Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 25
Filter
Add more filters










Publication year range
1.
Food Res Int ; 159: 111609, 2022 09.
Article in English | MEDLINE | ID: mdl-35940804

ABSTRACT

Current trends towards the use of ingredients from natural origin in food, cosmetic and pharmaceutical industry, place macroalgae as a good reservoir of novel compounds. Among them, lipophilic major pigments such as chlorophylls and fucoxanthin, are of great interest because of their multiple applications as bioactive compounds and dyes. In this work, a mid-polarity medium was used to extract pigments from twenty-four species from North coast of Spain, including brown (Phaeophyceae) and red macroalgae (Rhodophyta). The fucoxanthin and chlorophyll a content was assessed by means of two different methods, spectrophotometric and high-performance liquid chromatography coupled to diode array detection (HPLC-DAD). The effect of dried processing on the pigment content of selected species was also evaluated. A linear relationship between the extractability of fucoxanthin and chlorophyll a was observed, being the highest content recorded among members belonging to the order Fucales and Undaria pinnatifida. This work provides good insights about the content on pigments in Spanish North Atlantic macroalgae with future commercial value in different industrial fields, as well as a critical overview of the suitability of the quantification methods and challenges related to their effect in results evaluation.


Subject(s)
Food Ingredients , Phaeophyceae , Seaweed , Undaria , Chlorophyll A , Phaeophyceae/chemistry , Seaweed/chemistry , Undaria/chemistry
2.
Meat Sci ; 123: 120-125, 2017 Jan.
Article in English | MEDLINE | ID: mdl-27710771

ABSTRACT

This work aimed to quantify the impact of aw and fat content of dry-cured ham on the Log reduction of Salmonella enterica by high pressure (HP). Dry-cured ham with adjusted aw (0.86-0.96) and fat content (10-50%) was inoculated with S. enterica and pressurised (347-852MPa, 5min/15°C), following a Central Composite Design. Polynomial regression indicated a significant impact of pressure and aw on S. enterica HP-lethality. By lowering aw a clear piezoprotection was observed. At low aw (0.88) the S. enterica reduction was little affected by increasing pressure (e.g. 2.3 to 3.2 Logs at 450 to 750MPa, respectively). At the highest aw the estimated inactivation ranged from 3.3 to 8.9 Logs at 450 to 750MPa, respectively. No significant piezoprotective effect on S. enterica was recorded by the fat content. The relevance of food characteristics on the HP-lethality of S. enterica indicate the need to validate the HP effectiveness on the specific product.


Subject(s)
Adipose Tissue , Food Contamination/prevention & control , Food Microbiology , Meat Products/microbiology , Water/analysis , Animals , Consumer Product Safety , Food Handling , Hydrogen-Ion Concentration , Models, Theoretical , Pressure , Salmonella enterica/isolation & purification , Swine
3.
Food Res Int ; 75: 194-199, 2015 Sep.
Article in English | MEDLINE | ID: mdl-28454947

ABSTRACT

High pressure processing (HPP) is a promising food preservation technology as an alternative to thermal processing for microbial inactivation. The technological parameters, the type of microorganism, and the food composition can greatly affect the microbicidal potential of HPP against spoilage and pathogenic microorganisms. Presently, the number of available models quantifying the influence of food characteristics on the pathogen inactivation is scarce. The aim of this study was to model the inactivation of Listeria monocytogenes CTC1034 in dry-cured ham, as a function of pressure (347-852MPa, 5min/15°C), water activity (aw, 0.86-0.96) and fat content (10-50%) according to a Central Composite Design. The response surface methodology, based on the equation obtained with a stepwise multivariate linear regression, was used to describe the relationship between bacterial inactivation and the studied variables. According to the best fitting polynomial equation, besides pressure intensity, both aw and fat content exerted a significant influence on HP-inactivation of L. monocytogenes. A clear linear piezoprotection trend was found lowering the aw of the substrate within the whole range of tested pressure. Fat content was included in the model through the quadratic term and as interaction term with pressure, resulting in a particular behavior. A protective effect due to the presence of high fat content was identified for pressure treatments above ca. 700MPa. At lower pressure, higher inactivation of L. monocytogenes occurred by increasing the fat content above 30%. The results emphasize the relevant influence of intrinsic factors on the L. monocytogenes inactivation by HPP, making necessary to assess and validate the effectiveness of HPP on specific food products and consequently set process criteria adjusted to each particular food product.

