RESUMEN

Oleaster (wild olive tree) by-products represent a renewable and low-cost source of biopolyphenols. Leaf extracts (sylv.OLE) of Algerian oleaster, locally called a'hachad (Olea europaea subsp. europaea var. sylvestris), were applied at 1 and 5% (v/w) to raw Halal minced beef (HMB) in order to test its safety and shelf-life prolongation during retail/display. The total phenolic compound content in the extract was 198.7 ± 3.6 mg gallic acid equivalent. Ten compounds were identified in the sylv.OLE by High Performance Liquid Chromatography/Diode Array Detector (HPLC/DAD), of which oleuropein was the most abundant (43.25%). Samples treated with 5% sylv.OLE had significantly higher antimicrobial and antioxidant effects than those treated with 1% extract (p < 0.05). The addition of sylv.OLE reduced psychrotrophic counts as well as the level of pathogens (Salmonella enterica ser. Enteritidis and Shiga toxin-producing Escherichia coli O157:H7). A thiobarbituric acid reactive substance (TBARS) value of 2.42 ± 0.11 was reached throughout six days of retail/display in control samples, while the addition of 5% sylv.OLE reduced TBARS value by 58% (p < 0.05). The presence of sylv.OLE at the tested concentrations did not negatively influence the overall acceptability and bitterness of HMB.

RESUMEN

The aim of this work was to study the occurrence of Listeria monocytogenes in several types of ready-to-eat (RTE) meat products and in the environment of meat processing plants. A total of 129 samples of RTE meat products and 110 samples from work surfaces and equipment were analyzed. L. monocytogenes was detected in 6 out of 35 cooked products (17.14%), 21 out of 57 raw-cured products (36.84%), and 9 out of 37 dry-cured, salted products (24.32%). The number of sample units that exceeded the food safety limit of 100 cfu/g decreased from the manufacture date to half shelf life, and then it was further reduced at the end of shelf life. L. monocytogenes was detected in 25 out of 110 (22.72%) food contact surfaces. The number of positive and negative results from both food and environmental samples were cross-tabulated and the calculated Cohen's kappa coefficient (κ) was 0.3233, indicating a fair agreement in terms of Listeria contamination. L.monocytogenes was recovered after cleaning and disinfection procedures in four plants, highlighting the importance of thorough cleaning and disinfection.

RESUMEN

Listeria monocytogenes is a major concern for the meat processing industry because many listeriosis outbreaks have been linked to meat product consumption. The aim of this study was to elucidate L. monocytogenes diversity and distribution across different Spanish meat processing plants. L. monocytogenes isolates (N = 106) collected from food contact surfaces of meat processing plants and meat products were serotyped and then characterised by multilocus sequence typing (MLST). The isolates were serotyped as 1/2a (36.8%), 1/2c (34%), 1/2b (17.9%) and 4b (11.3%). MLST identified ST9 as the most predominant allelic profile (33% of isolates) followed by ST121 (16%), both of which were detected from several processing plants and meat products sampled in different years, suggesting that those STs are highly adapted to the meat processing environment. Food contact surfaces during processing were established as an important source of L. monocytogenes in meat products because the same STs were obtained in isolates recovered from surfaces and products. L. monocytogenes was recovered after cleaning and disinfection procedures in two processing plants, highlighting the importance of thorough cleaning and disinfection procedures. Epidemic clone (EC) marker ECI was identified in 8.5%, ECIII was identified in 2.8%, and ECV was identified in 7.5% of the 106 isolates. Furthermore, a selection of presumably unrelated ST9 isolates was analysed by multi-virulence-locus sequence typing (MVLST). Most ST9 isolates had the same virulence type (VT11), confirming the clonal origin of ST9 isolates; however, one ST9 isolate was assigned to a new VT (VT95). Consequently, MLST is a reliable tool for identification of contamination routes and niches in processing plants, and MVLST clearly differentiates EC strains, which both contribute to the improvement of L. monocytogenes control programs in the meat industry.

