASSES DUE TO "HOT" LACTIC ACID DECONTAMINATION

We studied the microbial changes on fresh (still warm) pork carcasses immediately after electrostatic spraying of lactic acid solutions and during chilled storage. Lactic acid decontamination (LAD) included electrostatic spraying of hot (55C) solutions of 1% lactic acid for 90 s and 2%- and 5% lactic acid for 30 and 90 s. The treatments increased the carcass surface temperature from 22C to about 32–43C. The bactericidal activity of lactic acid killed mainly Gram-negative bacteria. Reductions in "total" psychrotrophic Gram-negative and Entero-bacteriaceae counts were found reliable indicators for the efficacy of LAD. Hot 2–5% LAD treatments achieved overall reductions in Gram-negative psychrotrophs ranging from 0.8 to more than 1.4 log₁₀ cfu per cm². Overall reductions in mesophilic Enterobacteriaceae counts ranged from approximately 1.2 to more than 1.8 log₁₀ cfu per cm². Treatments with 1% lactic acid achieved marginal 0.5–0.6 overall log₁₀ reductions in these groups of organisms. Bactericidal effects after LAD occurred during a lag period of whose duration increased with the lactic acid concentration of the spray solution. The lag lasted less than 1 day on 1% LAD, 2 days on 2% LAD and 4 days on 5% LAD meat. During these lags the meat surface pH rose from pH 2.7 to 3.2 immediately after LAD to pH 4.8 to 5.2. During aerobic chilled storage after LAD the growth of Gram-negative psychrotrophs was controlled only temporarily. These organisms became the dominant group of organisms. The practical utility of electrostatic spraying of fresh pork carcasses with hot 1–5% LAD to improve the keeping quality is questionable .     

Behaviour of Listeria monocytogenes in raw sausages (merguez) in presence of a bacteriocin-producing lactococcal strain as a protective culture

The effectiveness of a bacteriocin produced by Lactococcus lactis subsp. lactis M in reducing population level and growth of Listeria monocytogenes ATCC 7644 in fermented merguez sausage was examined. Two different formulas (with or without added nitrites) were assayed and predetermined numbers of Listeria (ca 10⁶ cfu g⁻¹) were added to sausage mixture. The effect of in situ production of the bacteriocin by Lactococcus lactis M on Listeria monocytogenes ATCC 7644 during fermentation and storage of merguez sausages at room (ca 22 °C) or at refrigeration (ca 7 °C) temperature was tested. Results indicated that counts of Listeria monocytogenes were decreased during fermentation of merguez samples fermented with either the bacteriocin-producing Lactococcus lactis M (Bac⁺) or a nonbacteriocin-producing Lactococcus lactis J (Bac⁻). However, reduction in Listeria cfu's was greater in samples fermented with the Bac⁺ than in those fermented with the Bac⁻ starter. In merguez sausage made without nitrites addition, the Bac⁺ starter induced further decrease in Listeria counts by 1.5 log cycles compared with that induced by the Bac⁻ starter. While in merguez samples with added nitrites (0.4%), the effect of the bacteriocin produced in situ was less important than in those made without nitrites addition.     

Growth of Listeria monocytogenes on vacuum-packaged horsemeat for human consumption

In order to investigate the likelihood of Listeria monocytogenes (serotype 4b, ATCC 19115) growth on vacuum-packaged horsemeat at refrigeration temperature, fourteen horsemeat surface/volume homogeneous 150 g weight pieces were superficially inoculated with serotype 4b L. monocytogenes and vacuum packaged. The samples were stored at 4 ± 1 °C. Two pieces (one for pH determination and one for L. monocytogenes counts) were examined at days 0, 7, 14, 21, 28, 35 and 42. Surface pH did not show significant variations during the experiment. The average L. monocytogenes initial contamination level was 1.77log₁₀ CFU/g. A lag phase of 7 days was recorded. The exponential growth rate between day 7 to day 35 was 0.125log₁₀ CFU/day, corresponding to 3.51log₁₀ CFU/g in 28 days. At the end of the experiment the mean L. monocytogenes log₁₀ CFU/g was 5.78.     

Assessment of the microbiological conditions of red-meat carcasses from bacterial counts recovered by sampling via excision or swabbing with cotton wool

Samples from 240 carcasses were collected from four animal species (porcine, ovine, bovine and equine). Two samples were taken from each carcass, one using the excision method (EX) and the other the wet–dry swabbing method (SW). Eight areas from each carcass were sampled. Most of the samples obtained by SW revealed total aerobic viable counts (TVC) levels of between 3.1 and 4.0 log CFU cm⁻², while most of the values corresponding to excision were located between 4.1 and 5.0 log CFU cm⁻². Moreover, Enterobacteriaceae (EC) counts were only detected above 3.0 log CFU cm⁻² in 0.85% of the carcasses when the samples were collected by swabbing, while the excision method revealed that 13.75% of the carcasses presented EC greater than 3.0 log CFU cm⁻². TVC and EC by EX revealed statistically significant differences compared to SW, while no significant linear relationship was found between carcass surface bacterial counts obtained by SW and EX.     

Selective enumeration and survival of bifidobacteria in fresh cheese

Five species of bifidobacteria (15 strains), two strains of Lactococcus lactis ssp. lactis, two strains of L. lactis ssp. cremoris, and one strain of L. lactis ssp. lactis var diacetylactis were included in a study to develop a selective medium for enumeration of bifidobacteria from fresh cheese. Viable counts of bifidobacteria or lactococci on modified Columbia agar base (CAB with 0.05% cysteine-HCl) plus raffinose (0.5%) containing various selective agents were compared with non-selective media. The mCAB plus raffinose with lithium chloride (2 g L⁻¹) and sodium propionate (3 g L⁻¹) with pH adjusted to 5.1 was used successfully as a selective medium for the enumeration of bifidobacteria from fresh cheese. Using this medium, it was determined that bifidobacteria could survive up to 15 days at a level higher than 10⁶ cfu g⁻¹ in a fresh cheese stored at 4 or 12°C. The decrease in the viable counts of bifidobacteria was faster during storage at 4°C than at 12°C.     

酶法脱毛和烫毛燎毛对牛皮营养特性和卫生质量特性的影响

本研究旨在研究脱毛方法对牛皮质量特性的影响,以烫毛燎毛、酶法脱毛的牛皮为实验对象,参照国家标准测定牛皮的微生物、重金属和营养成分含量。结果表明,烫毛燎毛、酶法脱毛的牛皮中均未检出重金属(总砷、总汞、铅、镉、铬)、金黄色葡萄球菌、沙门氏菌、志贺氏菌和大肠杆菌O157∶H7,但酶法脱毛的牛皮的菌落总数和大肠菌群为5.5×104CFU/g、120 MPN/g,而烫毛燎毛的为7.2×102CFU/g、40 MPN/g;两种脱毛方法对牛皮的蛋白质、脂肪酸、水分含量方面有影响;烫毛燎毛、酶法脱毛的牛皮中均检出17种氨基酸,在含量上没有显著性差异(p>0.05)。这说明酶法脱毛具有一定的可行性,为进一步研究畜禽体脱毛提供理论参考。