4.
Benef Microbes ; 6(3): 381-6, 2015.
Article in English | MEDLINE | ID: mdl-25380798

ABSTRACT

The production of long shelf-life highly concentrated dried probiotic/starter cultures is of paramount importance for the food industry. The aim of the present study was to evaluate the protective effect of glucose, lactose, trehalose, and skim milk applied alone or combined upon the survival of potentially probiotic Lactobacillus rhamnosus CTC1679, Lactobacillus casei/paracasei CTC1677 and L. casei/paracasei CTC1678 during freeze-drying and after 39 weeks of storage at 4 and 22 °C. Immediately after freeze-drying, the percentage of survivors was very high (≥ 94%) and only slight differences were observed among strains and cryoprotectants. In contrast, during storage, survival in the dried state depended on the cryoprotectant, temperature and strain. For all the protectants assayed, the stability of the cultures was remarkably higher when stored under refrigeration (4 °C). Under these conditions, skim milk alone or supplemented with trehalose or lactose showed the best performance (reductions ≤ 0.9 log units after 39 weeks of storage). The lowest survival was observed during non-refrigerated storage and with glucose and glucose plus milk; no viable cells left at the end of the storage period. Thus, freeze-drying in the presence of appropriate cryoprotectants allows the production of long shelf-life highly concentrated dried cultures ready for incorporation in high numbers into food products as starter/potential probiotic cultures.


Subject(s)
Cryoprotective Agents/pharmacology , Lacticaseibacillus casei/growth & development , Lacticaseibacillus rhamnosus/growth & development , Lactobacillus/growth & development , Preservation, Biological/methods , Lactobacillus/drug effects , Lacticaseibacillus casei/drug effects , Lacticaseibacillus rhamnosus/drug effects , Microbial Viability/drug effects , Preservation, Biological/instrumentation , Probiotics/chemistry , Temperature
5.
Benef Microbes ; 6(3): 337-43, 2015.
Article in English | MEDLINE | ID: mdl-25488261

ABSTRACT

The capability of five lactic acid bacteria (LAB) to counteract the adhesion of Listeria monocytogenes to the epithelial intestinal cell line HT29 was studied. The highest adhesion ability to HT29 was achieved by the intestinal strain Lactobacillus rhamnosus CTC1679, followed by the meat-derived strains Lactobacillus sakei CTC494 and Enterococcus faecium CTC8005. Surprisingly, the meat strains showed significantly better adhesion to HT29 than two faecal isolates of Lactobacillus casei and even significantly higher than the reference strain L. rhamnosus GG. Additionally, the anti-listerial, bacteriocin-producer starter culture L. sakei CTC494 was able to significantly reduce the adhesion of L. monocytogenes to HT29 in experiments of exclusion, competition and inhibition. The performance was better than the faecal isolate L. rhamnosus CTC1679. Our results reinforce the fact that the ability of LAB to interact with a host epithelium model, as well as to antagonise with foodborne pathogens, is a strain-specific characteristic. Additionally, it is underlined that this trait is not dependent on the origin of the bacterium, since some food LAB behave better than intestinal ones. Therefore, the search for novel strains in food niches is a suitable approach to find those with potential health benefits. These strains are likely pre-adapted to the food environment, which would make their inclusion in the formulation of probiotic foods more feasible.


Subject(s)
Bacterial Adhesion/drug effects , Colon/microbiology , Lactobacillales/physiology , Listeria monocytogenes/drug effects , Probiotics/pharmacology , Colon/cytology , Feces/microbiology , HT29 Cells , Humans , Listeria monocytogenes/physiology
6.
Int J Food Microbiol ; 186: 84-94, 2014 Sep 01.
Article in English | MEDLINE | ID: mdl-25016207