Asunto(s)

Biodiversidad , Contaminación de Alimentos/análisis , Manipulación de Alimentos/instrumentación , Listeria monocytogenes/aislamiento & purificación , Carne/microbiología , Animales , Técnicas de Tipificación Bacteriana , Listeria monocytogenes/clasificación , Listeria monocytogenes/genética , España

RESUMEN

A total of 336 Listeria isolates from ready-to-eat (RTE) meat products and meat-processing environments, consisting of 206 Listeria monocytogenes, and 130 Listeria innocua isolates, were characterized by disc diffusion assay and minimum inhibitory concentration (MIC) values for antimicrobial susceptibility against twenty antimicrobials. Resistance to one or two antimicrobials was observed in 71 L. monocytogenes isolates (34.5%), and 56 L. innocua isolates (43.1%). Multidrug resistance was identified in 24 Listeria isolates, 18 belonging to L. innocua (13.9%) and 6 to L. monocytogenes (2.9%). Oxacillin resistance was the most common resistance phenotype and was identified in 100% Listeria isolates. A medium prevalence of resistance to clindamycin (39.3% isolates) and low incidence of resistance to tetracycline (3.9% isolates) were also detected. Listeria isolates from RTE meat products displayed higher overall antimicrobial resistance (31.3%) than those from the environment (13.4%). All the strains assayed were sensitive to the preferred antibiotics used to treat listeriosis. Results showed that although antimicrobial resistance in L. monocytogenes still occurs at a low prevalence, L. innocua can form a reservoir of resistance genes which may transfer between bacterial species, including transference to organisms capable of causing disease in humans.

Asunto(s)

Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Manipulación de Alimentos/instrumentación , Listeria monocytogenes/aislamiento & purificación , Listeria/aislamiento & purificación , Productos de la Carne/microbiología , Mataderos , Contaminación de Alimentos/análisis , Listeria/efectos de los fármacos , Listeria/genética , Listeria monocytogenes/efectos de los fármacos , Listeria monocytogenes/genética , Pruebas de Sensibilidad Microbiana

RESUMEN

The essential oils (EOs) of Lavandula angustifolia L. and Mentha piperita L. were analyzed by gas chromatography mass spectrometry (GC/MS). The major constituents were linalool (22.35%), linalyl acetate (21.80%), trans-ocimene (6.16%) and 4-terpineol (5.19%) for L. angustifolia and menthol (33.28%), menthone (22.03%), and menthyl acetate (6.40%) for M. piperita. In vitro antibacterial activity of both EOs against Escherichia coli O157:H7 and Staphylococcus aureus CECT 4459 showed high inhibition against S. aureus. The lowest minimal inhibitory concentrations (MIC) were obtained with L. angustifolia (0.25 µL/mL) against S. aureus; M. piperita exhibited a MIC of 0.50 µL/mL against both microorganisms. Both EOs caused a significant decrease of bacterial growth in minced beef (p<0.05) stored at 9±1 °C. Minced beef treated with EOs showed the lowest TBARS values (lipid oxidation). Moreover, the results showed that the addition of EOs significantly extended fresh meat odor even at abuse temperature.

Asunto(s)

Antibacterianos/química , Antioxidantes/química , Escherichia coli O157/crecimiento & desarrollo , Conservantes de Alimentos/química , Carne/microbiología , Aceites Volátiles/química , Staphylococcus aureus/crecimiento & desarrollo , Argelia , Animales , Antibacterianos/farmacología , Antioxidantes/farmacología , Bovinos , Dieta/etnología , Escherichia coli O157/efectos de los fármacos , Escherichia coli O157/aislamiento & purificación , Conservantes de Alimentos/farmacología , Almacenamiento de Alimentos , Enfermedades Transmitidas por los Alimentos/prevención & control , Humanos , Lavandula/química , Peroxidación de Lípido , Carne/análisis , Mentha piperita/química , Pruebas de Sensibilidad Microbiana , Viabilidad Microbiana , Monoterpenos/análisis , Aceites Volátiles/farmacología , Refrigeración , Sensación , Staphylococcus aureus/efectos de los fármacos , Staphylococcus aureus/aislamiento & purificación

