Benito Moreno

Yeast populations on Spanish fermented sausages

Yeast populations on 24 lots of Spanish fermented sausages, made by four factories (F1, F2 and F4, artisanal; F3, industrial) were investigated throughout manufacture and the influence of different variables evaluated. In addition, 41 yeast strains were identified at the species level using two miniaturised systems: ATB32C (API System) and Vitek Yeast Biochemical Card (Vitek YBC). Levels of yeasts found in the sausage mixture (mean counts around 4 log units/g) were similar to those described by other authors. In sausages from factories F1 and F2, a further increase was noted, reaching 5.5 log units/g after fermentation. Counts subsequently decreased to 3.6 and 5 log units/g, respectively. In sausages from factories F3 and F4, decreasing counts were observed from the beginning, particularly in sausages from F3, where yeasts were almost absent in the finished product. Type of manufacture and sausage diameter, were the variables most influencing yeast counts. Debaryomyces hansenii (teleomorph of C. famata) was the dominant species, being found at all stages of manufacture. Trichosporon ovoides (formerly T. beigelii), Yarrowia lipolytica (perfect form of C. lipolytica), C. intermedia/curvata, C. parapsilosis, C. zeylanoides and Citeromyces matritensis (teleomorph of C. globosa) were also present. Direct identification was possible only with 50% of the total of strains investigated, although a higher number of strains was identified using the API than the Vitek YBC system.

Microbiological quality of retail chicken by-products in Spain

The microbiological quality of retail chicken parts (legs, wings and giblets) and processed chicken products (hamburgers and sausages) in Spain was investigated. Mean counts (log(10) cfu/g) ranged from 5.56 to 7.28, 5.96 to 7.87, 3.49 to 5.42, 2.60 to 4.33 and 2.47 to 3.48 for mesophiles, psychrotrophs, coliforms, Escherichia coli and Staphylococcus aureus, respectively. Chicken parts were generally regarded as being of unacceptable quality, since psychrotrophs, E. coli and S. aureus counts were higher than the maximum limits established in the guidelines for poultry meat. On the basis of Spanish Microbiological Standards, 80% of the samples of hamburgers and sausages were also regarded as being of unacceptable quality. The main reason for the lack of acceptability was excessive counts of mesophiles. The results in this study indicate that chicken by-products (especially those made with ground meat) could represent notable hazards to humans and are a cause of public health concern.

Occurrence of Listeria species in retail poultry meat and comparison of a cultural/immunoassay for their detection

The prevalence of Listeria spp. on the skin of a hundred fresh chicken carcasses purchased from 20 retail stores in León was investigated using the routine test procedure recommended by the United States Department of Agriculture (USDA). PALCAM and Modified Oxford agar (MOX) were used for isolation. Listeria spp., Listeria monocytogenes, L. innocua, L. welshimeri, L. grayi and L. ivanovii were present in 95%, 32%, 66%, 7%, 4% and 2% of the samples, respectively. Next, an immunoassay test (Listeria Rapid Test; Oxoid, Unipath) and the routine test procedure (USDA) were compared for their ability to detect Listeria spp. on 40 chicken carcasses. When we used MOX for the isolations, the sensitivity of the immunoassay test was 100% and the specificity 85.7%. When we used PALCAM medium the sensitivity and specificity of the test was 94.29% and 80%, respectively.

Occurrence of salmonellae in retail chicken carcasses and their products in Spain.

This study examined the incidence of Salmonella in Spanish poultry products. Samples included chicken carcasses, chicken parts (wings, legs and giblets-livers and hearts) and processed chicken products (red sausages, white sausages and hamburgers). The average detection rate was 49%, with the highest (55%) in chicken carcasses (skin) and the lowest (20%) in hamburgers. The chicken carcasses purchased in supermarkets were more contaminated (75%) than those from poulterers shops (25%). Salmonella Enteritidis, S. Poona, S. Paratyphi B and S. Worthington were isolated in 34.3%, 11.4%, 2.8% and 1.4% of the samples, respectively. One (1.4%) red sausage sample harboured two serotypes (S. Enteritidis and S. Worthington). This fact emphasizes the usefulness of subtyping several Salmonella isolates from the same sample in epidemiological studies.

