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Ultrasound May Be Useful for Reducing Salmonella Levels in Chicken Meat

11 March 2014

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A research project at the Georgia Tech Research Institute in Atlanta demonstrates that ultrasound may be useful for reducing Salmonella levels on poultry meat in the processing plant. Its efficacy was enhanced when it was used in addition to chemicals.

The project, sponsored by US Poultry & Egg Association (USPoultry) and the USPoultry Foundation and reported by Dr Aklilu Giorges, Dr Doug Britton, Dr John Pierson, Dr Samantha Williams, Dr Athrisa Divya Varahabhatla and Dr Elizabeth McMillan, is part of the Association’s comprehensive research program encompassing all phases of poultry and egg production and processing.

Researchers at the Georgia Tech Research Institute, led by Dr Aklilu Giorges, examined the effect of using ultrasonic energy in combination with commonly used antimicrobials on the inactivation of Salmonella in chiller water.

In experiments using intentionally contaminated water, simulated chiller water and actual chiller water, it was found in all cases that samples treated with ultrasound, combined with either different concentrations of chlorine or peracetic acid, exhibited better disinfection than samples treated with the chemicals alone.

In their summary, the researchers conclude the study indicates that it may be feasible to use ultrasonic energy to enhance product safety.

The pathogen intervention system is a key part of poultry processing and is continuously evolving to meet regulations as well as to ensure safe products, according to Dr Giorges and colleagues. A disinfection system that can use chemical disinfectants effectively and reduce and/or eliminate harmful byproducts is in demand more than ever.

The goal of their project was to evaluate the effectiveness of sonication (ultrasound) for inactivation of Salmonella, with and without a disinfection agent (chlorine, peracetic acid), in poultry chiller water.

Furthermore, food safety, poultry processing efficiencies and natural resources (water and energy) are matters that poultry processors need to successfully manage to be viable in today's global food market. Improvements in one area can have a direct and/or indirect effect on the other. Thus, an innovative and economical disinfection system is a critical part of providing safe food.

The first part of this project was designed to determine the antimicrobial effects and efficiency of ultrasound inactivation of Salmonella typhimurium. The experiment was designed to investigate the ultrasonic effect of various power intensities, volumes, and exposure times with several repetitions. All ultrasound experiments were conducted in isothermal conditions to eliminate disinfection via indirect heat input from the ultrasonic probe.

The data from the Salmonella-inoculated water tests showed a correlation between an increase in ultrasonic energy, increase in exposure time and decrease in volume that led to better disinfection of Salmonella. The data demonstrates that ultrasound can be used to inhibit Salmonella growth. However, the extent of disinfection from the ultrasonic energy magnitude was not significant enough to be used as the only means of disinfection.

This study also evaluated the effectiveness of ultrasound and chemical disinfection agents (chlorine or peracetic acid (PAA)) in Salmonella-inoculated water, simulated chiller water and actual poultry chiller water.

Based on previous results, a volume of 500ml and a single ultrasonic energy were selected to determine the synergistic effects in most tests. The synergy effect for chlorine (1.66, 3.32 and 4.98ppm) and PAA (0.75, 1.5 and 2.25ppm) in water was evaluated by assessing the disinfection agents with approximately 40kJ of ultrasonic energy (65W for 10 minutes) in Salmonella-inoculated water.

When comparing the data of chemical disinfection with the combination of ultrasonic and chemical, the disinfection was greater for the combined system than the disinfection observed with chemicals only.

Simulated chiller water (5g of chicken skin and fat per litre of water) was treated with combined chlorine (16.6ppm) and ultrasound and compared to chlorine treatment alone. This experiment was also repeated using peracetic acid concentrations of 0.75, 1.5 and 2.25ppm. A similar trend of log-reduction was observed for combination ultrasound and chemicals treatment for all concentrations of chlorine and PAA.

Actual poultry chiller water was found to be more challenging to evaluate, the researchers report.

Since the chiller from a poultry plant has chemical residue, more work was needed to characterise and evaluate the efficacy of the chemical residue.

Poultry chiller water (TS=6.34g per litre and chemical residue of 10ppm total chlorine, and 0 free chlorine) was used to evaluate the disinfection of ultrasonic treatment and its synergy with chemicals.

The Salmonella-inoculated poultry water test showed no inactivation from residue chemical. The ultrasonic disinfection trend in poultry chiller water was found to be similar to that of the Salmonella-inoculated water experiments.

Furthermore, the poultry chiller water with additional chemicals (16.6ppm chlorine and 2.25ppm PAA) and ultrasonic were also tested.

The data showed that the combined disinfection system performed better than the chemical alone. However, more work is needed to characterise the actual chiller water.

In all cases, samples treated with combined ultrasound and chemicals exhibited better disinfection than samples treated with chemicals alone.

March 2014

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