RESUMEN
The ability of Campylobacter jejuni ATCC 11168 to survive on beef and pork stored under chilled, vacuum packaged and retail display conditions were examined. In addition, the effect of natural microflora on commercial beef and pork on the survival of C. jejuni under these storage conditions was examined. When sterile cores of beef and pork were inoculated with â¼ 10(5) to 10(6) cfu cm(-2)C. jejuni, and were stored under aerobic or vacuum packaged conditions at -1.5 or 4 °C, its numbers dropped significantly and C. jejuni could not be enumerated by direct plating after 21 d of the 6 wks study. In contrast, survival of C. jejuni on commercial vacuum packaged beef and pork was significantly enhanced, resulting in only 1 log cfu cm(-2) reduction at the end of 6 wks. During 7 d of display in a retail case, numbers of C. jejuni dropped quickly, but could be enumerated by direct plating even after the 7 d. The presence of high numbers of inoculated C. jejuni on beef and pork had no significant effect on the natural microflora numbers compared to uninoculated controls when the meat was stored either in vacuum or in a retail display case. These results show that natural microflora on vacuum packaged meat afford enhanced survival of C. jejuni present on the surfaces of both beef and pork when stored at refrigeration temperatures. Hence, strict hygienic practices or the implementation of decontamination technologies are recommended to ensure safety of meat with respect to this pathogen.
Asunto(s)
Campylobacter jejuni/crecimiento & desarrollo , Campylobacter jejuni/aislamiento & purificación , Manipulación de Alimentos/métodos , Carne/microbiología , Viabilidad Microbiana , Animales , Campylobacter jejuni/genética , Bovinos , Contaminación de Alimentos , Embalaje de Alimentos/métodos , PorcinosRESUMEN
In a commercial process for the production of moisture-enhanced pork, boneless pork loins were conveyed through a recirculating injection apparatus, and brine (sodium phosphate, sodium chloride, and lemon juice solids) was pumped into the meat through banks of needles inserted automatically into the upper surfaces of cuts. Brine samples were collected at intervals during the production process and analyzed to determine the total plate count and the numbers of lactic acid bacteria, pseudomonads, Brochothrix thermosphacta, and Enterobacteriaceae. Listeria monocytogenes numbers in the brine were determined using a PCR with primers for the hemolysin gene in combination with a most probable numbers determination. Maximum numbers of bacteria (log CFU/ml) recovered from the brine after 2.5 h of recirculation were as follows: total plate count, 4.50; lactic acid bacteria, 2.99; pseudomonads, 3.95; B. thermosphacta, 2.79; and enterics, 3.01. There was an increase in the number of L. monocytogenes in the recirculating brine with time, reaching a maximum of 2.34 log CFU/100 ml after 2.5 h of moisture-enhanced pork production. Thus, recirculating brines can harbor large populations of spoilage bacteria and L. monocytogenes and are an important source of contamination for moisture-enhanced pork.
Asunto(s)
Bacterias/crecimiento & desarrollo , Manipulación de Alimentos/métodos , Microbiología de Alimentos , Carne/microbiología , Sales (Química)/farmacología , Animales , Recuento de Colonia Microbiana , Contaminación de Alimentos , Higiene , Carne/normas , PorcinosRESUMEN
A mixture of lysozyme and nisin at a ratio of 3:1 (w/w) and at a surface concentration of approximately 260 microg/cm2 was effective in controlling the growth of lactic acid bacteria, lactic acid bacteria able to grow in the presence of acetate and Brochothrix thermosphacta on naturally contaminated pork loins that were stored in vacuum packages at 2 degrees C for up to 6 weeks. When loins were removed, cut into chops, and displayed in a retail display case, the efficacy of the antimicrobial mixture decreased with increasing display time. At most sampling times, bacterial numbers were lower in treated samples than in untreated samples. The numbers of Enterobacteriaceae were higher in treated samples than in untreated samples. The growth of Enterobacteriaceae may have been reduced as a result of antimicrobial activity of the lactic acid bacteria because when the growth of lactic acid bacteria was inhibited by the antimicrobial treatment, the Enterobacteriaceae were able to grow to higher numbers. Sensory evaluation of the loins showed no difference between treated and untreated samples, but aerobically displayed chops treated with antimicrobial had more prevalent off-odours and reduced odour acceptability than untreated samples.