Review: Trisodium Phosphate (TSP) Treatment for Decontamination of Poultry

Use of trisodium phosphate (TSP) treatment for reducing levels of bacteria in poultry is discussed with reference to: health and economic consequences of poultry contamination, causes or routes of contamination, possibilities for reduction of microbial loads, mechanisms of action of TSP, sensory properties and quality of TSP-treated poultry, antimicrobial effectiveness, influences on shelf-life, and worldwide authorization of this process, with special reference to the situation in the European Union. A summary of the main results of microbial reductions on poultry following TSP treatment is shown for Salmonella, coliforms/Escherichia coli, Enterobacteriaceae, Campylobacter, Pseudomonas, total counts, Listeria, Staphylococcus aureus and Lactobacillus. The main results on microbial reductions assessed in foodstuffs other than poultry (beef, fruit, fish and shellfish) are also shown. En este artículo se discute el uso del tratamiento con fosfato trisódico (TSP) para reducir la contaminación bacteriana de la carne de ave con referencia a: consecuencias económicas y para la salud de la contaminación de la carne de ave, causas o rutas de contaminación, posibilidades de reducir la carga microbiana, mecanismos de acción del TSP, características organolépticas y calidad de la carne de ave tratada con TSP, eficacia antimicrobiana y factores que la afectan, influencia de este tratamiento en el tiempo de vida útil, y autorización de este proceso en el mundo, con especial referencia a la situación dentro de la Unión Europea. Se han resumido los resultados de las reducciones microbianas obtenidas en carne de ave tratada con TSP para Salmonella, coliformes/Escherichia coli, Enterobacteriaceae, Campylobacter, Pseudomonas, microorganismos totales, Listeria, Staphylococcus aureus y Lactobacillus. También se han contemplado los principales resultados obtenidos en otros alimentos distintos de la carne de ave (carne de vacuno, fruta, pescado y marisco).

Characterization and Enterotoxigenicity of Staphylococci Isolated from Mastitic Ovine Milk in Spain

On the basis of glucose fermentation and lysostaphin sensitivity, 71 gram-positive, catalase-positive cocci, isolated from mastitic ovine milk in Spain, were classified as members of the genus Staphylococcus . Identification at the species level was accomplished by complete characterization of the staphylococcal strains. Fifty-nine of the isolates were classified as S. aureus , 1 as S. simulans , 5 as S. epidermidis , a as S. haemolyticus and 5 could not be classified as any accepted or newly proposed species. The number of strains lysed by phages of S. aureus of human and bovine origin was 8 and 40, respectively. The phage pattern most frequently found was 78 (34 strains). Fifty of the S. aureus strains belonged to biotype C. Forty-nine of the S. aureus strains and 2 of the unclassified ones produced enterotoxin: 46 produced enterotoxin C, 2 produced enterotoxin A, 1 produced enterotoxin D and 2 produced both enterotoxins A and C. Forty-one of the 46 enterotoxin C producers belonged to biotype C, and 31 of these were lysed by phage 78.

Microbiological quality and composition of two types of Spanish sheep's milk cheeses (Manchego and Burgos varieties)

Thirty six samples of Manchego and 36 of Burgos cheese from retail outlets were examined. The mean log microbiological counts/g in Manchego cheese were 2·6 coliforms, 3·76 enterococci, 7·07 lactic acid bacteria, 8·02 mesophiles, 3·84 psychrotrophs 4·47 yeasts and moulds and 4·11 staphylococci, and in Burgos cheese were 7·17, 3·45, 7·25, 8·89, 8·18, 5·09 and 5·12 respectively. Coagulase-positive staphylococci were detected only in three samples of Manchego cheese, one of these isolates producing enterotoxin A. Staphylococcal thermonuclease was detected in eight samples of Manchego and 12 of Burgos cheese, the mean values of enzyme detected being 0·29 and 0·32 ng/g cheese respectively. Staphylococcal enterotoxins were not detected in any of the cheeses tested. Possible relationships between microbial counts and physicochemical characteristics were investigated by regression analysis.

