Prevalence and antimicrobial resistance of Salmonella serotypes isolated from poultry in Spain: comparison between 1993 and 2006

A total of 226 chicken samples (carcasses, legs, wings, necks and breasts) were obtained (73 in 1993 and 153 in 2006) from 10 retail outlets in North-Western Spain and screened for the presence of Salmonella. Isolates were subjected to serotyping, phage typing (Salmonella Enteritidis and Salmonella Typhimurium) and antimicrobial susceptibility testing (15 antimicrobials; disk diffusion method). Salmonella was detected in 40 (55%) samples in 1993 and 19 (12.4%) in 2006 (P < 0.001). The serotypes (S. Enteritidis, Salmonella Poona, Salmonella Infantis, Salmonella Newport and S. Typhimurium) and phage types (1, 4, 14b and 35 in the case of S. Enteritidis and 193 for S. Typhimurium) detected are among the main types responsible for human salmonellosis in Spain. All strains were multi-resistant (resistant to 3-13 antimicrobials). The average number of resistances per strain increased (P < 0.05) from 3.98 in 1993 to 5.00 in 2006. An increase in the incidence of resistance was observed between 1993 and 2006 for cephalothin (P < 0.01), enrofloxacin (P < 0.001) and tetracycline (P < 0.01). The decreases in the prevalence of Salmonella between 1993 and 2006 suggest that the mandatory measures introduced over the last decade in the European Union to reduce the incidence of Salmonella in poultry have apparently been successful. However, the increase in antibiotic resistance rates is of concern and constitutes a threat to public health. Because the data in this study demonstrated that chicken in North-Western Spain is a potential source of antibiotic-resistant Salmonella strains, the need of consumer education on good sanitary practices is highlighted.     

Evaluation of porous starch as a flavour carrier

A commercial porous starch was evaluated for the use as a carrier for liquid flavours. Encapsulation trials performed with diacetyl showed a high initial load and good retention over time when more polar solvents commonly used in flavour creation were used. The physical interactions between the porous starch and solvents used in flavour creation were also studied. The glass transition temperature of the starch decreased upon addition of the polar solvents, ethanol and propylene glycol. Propylene glycol also produced an exothermic peak when mixed with porous starch, possibly due to the formation of complexes between the two components. Low resolution (1)H-NMR results suggested that a stronger interaction was established between more polar solvents and the porous starch, as indicated by a more marked decrease in relaxation times and proton diffusion coefficient of the solvents on adding porous starch.     

Influence of housing systems on microbial load and antimicrobial resistance patterns of Escherichia coli isolates from eggs produced for human consumption

Microbial counts (aerobic bacteria, psychrotrophs, Enterobacteriaceae, coliforms, Pseudomonas spp., Enterococcus spp., Staphylococcus spp., and molds and yeasts) were obtained for the shells of 240 table eggs in northwestern Spain. Eggs from six sources (40 samples in each) were analyzed: chicken eggs from five different housing systems (conventional battery cages, barn, free range, organic, and domestic breeding) and quail eggs (cages). A total of 120 Escherichia coli strains (20 from each source) were tested by the disk diffusion method for resistance to 12 antimicrobial drugs of veterinary and human health significance. Aerobic plate counts ranged from 1.96 ± 1.0 (barn) to 3.69 ± 0.7 (domestic) log CFU/cm(2). Counts for most microbial groups differed significantly between sources. Eggs from domestic production had the highest contamination loads (P < 0.05) for aerobic bacteria, Enterococcus spp., and molds and yeasts and the highest prevalence of E. coli. Twenty-three E. coli isolates (19.17%) were susceptible to all antimicrobials tested, and 80.83 % were resistant to one (22.50%) or more (58.33%) antimicrobials. The housing system had a significant influence (P < 0.05) on the average resistance per strain, with the highest resistance in conventional cage (2.85) and barn (3.10) systems followed by free range (1.55) and quail (1.95). Eggs from organic (1.00) and domestic (0.75) production systems had the lowest resistance per strain. The highest prevalence of resistance was observed for the groups of antimicrobials more frequently used on poultry farms. Our results suggest that a relationship exists between the prevalence of antimicrobial resistance in E. coli strains and the more frequent use of antimicrobials in conventional (cage, barn, and free range) than in domestic and organic chicken housing systems. Education covering good sanitary practices for handling eggs to avoid cross-contamination or inadequate cooking is needed.     

The effects of active and passive modified atmosphere packaging on the survival of Salmonella enterica serotype Typhimurium on washed romaine lettuce leaves

Modified atmosphere packaging (MAP) is commonly used to preserve the quality of ready-to-eat lettuce by inhibiting oxidative browning and growth of microbial populations. The efficacy of MAP is improved by the initial displacement of air with a gas mixture of a desirable composition (active MAP). The present work focused on the effects of MAP on indigenous microbial populations and the survival of Salmonella enterica on the surface of the lettuce. Chlorine-washed leaves of romaine lettuce were inoculated with S. enterica serotype Typhimurium or not inoculated and packaged in one of the three systems: (a) passive MAP in polyethylene bags; (b) active MAP in the same bags with a gas mixture of 10% O₂, 10% CO₂, and 80% N₂; and (c) control without MAP. Active MAP ensured the more rapid establishment of a steady-state atmosphere and favorable conditions during the transitional period preceding the steady state. The active MAP had an antimicrobial effect on indigenous lettuce microflora, but not on Salmonella and even favored the survival of the pathogen, possibly due to the elimination of its natural antagonists. The effects of the passive MAP were less pronounced. The results obtained draw attention to potential safety risks of ready-to-eat fresh produce kept in active MAP and require further investigation.     