ABSTRACT

Various predictive models are available for high pressure inactivation of Listeria monocytogenes in food, but currently available models do not consider the growth kinetics of surviving cells during the subsequent storage of products. Therefore, we characterised the growth of L. monocytogenes in sliced cooked meat products after a pressurization treatment. Two inoculum levels (10(7) or 10(4) CFU/g) and two physiological states before pressurization (freeze-stressed or cold-adapted) were evaluated. Samples of cooked ham and mortadella were inoculated, high pressure processed (400 MPa, 5 min) and subsequently stored at 4, 8 and 12 °C. The Logistic model with delay was used to estimate lag phase (λ) and maximum specific growth rate (µmax) values from the obtained growth curves. The effect of storage temperature on µmax and λ was modelled using the Ratkowsky square root model and the relative lag time (RLT) concept. Compared with cold-adapted cells the freeze-stressed cells were more pressure-resistant and showed a much longer lag phase during growth after the pressure treatment. Interestingly, for high-pressure inactivation and subsequent growth, the time to achieve a concentration of L. monocytogenes 100-fold (2-log) higher than the cell concentration prior to the pressure treatment was similar for the two studied physiological states of the inoculum. Two secondary models were necessary to describe the different growth behaviour of L. monocytogenes on ready-to-eat cooked ham (lean product) and mortadella (fatty product). This supported the need of a product-oriented approach to assess growth after high pressure processing. The performance of the developed predictive models for the growth of L. monocytogenes in high-pressure processed cooked ham and mortadella was evaluated by comparison with available data from the literature and by using the Acceptable Simulation Zone approach. Overall, 91% of the relative errors fell into the Acceptable Simulation Zone.


Subject(s)
Listeria monocytogenes/growth & development , Meat Products/microbiology , Models, Biological , Pressure , Animals , Colony Count, Microbial , Computer Simulation , Cooking , Kinetics
7.
Food Microbiol ; 35(1): 34-7, 2013 Aug.
Article in English | MEDLINE | ID: mdl-23628612

ABSTRACT

To quantify the inactivation of Serratia liquefaciens exerted by high pressure processing (HPP), slices of dry-cured ham were inoculated and processed combining different levels of technological parameters: pressure (347-852 MPa), time (2.3-15.8 min) and temperature (7.6-24.4 °C) according to a central composite design. Bacterial inactivation, as logarithmic reduction, indicated that S. liquefaciens was relatively sensitive to HPP. Six log reductions were achieved in a total of 10 trials combining pressures of 600 MPa or above with different holding times and temperatures. The inactivation of S. liquefaciens was analysed through the multiple regression analysis to generate a second order polynomial equation. Pressure and time were the two factors which significantly determined the inactivation of S. liquefaciens on dry-cured ham. Temperature did not significantly affect the lethality of the process. The response surface methodology was used to determine optimum process conditions to maximize the inactivation of S. liquefaciens in the experimental range tested. The maximum inactivation of S. liquefaciens in dry-cured ham was achieved by combining a pressure of 650 MPa with a holding time of 8 min. Combinations above these values (i.e. 750 MPa for 13 min) would not significantly improve the lethality of the process.


Subject(s)
Food Contamination/prevention & control , Food Microbiology/methods , Meat/microbiology , Serratia liquefaciens/growth & development , Animals , Bacterial Load , Colony Count, Microbial , Consumer Product Safety , Food Preservation/methods , Models, Theoretical , Pressure , Regression Analysis , Swine , Temperature
8.
Food Microbiol ; 28(4): 804-9, 2011 Jun.
Article in English | MEDLINE | ID: mdl-21511142

ABSTRACT

The aim of the work was to develop and validate a model of the inactivation of Listeria monocytogenes on dry-cured ham by high hydrostatic pressure (HHP) processing, as a function of the technological parameters: intensity, length and fluid temperature. Dry-cured ham inoculated with L. monocytogenes was treated at different HHP conditions (at 347-852 MPa; for 2.3 to 15.75 min; at 7.6 to 24.4 °C) following a central composite design. Bacterial inactivation was assessed in terms of logarithmic reductions of L. monocytogenes counts on selective media. According to the best fitting and most significant polynomial equation, pressure and time were the most important factors determining the inactivation extent. The significance of the quadratic term of pressure and time indicated that little effect was observed below 450 MPa, whereas holding time longer than 10 min did not result in a meaningful reduction of L. monocytogenes counts. Temperature did not show significant influence at the range assayed. The model was validated with results obtained from further experiments and bibliographical data within the range of the experimental domain. The accuracy factor and bias factor were within the proposed acceptable values indicating the suitability of the model for predictive purposes, such as prediction of the process criteria to meet the Food Safety Objectives. The results of this work may help food processors to select optimum processing conditions of HHP.


