surface disinfection

Surface disinfection

After the cleaning of surfaces and equipment there may be a need to reduce any residual micro-organisms present, to a safe level, by using a disinfectant.

To achieve the required hygiene result it is vital that the surface to be disinfected is free of food soil or chemical residues as if these are present, it could prevent the disinfectant working as it should.

Disinfectants used in the food, beverage and food service sectors are designed to have low toxicity and taint profiles, working against the organisms of concern which are generally pathogens and food spoilage organisms.

It is crucial to follow the concentration and contact time recommended by the manufacturer, whilst ensuring an even coverage of the surface.

Choosing the correct disinfectant

The following factors should be considered when choosing a disinfectant:

  1. Microorganisms to be destroyed
  2. Contact time available
  3. Type of surfaces to be disinfected
  4. Risk of food taint
  5. Toxicity of disinfectant and effect on personnel
  6. Disinfectant method of application
  7. Application temperature
  8. Stability
  9. Water hardness
  10. Ionic nature of detergent used before disinfection.
Where to disinfect

Disinfection is not applicable to all surfaces in a food manufacturing environment and should only be used on those surfaces where the presence of significant numbers of microorganisms will have an adverse effect on the safety and quality of the food handled.  If disinfection is deemed to be necessary, then the following areas should be considered:

  1. Food contact surfaces
  2. Operator contact surfaces
  3. Cleaning materials and equipment
  4. Hands
  5. Evaporator components
  6. Airspace
  7. Drains and floors.
Rinsing of disinfectants

In some cases, it may be necessary to rinse off disinfectant solutions.  These are:

  1. If an oxidising disinfectant such as Sodium Hypochlorite has been used
  2. If the disinfectant has been used above its recommended non-taint concentration rate
  3. If an organic food product is to be processed or produced
  4. If industry specific regulations determine it must be rinsed.
Thermal disinfection

Hot water or steam can be used to achieve disinfection and is a good method of doing so.  However, it is very difficult to achieve on large items of equipment in a food manufacturing operation so in the vast majority of circumstances chemicals will be used for disinfection.

Previous thinking about thermal disinfection recommended using hot water at 82°C for 30 seconds.  However, recent evidence has recommended that this is only achieved when using hot water at 90°C for a period of 60 seconds.  This method of disinfection tends to be restricted to tray wash machines, soak applications and CIP.

Steam disinfection of surfaces via a lance has had some success in certain environments but care should be taken as the steam can have an adverse effect on some plastics, paint and machinery and lubricants/grease.  They also pose a safety hazard to untrained personnel and could cause condensation to form on other equipment or surfaces.

Spray disinfection

Spray disinfection is the most common method for applying disinfectant to surfaces. It is versatile, gives good coverage and is an economic means of applying disinfectant solution.

It can be carried out by using a variety of different applicators. The most common are: small trigger sprayers, pump-up sprayers, compressed air driven sprayers, via a high pressure washdown system using a high pressure injector or via a medium pressure system.

Soak disinfection

This is probably the most effective means of disinfection as the item to be disinfected is fully immersed in the disinfectant solution, giving good contact time to all surfaces.  It is important that items are effectively rinsed as detergent residue or debris will inactivate the disinfectant. 

This type of disinfection method is usually confined to small items such as utensils, knives, blades, small machinery parts, cutting boards etc.

The disinfectant solution in the sink can be made up by using a wall mounted plunger dosing unit or a proportioning unit such as a venturi or Dosatron.