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Problem
Harvested vegetables get transported in ambient conditions from the growing farms to the pack house. Since temperature and bacterial contamination are the main contributors to decay rate, these factors need to be addressed as soon as the vegetables are received by the pack house. It is therefore important to maintain sanitary conditions in all areas where produce is washed and packed. SolutionChlorine readily kills microorganisms suspended in dump tanks and flumes if the amount of available chlorine is adequate. Organic matter in the water inactivates chlorine and these levels should be monitored constantly. Chlorine is sensitive to the pH level of water, hypochlorite solutions with higher pH values (7.5 to 8.5) are more stable but less fungicidal, whereas at lower pH values (5.5 to 6.5) the solutions are less stable but more fungicidal.
The effect of pH on chlorine dissociation products It is important to ensure that water used for washing and sanitizing purposes is clean so that it does not become a vehicle for contamination. All water that comes in contact with produce for washing or hydro-cooling must be potable grade. To achieve this, water should contain at least 0.5 ppm free chlorine and have a pH between 6 and 8. Rinsing produce with potable water will reduce the number of microorganisms present on the produce but it will not remove all bacteria. Using an oxidative sanitizer like Frexus CH will ensure that bacteria in the water are killed on contact. It will also prevent cross contamination of produce in the washing or hydro-cooling system and also minimizes microbiological contamination on produce to acceptable levels to increase the shelf life of these produce and ultimately its quality. Washing Bath Chlorination and pH control with HG602
By installing HG602 controller systems the washing baths are fully automated to ensure that correct Chlorine levels as well as pH is maintained at all times. In order to achieve this, an independent re-circulating pump and line was installed on each of the 2nd baths. From the re-circulating line a sample point was installed in order to direct water flow continuously to the measuring/controlling unit. The controller system will continuously measure the pH level and Chlorine residual level in the re-circulated chilled water amperometric (with probes) and will effectively control these levels by dosing the required amount of Frexus CH (Chlorine chips) and food grade Hydrochloric acid into the water. Chlorination of the water circuit is done through the installation of a Pulsar 1 chip doser unit on each re-circulating line. A small solenoid valve, receiving a signal from the HG602 controller, will open and close based on the actual Chlorine residual value in relation to the set point entered, which is 200 ppm. Due to the changes in pH of the water when Chlorine is dosed, the effective control of pH levels is therefore very important. In order to control the pH level, small dosing pumps are automatically activated by the HG602 controller should the pH increase above the set point of 6.8.
HG602 High Chlorine controller system at low risk section
Results
A sample of the mixed lettuce was taken for microbiological contamination analysis before and after washing/disinfection. The following table reflects the test results:
Benefits
The benefits in controlling the chlorine and pH levels proved to be the following:
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Food & Farming Case Studies Harvest Fresh