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!