Subject(s)
Food Microbiology/methods , Food Preservation/methods , Listeria monocytogenes/growth & development , Meat Products/microbiology , Models, Biological , Animals , Colony Count, Microbial , Hydrostatic Pressure , Linear Models , Swine
9.
J Food Prot ; 73(3): 524-8, 2010 Mar.
Article in English | MEDLINE | ID: mdl-20202339

ABSTRACT

Any bacterial strain to be used as starter culture should have suitable characteristics, including a lack of amino acid decarboxylase activity. In this study, the decarboxylase activity of 76 bacterial strains, including lactic acid bacteria and gram-positive, catalase-positive cocci, was investigated. These strains were previously isolated from European traditional fermented sausages to develop autochthonous starter cultures. Of all the strains tested, 48% of the lactic acid bacteria strains and 13% of gram-positive, catalase-positive cocci decarboxylated one or more amino acids. Aminogenic potential was strain dependent, although some species had a higher proportion of aminogenic strains than did others. Thus, all Lactobacillus curvatus strains and 70% of Lactobacillus brevis strains had the capacity to produce tyramine and beta-phenylethylamine. Some strains also produced other aromatic amines, such as tryptamine and the diamines putrescine and cadaverine. All the enterococcal strains tested were decarboxylase positive, producing high amounts of tyramine and considerable amounts of beta-phenylethylamine. None of the staphylococcal strains had tyrosine-decarboxylase activity, but some produced other amines. From the aminogenic point of view, Lactobacillus plantarum, Lactobacillus sakei, and Staphylococcus xylosus strains would be the most suitable for use as autochthonous starter cultures for traditional fermented sausages.


Subject(s)
Aromatic-L-Amino-Acid Decarboxylases/metabolism , Consumer Product Safety , Food Handling/methods , Food Microbiology , Meat Products/microbiology , Amino Acids/analysis , Amino Acids/biosynthesis , Animals , Biogenic Amines/analysis , Biogenic Amines/biosynthesis , Colony Count, Microbial , Enterobacteriaceae/enzymology , Enterobacteriaceae/metabolism , Fermentation , Humans , Lactobacillus/enzymology , Lactobacillus/metabolism , Staphylococcus/enzymology , Staphylococcus/metabolism , Swine , Tyramine/analysis , Tyramine/biosynthesis
10.
J Appl Microbiol ; 106(1): 66-77, 2009 Jan.
Article in English | MEDLINE | ID: mdl-19120623

ABSTRACT

AIMS: Four local small-scale factories were studied to determine the sources of enterococci in traditional fermented sausages. METHODS AND RESULTS: Different points during the production of a traditional fermented sausage type (fuet) were evaluated. Randomly amplified polymorphic DNA (RAPD)-PCR was used to type 596 Enterococcus isolates from the final products, the initial meat batter, the casing, the workers' hands and the equipment. Species-specific PCR-multiplex and the partial sequencing of atpA gene and 16S rRNA gene sequencing allowed the identification of the isolates: Enterococcus faecalis (31.4%), Enterococcus faecium (30.7%), Enterococcus sanguinicola (14.9%), Enterococcus devriesei (9.7%), Enterococcus malodoratus (7.2%), Enterococcus gilvus (1.0%), Enterococcus gallinarum (1.3%), Enterococcus casseliflavus (3.4%), Enterococcus hermanniensis (0.2%), and Enterococcus durans (0.2%). A total of 92 different RAPD-PCR profiles were distributed among the different factories and samples evaluated. Most of the genotypes found in fuet samples were traced back to their source. CONCLUSIONS: The major sources of enterococci in the traditional fermented sausages studied were mainly the equipment followed by the raw ingredients, although a low proportion was traced back to human origin. SIGNIFICANCE AND IMPACT OF THE STUDY: This work contributes to determine the source of enterococcal contamination in fermented sausages and also to the knowledge of the meat environment.