RESUMEN

A number of techniques exist for microbiological sampling of food processing environments in food industries. In the present study the efficacies of nine sampling procedures for the recovery of Listeria monocytogenes from food contact surfaces, including a new sampling device consisting of a miniroller, were evaluated and compared. A stainless steel table was inoculated with L. monocytogenes strain 935 (serovar 4b, human origin) and L. monocytogenes strain 437/07 (serovar 1/2b, food origin), at 10(5) CFU/100 cm(2). L. monocytogenes strain 935 was best recovered with the minirollers (recovery of up to 6.27%), while poor recoveries (<0.30%) were obtained with the towel (one-ply composite tissue), alginate swab, metallic swab, and Petrifilm methods. In the case of L. monocytogenes strain 437/07 the replicate organism detection and counting (RODAC) ALOA contact plates yielded the best recoveries (4.15%), followed by the minirollers (up to 1.52%). Overall, recovery percentages with the minirollers were higher with stomacher homogenization than with Vibromatic agitation. The recovery percentages obtained for the Listeria strain of human origin were higher than those obtained with the food strain for all sampling procedures except Petrifilm and RODAC ALOA. With the miniroller device coated with wool fiber, the recovery of L. monocytogenes can be improved from 2 to 17 times over recoveries obtained with the sponge and cotton swab. This is the first report of a miniroller device for microbiological sampling in the available literature. The novel sampling procedure is convenient to apply on surfaces, is cost-effective, and results in better recovery of L. monocytogenes than do the conventional methods.

Asunto(s)

Técnicas Bacteriológicas/métodos , Contaminación de Alimentos/prevención & control , Listeria monocytogenes/aislamiento & purificación , Acero Inoxidable , Adhesión Bacteriana , Recuento de Colonia Microbiana/métodos , Microbiología Ambiental , Contaminación de Equipos , Microbiología de Alimentos , Humanos , Listeria monocytogenes/fisiología , Propiedades de Superficie

RESUMEN

Fatias de carne bovina foram inoculadas com uma de duas bactérias láticas protetoras (Lactobacillus sakei CTC 372 bacteriocinogênica e Lactobacillus CTC 711 não caracterizado) e armazenadas em atmosfera modificada (20-40 por cento CO2). A inoculação da carne com bactérias láticas protetoras inibiu a multiplicação de bactérias deteriorantes. O CO2 da atmosfera e/ou a presença de bactérias láticas não causou a formação de metmioglobina ou de odores indesejáveis. A formação de metmioglobina e as características sensoriais foram equivalentes às apresentadas por carne fresca não deteriorada e não submetida a tratamento. A multiplicação de Listeria monocytogenes em caldo foi inibida por bactérias isoladas da superfície das carnes inoculadas com as bactérias láticas. Após 7 dias a 3ºC, a contagem inicial de L. monocytogenes de 5.6 log UFC.mL-1 caiu para 2.8 log UFC.mL-1 na ausência de bactéria lática protetora. A 8ºC, as contagens de L. monocytogenes foram reduzidas em 2.5 ou 1.5 log na presença de Lb. sakei CTC 372 ou Lb. CTC 711, respectivamente. A 25ºC, as contagens de L. monocytogenes no caldo contendo uma das bactérias láticas protetoras foram 5 log mais baixas do que nos caldos contendo L. monocytogenes somente.

Asunto(s)

Contaminación de Alimentos , Conservación de Alimentos , Técnicas In Vitro , Listeria monocytogenes , Carne , Bovinos , Muestras de Alimentos , Métodos

RESUMEN

Samples of Spanish dry-cured hams were analyzed using several physico-chemical parameters (moisture content, chlorides, water activity, nitrate, nitrite, total volatile basic nitrogen [TVBN], pH, and oxidation-reduction potential [Eh]). The samples (n = 76) were taken from three basic types of dry-cured hams produced in Spain: slow-cured hams from white pigs (n = 39), fast-cured hams from white pigs (n = 15), and hams from black-skinned Iberian pigs (n = 22). Overall, 56 samples (73.7%) showed the "bone taint" condition, and the remaining 20 hams (26.3%) were normal, and therefore considered as a control group. The objective of this research was to establish the possible circumstances that determine the alteration by means of the differences found in the values of the analyzed measurements in both groups of samples (altered versus normal ones). The hams with "bone taint" were, in general terms, those with a higher TVBN content, a greater pH, and a lower Eh, attributable to an anomalous development of the proteolytic phenomena. The conjunction of a lower concentration of chlorides, greater moisture content, and a higher aw in the affected hams may have created the conditions favorable for tissue enzyme and/or microbial activity.

