Dip, dry or dump tanks and chillers are used to process a range of fresh produce and poultry products. These are usually large containers of water and disinfectants, where objects are fully or partially submerged, but in some instances a vapour is instead used to coat the produce.
Dip tanks, also known as dump tanks, are used as a primary wash to remove bulk contaminants in fresh produce. They are also used in combination with chillers in poultry processing to reduce microbial pathogens.
Dip tanks are highly effective because they provide complete contact of the product with the sanitizing solution. However, the water can quickly accumulate organic, particulate and coloured matter so monitoring sanitizer levels is crucial.
Immersion chilling is often used in poultry processing to lower the total microbial load on the product whilst it is cooling.
Dip tank and chiller systems use chlorine, chlorine dioxide or peracetic acid to achieve sanitisation. In fresh produce, dip tanks are used to remove surface contamination, such as soil or decay, prior to packing or further processing. There is no industry wide standard and the use of a sanitiser will vary depending on the producer, process, buyer and regulator.
Chlorine is one of the most common and cost-effective disinfectants used in chiller water, safely preventing cross-contamination between batches of poultry so long as water pH is carefully controlled. Chlorine dioxide is more expensive but has shown greater efficacy at reducing pathogens on the surface of poultry products, even with much lower dosing concentrations compared to chlorine.
The use of peracetic acid is becoming more popular in poultry chiller systems, largely because it shows good efficacy at preventing cross-contamination and reducing surface pathogens on poultry, with no harmful by products formed.
Tanks and chillers are high-risk areas for cross-contamination between batches, an example of this would be if a Salmonella-positive flock is processed. It is therefore critical to maintain sanitiser concentrations in the chiller or dip tanks to decrease pathogen survival. Unfortunately, many traditional test methods are unsuitable because of the high levels of organic, particulate and coloured matter in the sample.
Palintest recommends the use of Kemio system to deliver repeatable and reliable results to ensure maximum produce control. Whilst DPD can also be used, the low measurement range for DPD means high dilutions often need to be performed. In addition, the presence of particulate matter, fats and coloured materials can strongly interfere with colorimetric testing. Kemio technology minimises user input and is not affected by solids or colour in the sample, providing more control of sanitisers in critical process areas.
Drop count kits are a popular method for measuring peracetic acid (PAA) but they are reliant on the capability and concentration of the user. The counting of very high numbers of drops, increases the chance of user error and lengthens test time. As with DPD testing, the colour change in the method can be subjective and dependent on the operator and/or ambient light conditions. Many kits do not fully compensate for hydrogen peroxide interference, creating false positives.
Kemio is a multi-parameter instrument. Each batch of sensors has its unique batch calibration information. Scanning the sensor allows Kemio to select the correct test type and use the specific batch information. Using the correct batch is imperative to ensure the accuracy of your results.
To perform additional tests using a sensor from the same batch, you can select ‘retest’ after performing a test. Alternatively, you can change your scanning settings from Configuration > Settings > Test Settings > Scanner Settings.
Check standards are used to determine if an instrument is still within calibration.
Photometers work by sending light through the sample, check standards for these instruments are usually either Coloured Solutions or Neutral Density Filters (NDF). Both types have known and certified transmittance or absorbance values so they should give these values when read in a photometer. To make the checking process even simpler some instruments will convert these to a parameter such as chlorine and give the value mg/L. The ‘target’ value is on the certificate supplied with the set of Check Standards.
Kemio and sensor instrument check standards verify that the instrument correctly measures electric signals. As with electrochemical sensors in samples, the instrument applies a voltage to the check standard and measures the resulting current. Check standards include verified resistors, which produce a consistent electric current. Kemio validates the measured current internally. Sensor instruments display the corresponding concentration value, which is compared manually to target values on the certificate supplied with the set of check standards. Check standard kits come with three standards to test across the measurement range.