ice slurry
Researchers are looking at the use of ice slurry to reduce the presence of pathogens in poultry chillers.
Researchers at the Georgia Tech Research Institute (GTRI) are investigating ice slurry for possible application in poultry immersion chillers where carcasses are chilled to a temperature that can inhibit pathogen growth. Through early testing, the GTRI team has seen better results in thermal and antimicrobial aspects than conventional chilled water methods.

Incorporating ice slurry, which is a mixture of small (sub-millimeter) ice crystals and liquid water, to chill poultry products is an innovative process for producers to explore.

“Cooling effects hinder the proliferation of pathogens and spoilage mechanisms, and there is a modest timeframe within which product temperature reduction must be accomplished,” says Dr. Comas Haynes, GTRI principal research engineer and project director. “A medium (slurry) that facilitates this effect via more cooling capacity than chilled water thus aids food safety and preservation.”

Experiments were carried out using whole bird carcasses inoculated with Salmonella and chilled by either water or ice slurry that contained various levels of the antimicrobial agent peracetic acid (PAA) in a 250-gallon auger chiller. The core temperature and microbial reductions of the carcasses were then compared with a control set.

GTRI also used a 15-gallon micro-tester opposed to the 250-gallon auger chiller that is usually in place for poultry testing.

“It does allow us to try different scenarios,” Haynes says. “We have to change the flow patterns within those micro chillers.”

Haynes and his fellow researchers showed that ice slurry carcasses’ core temperatures decreased on average an additional 25 percent in degrees Celsius compared with chilled water carcasses in 45-minute trials. Regarding microbial reduction, favorable contrasts included a case of ice slurry having an overall reduction of 1.2 log compared with a chilled water reduction of 0.6 log.

“You get more cooling capacity and antimicrobial potency,” Haynes says. “I think you get the best of both worlds because ice and chillers are not brand new, but I think the whole aspect of using slurry is novel.”

The team hypothesizes that the additional antimicrobial activity is due to a scrubbing-like phenomenon of the slurry. The GTRI study found that ice slurry can work as a scrubber along the poultry carcasses’ skin. The idea is that the scrubbing motion would be an abrasive force that could help to loosen or erode potential microbial colonies or biofilms attached to the carcasses and thus create an aid to antimicrobial activity with the slurry.

“Ice slurry has more scrubbing capacity per unit mass of ‘water’ than does an all liquid phase because the ice particles are suspended solids that add to the viscosity,” Haynes says. “The reason that slurry is a better scrubber than typical ice water with larger pieces or ‘chunks’ of ice is that the slurry provides more area per unit mass of ice for surface-to-surface contact with the carcasses.”

This benefit includes more contouring capability of the “finer” ice slurry particles around the poultry product.
 Ice Slurry
The Georgia Tech Research Institute team includes (from left): Comas Haynes, Ph.D., Stephanie Richter and Daniel Sabo, Ph.D.

Larger Scale

Testing on whole birds was also a big step for the team.

“Most lab testing starts on a smaller scale before moving towards a larger scale,” says Stephanie Richter, GTRI graduate research assistant. “We started on a large scale to see if our hypothesis was correct and found viable thermal benefits as well as microbial reduction. By scaling down and testing wings in micro-testers, we can fine tune our tests to discover the optimum settings for the best thermal and antimicrobial results.”

“This parts (wings) testing allows us to get a representative scenario for whole bird testing while conserving experimental time and resources,” Haynes adds. The testing on wings could become more relevant to large producers who are interested in chilling or applying antimicrobial interventions to individual parts only.

Haynes also says the team is hoping to determine if these results will continue for future poultry testing.

“We’re trying to show the thermal benefits – the antimicrobial benefits,” Haynes says. “We’re still tracking those and seeing what can be done to lower the salinity requirement.”

With all these benefits listed, the bottom line of safe poultry is something that the GTRI team is excited about because it’s relevant to both poultry producers and consumers.

“As a poultry consumer, I never really realized the amount of resources required for poultry processing,” Richter says. “With our research, we are hoping to develop a less resources-intensive, more environmentally friendly chilling process.”