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Chiller Water Disinfection Management Practices
In this step, eviscerated and defeathered carcasses are dropped into an immersion chiller, which rapidly chills the carcasses to 40 ºF or below and inhibits microbial growth. To further ensure food safety, processors add chlorine or other chemicals to disinfect and sanitize the chiller water.
In recent years, the U.S. Food Safety and Inspection Service has begun targeting the efficiency of microbial intervention methods used to reduce bacterial counts on poultry carcasses. The goal has been to ensure the industry is taking effective steps to control potentially harmful pathogens, such as Salmonella, E-coli, and Campylobacter, on raw product. As a result, processing plants have increased their use of rinses and antimicrobial interventions, including those used in the chiller. However, antimicrobial effectiveness in chiller baths, particularly chlorine, is impacted by the level of organics (fats, greases, and oils) released in the bath by the rinse process.
In response, researchers at the Georgia Tech Research Institute are examining current immersion chilling practices in an effort to better understand the antimicrobial intervention strategies being used. Their ultimate goal is to be able to define best management practices (BMPs) that enhance chiller efficiency.
"Understanding current chiller management practices and the implications of various antimicrobial interventions used in chiller baths is the core of this project that will serve as the guide for identifying best management practices," explains Aklilu Giorges, research engineer and project director.
To begin, researchers reviewed the most common chiller designs and disinfection chemicals used in poultry processing plants. They found three major chiller designs (auger-93 percent, drag, and spin), three major chemicals used for disinfection (hypochlorous acid, peracetic acid, and monochloramine), and three major chemicals used to manage pH (carbon dioxide gas, citrus acid, and sulfuric acid).
Next, they conducted a chiller concentration change case study. A two-stage, counter-flow immersion chiller was periodically monitored for variations in pH, free chlorine, and total chlorine concentrations during the initial 2 hours of bird loading. The data indicated that the chiller reached a chemical steady state after 2 hours of operation. In addition, the chiller water was characterized for solids loading. The preliminary results indicated that the total suspended solids loading was mainly organic matter, while the inorganic solids loading was found to be near 45 percent. However, currently there are no reliable on-line sensors that measure solids buildup during chiller operation. Researchers believe more field data from different facilities using different chemical and operational procedures will be needed to gauge industry standards.
"Additional testing at different facilities is recommended for not only startup but also throughout the processing day and week to confirm preliminary results," says Giorges. "The protocol appears to be reasonable for use at other facilities with different chemistries to understand the broader aspects of strategies for chiller management. Real-time monitoring of chiller chlorine conditions could be beneficial, especially as conditions approach steady state. However, solids build up as processing occurs, and the impact of this on liquid disinfection requires further evaluation."
November 2009