Subject(s)
Enterococcus/classification , Food Contamination , Food Microbiology , Meat Products/microbiology , Polymerase Chain Reaction/methods , DNA, Bacterial/analysis , DNA, Bacterial/genetics , Enterococcus/isolation & purification , Food Industry , RNA, Ribosomal, 16S/genetics , Random Amplified Polymorphic DNA Technique
11.
Meat Sci ; 78(1-2): 114-29, 2008 Jan.
Article in English | MEDLINE | ID: mdl-22062101

ABSTRACT

Consumers demand high quality, natural, nutritious, fresh appearance and convenient meat products with natural flavour and taste and an extended shelf-life. To match all these demands without compromising safety, in the last decades alternative non-thermal preservation technologies such as HHP, irradiation, light pulses, natural biopreservatives together with active packaging have been proposed and further investigated. They are efficient to inactivate the vegetative microorganisms, most commonly related to food-borne diseases, but not spores. The combination of several non-thermal and thermal preservation technologies under the so-called hurdle concept has also been investigated in order to increase their efficiency. Quick thermal technologies such as microwave and radiofrequency tunnels or steam pasteurization bring new possibilities to the pasteurization of meat products especially in ready to eat meals. Their application after final packaging will prevent further cross-contamination during post-processing handling. The benefits of these new technologies and their limitations in an industrial application will be presented and discussed.

12.
J Appl Microbiol ; 103(1): 1-10, 2007 Jul.
Article in English | MEDLINE | ID: mdl-17584447

ABSTRACT

AIMS: To investigate the sources of Salmonella spp. in Alheira and how to trace it, by studying the way that Salmonella spp. is distributed across production lines, by applying multifactorial correspondence analysis to occurrence data, and through the use of polymerase chain reaction (PCR) molecular typing methods. METHODS AND RESULTS: Four production lines, four batches of Alheira and 14 sampling sites were analysed over four sampling periods. Eighty-five Salmonella spp. isolates were obtained from the 896 microbial analyses performed. The basic occurrence analysis values, multiple correspondence analysis and PCR molecular typing methods confirmed that the presence of Salmonella spp. in Alheira was directly related to it being present in casings. Results obtained from PCR molecular typing added a measure of detail, highlighting potential cross-path contamination caused by contaminated surfaces. CONCLUSIONS: The presence of Salmonella spp. in Alheira was a result of the use of contaminated casings, as well as cross-path contamination caused by contaminated surfaces. An analysis of the occurrence data indicated that these casings were the source of Salmonella spp. contamination in Alheira. PCR molecular typing methodology, which is known to have a greater discriminatory power and tracing capacity, indicated the presence of cross-path contamination. SIGNIFICANCE AND IMPACT OF THIS STUDY: Increased awareness of Salmonella spp. contamination sources and their spread across the production line helps shape the development of new strategies for controlling this pathogen.


Subject(s)
Food Microbiology , Food-Processing Industry , Meat Products/microbiology , Salmonella/isolation & purification , Bacterial Typing Techniques/methods , Food Handling , Humans , Polymerase Chain Reaction/methods , Salmonella/classification , Salmonella/genetics
13.
J Food Prot ; 70(3): 685-91, 2007 Mar.
Article in English | MEDLINE | ID: mdl-17388060

ABSTRACT

Sources and tracing of Staphylococcus aureus in alheira (garlic sausage) production were evaluated by multifactorial correspondence analysis (MCA) of occurrence data and a random amplified polymorphic DNA (RAPD) on S. aureus isolates. Samples from four production lines, four different production batches, and 14 different sampling sites (including raw material, different contact surfaces, and several stages of alheira manufacturing) were analyzed at four sampling times. From the 896 microbial analyses completed, a collection of 170 S. aureus isolates was obtained. Although analysis of the occurrence data alone was not elucidative enough, MCA and RAPD-PCR were able to assess the sources of contamination and to trace the spread of this microorganism along the production lines. MCA results indicated that the presence of S. aureus in alheira was related to its presence in the intermediate manufacturing stages after heat treatment but before stuffing in the casings. It was also possible to associate a cross-contamination path related to handler procedures. RAPD-PCR typing in accordance to MCA results confirmed the cross-contamination path between the raw material and casings and the role of handlers as an important cross-contamination vehicle.


