Team:UNITN-Trento/Extra/Fruit Info

Plants naturally produce ethylene starting from a common amino acid: methionine (MET), which is transformed in S-adenosyl-methionine (SAM) by a reaction catalyzed by SAM synthetase. The key enzyme of the pathway, ACC synthase, converts SAM to 1-aminocycloprane-1-carboxylic acid (ACC), the immediate precursor of ethylene. Quite recently, the final enzyme of the pathway was identified: ACC oxidase, which converts ACC to ethylene.

All fruit, with a few exceptions (European pears, avocados and bananas), reach their best eating quality when allowed to ripen on the tree or plant. However, some fruits are usually picked mature but unripe, and threated with ethylene during transport or when they arrive at destination, before being brought to the market. Bananas for example are threated with 10 to 100 ppm of ethylene to trigger the ripening process. This approach allows long term storage of fruit and helps the distributors to bring fruit to the consumer.

Fruit is generally classified in two main groups: climacteric and non-climacteric.

Some examples are: apples, bananas, pears, melons, apricoats and tomatoes.
This kind of fruit presents a characteristic climacteric peak, which consists in an acceleration of both cellular respiration and ethylene production. Depending on the fruit, ethylene can influence all the different steps of the ripening process like colour, pulp texture, flavour... Exogenous ethylene treatment can have an effect on these fruit before the climacteric peak.

Some examples are: strawberries, citrus, oranges, cherries and grapes.
This type of fruit have a constant low endogenous production of ethylene with no climacteric peak. Non-climacteric fruit do not respond to exogenous ethylene treatment except for in term of degreening and they should be picked up only when completely ripened in order to mantain all the flavour quality (Mary Lu Arpaia et Al., Fruit Ripening & Ethylene Management 2010, 3-10).