Post-harvest ripening is a process of bringing unripe fruits and vegetables to the state of consumer quality products. In order to speed up the ripening, a combined approach is used, namely, physical and chemical effects. This implies regulation of Ethylene, Carbon Dioxide, ambient temperature and relative humidity levels in specially equipped rooms - ripening rooms.
Being a naturally occurring growth hormone, Ethylene became an integral part of the ripening process and even received the name “banana gas” in this industry. To speed up ripening, fruits and vegetables are placed in air-tight rooms, which are then filled with gaseous C2H4 in concentrations up to 1 500 ppm depending on product type and distance between distribution centers and stores. Ethylene gas exposure levels should be controlled such that vegetables and fruits can be brought to ideal ripeness and remain fresh before they reach a shop counter. This can be achieved by using Evikon MCI´s C2H4 gas detectors of the E26xx series (measurement ranges 0...10 ppm, 0...200 ppm and 0...1 500 ppm of C2H4).
* All detectors with electrochemical sensors have in-build heating to be able to work correctly in high humidity (up to 100% RH) in this application.
Carbon Dioxide (СО2)
During respiration, plants release Carbon Dioxide, which reduces Oxygen (highly important for fruits and vegetables metabolism) levels and Ethylene effect, and therefore delay ripening. Carbon Dioxide concentrations in excess of 1% (10 000 ppm) already slows down the ripening process and can affect product quality. If the CO2 concentration rises (above 5 000 ppm), room must be ventilated. Carbon Dioxide level measurement with Evikon MCI E26xx series gas detectors (measurement range 0...10 000 ppm of CO2) help to understand when to activate the ventilation system. This will allow for more efficient control and optimization of the ripening process and improved production.
Ambient temperature (T) and relative humidity (RH)
To accelerate the ripening process, air temperature is usually increased to 20 °C (but not higher than 25 °C). Excessive increase in temperature delays the ripening rate and contributes to some vitamins destruction. Bananas, for example, generate heat that reaches temperatures of over 30 °C in ripening rooms. Therefore, ambient temperature must be constantly monitored and kept at the optimal level for ripening.
It should be also remembered that processing with Ethylene dehydrates fruits and vegetables. As a result, cracks and spotting appear on them, which leads to market quality loss. For this reason, it is necessary to maintain the relative humidity (RH) at a high level (85-100% RH) in ripening rooms, which makes the ripening process gradual and significantly improves product quality.