Subject(s)
Food Contamination/analysis , Food Handling/methods , Food-Processing Industry/methods , Meat Products/microbiology , Random Amplified Polymorphic DNA Technique , Staphylococcus aureus/isolation & purification , Animals , Colony Count, Microbial , Food Handling/standards , Food Microbiology , Food-Processing Industry/standards , Humans , Hygiene , Intestines/microbiology , Staphylococcus aureus/classification , Swine
14.
Meat Sci ; 77(4): 570-9, 2007 Dec.
Article in English | MEDLINE | ID: mdl-22061943

ABSTRACT

Microbial ecosystems were surveyed in 314 environmental samples from 54 Southern and Eastern European small-scale processing units (PUs) manufacturing traditional dry fermented sausages. The residual microflora contaminating the surfaces and the equipment were analysed after cleaning and disinfection procedures. All the PU environments were colonised at various levels by spoilage and technological microflora with excessive contamination levels in some of the PUs. Sporadic contamination by pathogenic microflora was recorded. Salmonella and Listeria monocytogenes were detected in 4.8% and 6.7% of the samples, respectively, and Staphylococcus aureus was enumerated in 6.1% of the samples. Several critical points were identified, such as the machines for S. aureus and the tables and the knives for L. monocytogenes; this knowledge is crucial for the improvement of hygiene control systems in small and traditional meat processing industries. The variability of the residual contamination emphasized the different cleaning, disinfecting and manufacturing practices routinely followed by these small-scale processing units.

15.
Meat Sci ; 75(3): 460-9, 2007 Mar.
Article in English | MEDLINE | ID: mdl-22063802

ABSTRACT

The application of high hydrostatic pressure (200MPa) to meat batter just before sausage fermentation and the inoculation of starter culture were studied to improve the safety and quality of traditional Spanish fermented sausages (fuet and chorizo). Higher amounts of biogenic amines were formed in chorizo than in fuet. Without interfering with the ripening performance in terms of acidification, drying and proteolysis, hydrostatic pressure prevented enterobacteria growth but did not affect Gram-positive bacteria significantly. Subsequently, a strong inhibition of diamine (putrescine and cadaverine) accumulation was observed, but that of tyramine was not affected. The inoculated decarboxylase-negative strains, selected from indigenous bacteria of traditional sausages, were resistant to the HHP treatment, being able to lead the fermentation process, prevent enterococci development and significantly reduce enterobacteria counts. In sausages manufactured with either non-pressurized or pressurized meat batter, starter culture was the most protective measure against the accumulation of tyramine and both diamines.

16.
J Appl Microbiol ; 100(1): 40-9, 2006.
Article in English | MEDLINE | ID: mdl-16405683

ABSTRACT

AIM: To evaluate the biodiversity of lactobacilli from slightly fermented sausages (chorizo, fuet and salchichon) by molecular typing, while considering their safety aspects. METHODS AND RESULTS: Species-specific PCR, plasmid profiling and randomly amplified polymorphic DNA (RAPD)-PCR were used to characterize 250 lactic acid bacteria (LAB) isolated from 21 low acid Spanish fermented sausages. Lactobacillus sakei was the predominant species (74%) followed by Lactobacillus curvatus (21.2%) and Leuconostoc mesenteroides (4.8%). By plasmid profiling and RAPD-PCR 144 different strains could be differentiated, 112 belonging to Lact. sakei, 23 to Lact. curvatus and 9 to Leuc. mesenteroides. Ion-pair high performance liquid chromatography was used to detect biogenic amine production. Tyramine and phenylethylamine were produced by 14.4 and 12.4% of the isolates, respectively, all belonging to the species Lact. curvatus. The production of tyramine was stronger than that of phenylethylamine. Partial sequencing of the tyrosine decarboxylase gene from Lact. curvatus was achieved. A specific PCR assay to detect the Lact. curvatus tyramine-producers was designed. The disc diffusion test was used to detect antibiotic resistance among the isolates. Most isolates displayed resistance to vancomycin and gentamicin. Only four strains were resistant to most of the antibiotics tested. None of the isolates were resistant to erythromycin. CONCLUSIONS: Lactobacillus sakei would be the species of choice for further use as starter culture in fermented sausage production. Strain typing and characterization of biogenic amine production together with antibiotic susceptibility testing for the selection of starter cultures could help to increase the quality and safety of the products. SIGNIFICANCE AND IMPACT OF THE STUDY: Species-specific PCR, RAPD and plasmid profiling proved to be efficient at typing LAB at species and strain level. Information on biogenic amine production and transferable antibiotic resistance is important in order to avoid selection of strains with undesirable properties as starter cultures.


