Chilling broilers during processing reduces spoilage, increases shelf life, and enhances yield and quality. Originally, batch methods were used, with the product placed in refrigerated rooms or large ice tanks, sometimes with water, and held until carcass temperature was reduced.
As demand for poultry grew, processing capacity needed to increase, and the time required to chill dressed chickens in batch containers created a bottleneck.
To address this, in the 1950s, the poultry industry began to develop a continuous in-line process. Today, while some very small companies still use batch chilling, most operations use in-line chillers.
Variety of approach
Capacity has increased, but the technology has been influenced by regional consumer preference and diverse regulatory requirements, leading to very different chilling methods being developed.
Most operations use variations of three chilling processes. The most commonly used is continuous water immersion chilling; second are air chill system variations; third, which is increasingly being adopted, is a combination of water and air chill technology.
Regardless of method, temperatures must be brought quickly below 4C (40F). The ideal situation is to reach 4C at the end of the continuous chilling step, and before secondary processing and packing. Colder product will have much less cutting loss, floor shrink and cooler shrink, so increasing final yields.
Water chilling poultry
Continuous water chilling systems are the most used - they will always provide more yield than other systems – and when combined with good agitation, adequate refrigeration and dwell time, are the most efficient. Advantages of water chill include:
- Initial cost is much lower compared with air chill
- Operational cost in refrigeration and electricity is much lower
- Floor footprint is up to eight times smaller
- Water chilling requires a much shorter dwell time than other methods
- Yield advantage. Water chilling prevents dehydration and, when combined with proper scalding and picking, allows for increases in retainable moisture. With the new Rocker chiller technology, the process can even increase the yield of boneless skinless breast meat.
- Microbial reduction through the washing action of the pre-chiller. Where permitted, the water chiller is also an excellent place for chemical intervention.
Water systems do, however, have some major disadvantages:
- Moisture fluctuation will cause serious issues with product sizing in whole birds
- Labor costs are much higher as birds must be rehung after the water chillers
- Market perception in parts of the world is that water chilling means lower quality than air chilling
- Loss of product identity, as birds co-mingle and not ‘first in - first out’
Air chilling advantages
While there are few air chill systems in the U.S., there are many in Canada. Air chilling is preferred in most of Europe and many other parts of the world.
There are basically three types of air chillers: the traditional down flow dry air chillers, multi-stage air chillers with humidity added, and combination air/water chill systems. However, while the down flow dry air systems are still being used, almost all the new systems are the multi-stage units with humidity systems which provide much better performance. In specific applications, the combination air/water chill systems is increasing in use and giving different results to the other two types.
When comparing the traditional dry air and the multi-stage with humidity, there are clear advantages and disadvantages compared to water chill. Advantages include:
- Labor cost improves because carcasses can be auto-rehung
- Product identity is maintained as the birds entering the chiller first exit first. This allows easier integration with technology as the identification and grading process can be started before chilling.
- No moisture variation, allowing more precise sizing
- No purged moisture in the finished packaging, particularly an issue in the tray pack product
- Perception in many markets that air chill delivers higher quality
There are also some disadvantages:
- Initial costs and operational costs are much higher than for water chilling
- Required floor space can be up to eight times more than for water chilling
- Up to twice as much dwell time is required to reach the same internal temperature
- Yield is lower. With traditional dry air systems, dehydration loss in the chill step can be up to 2.5 percent. With the new multi-stage systems utilizing humidity cabinets, the results are better with a dehydration loss of 0.25-0 percent.
- Product appearance can be an issue. If there is cuticle damage, the birds can have very dry, dark patches after air chilling. Air-chilled products can look drier and have a higher value of red and yellow on the skin, often negatively perceived.
- Microbiological issues cannot be dealt with as easily. In air-chilled systems, there is no carcass washing effect, or chemical intervention if allowed.
Combination chilling systems
The combination water/air systems have been in limited use for several years.
Some plants use spin water chillers as a first step and then manually hang on an air chill line. The fastest-growing and most widely used combination systems are from TopKip, Stork and Meyn, who all make scalder tank-type water chillers that are part of the air chill line with no manual rehang necessary.
Most of these in-line systems will be located in air chill rooms underneath the air chill line. They combine many of the advantages of water and air chill:
- The product can still be classified as air chill if the system is properly operated
- Moisture pickup can be controlled from 0 to more than 2 percent, allowing an increase in yield
- Maximizes the air chill floor space
- Reduces dwell time compared to air chill - TopKip claims over 30 percent dwell reduction with its system
- Provides a medium for antimicrobial application if allowed
- Product quality improves as the brown patches and red and yellow attributes are decreased