Methods of ripening and degreening

1.Use of ethylene gas:

• Ethylene is available in gas tank, more expensive for small producer and retailer, threshold level-0.2-1.0 ppm.
• Recommended conc.-Varies depending upon method of application, commodity and cultivar.
• The greener and younger the fruit the longer is the degreening and ripening period require.
• It is explosive at 30,000 ppm or 3%. However, effective degreening concentrations range from 100-1000 ppm.

2.Use of polyethylene tent for ethylene treatment:

• This technique was developed by itagawa of Japan and used for degreening citrus.

3.Treatment with ethephon:

• An expensive methods for small farmers and traders. It is sold as ethrel, which contains 4 lbs./gal or 480 g/l of ethephone as active ingredient.
• Concentration for ripening- 2500- 5000 ppm for banana, 1000 ppm for mango.
• For degreening- 100 kg of orange 2 ml of ethrel with 100-200 ml of water in a open bottle (4800-9600 ppm).

Method- dipping, spraying

4.Treatments with acetylene gas:

• Activity of acetylene is 100 times less than that of ethylene.

5.Treatments with calcium carbide:

• It is cheap and a readily available source of acetylene in rural areas sold in the form of irregular size chunks.
• Acetylene is released through reaction with water released from transpiring fruits.

CaC2 +       H2O —-> C2H2 +       CaO

• A lot of heat is produced during above reaction. The heat increases temperature and makes suitable environment for ripening.
• It leaves a distinctive odor when a container with carbide is opened but the odor disappears after aeration.

Method of application-

• Usually-small chunk is wrapped and placed at the bottom, middle of the container or among the fruit.
• The container is then sealed tightly and opened after 1-3 days depending on the commodity.
• Wrapping material for calcium carbide should be porous or allow diffusion of gases.
• Majorities of banana sold in Nepalese markets are treated with calcium carbide.
• Amount of calcium carbide- 162 g of CaC2 gives of 2 cu ft of acetylene. Usually 1 g/ k.g fruit.

6.Use of bioethylene:

• Ripening fruits of climacteric type and leaves of some tree that produce more ethylene ex. Bauhinia sp., Gliricidia sepium (70-100 gm leaves / kg of fruits).

7.Use of stress ethylene:

• Wounding (inserting a stick in the pedicel, pinching, twisting, pricking with a pin) plasmolysis (putting salt on the stem scar, soaking short period of time in sea water), moisture loss

8.Use of smoke:

9.Use of increased temperature to accelerate ripening