Subject(s)
Food Microbiology , Lactobacillus/isolation & purification , Meat Products/microbiology , Animals , Anti-Bacterial Agents/pharmacology , Bacteriocins/biosynthesis , Base Sequence , Biodiversity , Consumer Product Safety , Drug Resistance, Bacterial , Fermentation , Genes, Bacterial/genetics , Lactobacillus/drug effects , Leuconostoc/drug effects , Leuconostoc/isolation & purification , Phenethylamines/metabolism , Plasmids , Putrescine/biosynthesis , Tryptamines/biosynthesis , Tyramine/biosynthesis
17.
Int J Food Microbiol ; 107(2): 148-58, 2006 Mar 15.
Article in English | MEDLINE | ID: mdl-16297478

ABSTRACT

The population of Gram-positive catalase-positive cocci from slightly fermented sausages was characterized at species and strain level by molecular techniques and some technological and hygienic aspects were also considered. Staphylococcus xylosus was the predominant species (80.8%) followed by Staphylococcus warneri (8.3%), Staphylococcus epidermidis (5.8%) Staphylococcus carnosus (4.6%), and Kocuria varians (0.4%). Proteolytic activity was observed in 23% of the isolates. The species with the highest percentage of proteolytic strains was S. warneri. Lipolytic activity was found in 45.8% of the isolates and S. xylosus was the species with the highest percentage of lipolytic isolates. Biogenic amine production was not widely distributed (only 14.6% of the isolates). Tyramine was the most intense amine produced, although by only 4.6% of the isolates. Phenylethylamine was more frequently detected (10.8% of isolates) but at lower levels. Some strains also produced putrescine (3.3%), cadaverine (2.9%), histamine (1.3%) and tryptamine (0.4%). All isolates were susceptible to linezolid and vancomicin and over 70% were resistant to penicillin G, ampicillin and sulphonamides. Most of the mecA+ strains (only 4.6% of isolates) also displayed resistance to multiple antibiotics. A reduced enterotoxigenic potential was found. Only 3.3% of isolates showed staphylococcal enterotoxins genes, all identified as entC gene. The combination of RAPD-PCR and plasmid profiling allowed the discrimination of 208 different profiles among the 240 Gram-positive catalase-positive cocci characterized, indicating a great genetic variability.


Subject(s)
Catalase/metabolism , DNA, Bacterial/analysis , Meat Products/microbiology , Random Amplified Polymorphic DNA Technique/methods , Staphylococcus/classification , Staphylococcus/isolation & purification , Animals , Anti-Bacterial Agents/pharmacology , Base Sequence , Biogenic Amines/biosynthesis , Drug Resistance, Bacterial , Enterotoxins/biosynthesis , Fermentation , Lipolysis , Microbial Sensitivity Tests , Peptide Hydrolases/metabolism , Phylogeny , Plasmids , Species Specificity , Staphylococcus/drug effects , Staphylococcus/enzymology , Swine
18.
J Appl Microbiol ; 98(5): 1177-90, 2005.
Article in English | MEDLINE | ID: mdl-15836488

