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Scientific literature review

The characterization of Listeria spp. isolated from food products and the food-processing environment.
This paper describes the epidemiology of a collection of 378 Listeria spp. isolates obtained from several food-processing plants in Ireland over a 3-year period (2004-2007). The collection was characterised by pulsed-field gel electrophoresis (PFGE). The most prevalent pulse-type was PFGE profile that consisted mainly of environmental Listeria spp. samples. Serotyping of 145 Listeria monocytogenes isolates was performed. The most common serovar was 1/2a and comprised 57·4% of the L. monocytogenes collection. Eleven isolates were identified as non-Listeria spp., the remaining ten L. monocytogenes isolates were non typeable. The antimicrobial susceptibility testing revealed that the antibiotic to which isolates displayed the most resistance was gentamicin (5%) followed by sulfamethoxazole-trimethoprim (2%), tetracycline and ciprofloxacin (1·5%).  Overall this paper shows that subtyping can indicate the diversity of Listeria spp. The presence of serotype 1/2a, 1/2b and 4b in both raw and cooked ready-to-eat food products is a public health concern, as these serotypes are frequently associated with foodborne outbreaks and sporadic cases of human listeriosis. In addition, the emergence of antimicrobial-resistant L. monocytogenes isolates could have serious therapeutic consequences. The significance of this study is that it shows that molecular subtyping and the further characterisation of these isolates may be valuable particularly in the context of a suspected common source outbreak in the future.
O’Connor et al Lett Appl Microbiol 2010 Aug 20.

Pig liver sausage as a source of hepatitis E virus transmission to humans.
The source and route of autochthonous hepatitis E virus (HEV) infections are not clearly established in industrialized countries despite evidence that it is a zoonosis in pigs. The role of figatellu, a traditional pig liver sausage widely eaten in France and commonly consumed raw, was investigated as a source of HEV infection. A case-control study was conducted of 3 patients who presented autochthonous hepatitis E and 15 members of their 3 different families. Anti-HEV immunoglobulin G and immunoglobulin M antibody testing was performed with commercial assays. HEV RNA was detected in serum samples of patients and in pig liver sausages by means of real-time polymerase chain reaction and sequenced by means of in-house sequencing assays. Genetic links between HEV sequences were analysed. Acute or recent HEV infection, defined by detection of anti-HEV immunoglobulin M antibodies and/or HEV RNA, was observed in 7 of 13 individuals who ate raw figatellu and 0 of 5 individuals who did not eat raw figatellu (P=.041). Moreover, HEV RNA of genotype 3 was recovered from 7 of 12 figatelli purchased in supermarkets, and statistically significant genetic links were found between these sequences and those recovered from patients who ate raw figatellu. The findings strongly support the hypothesis of HEV infection through ingestion of raw figatellu.
Colson P et al J Infect Dis. 2010;202(6):825-34.

Reduction of Listeria mono­cytogenes on frankfurters treated with lactic acid solutions of various temperatures.
United States regulations require ready-to-eat meat and poultry processors to control Listeria monocytogenes using interventions which may include antimicrobials that reduce post-processing contamination by at least 1 log-cycle; if the treatment achieves ≥≥ more than 2 log reductions, the plant is subject to less frequent microbial testing. Lactic acid (LA) may be useful as a post-lethality intervention and its antimicrobial properties may increase with temperature of application. The aim of this study was to evaluate the effect of LA solution concentration and temperature on L. monocytogenes counts of inoculated frankfurters and to identify parameters (concentration, temperature, and time) that achieve 1 and 2 log-unit immediate reductions. Frankfurters were surface-inoculated with a 10-strain mixture of L. monocytogenes and then immersed in distilled water or LA solutions (0-3%) at 4, 25, 40, or 55 degrees C for 0-120 seconds. A regression equation for L. monocytogenes reduction showed that concentration, time, temperature, and the interaction of concentration and temperature had significant effects whereas other tested parameters within the experimental range examined did not affect the extent of reduction. The results thus indicate the effectiveness of LA against L. monocytogenes, which depended not only on LA concentration but also on solution temperature. The equation developed in this work may allow processors to vary conditions of treatment with LA to achieve a 1 or 2 log-unit reduction of the pathogen and so comply with regulations.
Byelashov OA et al Food Microbiol. 2010; 27(6):783.

