In order to efficiently use these important substances, one must first understand the role that they play. Clean, disinfected water minimizes the transmission of pathogens from water to produce, or from infected to healthy produce, either within a lot or from lot to lot. Plant surface contours and cuts can introduce pathogens into the fruit, and provide growth opportunities for them. It is essential that a sufficient quantity of sanitizer be available to kill these pathogenic microbes before they find a home on or in the produce. To ensure this availability, the following facts are important to remember.

1. Pre-harvest practices. Excessive use of chlorine (or other sanitizers) has negative effects on product quality. As harvest approaches, therefore, the microbial standards used for water should increase gradually to minimize infestation and potential contamination.

2. Water. Potable water should be used for all postharvest activities, including washing, grading, material handling (fluming), and cooling. Sanitizers do not easily kill some pathogens that are harmful to humans, so clean potable water is the best preventive step available. When quality is in doubt, a certified analytical lab should perform a water quality evaluation.

3. Organic Matter. The power of chlorine and other sanitizers to kill pathogens is because they are powerful oxidizers, and highly reactive. Unfortunately, they do not discriminate what they react with. Reacting with both organics and inorganics in wash water rapidly uses up chlorine in particular. Care should be taken to filter out soil, leaves, and other debris, and to periodically change water as it becomes full of exudates such as sap from cut or scuffed produce.

4. Performance Enhancers. Sanitizers will only kill what they contact. Water films that form on small surface contours may prevent contact with target microorganisms. Surfactants decrease water surface tension, and in effect, "make water wetter" by allowing freer flow and can make chlorine and other sanitizers more effective. Examples of approved materials are polysorbate 80 and Chlorine Potentiator from Bonagra Technologies, Inc.

5. Temperature. Sanitizers such as chlorine tend to be more active as temperatures increase, but in general, the need for cooling from water is more important than the slight increase in performance from higher temperatures.

6. pH. As those with home swimming pools realize, the performance of chlorine is affected by the pH (acidity/alkalinity) of the water. This is because chlorinated water actually has three components; chlorine gas, hypochlorous acid (HOCL), and hypochlorite ions. Of these, HOCL is the most effective and desirable as a bactericide, and is the one which varies the most with changes in the pH. In general, a pH of 6.5-7.5 produces the optimum balance of activity, stability, and safety (at a low, or acidic pH, chlorine gas is actually released from water). pH should be frequently if not continuously monitored. Both chlorine and pH can and should be monitored using test paper strips, colorimetric kits, or electronic sensors. Muriatic acid (HCL) or citric acid (C6H8O7) are commonly used to keep pH within the proper range.

7. Concentration. The optimum sanitizer concentration and dwell time varies from product to product, but exposure time of 3-5 minutes in a solution with a sanitizer concentration of 50 to 75 parts per million in a solution of slightly acidic (6.5 pH) is generally viewed as adequate. Caution must be used, however, as some products will lose color or develop surface defects when levels are too high or exposure times too long. Most extension offices can provide data on specific crops.

Proper and efficient use of sanitizers will maximize the benefits of the substances to product safety and quality, while minimizing the expense and risks associated with them.

Food Safety Initiative Introduction
Work Plan