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Ethylene Gas Testing and Chromatography


Ethylene gas is a naturally occurring ripening hormone.

The significance of the presence of ethylene is that fruit can exhibit accelerated ripening and flowers will wilt in the presence of very small quantities.

Most green vegetables, salad leaves and cucumbers are highly sensitive to the presence of the gas, which causes yellowing.

Many commodities are sensitive to ethylene concentrations in air of less than 0.1 ppm (parts per million). Sources of Ethylene are usually fruit but can be florescent lights or even pollution, from one example gas operated fork lift trucks.

Measurement of ethylene gas is a relatively complex business because of the extremely low concentrations that it has an effect at and therefore need to be measured. For this purpose CRT own and operate a portable gas chromatograph, which is capable of measuring ethylene down to 0.01 ppm.

It works by taking a one-millilitre sample and passing it through a column using a carrier gas of extremely pure air.

A photo ionisation sensor detects ethylene and the concentration calculated by an on-board computer by referencing to a calibrated sample.

CRT can carry out measurements at your premises and air samples from all your storage areas can be analysed in a few hours.

Alternatively we can provide sample cylinders and pump with which you can collect samples for return to CRT for analysis.

In most cases if a problem is identified the solution is usually straightforward and can be easily solved by changing ventilation patterns or even arranging slight under pressure or over pressure of stores. Such pressure differences can be easily achieved by a small electric fan.

Ethylene Scrubbing (Gas Removal)

The best method of ethylene scrubbing, gas removal is by fresh air ventilation. Fresh air is required in most cases anyway to remove Carbon Dioxide but also has the advantage of humidifying the storage air.

Where products of differing ethylene production rates and sensitivity are stored in close proximity, protection can be achieved by under/ overpressures as described above easily achieved by a small electric fan.

Various Ethylene scrubbing systems are available though all have disadvantages and are only really necessary for some controlled atmosphere applications. These include, potassium permanganate on substrate, heated catalyst or UV/carbon bed based removal systems. 

  • Permanganate systems   simple,  though efficiency affected by humidity. Principal problem is the large quantities required and if sachets are used these are usually mixed with packaging, which is a problem as it is illegal to dispose of permanganate in landfill within the EU.

http://www.netregs.gov.uk/netregs/275207/663559/1499201/

  • Heated catalyst less effective at low concentrations of gas, energy hungry and caused store dehumidification.
  • UV/carbon bed based systems Potentially a good method but expensive and require maintenance.

 

 


related information

BS EN standards

american ANSI standards

ventilation effects and requirements

measurement of ethylene gas prior to and during transport

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