Notes

Outline

Safety of the Water that Comes in Contact with Food or Food-Contact Surfaces

Key points Uses for water Potential hazards associated with water Source Cross-connections Dump tanks / flumes Disinfection of Water Prevents cross contamination

; Uses for water - Pre-harvest

Uses for water - Post-harvest

Potential hazards associated with water

Monitoring goal: To provide assurance that water that contacts food or food contact surfaces meets EPA National Primary Drinking Water Regulations

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Characteristics of municipal water High chemical and microbiological standards; Has been purified or treated; Has been tested on a pre-determined schedule; Can be monitored by receipt of annual water bill and/or laboratory results optional

Characteristics of well water Can become contaminated by floods or heavy rains; Location too close to cesspools, septic tanks, agricultural sites, manure storage areas, or drainage fields may result in contamination

Characteristics of well water Cracked or improperly sealed well casings or liners may cause contamination; Requires more frequent monitoring

Well water monitoring

Characteristics of surface water (ponds, lakes, rivers, irrigation canals, etc.) Highest potential for contamination Safety can vary greatly over short periods of time

Characteristics of surface water Easily contaminated by upstream cattle operations, sewage discharge, or runoff from fields and manure piles

Using surface water – Orchards and fields

Using surface water – packinghouses Untreated surface water should not be used in packing houses

In-plant water contamination Cross-connections - a physical connection between a potable (drinkable) water supply and a source of contamination Backflow Back pressure (pressure of the non-potable system exceeds the positive pressure in the water distribution lines) Back siphonage (a partial vacuum in a water-supply draws water from a contaminated source)

Cross-connections Stoppage in toilet or sink may allow contaminated water to reach water line and exit lower faucet

Cross-connections

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Water Disinfection

Goal of water disinfection

Goal of water disinfection

Why do microorganisms resist removal from fruits and vegetables? Occlusion (hiding) Internalization Attachment and biofilm formation

1. Occlusion Because of their extremely small size, complete removal of microorganisms from produce surfaces is impossible

Comparison of size of bacterial cell and apple

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2) Attachment and Biofilm Formation Bacteria prefer to be attached to a surface and to each other rather than remain suspended in a solution

Biofilm formation Adsorption (sec) Attachment (sec–min - hrs) Growth and division (hr-day) Slime formation (exopolymers) (hr-day) Attachment of other microorganisms (day-mo)

Biofilm Formation on Apple Tissue

3) Internalization Bacteria can be drawn into the stem and calyx areas when submerged in cold water

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Recommendation: Maintain dump tank water at least 10oF warmer than apples

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Chlorine (Hypochlorite) Chlorine gas (Cl2) Sodium, calcium hypochlorites Powdered organic chlorine Maximum concentration 200 ppm available chlorine

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Chlorine Dioxide Effective on bacteria, fungi, virus Good effectiveness on biofilm penetration Very low impact of pH on efficacy Good stability in water (=HOCl; >O3) Low off-gassing in soluble form Less corrosive than chlorine No chlorinated Disinfection-By-Products Inactivated/decompose in sunlight

Methods of Production of ClO2 On-site generation; typically for large operations Can’t be shipped; > 10% is explosive!! Very toxic and strong irritant Engineer and restricted space controls required Stabilized (as Sodium Chlorite) Acid activation forms chlorine dioxide in batch Manual acid activation and proportion-pump feed Automated acid activation and in-line feed

Commercially Available Stabilized ClO2 Sanova Acidified Sodium Chlorate forms ClO2 on acid activation Biocide International Oxineâ Purogeneâ Sanogeneâ

Typical Reported Use Rates of ClO2 Produce mist (potable water only)                 5 ppm Produce wash (clean water rinse)            25-35 ppm Water disinfection (flumes)            25-50 ppm Biofilm removal (flumes and lines)                100 ppm Clean out (tanks, trays, bins)                    100-200* ppm Storage room walls and floors                    200-500 ppm* * Requires ClO2 protective mask

Ozone Formed by electrical discharge or UV light As gas or dissolved in water More powerful oxidant than chlorine More effective against parasites Less sensitive to organic load No affected by pH between 6 and 8

Ozone Unstable, must be generated onsite Not very soluble - Continuous generation required to maintain levels Gas is corrosive at high levels (> 4 ppm) Pungent odor at < 1 ppm

Oxidation Reduction Potential (ORP) Most disinfectants are oxidizing agents ORP measures oxidizing potential in millivolts rather than chemical concentration Measures the direct killing effect on microorganisms Useful across many disinfectants

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Relationship of Hypochlorite Concentration to ORP (pH 7.0)

Influence of pH on ORP and microbial survival

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Key points Uses for water Potential hazards associated with water Source Cross-connections Dump tanks / flumes Disinfection of Water Prevents cross contamination

Safety of the Water that Comes in Contact with Food or Food-Contact Surfaces