University of California

Ask the Produce Docs (General)

How many pounds of ethylene would I need for my kiwi ripening chamber?

  • Ripening

Could you tell me how many pounds of ethylene I would need to put in a kiwi ripening chamber that is 73,000 cubic feet, in order to reach 200ppm? (S.M.)


For ripening we use ethylene as a gas in a cylinder using a flow meter. It is very hard and erratic to measure by weight very small amounts of ethylene for this application. We calculated that you will need approximately 0.0011 lb of ethylene (C2H4) for your conditions.

I suggest that for your case, you should use the "shot" system for ethylene application technique. The "Shot" system is one technique by which ethylene can be applied to kiwifruit. Always make sure the ripening room or truck is "well sealed".  A measured amount of ethylene is introduced into the room. The room can be completely full.  Ethylene shots from a cylinder may be applied by flow using a gauge (flow meter) that registers the discharge of ethylene in cubic feet per minute. The required ethylene application is made by adjusting the regulator to give the appropriate flow rate and then timing the delivery of gas. The amount of gas needed for a room is calculated by using the following information:

C = ppm of ethylene required

V = volume of room in cubic feet

F = flow rate of gas (measured from flow meter) in cubic feet per minute (CFM)

T = time (in minutes) for which gas is allowed to flow

 Plug this information into the following formula:

T = (C x V) / (F x 1,000,000)

For your 73,000 cubic feet chamber, a desired ethylene concentration of 200 ppm, and ethylene flow rate of 5 cubic feet per minute (CFM), the equation would be as shown below:

(200 ppm x 73,000 cubic feet) / (10 cubic feet per min* x 1,000,000) = Time (minutes)

14,600,000/5,000,000 = 2.92 minutes =~3 minutes

(To convert the above equation from cubic feet per minute to milliliters per minute, multiply by 28.32).

Time of application is easily measured with a stopwatch. The room should be ventilated before each application by opening the doors for at least one-half hour after 6 or 12 hours of application.  In the case of kiwifruit just harvested or stored for less than a week, kiwifruit should be treated for at least 12 hours (then venting). If kiwifruit have been in cold storage for more than a week, a 6 hour ethylene treatment will trigger ripening.  In both cases, a ventilation fan should be provided.

It looks complicated but it is not.   --Carlos H. Crisosto

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