Technological characterisation by free zone capillary electrophoresis (FCZE) of the vegetable rennet (Cynara cardunculus) used in “Torta del Casar” cheese-making

The purpose of this work was to develop a procedure based on protein analysis by free zone capillary electrophoresis (FZCE) that can be used as an alternative to other methods in the determination of the technological quality of vegetable rennet to use in “Torta del Casar” cheese-making. Samples of cardoon flowers (Cynara cardunculus) grouped according to location, harvest year, and ripening stages were used in the study. For the FZCE, a protocol for extracting the methanol-soluble proteins was tested. This method was found to give good repeatability of the corrected migration time (CMT), and showed higher effectiveness in discriminating the technological properties (milk-clotting and casein degradation activities) of vegetal rennets than the SDS–PAGE technique. In addition, three peaks found in the FZCE electropherograms were examined as a good tool to predict the impact of vegetable rennet on the creaminess and overall acceptability of the “Torta del Casar” cheese.     

Effects of tiger nut (Cyperus esculentus) milk liquid co‐products on the quality of pork burgers

Co‐products from the tiger nut milk industry can be given added value if they are used in the manufacturing process of other food products. The aim of this study was to analyse the effect of using tiger nut milk liquid co‐product as a substitute for the water added to pork burger formulations. The results showed that its use in pork burger delayed lipid oxidation and improved cooking properties (less shrinkage), while no significant changes in nutritional value were observed. Pork burgers containing tiger nut liquid co‐product were perceived to be juicier and less fatty than the control, contributing to higher scores for overall liking.     

Technological properties of date paste obtained from date by-products and its effect on the quality of a cooked meat product

Fresh date processing (picking, storage or conditioning) may lead to date losses. Such by-products from fresh dates (Medjoul variety) can be processed to prepare date paste. Chemical composition, physicochemical and technological properties of this date paste were determined regarding its potential application as an ingredient in the elaboration of meat products. The date paste had a high content of sugars (53.00 g/100 g) especially reducing sugars (fructose and glucose), total and insoluble dietary fiber (7.00 g/100 g and 4.04 g/100 g, respectively) and natural antioxidants (polyphenol content; 225 mg GAE/100 g). Its emulsion capacity was 57.00 mL/100 mL and it showed also a high emulsion stability (98.59 mL/100 mL). The addition of up to 15% date paste in the formulation of bologna-type products leads to the enhancement of the nutritional (lower fat content and higher fiber content than control) and technological quality (redder-colored and less hard, chewy and cohesive product than the control) together with a satisfactory sensory quality.     

Toxigenic microorganisms in medicinal plants used for ritual protection of infants

Plants used as a part of infant protective rituals in some countries of South Eastern Africa and which use has been associated to food poisoning episodes were submitted to a microbiological analysis to investigate potential microbiological hazards. This characterization led to the detection of a high load of moulds and aerobic spore-formers microorganisms. Isolates of Bacillus cereus and Bacillus thuringiensis were observed to contained different toxin-encoding genes, and the production of diarrheal enterotoxin was confirmed in some of them. The production of aflatoxin B₁ and cyclopiazonic acid by strains of Aspergillus flavus, and citrinin and penicillic acid by Penicillium citrinum was revealed by HPLC. The toxicity of these isolates was also showed by the Artemia salina lethality test. The results indicate the presence of microorganisms with toxigenic potential in plants used as folk medicine in South Eastern Africa. The traditional use of these preparations should be carefully reconsidered due to the microbiological risks associated with their ingestion.     

Microstructure of highly concentrated tomato suspensions on homogenisation and subsequent shearing

The changes in the microstructure of tomato paste suspensions have been investigated during homogenisation and subsequent shearing in suspensions with similar composition, at three tomato paste concentrations 10, 30 and 40%. The suspensions were characterised by the particle size distribution (PSD), volume fraction (ø), and dynamic rheological properties (G′, G″). All suspensions exhibit a solid-like behaviour with G′ > G″. Micrographs indicate that the process of homogenisation creates a smooth network of finer particles, that is easily disrupted by prolonged shearing, giving rise to the formation of densely packed flocs that become clearly oriented in the direction of the shearing. At high concentrations, these changes in the microstructure on homogenisation and subsequent shearing were better reflected by differences in ø than in G′. The rheological behaviour of the suspensions exhibits a power-law dependence on ø, over a large range of PSD and for 0.05 < ø < 0.55. Finally, an experimental equation, including ø and the size of the coarse particles in the surface-weighted PSD, is found to accurately estimate G′ (R² > 99.3%, p < 0.001).