Ethylene in Post-harvest Quality Management of Horticultural Crops: A Review

Abstract

Ethylene is a naturally occurring plant hormone that is produced by many fruits and vegetables. It initiates the ripening process when internal concentrations increase to 0.1 to 1.0 ppm. Externally applied ethylene can also initiate the ripening process in climacteric fruits. Ethylene is flammable at a concentration of 3.1–32% in air. The minimum flammable concentration of 3.1% or 31,000 ppm is about 200 times the concentration suggested for tomato ripening. Fruit and fruit type vegetables are ripened artificially in specially built rooms that must be gas tight, have systems for controlling temperature (18–25°C), relative humidity (90–95%) and carbon dioxide concentrations (less than 4%  and maintain ethylene @ 100 to 150 ppm with sufficient air circulation (about 0.1 to 0.2 ft³ per min. per. lb. product). The flow-thru system is the most efficient and economical method for initiating ripening. The presence of ethylene is not always beneficial, especially in terms of postharvest shelf life. The degree of damage depends upon the concentration of ethylene, length of exposure time and product temperature. The effect of ethylene is accumulative, so continuous exposure to a low concentration of ethylene throughout marketing can cause significant harm. There are many sources of ethylene pollution during postharvest handling of perishables, but the most important are internal combustion engines, ripening rooms and ripening fruits. A number of techniques have been developed to protect sensitive commodities from the effects of ethylene. Selection of the appropriate method obviously depends on the commodity and the handling techniques used in its marketing. Removing ethylene from the atmosphere around the commodity is the preferable method of preventing deterioration of ethylene-sensitive produce.

Keywords: de-greening, ethephon, ethylene gas, flavor, firmness, ripening, texture