ABSTRACT

AIMS: To determine the biodiversity of enterococci from slightly fermented sausages (chorizo and fuet) at species and strain level by molecular typing, while considering their safety aspects. METHODS AND RESULTS: Species-specific PCR and partial sequencing of 16S rRNA and sodA genes were used to identify enterococcal population. Enterococcus faecium was the most frequently isolated species followed by E. faecalis, E. hirae and E. durans. Randomly amplified polymorphic DNA (RAPD)-PCR revealed species-specific clusters and allowed strain typing. Sixty strains of 106 isolates exhibited different RAPD profiles indicating a high genetic variability. All the E. faecalis strains carried virulence genes (efaAfs, esp, agg and gelE) and all E. faecium isolates carried efaAfm gene. Enterococcus faecalis showed higher antibiotic resistance than the other species. Only one E. faecium strain showed vanA genotype (high-level resistance to glycopeptides) and E. gallinarum and E. casseliflavus/flavescens isolates showed vanC1 and vanC2/C3 genotypes (low-level resistance only to vancomycin) respectively. CONCLUSIONS: E. faecalis has been mainly associated with virulence factors and antimicrobial multi-resistance and, although potential risk for human health is low, the presence of this species in slightly fermented sausages should be avoided to obtain high quality products. SIGNIFICANCE AND IMPACT OF THE STUDY: The enterococcal population of slightly fermented sausages has been thoroughly characterized. Several relevant safety aspects have been revealed.


Subject(s)
Enterococcus/genetics , Food Contamination , Food Microbiology , Meat Products , Base Sequence , DNA, Bacterial/analysis , Drug Resistance, Bacterial , Enterococcus/pathogenicity , Fermentation , Genetic Variation , Molecular Sequence Data , Phylogeny , Random Amplified Polymorphic DNA Technique , Virulence
19.
Lett Appl Microbiol ; 39(3): 290-5, 2004.
Article in English | MEDLINE | ID: mdl-15287877

ABSTRACT

AIMS: To combine the principles of most-probable-number (MPN) statistics and the conventional PCR technique to enumerate Listeria monocytogenes in fermented sausages. METHODS AND RESULTS: A simple method to enumerate L. monocytogenes in fermented sausages was developed and compared with direct plating in Palcam agar. Species-specific MPN-PCR, but not direct plating, made the enumeration of L. monocytogenes possible in all assayed samples. CONCLUSIONS: MPN-PCR proved to be a rapid and reliable method for enumerating L. monocytogenes in fermented sausages, including low contaminated samples. SIGNIFICANCE AND IMPACT OF THE STUDY: This MPN-PCR technique may facilitate the enumeration of L. monocytogenes for routine analyses in fermented sausages without excessive work.


Subject(s)
Meat Products/microbiology , Animals , Colony Count, Microbial , DNA, Bacterial/analysis , DNA, Ribosomal/analysis , Fermentation , Listeria monocytogenes/genetics , Listeria monocytogenes/isolation & purification , Polymerase Chain Reaction/methods , RNA, Ribosomal, 16S/genetics , Species Specificity
20.
Appl Environ Microbiol ; 69(8): 4583-94, 2003 Aug.
Article in English | MEDLINE | ID: mdl-12902246

ABSTRACT

Detection of six species of lactic acid bacteria and six species of gram-positive catalase-positive cocci from low-acid fermented sausages (fuets and chorizos) was assessed by species-specific PCR. Without enrichment, Lactobacillus sakei and Lactobacillus curvatus were detected in 11.8% of the samples, and Lactobacillus plantarum and Staphylococcus xylosus were detected in 17.6%. Enriched samples allowed the detection of L. sakei and S. xylosus in all of the samples (100%) and of Enterococcus faecium in 11.8% of the sausages. The percentages of L. curvatus, L. plantarum, Staphylococcus carnosus, and Staphylococcus epidermidis varied depending on the sausage type. L. curvatus was detected in 80% of fuets and in 57% of chorizos. L. plantarum was found in 50% of fuets and 100% of chorizos. S. epidermidis was detected in only 11.8% of fuets, and S. carnosus was detected in only 5.9% of chorizos. Lactococcus lactis, Staphylococcus warneri, and Staphylococcus simulans were not detected in any sausage type. From a microbiological point of view, 70.6% of the samples could be considered of high quality, as they had low counts of Enterobacteriaceae and did not contain any of the food-borne pathogens assayed.


Subject(s)
Colony Count, Microbial , Lactobacillus/isolation & purification , Meat Products/microbiology , Polymerase Chain Reaction/methods , Staphylococcus/isolation & purification , Base Sequence , Molecular Sequence Data , Species Specificity
SELECTION OF CITATIONS
SEARCH DETAIL
...