Climacteric fruits and Ethylene

Climacteric fruit normally ripe after harvest, have higher ethylene production rate response with applied ethylene and result faster and more uniform ripening. Example; mango, apricot, banana, kiwi fruit, avocado, tomato etc. Therefore, climacteric fruits are commercially harvested at their maturity stage before onset of ripening to prevent damage and injury during handling and storage. In other hand, non-climacteric fruits do not ripe if they are harvested before they are ripen.

Climacteric fruit   Non-climacteric fruits
1 Ethylene formation increases with rise in respiration rate Ethylene formation doesn’t rise
2 Produce much larger amount of ethylene (up to 100 ppm in avocado during ripening) Produce much less amount of ethylene (less than 1 ppm)
3 Applied ethylene hastens ripening Applied ethylene increase respiration rate
4 Response to ethylene occurs only once Response to ethylene occurs more than once
5 Magnitude of respiration is independent of applied ethylene Magnitude of respiration is dependent on applied ethylene
6 Sensitive to exogenous ethylene at onset of ripening Sensitivity is equal throughout the maturity till ripening
7 Harvested at matured stage Harvested after ripening on tree.

Undesirable effect of use of ethylene in fruits and vegetables:

As little as 0.5 ppm ethylene is required for carnation (preventing buds from opening). Lemons are de-greened by 0.025 -0.05 ppm, bananas are ripened by 0.1 to 1 ppm and avocados by 0.1 ppm. However, if the fruit has not reached the stage of ripening, it may not response to ethylene at such low concentration. When the ripening response is started, it is irreversible. Although ethylene is useful tool in the control of growth and ripening responses, it has some damaging effect as well. Undesirable effect of ethylene in fruits and vegetables is summarized below

  1. Accelerates senescence and loss of green color in some immature fruit and leafy vegetables.
  2. Accelerated ripening and decreased storage life of fruits and vegetables during handling and storage.
  3. Formation of bitter principle in carrots (coumarin)
  4. Sprouting of potatoes
  5. Abscission of leaves of cauliflower and cabbages
  6. Russet spotting in lettuce
  7. Increase decay susceptibility in citrus fruits

Removal of ethylene: removal of ethylene is also called scrubbing process. Generally potassium permanganate (KMnO4) and ozone (O3) are used in removal of ethylene from fruits and vegetables.