Asunto(s)
Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Conservación de Alimentos/métodos , Carne/microbiología , Muramidasa/farmacología , Nisina/farmacología , Animales , Bacterias/crecimiento & desarrollo , Recuento de Colonia Microbiana , Microbiología de Alimentos , Embalaje de Alimentos , Odorantes/análisis , Porcinos , Gusto , Factores de Tiempo , Resultado del Tratamiento , VacioRESUMEN
The possible origin of beef contamination and genetic diversity of Escherichia coli populations in beef cattle, on carcasses and ground beef, was examined by using random amplification of polymorphic DNA (RAPD) and PCR-restriction fragment length polymorphism (PCR-RFLP) analysis of the fliC gene. E. coli was recovered from the feces of 10 beef cattle during pasture grazing and feedlot finishing and from hides, carcasses, and ground beef after slaughter. The 1,403 E. coli isolates (855 fecal, 320 hide, 153 carcass, and 75 ground beef) were grouped into 121 genetic subtypes by using the RAPD method. Some of the genetic subtypes in cattle feces were also recovered from hides, prechilled carcasses, chilled carcasses, and ground beef. E. coli genetic subtypes were shared among cattle at all sample times, but a number of transient types were unique to individual animals. The genetic diversity of the E. coli population changed over time within individual animals grazing on pasture and in the feedlot. Isolates from one animal (59 fecal, 30 hide, 19 carcass, and 12 ground beef) were characterized by the PCR-RFLP analysis of the fliC gene and were grouped into eight genotypes. There was good agreement between the results obtained with the RAPD and PCR-RFLP techniques. In conclusion, the E. coli contaminating meat can originate from cattle feces, and the E. coli population in beef cattle was highly diverse. Also, genetic subtypes can be shared among animals or can be unique to an animal, and they are constantly changing.
Asunto(s)
Escherichia coli/genética , Escherichia coli/aislamiento & purificación , Microbiología de Alimentos , Variación Genética , Animales , Bovinos , Recuento de Colonia Microbiana , Escherichia coli/clasificación , Escherichia coli/patogenicidad , Heces/microbiología , Femenino , Flagelina/genética , Genes Bacterianos , Genotipo , Masculino , Carne/microbiología , Polimorfismo de Longitud del Fragmento de Restricción , Técnica del ADN Polimorfo Amplificado Aleatorio , Piel/microbiologíaRESUMEN
The development of a community of lactic acid bacteria from vacuum-packaged beef was investigated during a 6-week storage trial at 2 degrees C. The lactic acid bacteria population was monitored by using molecular techniques to identify a random sample of isolates at biweekly intervals during the storage trial. The polymerase chain reaction and a randomly amplified polymorphic DNA technique were used to identify and distinguish populations of lactic acid bacteria that developed during the storage trial. At week 0, the population of lactic acid bacteria was 3.5 log cfu/120 cm2 and by week 6, the population reached a maximum of 7.6 log cfu/120 cm2. A sampling from the week 0 population indicated a mixed community of Lactobacillus curvatus, Lactobacillus sakei and Leuconostoc spp. However, the sampling from week 6 indicated the population composition had changed to one where a single Leuconostoc strain predominated. This strain demonstrated antagonism towards the growth of other lactic acid bacteria isolated during the study. Additionally, the strain inhibited the growth of foodborne pathogens Escherichia coli O157:H7 and Listeria monocytogenes. DNA sequence data from the 16S rRNA gene suggested that the isolate may be a Leuconostoc gelidum strain.