Process Water

Water is used extensively in almost all aspects of processing fresh produce. Water can be used for such things as;

• Cooling whole or cut produce before packaging

• Aiding and removing peels during abrasive peeling operations

• Washing whole produce to remove surface dirt before cutting 

• Washing produce to remove juices from cut surfaces

• Conveying produce 

• Rinsing cutting equipment and knives

• Sanitation
  

Wherever water is used during the processing of fresh produce, it should be from a safe and sanitary source. This is commonly referred to as being potable. The water used in a fresh produce processing plant should be documented and verified as being safe and adequate for its intended use and should meet all local state and federal standards for potable water. Municipal water sources can provide safety information and documentation for their water quality. 

If fresh produce processors have their own water source such as a deep water well, it should meet the same requirements. In addition, they should document the safety of their water by routinely performing water analyses. 

Coldwater that is commonly used to rinse and cool produce is often recirculated because of the high energy costs of chilling water. Whenever water recirculation or reuse occurs, whether it is for hydro-cooling whole produce or washing and cooling cut produce, precautions should be taken.

Rinse water disinfectant levels should be adequate to prevent the potential for cross-contamination via contamination of the rinse water system. Numerous chemical and physical methods are available to keep water intended for use with fresh fruits and vegetables disinfected such as use of; 

• Sodium Hypochlorite 

• Calcium Hypochlorite

• Chlorine Dioxide 

• Chlorine Gas 

• Peroxyacetic Acid

• Ultraviolet Light

Special safety precautions are required for certain chemicals so fresh-cut processors should review and follow the label directions. Processors can consult an agricultural extension agent, chemical suppliers or food safety consultants for help in deciding what chemicals and physical methods to use. Whatever system Is chosen to keep processing water disinfected, it should include the monitoring and maintenance of proper wash water disinfectant levels in the SOPs. 

Specific steps may include; 

• Document the functionality of the system

• Routinely monitored to assure that adequate disinfectant levels are present whenever processing is occurring 

• Use only food-grade disinfectants that are approved for use on fresh produce products

Monitoring the disinfectant levels within the wash water and/or cooling system can be accomplished by various means, such as test strips, test kits, or oxidation-reduction potential meters which can be automated to produce real-time, continuous monitoring as well as control of disinfectant levels. Be aware that the effectiveness of some disinfectants can be affected by such factors as the pH and temperature of the water and the amount of organic matter present in the water. The addition of food-grade processing aids such as acids to adjust water pH and mechanical screens to remove organic particulate matter may be necessary to achieve optimal disinfectant performance.

Sodium Hypochlorite solutions for example have;

• An alkaline pH (11 to 13) 

• Will only function effectively if the pH is lowered to a range of 6.5 to 7.5

Chlorine gas if used as a wash water disinfectant will;

• Lower wash water pH
  

Calcium Hypochlorite Pellets 

• Dissolve slowly (especially in cold water)

• Undissolved granules may damage produce as well as fail to maintain the desired chlorination level

• Granules should be dissolved in warm water before being added to cold water

• Raises the pH of wash water above 7.5 if not adjusted

Chlorine Dioxide; 

• Less affected by pH

• Has greater oxidising power than Hypochlorite

• More difficult to handle 

• Should be generated on-site

Chlorine reacts with organic matter such as soil and vegetable matter. This chemical reaction produces combined chlorine, which is not effective as a disinfectant. Changing the water frequently or filtering organic matter out of recirculated water is recommended to achieve good sanitation. 

Prewashing soil and produce along with monitoring disinfectant levels will prolong the useful life of chlorinated cooling water. Ozone, Acetic Acid or Peroxyacetic Acid may also be used as a wash water disinfectant and research is underway to find the best combinations of treatments. 

Any water contacting fresh produce should be potable especially when it is recirculated. This is so important that redundant methods may be warranted to assure that equipment is functioning properly and corrective actions have been taken if system failure does occur. If a human pathogen contaminates a recirculating water system each piece of produce that subsequently passes through the system will be contaminated.

For many produce items that are going to be processed, a pre-wash step is often included in the firm's SOPs. Prewashing whole produce before cutting helps remove field dirt from items such as melons, carrots, and radishes that have had direct contact with soil. Prewashing some produce is very effective at removing surface dirt which may harbour human pathogens. It may not be applicable for fresh produce such as cabbage or lettuce where outer leaves and cores are removed before cutting.

Lastly, water is used extensively to clean and sanitise equipment because fresh produce processing moves at such a quick pace, equipment cleaning and sanitation often occurs in the midst of a processing shift, particularly for equipment that may be used to process various products.

If equipment is cleaned during a processing shift, cleaning and sanitation should be done in a restricted area to prevent contamination of already processed produce by cleaning chemicals, sanitisers or water aerosols. Processors should be aware of and prevent cross-contamination by aerosolised water mists.