Analysis Of Free Chlorine In Poultry Chiller Water

Poultry processors are required to maintain a free chlorine level sufficient to control pathogenic bacteria found on bird carcasses. Bird carcasses are chilled at 32–34 ºF in a continuous counter-flow chlorinated water system. The challenge to the processor is to maintain a free chlorine level of 0.5 - 5.0 mg/L free chlorine in a chiller water which has a huge and changing chlorine demand load due to fresh carcasses being constantly added. The chlorine demand comes from the blood, fat, and proteins originating from the carcasses. Chlorine is continuously fed into the chiller system to counterbalance this incoming organic load in order to maintain the free chlorine residual.

Theoretically, the chlorine demand must be totally met before a free chlorine residual can be obtained. This is classical breakpoint chlorination theory and is well documented in the literature. However, these high organic-loaded chiller waters are not truly through breakpoint and free chlorine, monochloramine, dichloramine and excess organic chloramines are all present at any one time in a sort of “dynamic equilibrium” that is constantly changing and non-uniform throughout the chiller water system. These systems are optimized at pH 5.5 – 6.5 where chlorine present as hypochlorous acid is most efficient at destroying the pathogenic bacteria. The current understanding is that the residual “free chlorine” residing in these complex chiller water matrices is effective in controlling bacteria even though other competing chlorine demand species are still present.