Mapping the route to improved public health?

The contamination of poultry carcasses with Salmonella is a major health problem worldwide. As these bacteria are usually present as a diverse population, detailed mapping of Salmonella contamination on the young chicken carcass could help improve poultry inspection and food safety.

A method for mapping the incidence and number of antibiotic resistant strains of Salmonella on the chicken carcass has been developed,  in which the bacteria are enumerated as a function of detection time during whole-part incubations. However, this method is limited by its specificity to Salmonella that are resistant to chloramphenicol, tetracycline, ampicillin and streptomycin. Information is therefore needed on the antibiotic resistance of resident Salmonella in the poultry carcass.

Only one isolate of Salmonella is typically characterized for each whole carcass sample. There is also a lack of information on the potential diversity of Salmonella subtypes on individual carcasses. Sampling methods such as swabbing, sponging and whole-carcass rinse are not capable of detecting all forms of Salmonella, resulting in inaccurate maps and risk assessment. Although more labour-intensive, carrying out whole-carcass incubation with parts, and then subtyping multiple isolates for each carcass, may have potential for identifying contamination and critical control points for reducing the levels of pathogens on the poultry carcass.

A study by Oscar et al.¹ developed a qualitative map of the distribution of Salmonella on the young chicken carcass and characterized the diversity of subtypes within individual carcasses. The antibiotic resistance of resident Salmonella was also determined. Carcasses were sectioned into 12 parts and the obtained isolates were characterized by pulsed-field gel electrophoresis. The most common serotype was Typhimurium, with most isolates resistant to multiple antibiotics. There was a diverse pattern of Salmonella contamination on the carcasses, with multiple subtypes often present. Poultry carcass mapping could have great potential for improving poultry inspection and safety, especially by improving process hygiene through critical control points.

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¹ Oscar, TP; Rutto, GK; Ludwig, JB; Parveen, S (2010). Qualitative map of Salmonella contamination on young chicken carcasses. Journal of Food Protection 73 (9) 1596–1603.

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Melamine analysis – which technique is best?

Melamine (2,4,6-triamino-1,3,5-triazine) is mainly used in the synthesis of melamine formaldehyde resins. It has also been intentionally added to wheat gluten and other cereal-based ingredients in pet foods to economically increase the apparent protein content. However, concerns have arisen over melamine content of milk following recent cases of melamine-tainted infant formula in China.

The presence of melamine in food can arise from a number of different sources apart from adulteration. These include the breakdown of the pesticide cyromazine and migration from approved packaging materials. Melamine in cow’s milk may be due to melamine-contaminated ingredients, such as concentrate pellets, used for animal feeds. There is therefore a need for analytical methods to detect and quantify melamine in milk.

ELISA is a simple and cost-effective tool for controlling potential contamination of cow’s milk, while HPLC-UV provides accurate quantitative data, suitable for demonstrating compliance. Confirmatory methods for cow’s milk analysis are generally based on MS techniques such as GC-single quadrupole MS and LC-triple quadrupole MS/MS.

A study by Lutter et al.¹, investigated the use of 2 screening and 2 confirmatory methods for determining melamine in cow’s milk and milk-based powdered infant formula. The performance and validated data are presented for ELISA, HPLC-UV, GC-MS and LC-MS/MS. Results are compared and discussed in relation to internal and European proficiency tests.

GC-MS improved the selectivity and allowed quantitative determination and confirmation of melamine residues in the infant formula. The highest selectivity and reliability was obtained with LC-MS/MS.
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¹ Lutter, P; Savoy-Perroud, M-C; Campos-Gimenez, E; Meyer, L; Goldmann, T; Bertholet, M-C; Mottier, P; Desmarchelier, A; Monard, F; Perrin, C; Robert, F; Delatour, T (2011). Screening and confirmatory methods for the determination of melamine in cow’s milk and milk-based powdered infant formula: validation and proficiency tests of ELISA, HPLC-UV, GC-MS and LC-MS/MS. Food Control 22 903-913.

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Boar meat taint detection with a sting in the tail

Boar taint is a distinctive and unpleasant defect of pork from uncastrated male pigs that is a significant problem for the pig industry. The off-flavour is associated with skatole, androstenone and, to a lesser extent, indole. Consumers often have a strong aversion to meat exhibiting boar taint.

The majority of male piglets in Europe intended for pork production are surgically castrated. However, animal welfare concerns and resulting legal action mean that surgical castration could be banned in some countries or even across the EU. As there are currently no alternative approaches available to entirely eliminate meat with boar taint, reliable detection methods are needed to discriminate tainted carcasses at the slaughterhouse.

Several techniques have emerged with potential for boar taint detection. These include chemical sensor arrays (electronic noses), MS fingerprinting, ultrafast GC, gas-phase spectrometry and biosensors. However, all have limitations to their use. Invertebrate parasitoid species may provide good biological alternatives to chemical detection and can exhibit distinct behavioural responses and broad receptor sensitivity as biosensors. A portable “wasp hound” utilising Microplitis croceipes has been developed that contains several conditioned insects for the potential detection of boar taint compounds.

