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Water Quality Part 2

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Title: Water Quality Subject: SE Region Food Safety Training, Florida, Feb. 2001 Author: Mark A. Ritenour Last modified by: Default Created Date: 3/11/1997 3:20:32 PM – PowerPoint PPT presentation

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Title: Water Quality Part 2


1
Water QualityPart 2
  • Developed by
  • Mark A. Ritenour
  • University of Florida
  1. Introduction
  2. Agricultural Water
  3. Postharvest Processing Water
  4. Water Testing

2
Acknowledgements
  • Some of the information and slides used in
    preparing this presentation were provided by
  • FDA, Improving the Quality and Safety of Fresh
    Fruits and Vegetables Training Curriculum.
    (draft)
  • Trevor Suslow, Univ. Calif., Davis

3
II. Postharvest Processing Water
Singular critical control point capable of
amplifying an error in sanitation or hygiene
management
Suslow, UC Davis
4
Sources of Water to Monitor.
  • Dump or soak tanks.
  • Washing lines.
  • Hydrocoolers.
  • Infiltration into the commodity?
  • Top ice liquid-ice injecting.
  • Ice makers.
  • Melting ice is messy.
  • Anywhere Water Contacts Fruit!

5
The Problem with Water Handling Systems
  • Produce from the field usually harbors many
    pathogens (including dirty and decaying fruit).
  • Postharvest handling of fruits vegetables often
    includes the use of flumes, dump tanks, spray
    washers, or hydrocoolers.
  • Pathogens can quickly accumulate in these water
    sources and contaminate healthy fruit.

6
Sanitation vs. Sterilization
  • The application of chemical sanitizers can
    destroy vegetative cells of bacterial pathogens
    but may not be effective for the destruction of
    the more resistant spores
  • Commercial sterility refers to the complete
    elimination of pathogenic microorganisms,
    including the spores of foodborne pathogens (i.e.
    Clostridium botulinum). This can be achieved
    through heat treatments such as canning but not
    through the application of common disinfectants

7
Agents used to sanitize fruits and vegetables
  • Chlorine
  • Chlorine dioxide (Sanova, Oxine, etc.)
  • Bromine iodine
  • Hydrogen peroxide
  • Peroxyacetic acid (Tsunami)
  • Electrolyzed water
  • Ozone
  • UV-C illumination

8
Common Water Sanitizers
  • Chlorine is by far the most widely used in fruit
    vegetable packinghouses
  • Peroxyacetic acid commonly used in fresh-cut
    operations
  • Less affected by organic load
  • Ozone and UV used to some extent in fresh-cut
    operations
  • More effective treating a stream of clear water

9
Benefits of Chlorination
  • Relatively inexpensive (Cl2 least expensive)
  • Can effectively reduce pathogen inoculum in dump
    tanks, hydrocoolers, etc.
  • Reduces the transfer of decay organisms to
    healthy fruit.
  • Can kill some existing pathogens on fruit
    surfaces.

10
Sources of Chlorine
  • Sodium hypochlorite (NaOCl)
  • Liquid (5.25, 12.75, or 15)
  • Calcium hypochlorite Ca(OCl)2
  • Solid (65 or 68)
  • Chlorine gas (Cl2)
  • Gas cylinders
  • Chlorine dioxide (ClO2)
  • Generated on-site from sodium chlorite acid

11
Factors Affecting Chlorines Effectiveness
  • Water pH (ClO2 least affected)
  • Chlorine concentration
  • Contact time
  • Organic matter in the water
  • Water temperature
  • Type growth stage of pathogen

12
Water pH
  • Hypochlorite and Cl2 form hypochlorous acid
    (HOCl).
  • Hypochlorous acid is what kills pathogens.

NaOCl Ca(OCl)2 Cl2
gt
HOCl
13
High pH
  • At high pH, hypochlorous acid converts to
    hypochlorite ion (OCl-).
  • Hypochlorite ion is relatively ineffective
    against pathogens.

HOCl
H OCl-
14
100
90
80
OC (32F)
70
20C (68F)
30C (86F)
60
Chlorine in Available Form
50
40
30
20
10
0
5
6
7
8
9
10
SOLUTION pH
15
Low pH
  • At low pH, hypochlorous acid is quickly lost.
  • Increased corrosiveness to equipment.
  • Unpleasant working conditions due to increased
    chlorine odor.
  • Recommended pH is between 6.5 7.5.

16
Chlorine Concentration
  • Relatively low chlorine concentrations (lt 40
    ppm) can kill pathogens.
  • Higher concentrations are commonly used to
    compensate for various losses.
  • Recommendation 100 to 150 ppm free chlorine.

17
Contact Time
  • Higher chlorine concentrations kill microbes
    faster (e.g. lt 1 min).
  • Lower chlorine concentrations require longer
    exposure time.
  • More resistant microbes or stages of growth may
    require longer exposure times to kill.

18
Organic Matter in the Water
  • Organic matter reacts with chlorine and quickly
    reduces the amount of chlorine available to kill
    microbes.
  • However, this chlorine may still be measured by
    total chlorine testing kits.

19
Water Temperature
  • At higher temperatures, available chlorine kills
    microbes faster.
  • Higher temperatures also causes more rapid loss
    of chlorine activity.
  • In practice, water temperature is usually
    optimized for reasons other than optimized
    chlorine effectiveness (e.g. rapid cooling).

20
Type and Growth Stage of Microbe
  • Bacteria, and germinating fungal spores and
    mycelia are relatively easy to kill with
    chlorine.
  • Quiescent spores are much more resistant to
    chlorine.
  • Microbes inside fruits and vegetables are
    protected and will not be killed.

21
Chlorine Recommendations
  • Maintain free chlorine levels between 100 to 150
    parts per million.
  • Maintain pH between 6.5 and 7.5.
  • Drain tanks often (e.g., daily) and refill with
    clean water.
  • Use self-cleaning screens in dump tanks to remove
    large debris and organic matter.

22
Maintaining Adequate Chlorination
  • Manual monitoring and addition of chlorine.
  • Requires frequent monitoring of chlorine
    concentrations and pH.
  • Automated chlorine dispensing.
  • Timed release or based on measured chlorine
    concentrations or ORP.
  • With or without automatic pH adjustments.

23
Chlorine Test Kits
  • Use kits that measure free chlorine levels
  • Total chlorine kits can measure both free and
    bound chlorine.
  • If sample dilution is required, dilute with
    distilled water.

24
Chlorine Recommendations
  • Check free chlorine levels often or use automated
    systems.
  • Use all chemicals according to their labels.
  • Consult local regulations for disposal of
    chlorinated water.

25
Summary
  • Maintain water free of decay causing organisms.
  • Use potable water change daily.
  • Wash particularly dirty commodities prior to
    hydrocooling.
  • Use self-cleaning screens at pump intakes to
    remove larger debris.
  • Design water handling equipment for easy
    cleaning.
  • Use an approved sanitizer.

26
Thank you!
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