The USDA-FSIS requires broiler carcasses to be chilled to less than 4 C within 4 hours of slaughter. In order to meet this requirement most plants in the USA immersion chill carcasses. Technically speaking, this process is the first step in the cold chain for poultry meat processing and is a very important food safety intervention.

Temperature reduction is really the only non-chemical method to decrease bacterial growth, specifically pathogen but also spoilage bacteria, during processing. In addition, this temperature reduction is important for pH decline during the early post-mortem stages to ensure good meat quality that is acceptable to consumers. So, the chiller is a very important unit operation in poultry processing and maintenance of the chiller is critical to good quality meat and to food safety.

Unfortunately, if not managed properly, the chiller can be a major point of cross contamination. To ensure this does not occur, there are several important tips concerning chiller maintenance that should be followed.

Water quality  

Water is not water. Water pH and water hardness all contribute to decreased functionality in the chiller. A pH of above 7 will render chlorine ineffective. Therefore, keeping your pH at or below 6 is more economical for use with chlorine.
Hard water is defined as water with a high concentration of calcium and magnesium. Soft water can be in the range of 0-60 mg/L, moderately hard 61-120 mg/L, Hard 121-180 mg/L and Very Hard > 181 mg/L. The level of hardness can be determined by commercial testing kits or by your sanitation company.

Water hardness is an important number to know since hard water can affect equipment that can handle water, causing potential costly breakdowns. Water can be softened by several methods. Discussing this with your sanitation expert can help in deciding the best options for a facility.

In addition to the above considerations for water quality, there can also be contaminants and possible nitrite in water, especially well water. It is recommended to test water at least once yearly to determine presence of these contaminants that can decrease quality and shelf-life.

Antimicrobial use  

Immersion chilling has a benefit of an increased “washing effect” which lowers the total microbial load on the birds; however, it is also a potential place for cross contamination to occur if a Salmonella positive flock is processed.

There are several antimicrobials that are approved and effective for use in the chiller to decrease pathogens. In order for antimicrobials to be effective, time, coverage and concentration need to be considered. The chiller represents an unusual circumstance since the antimicrobials are applied in an immersion system.

Chlorine is the most common antimicrobial used in the chiller. General use is 50 ppm with a water pH of 6 for increased effectiveness. Since chlorine has lower activity due to the high organic load in the chiller, it is always a good practice to measure free chlorine. If there is free chlorine present (amount is dependent upon organic load) then that ensures there is enough chlorine to cause effective destruction of pathogens.

Peroxyacetic acid (220 ppm maximum level) has also been used effectively as a chlorine replacement for processing plants that wish to export poultry meat to chlorine-banned countries.

Other antimicrobials approved include Bromine, CPC, organic acids, TSP, acidified sodium chlorite and chlorine dioxide.
Whichever antimicrobial is chosen, ensure that limitations and usage levels are understood to have an effective and cost-effective product. A higher concentration than needed as well as too low of a concentration can both be costly.

Temperature management  

Immersion chilling also has a benefit of allowing a decrease in temperature rather quickly due to the increased heat exchange with water versus air. In order to decrease thermal layering of the carcasses and improve heat exchange, agitation is needed. Most chiller systems have air agitation systems that force air into the chiller from the bottom thus keeping the carcasses floating and moving to reduce thermal layering.

The use of air agitation is effective but cleaning and sanitizing of the air hoses is labor intensive and can be costly. If not cleaned and sanitized, the air agitation system can introduce bacteria increasing the load on the chlorine. A chiller company has developed a new technology, the Jet Bird system, which uses water jets to decrease thermal layering. This system is very effective and is easier to maintain.

Most chillers are a counter-current system, where the carcasses are entering into cleaner and colder water as they migrate through the chiller system. This counter-current method helps to reduce carcass temperature and helps to decrease the microbial load.

As a general rule, the warmer the water temperature during the pre-chill stage, the higher the water pick-up in the skin of the carcass. This water pick-up is generally controlled due to the Water Uptake Rule. However yield improvements can be made at this stage ensuring regulatory guidelines are followed.

Make-up water is also added to the chiller (1.79 L/ bird) to ensure that the volume of the chiller does not decrease and to ensure that the carcasses are supplied with clean water. Therefore, as stated above, ensuring good water quality in the make-up water is important.

Control incoming bacterial load  

“Dirty in, dirty out.” Research suggests that incoming load will increase pathogen-positive birds and decrease shelf life of product. Control of pathogens should begin in live production if a true multi-hurdle approach is to be effective.
The chiller system, even with antimicrobials, will not be a solution to all problems. If a “dirty” flock is processed then there is a high probability that the remainder of the birds that are exposed to the chiller water will be exposed to pathogens. However, the risk can be minimized with proper controls as state above- good water quality, proper antimicrobial use, and temperature management.

Know your sanitation practices  

Sanitation is not often considered as an important practice to include in chiller management. However, it is critical. There are many components to the chiller that if not cleaned properly can result in higher microbial load (decreased shelf-life) and higher pathogen positive birds. For example, if air agitation is used, the air lines should be cleaned and sanitized regularly to prevent mold and other bacteria from infiltrating the chiller. In addition, the Clean-In-Place system requires certain chemicals to ensure proper cleaning of the pipes and to prevent build- up of compounds that can decrease efficiency.

A best practice is to work with a chemical company and a sanitation expert who has experience in poultry meat plants and can develop a sanitation plan to ensure cleaning and sanitizing efficacy.

Following these chiller management techniques will ensure higher yields, increase profit margins, better meat quality, and a safer product.