A study by Wackers et al.¹, investigated the effectiveness and reliability of this wasp hound, using a cohort of trained wasps, to detect the boar taint aroma compounds skatole, andrestenone and indole. Ability of the wasps to detect the individual compounds and their mixtures was evaluated together with concentrations that the wasps were able to learn and report.

Wasps could successfully identify skatole and indole, and detect them in a 1:1:1 mixture, both as a single wasp bioassay and using the wasp hound device. However, they showed a weak conditioned response to androstenone. Use of these wasps as biosensors may have potential for the detection of boar taint.
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¹ Wackers, F; Olson, D; Rains, G; Luundby, F; Haugen, J-E (2011). Boar taint detection using parasitoid biosensors. Journal of Food Science 76 (1) 541-547.

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The perfect cuppa

Tea is one of the most widely consumed beverages worldwide and is readily available even in developing countries. Green tea in particular is associated with health benefits, mainly due to the presence of flavanols. It is known to have positive preventative effects against coronary heart diseases, cancer, neurological conditions such as Alzheimer’s and Parkinson’s diseases and metabolic syndrome.

The main flavanols in green tea are epicatachin, epicatechin gallate, epigallocatechin and epigallocatechin gallate. However, concentrations of flavanols in a cup of tea can vary considerably and studies have suggested a diffusion mechanism for these compounds in green and black tea. Flavanol concentration appears to increase with smaller tea particles, longer steeping time, higher temperature and higher tea leaf amounts per volume of water.

Tea brewing varies widely throughout the world, with multiple extraction being preferred in the Far East and Asia, while in the Western world a single extraction is common. Tea is often consumed with lemon and other additives, which may influence flavanol concentration and their bioavailability. The addition of lemon juice or vitamin C may also affect flavanol extraction during consumption.

A study by Zimmermann and Gleichenhagen¹, investigated the influence of steeping time (3-7 minutes), temperature (70-100^oC), low pH (3 and 4.8), and addition of ascorbic acid and citric acid on flavanol extraction from green tea. A single extraction was evaluated and levels of epicatachin, epicatechin gallate, epigallocatechin and epigallocatechin gallate were determined. Flavanol content varied significantly, depending on steeping time and temperature. Lowering the pH also increased the concentration of flavanols.

Two mechanisms are proposed for the diffusion of flavanols from the leaf into the aqueous phase and for their structural alteration. To maximise flavanol consumption, it is recommended that the tea is made with boiling water, steeped for approxiately 7 minutes and lemon juice added during steeping.
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¹ Zimmermann, BF; Gleichenhagen, M (2011). The effect of ascorbic acid, citric acid and low pH on the extraction of green tea: how to get most out of it. Food Chemistry 124 1543-1548.

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A juicy way to protect against atherosclerosis

Oxidative stress is known to contribute to the development and progression of atherosclerosis. Early signs of the disease include macrophage cholesterol accumulation and foam cell formation, which can result from increased uptake of oxidised low-density lipoprotein (LDL) and/or a reduced rate of high-density lipoprotein (HDL)-mediated cholesterol efflux from cells.

Dietary polyphenols, such as those present in some beverages, exhibit potent antioxidant and cardioprotective activity. Studies have shown that consumption of grape juice, red wine, blackcurrant and pomegranate juice can increase serum antioxidant potential, exert hypolipidaemic and anti-inflammatory effects, inhibit LDL oxidation and decrease monocyte migration. Wonderful-variety pomegranate juice (WPJ) was also found to protect atherosclerotic patients from further development of the disease.

The effects of these beverages have been mainly followed over relatively long periods of consumption. However, there are fewer studies on the acute effects of beverage consumption on serum oxidative stress and atherogenicity. It is also thought that differences in the anti-atherogenic properties of various berry and fruit juices could be related both to the quantity and quality of their polyphenols.

A study by Rosenblat et al.¹ investigated the antioxidative effects of various polyphenolic-rich beverages in vitro and the effects of short-term consumption of beverages on serum anti-atherogenic properties. Healthy subjects consumed pomegranate (WPJ), grape, black cherry, blackcurrant, blueberry and yumberry juices, superfruit juice blends, green tea and red wine for 2 hours or daily for up to 1 week. All of these polyphenol-rich beverages exhibited antioxidant and anti-atherogenic effects, even over a short period of consumption. Both 100% WPJ pomegranate and 100% blackcurrant juices had the most potent antioxidant activities in vitro.

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¹ Rosenblat, M; Volkova, N; Attias, J; Mahamid, R; Aviram, M (2010). Consumption of polyphenolic-rich beverages (mostly pomegranate and black currant juices) by healthy subjects for a short term increased serum antioxidant status, and the serum’s ability to attenuate macrophage cholesterol accumulation. Food & Function 1 (1) 99–109.

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