RESUMEN

A survey of contamination with Salmonella spp. was done at 11 sampling sites in a poultry slaughter establishment in Spain for a total of 192 samples. Samples included fecal material, utensils, water, and poultry carcasses and livers at several stages of processing. Salmonella incidence rates increased from 30% in fecal material collected from incoming birds to 60% in air-chilled carcasses and 80% in cold-stored livers, indicating that cross-contamination occurred. The rate of incidence of Salmonella organisms on carcasses averaged 56.7% through post-picking to post-air chilling and reached a maximum of 70% on carcasses at the post-spray wash site. Poultry livers were more heavily contaminated with salmonellae, as 55% and 80% samples after evisceration and cold storage, respectively, were positive for those pathogenic bacteria. From a total of 112 strains isolated, 87 (77.6%) were S. enteritidis , 7 (6.2%) Salmonella serotype 4,5,12:b:-(II), and 6 (5.4%) Salmonella serotype 4,12:b:-(II), and the remaining 12 strains were equally distributed among S. typhimurium . S. virchow , and S. blockley (3.6% each). Serotypes isolated from feces were later detected in matched carcasses and livers indicating a cross-contamination of carcasses by endogenous microflora in bird feces. The incidence of Salmonella serotype 4,5, 12:b:-(II) and that of S. typhimurium were significantly higher (P < 0.05) in samples obtained prior to evisceration than in those collected after that particular step. The situation with S. enteritidis was quite the reverse, since this serotype was more frequently detected in samples taken after the evisceration step (P < 0.01).

RESUMEN

The resistance to 12 commonly used antimicrobial agents of 144 foodborne isolates belonging to the genus Listeria (23 L. monocytogenes , 54 L. innocua , 66 L. seeligeri , and 1 L. welshimeri ) was tested by using the agar disc-diffusion assay. The Listeria strains were isolated from dairy products (different varieties of unripened fresh and bacteria-ripened hard cheeses made from ewe's, cow's, and goat's milk) and meat products ( longaniza , a type of pork sausage). A total of 84 (93%) and 54 (100%) Listeria strains isolated from cheese and pork sausage, respectively, were resistant to multiple antimicrobial agents. More than 80% of the Listeria strains of both food origins were found to be susceptible to penicillin G and ampicillin, whereas the proportion of isolates resistant to the cephalosporins cefotaxime and cefoxitin was nearly 100%. The prevalence of resistance was much higher for isolates from pork sausage (73.8% on average) than for isolates from cheese (20.9%). This marked difference was statistically significant (P < 0.05; chi-square test) for all antibiotics except ampicillin, cefotaxime, and cefoxitin. The strains of the foodborne pathogen L. monocytogenes isolated from cheese were all susceptible to 9 of the 12 antimicrobial agents evaluated. In contrast, more than 80% of the L. monocytogenes strains isolated from pork sausage exhibited resistance to cefotaxime, cefoxitin, tobramycin, amikacin, chloramphenicol, tetracycline, and erythromycin. The appearance of substantial resistance to antibiotics in foodborne Listeria isolates suggests the need for more prudent use of antibiotics by farmers, veterinarians, and physicians.

RESUMEN

Lamb liver samples from a commercial abattoir were packed separately and stored under aerobic conditions at 0 and 3°C for 8 d. Both surface microbiological [aerobic plate count (APC)] at 30°C, APC at 7°C, Enterobacteriaceae , Pseudomonas , and lactic acid bacteria counts and organoleptic analysis ("overall appearance", "odor", and "visible surface colonies") were performed on days 0, 3, 6, and 8. All microbial groups (except lactic acid bacteria) showed differences in the growth between 0 and 3°C. Both at 0 and 3°C, a statistical correlation was demonstrated between organoleptic spoilage and the increase in APCs at 30°C, APCs at 7°C, and Pseudomonas (r ≥ 0.9; p < 0.0001). When these three parameters reached 106-107 CFU/cm2, visible surface colonies appeared, which made the product rejectable. Among the three organoleptic parameters studied, this is the first to determine organoleptic spoilage and has hence enabled us to establish a shelf life of up to 6-7 d and up to 4-5.5 d for samples stored at 0 and 3°C, respectively. Off-odors were detected 2 d later since the three counts had already reached levels higher than 108 CFU/cm2.