BASIC DISINFECTANT TYPES
SELECTION AND PROPER USE FOR THE BEST RESULTS

Presented By N.E.M Business Solutions                                      
©2000

TOPICS: Disinfecting Flow-Through Areas (C.I.P.) Surface Disinfecting, Area Disinfecting,

Disinfecting of Working Environment      
      
The most important principle concerning disinfecting/disinfection is that a dirty surface can not be sanitary. The sanitiser cannot come into contact with bacteria trapped in and under soil.

The undisturbed growth of microorganism under ideal conditions is shown below. One bacterium under perfect conditions could produce one billion bacteria in ten hours. Clean and sanitary conditions are critical for product quality.

Time Count
30 minutes 2 cells
60 minutes 4 cells
90 minutes 8 cells
2 hours 16 cells
11 hours 10 million cells
Virus
0 minutes 1 virus
30 minutes 200 virus
60 minutes 400,000 virus
1.5 hours 8 million virus
2.0 hours 1.6 billion virus
2.5 hours 320 billion virus

 

Characteristics of disinfectants

Active Chlorine:

Active chlorine has been in use for many years as a disinfectant in the food industry because of its broad bactericidal spectrum and economic advantage. The active chlorine carrier has taken several forms with the liquid types based on inorganic chlorine compounds, such as sodium hypochlorites and the powder form based on organic chlorine compounds, such as the dichloroisocyanurate group.

Most often the bactericidal effect of active chlorine is best in a neutral or weakly acidic condition (pH 5 to pH 7), but the chlorinated alkaline cleaners also have an excellent bactericidal effect against all groups of microbes. Many tests, according to various methods, have proved that chlorine renders a very fast kill on viruses, bacteria, yeasts, and molds. The activity against spore forming bacteria is slightly slower.

The question of the corrosiveness of hypochlorite solutions on metals such as stainless steel and aluminum is still a matter of intense discussion, resulting in certain reservations regarding chlorine-based products.

Chlorine Sanitisers Have These Additional Advantages:

  1.  Unaffected by hard water scales,
  2.  Non-filming,
  3. Can be utilised at cool water temperatures without affecting activity.

Disadvantages Include:

  1. Precipitation when used in iron-laden water,
  2. Short residual effect after disinfecting.

The rule of thumb is that if chlorine is used as a sanitiser prior to production, the equipment should be used within one hour after the disinfecting procedure.

Hydrogen Peroxide:

Sanitisers based on hydrogen peroxide are most suitable for use in the dairy industry. This is attributed to its non-contaminating residues of water and oxygen. It has been used in the pharmaceutical and food processing industry for the aseptic packaging area. UHT milk in Europe is heated to 100oC with a 25 - 50% concentration of hydrogen peroxide and a short contact time. There is complete microbial destruction, including the destruction of Bacillus spores.

The Following Denote Advantages And Disadvantages Of Different Types Of Sanitisers:

Iodophor Sanitisers:

Acidic iodine-based sanitisers have a universal killing effect on all types of microbes. The amount of active ingredients to achieve the same killing power is lower in iodophors than in active chlorine-based products. Usually by increasing the temperature of the disinfecting solution, the killing time is reduced, and this is true for the iodine type products as well. Iodine will gas off at temperatures of 39oC-49oC and the loss of the iodine is high.

This and the possibilities of corrosion make it standard practice to use iodophors at room temperature.

Advantages Include:

  1. Stable, long shelf-life.
  2. They are active against all microorganisms except bactericidal spores and phages.
  3. They are unaffected by hard water salts, with the exception of water which contains large amounts of chlorides, leading to corrosion of stainless steel and aluminum.

Disadvantages Include:

  1. They are not as effective against spores and phages as chlorine.
  2. They are expensive.
  3. Iodophors stain porous metal surfaces and plastics.
  4. Iodophors are severely affected by alkaline conditions above pH 7.

Hypochlorites:

Advantages:

  1. Powerful germicides controlling a wide range of microorganisms.
  2. Deodoriser.
  3. Non-poisonous to man at use concentrations.
  4. Free of poisonous residuals.
  5. Colorless and non-staining.
  6. Easy to handle.
  7. Most economical to use.

Disadvantages:

  1. Short shelf life.
  2. Adverse effect on skin.
  3. Corrosive on some metals
  4. Gives off Chlorine gas when mixed with acids.

Use Concentrations:
50-100 ppm available chlorine should be employed for disinfecting large equipment and utensils and 200 ppm for spraying applications of large equipment.

The contact time for effective sanitation should be long enough to produce complete kill of bacteria, usually 10 seconds or longer.

Acid Anionic disinfectants:

Advantages:

  1. Non-staining, stable, long shelf life.
  2. No objectionable odour.
  3. Removes and prevents milkstone and waterstone formation.
  4. Effective against a wide spectrum of organisms.
  5. Stable in concentrated form or use dilutions, action enhanced by high temperatures.
  6. Non-corrosive to stainless steel.
  7. Provides short duration residual bacteriostatic effect on stainless steel equipment.

Disadvantages:

  1. Effectiveness at acid pH only.
  2. Generation of foam.
  3. Low activity against spore forming organisms.
  4. Corrosive to metals other than stainless steel. 

Use concentration: 
 100 - 200 ppm

Quaternary Ammonium Compound (Quat)

Advantages:

  1. Stable, long shelf life.
  2. Active against many microorganisms.
  3. Forms a bacteriostatic film.
  4. Non-corrosive and non-irritating to skin.
  5. Stable in the presence of organic matter.
  6. Stable to temperature changes.
  7. Good penetration qualities.
  8. Combined with non-ionic wetting agents, it makes a good detergent sanitiser.

Disadvantages:

  1. Expensive!
  2. Incompatible with common anionic detergent components.
  3. Slow to dissipate (residue problems).
  4. Germicidal efficiency varied and selective.
  5. Foam problem in mechanical application.

Use Concentrations:
For disinfecting of equipment a 200 ppm solution is sufficient to reduce bacterial counts with a one minute exposure.

Peroxyacetic Acid  ( PAA ):

Advantages:

  1. Wide spectrum of efficacy: gram positive, gram negative, spore forming bacteria, viruses, bacteriophages, yeast, and moulds.
  2. Rapid action, even at freezing temperatures.
  3. Incidental food contact does not affect taste of milk or beverages.
  4. Residuals turn into water and acetic acid (vinegar).
  5. VERY LOW toxicity!
  6. Low corrosivity at use concentration.
  7. Compatible with acid rinse.
  8. No staining!
  9. Long storage stability of concentrate.
  10. NO foaming!

Disadvantages:

  1. Concentrate has a strong odour.
  2. Concentrate is to be handled carefully.
  3. Expensive.

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