Advanced glycation end products in foods and a practical guide to their reduction in the diet.
Modern diets are largely heat-processed and as a result contain high levels of advanced glycation end products (AGEs). Dietary advanced glycation end products (dAGEs) are known to contribute to increased oxidant stress and inflammation, which are linked to the recent epidemics of diabetes and cardiovascular disease. This report significantly expands the available dAGE database, validates the dAGE testing methodology, compares cooking procedures and inhibitory agents on new dAGE formation, and introduces practical approaches for reducing dAGE consumption in daily life. Based on the findings, it can be seen that dry heat promotes new dAGE formation by >10- to 100-fold above the uncooked state across food categories. Animal-derived foods that are high in fat and protein are generally AGE-rich and prone to new AGE formation during cooking. In contrast, carbohydrate-rich foods such as vegetables, fruits, whole grains, and milk contain relatively few AGEs, even after cooking. The formation of new dAGEs during cooking was prevented by the AGE inhibitory compound aminoguanidine and significantly reduced by cooking with moist heat, using shorter cooking times, cooking at lower temperatures, and by use of acidic ingredients such as lemon juice or vinegar. The new dAGE database provides a valuable instrument for estimating dAGE intake and for guiding food choices to reduce dAGE intake.
Uribarri J et al J Am Diet Assoc. 2010; 110: 911.

Short-term effects of alcohol on appetite in humans. Effects of context and restrained eating.
The study described in this paper examined the short-term effects of alcohol on food intake and appetite in women volunteers, testing the extent to which the apparent appetizing effects of alcohol depend on (a) expectations following alcohol consumption and (b) disinhibition of dietary restraint. Twenty restrained and 20 unrestrained women consumed a drink preload 30min before a test meal on four different days, with preloads varying in alcohol content (alcohol or energy-matched control) and drink context (alcohol-related / beer or alcohol-unrelated / juice). Significantly more energy was consumed following alcohol than no-alcohol, but this effect depended on the drink consumed: least was eaten after the alcohol-free juice drink, and most after the same juice drink with added alcohol. There was no evidence that the effect of alcohol on intake was due to disinhibition of restrained eating, nor did alcohol increase liking for the test foods. The change in energy intake at lunch was mainly due to greater intake of energy-rich foods on days when alcohol had been consumed. Alcohol also increased rated appetite once food had been tasted, suggesting alcohol may increase food-related reward. Overall these data suggest that effects of alcoholic drinks represent a complex interaction between physiological effects of alcohol and expectations and associations generated by past experience of alcoholic drinks.
Yeomans MR Appetite 2010 Sep 22.

Visual detection of melamine in milk products by label-free gold nanoparticles.
This paper describes the development of a simple, rapid, field-portable colourimetric method for the detection of melamine based on melamine-induced colour change of label-free gold nanoparticles (Au NPs) the presence of melamine induces the aggregation of Au NPs and results in the colour change from wine-red to purple, thus providing a platform for rapid and field-portable colourimetric detection of melamine. The proposed method can be used to detect melamine in liquid milk and infant formula with a detection limit of 1.0 and 4.2ppm, respectively. Results are available within 30 min by naked eye observation and without the need for any advanced instrumentation or complex sample pre-treatment. Detection levels are as low as 0.15ppm of melamine in liquid milk and 2.5ppm of melamine in infant formula. The proposed method has potential for on-site screening of melamine adulterant in milk products.
Guo L et al. Talanta 2010 5;82(5):1654.

An HPLC method to monitor the residues of benzimidazoles in bovine milk.
 A reversed-phase high-performance liquid chromatography with ultraviolet (UV) detection was developed that can determine 11 benzimidazole (BZDs) and 10 metabolites of albendazole, fenbendazole and mebendazole in bovine milk. The method is very sensitive to each analyte with limits of quantification (LOQs) of lower than 10μg/kg. The recoveries of the BZDs and their metabolites spiked in milk were more than 78%.
Chen D et al J Chromatogr B Sci 2010 Sept (epub)


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