Scant raw poultry promise for pulsed electric fields, study

That’s the conclusion of a new study from scientists at University College Dublin (UCD), who found that Campylobacter was more susceptible to destruction via PEF treatment in liquid media than Escherichia coli ​(E.coli) and Salmonella Enterititidis.​

Haughton et al. also found previously unreported “significant differences”​ in susceptibility to PEF between 10 different Campylobacter isolates.

Previously, a team at UCD found that high-intensity pulsed light significantly reduced bacteria counts for the same 3 pathogens on chicken and associated packaging.

Continued research into pathogen control reflects European Food Safety Authority (EFSA) estimates that there are 9m EU cases of Campylobacter infection each year, with a large proportion due to handling, preparation and consumption of chicken meat, as well as contaminated processing water.

‘Lethal’ to spoilage bacteria​

Against this backdrop, Haughton et al. noted that PEF – applying short pulses of high-voltage electric fields to food flowing through or placed between 2 electrodes – was a non-thermal decontamination treatment “lethal to many pathogenic and spoilage bacteria”.​

The scientists said previous data suggested that PEF technology was better-suited to inactivating micro-organisms in liquid or semi-solid foods (Mosqueda-Melgar et al. 2008), but that its effectiveness upon poultry had not been studied.

Haughton et al. added: “The authors are unaware of any studies that may have investigated the potential of PEF for the decontamination of solid foods such as chicken.​

“There is growing interest in exploring and identifying technologies that could reduce contamination of chicken carcasses, as risk assessment studies predict that reducing the microbial load on carcasses can result in a significant reduction in the incidence of gastroenteritis in humans.”​

And while traditional thermal treatments were effective to a degree, the authors noted that they may have a negative impact on the appearance of broiler skin.

Haughton et al. found that PEF was an effective intervention measure in liquid media, with all Campylobacter isolates tested in liquid registering reductions of 4.33-7.22 log CFU/ml (colony-forming units per millilitre) after 30 seconds of treatment.

However, significant differences in susceptibility were observed across Campylobacter isolates, with those processed in liquid media showing reductions of 2.41-5.19 log CFU/ml.

Chicken appearance deteriorates​

Meanwhile, E.coli and S.Enteritidis in liquid were both found to be less sensitive than Campylobacter (P < 0.05), while the application of PET to raw chicken samples did not result in any significant reductions in total viable counts.

Asked if he was surprised by this finding, corresponding author Paul Whyte told FoodProductionDaily.com: "A few other studies have looked at effect of PEF on bacteria in various solid foods and found similar modest reductions in bug counts, so we were not surprised. ​

"Also the maximum field strength we applied was limited, as once you go above certain strengths and [PEF] exposure times, the appearance of the chicken deteriorates (you get a cooked appearance on surface of product)."​

The team said this finding highlighted the importance of strain selection in PET inactivation studies involving Campylobacter spp.​

Haughton et al. wrote: “​Although the results of this study indicate the unsuitability of PEF for decontaminating raw chicken, it may have a potential application in controlling levels of Campylobacter in scald or chill water used during the processing of chicken.”​

Whyte told this publication that use of PEF in food processing had been fairly limited thus far "although good efficacy has been shown for decontaminating bacteria in liquid foods". ​

"Its use on scald water or chill water is likely feasible. We used a ‘batch’ setup on our equipment, but in order to process liquids a continuous system/cell would be necessary...so that the process water could be continuously circulated between the PEF equipment and scald/chill tanks."​

Commenting on future directions for PEF research in regard to food pathogen control, Whyte said: "Really is a matter of validating for various food types on a case-by-case basis, and testing against relevant target pathogens likely to be present on or in each food category. But again based on our study it [PEF] is most likely to be successful for liquid, semi-liquid or pumpable foods."​

Title: ​‘Efficacy of pulsed electric fields for the inactivation of indicator micro-organisms and foodborne pathogens in liquids and raw chicken.’

Source: ​Food Control ​(2011). Published online ahead of print, doi: 10.1016/j.foodcont.2011.10.030​

Authors: ​P.N Haughton, J.G Lyng, D.A Cronin, D.J Morgan, S.Fanning, P.Whyte