ATRP HOME
PROJECT SPOTLIGHT
Prototype Sensor Under Development to Automatically Detect Chlorine
Levels in Poultry Chiller Water
Each year the U.S. poultry industry processes 20 billion pounds of
chicken. In one of the closing steps in first-processing, eviscerated
and defeathered carcasses are dropped into an immersion chiller, which
rapidly chills the carcasses to 40 °F or below. To further ensure
microbiological safety, processors also add chlorine to sanitize and
disinfect the chiller water. Because varying levels of chlorine can
affect product quality and taste as well as disinfection efficiency,
the chiller water must be constantly monitored.
|
Research Scientist Jie Xu tests the electronic sensor, which
she believes will more accurately track chlorine compounds in
poultry chiller water.
|
Free chlorine levels
are typically measured by colorimetric analysis. The most commonly
used method is based on a chemical reagent known
as DPD (N, N-diethyl-p-phenylenediamine). However, the current DPD-based
method has a narrow working range and suffers from interferences
by organic material present in the chiller water and chloramine formation.
In response, researchers with Georgia Tech’s Food Processing
Technology Division are developing an electronic sensor that they believe
will more accurately track chlorine compounds, including free chlorine,
and their concentrations.
“Our research is focused on developing an accurate, cost-effective,
and field-deployable approach capable of replacing or complementing
the current DPD method for the measure-ment of free chlorine concentration
in process waters, particularly red-water chillers,” says Jie
Xu, research scientist and project director.
“Colorimetric analysis such as the DPD-based method can suffer
from interferences caused by turbidity and natural organic coloring
constituents
like chicken blood,” explains Xu. In addition, she notes, several
significant problems are associated with the DPD-based method: (1)
the DPD reagent is not very stable; (2) the oxidized colored products
show fading within a few minutes; (3) the color developed with DPD
is reported to be temperature sensitive; (4) there is interference
from combined chlorine, and (5) it is typically a manual, off-line
method. As a result, says Xu, the concentration of free chlorine measured
by the DPD method can be inaccurate resulting either in a marginal
disinfection process or wasted money associated with adding unnecessary
chlorine.
The sensor under development by Xu and her team uses an interferometric
measurement principle previously developed by Georgia Tech researchers.
The technique can be used to detect both chemical and biological
species, and is fast, has high sensitivity, and provides a direct measurement
with no additional steps or consumable reagents. The sensor platform
is designed for mobile, on-site field analysis with real-time results.
For the current project, researchers have incorporated a novel reactive
sensing film into the sensor to create an assay for rapid, on-line
quantification of free chlorine (hypochlorous acid). According to
Xu,
preliminary data suggest it will be possible to detect levels below
one part-per-million of chlorine within a matter of minutes, independent
of sample matrix or interfering substances.
In addition, researchers
are exploring sensing chemistry development for monochloramine (which
measures combined chlorine). “Monochloramine
has become a disinfectant with widespread acceptance due to its biocidal
capability, persistence in water, and lower formation of disinfection
byproduct trihalomethanes,” explains Xu. Several sensing chemistries
have already been investigated based on the specific reactivities of
monochloramine, and initial results indicate a sensitive, reversible
measurement for monochloramine.
The team has also designed and fabricated a waveguide chip with eight
interferometers. With this new design, simultaneous multiple detection
becomes achievable. In addition, researchers plan to integrate sensing
chemistries for free chlorine, combined chlorine, and pH on a single-chip
to provide real-time measurement for free chlorine, combined chlorine,
and pH.
“A well-managed chiller will provide an important step in helping
control bacterial counts and prevalence. This sensor, which provides
near real-time
information on chiller killing power, should be able to more dynamically
track and hence control chiller management,” says Xu.
Funding
for the project is being provided by Georgia’s Traditional
Industries Program for Food Processing with additional support from
Georgia Tech’s Agricultural Technology Research Program (ATRP).
|