Distribution and evolution of bacteria on lamb carcasses during aerobic storage

The change of bacterial counts during storage life of chilled (3±1°C) lamb carcasses was determined by sampling at 0, 5, 10, and 15 d postslaughter and at the spoilage time. Three sites (neck, brisket, and leg) of each carcass were sampled using three sampling methods (swabbing, scraping, and excision of the swabbed and scraped areas). After slaughter, mean count of mesophiles (30°C) was 4.96 log10 CFU/cm2. The initial mean count of psychrotrophs (7°C) expressed as a percentage of the mean count of mesophiles was 33.4%. The mean values of mesophiles and psychrotrophs associated with spoilage were 7.4 log10/cm2 and 7.95 log10/cm2, respectively. Carcasses always had pH values above 5.8 and kept unspoiled 23-29 d. Brisket and leg were the most contaminated areas. Percentages of bacteria recovered by scraping were higher than those obtained by swabbing (ca. 20%). Bacterial counts were significantly affected by day of storage (p<0.001), sampling point (p<0.001), and temperature of incubation (p<0.05). Interaction between sampling day and sampling site was also observed.

Influence of poultry carcass skin sample site on the effectiveness of trisodium phosphate against Listeria monocytogenes.

The aim of this study was to determine the influence of skin sample site on the efficacy of trisodium phosphate (TSP) solutions in reducing Listeria monocytogenes populations on chicken carcasses during refrigerated storage. Chicken skin samples from the legs, the breasts, and the dorsal area inoculated with L. monocytogenes (10(8) CFU/ml) were dipped for 15 min in sterile tap water (control) or in 8, 10, or 12% TSP. L. monocytogenes counts and surface pH values were determined after 0, 1, 3, and 5 days of storage at 2 degrees C. For all sampling times and TSP concentrations, the reductions in L. monocytogenes numbers in breast skin were significantly larger (P < 0.05) than those in leg skin or dorsal skin. No significant differences were found in pH values as an effect of skin site. Our results suggest that skin sampling site is an important factor that needs to be considered when decontamination protocols are developed for poultry carcasses with the TSP treatment.

Efficacy of trisodium phosphate solutions in reducing Listeria monocytogenes populations on chicken skin during refrigerated storage.

Chicken skin inoculated with l0(8) CFU/ml of Listeria monocytogenes was dipped for 15 min in sterile water (control) and in 8, 10, or 12% trisodium phosphate (TSP) solutions. Skin samples were stored at 2 degrees C for 5 days, with microbial monitoring on days 0, 1, 3, and 5 after treatment. Compared to the water dip, all TSP treatments significantly (P < 0.05) reduced L monocytogenes populations on chicken skin. The concentration of the TSP was a significant factor in reducing the populations of the bacteria at days 0, 1, 3, and 5 of refrigerated storage. For all sampling times, the best outcomes were attained with the highest TSP concentration studied (12%). Bacterial reductions in counts during the first day of storage were between 1.52 and 2.70 log10 cycles for 8 and 12% TSP-treated samples, respectively. Significantly greater reductions were observed from the third day of refrigerated storage onward. This occurred largely because populations of L. monocytogenes on control samples increased somewhat, but on TSP-treated samples the pathogen remained practically constant. Differences between L monocytogenes counts in skin samples immersed in water and those treated with TSP ranged from 2.10 (8% TSP-treated samples) and 3.63 (12% TSP-treated samples) log10 cycles on day 5 of storage. These results indicated that TSP is effective against L. monocytogenes in chicken meat, especially after several days of refrigerated storage.