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Knife Sterilizing - Pitfalls and traps - water and energy saving solutions.

Posted by Warren Leamy on 23rd Jun 2015

Why do we Sterilize? 

The point of sterilizing and washing a knife is pretty obvious and is regulated, or at least should be regulated, to ensure good hygiene and safe food. Knives for cutting meat as in processing plants, butchers and abattoirs would need to be washed and sterilized at regular intervals, that is, a minimum of between every carcass  This regular sterilizing avoids cross contamination. The knives not only need to be sterilized but at the same time should be washed and rinsed, this in itself rules out autoclaves and UV or Ozone type sterilizers unless the knives are washed prior to entering the sterilizer . The most economical way to wash and sterilize is to use hot water in a knife sterilizing unit as shown.


Chemical Sterilization

It is our understanding that chemical sterilizing and washing is possible however is not economical or common as the chemicals are cost inhibiting, especially in food contact knives where the chemicals have to be food safe. 

UV or Ozone Sterilization

As mentioned Ozone or UV sterilizers to work and are effective if the knives are washed and rinsed prior to sterilization


Hot Water Sterilization

                   Knife Sterilizer                      Knife sterilizer

Clean water in a sterilizer heated and maintained at or above 82 Degrees C is the best solution. For security we say 85 degrees is the optimum for best results. This clean water and 85 degrees is where the problems and catches start. 

Flushing water for wash & rinse

To maintain clean water the sterilizer should be constantly flushed. The Sterilizer is flushed by way of placing the inlet of the water supply on the bottom of the sterilizer and the outlet or overflow,  at the top. This ensures that all the fats and oils are skimmed off the top of the sterilizer. 

Maintaining and controlling temperature

To maintain the 85 degrees needed for sterilization a number of effective and ineffective methods are used. 

Steam heated

Steam or hot water from a external boiler may be used. This method may be the largest culprit of water wastage and the reasons will soon become obvious.  As the steam enters the sterilizer it immediately starts to cool, and since the hottest it can be when entering the sterilizer is 100 degrees it it only a relatively short period of time before it is below 85 degrees, to again get it above 85 degrees more steam is needed to bring it back above 85, this results in a constant flow of steam, dependent on the ambient temperature and usage this amount of water that is being used can be astronomical.

Electric element heated

The most common method of heating and maintaining the water temperature is via a electric element and thermostat. This is very similar to a standard kettle and when combined with a thermostat will switch on and off as required holding the water temperature above 85 degrees. To gain an even greater advantage the water introduced may be from a boiler as in 1 above. The problem here or with this method is the flushing of the sterilizer and to overcome this the introduced water is generally needed to be a constant flow, this flow of water is generally way lower as in one above but can still be a huge waste of water. 



To overcome all the problems above it is advised that the following be introduced.

Use Insulated sterilizers

 Ensure the sterilizer is fully insulated  - double jacketed and preferably with polystyrene - this will help eliminate heat loss.

Use electric element to maintain heat 

Ensure the sterilizer has its own internal electric element and the thermostat is set at 82 -85 degrees - no hotter

Introduce hot water for flushing

If possible introduce flushing and filling clean water from a central boiler or heat exchanger

Control the flow of water introduced 

Controlling the flow of flushing water or steam. Generally and traditionally this control has been via a valve that is slightly open, or more accurately via a valve and orifice that only allows a measured flow. The problem here is that the element is flushed on a continuous basis, even if its not being used or with minimal use will encounter the same water wastage as a sterilizer that is in constant use. Water flow and wastage within the sterilizer can be huge.


To effectively and securely control the flush water we advise installing on each sterilizer a simple 6 v solenoid valve. 6 Volts as this can easily be wired and controlled from a central point. At the central control point the possibilities become endless as now each sterilizer can be flushed as and when required, as a group in usage, individually when needed, or simply on a timer. The complete system can also be switched off during breaks and between shifts. This will not only save massive amounts of water it will also save huge amounts of power.