Updated: Jan 11
The Silent Killer of Produce & Flowers
By Jan Lievens
Taking perishable products, whether fruits, vegetables, or fresh cut flowers, from the field safely to the home of the consumer is tricky business. Postharvest handlers must do everything they can to maintain the best possible environmental conditions for those delicate parcels.
When considering the control of environmental conditions, never overlook the power of ethylene gas – Mother Nature’s silent killer.
What is Ethylene Gas?
Ethylene gas (C2H4) is a natural growth hormone that is produced by plant tissue as well as the combustion of synthetic materials. It is the only member of its class and has the simplest structure of all plant growth substances.
Its impact on the postharvest industry is tremendous because it is active at exceptionally low concentrations and effects plants in so many ways. Ethylene is involved in a plant’s growth process from seed germination to its eventual death. Unlike most plant hormone compounds; ethylene is a gaseous hormone. Even moderately high concentrations of the gas cannot be seen or smelled, making it impossible to detect without mechanical measuring devices.
Ethylene is not harmful or toxic to humans, however, at extremely high concentrations it is combustible.
Natural law is a powerful force. Ethylene gas has a job to do which cannot be reversed, no matter how hard one tries. That job is to help a plant through the natural process of growth and dying.
That is a good thing when the plant is growing in the earth – death and decay of all plants is necessary for healthy ecosystems. But death and decay of perishables in postharvest storage areas means loss of viable product and a large amount of money.
What Does Ethylene Gas Do?
Some of the most detrimental effects of ethylene are abscission of leaves and flower petals of fresh cut flowers, hasted senescence (aging) of all types of plants and accelerated ripening of fruits and vegetables.
Abscission is the separation of an organ or plant part from the parent plant. Ethylene is a stimulant for abscission and is particularly harmful to the floral industry.
Fresh cut flowers that are exposed to ethylene gas will lose their leaves and petals faster than those that are stored in ethylene-free environment. Not only does this hurt flower sales by giving the flowers an undesirable appearance, but scars left from abscission of leaves and petals make the plants more susceptible to disease.
Senescence is the last phase of plant and extends from full maturity to death. It is the slowing down and eventual end of a plant’s metabolism, which characterizes it as a living thing. The result is discoloration, unpleasant odors, shrinkage and the general rotting of produce and flowers.
Ethylene is one of the hormones that naturally brings about this last phase of a plant’s life. When fruits, vegetables and flowers are stored in enclosed areas, and the ethylene levels build up, plants senesce, or age, at an unusually fast pace. In practical terms, the post-harvest “life” of the product is cut short and it must be discarded as waste.
Ripening is the phase of a plant just before senescence. It is the time in which the fruit of the plant changes color and develops the flavor, texture and aroma that makes it best suitable for consumption.
The effects of ethylene on ripening must be given attention. On one hand, ripening is important to the sale of produce.
Consumers want to purchase food they can eat and not have to wait for it to ripen. But on the other hand, once the ripening process begins it cannot be reversed or stopped, only slowed. So, the quicker the produce ripens after it is harvested, the less time there is to get it to the consumer and the greater the chance of it moving on to the senescence phase and rotting.
In a natural setting, when a plant is growing in the earth, the ripening process is triggered when the internal ethylene concentration of a plant’s fruit is 0.1-1 ppm. However, plants cannot distinguish between internal and external sources. Any external ethylene gas that the produce is exposed to will speed up the ripening. To keep produce from ripening too quickly, as much ethylene as possible should be removed from the surrounding air.
Most wounded plants give off ethylene gas. The gas evolves naturally from plant material that is rotting, ageing, or ripening. Since a harvested plant is a wounded plant, that means most perishable storage areas are virtual ethylene factories.
But plants are not the only producers of ethylene. It is produced when almost any material is incompletely combusted or burned. Some common external sources are trash burning, fluorescent lights, cigarette smoke and exhaust fumes. It also comes from certain fungi, like botrytis, and other micro-organisms.
Pure automobile exhaust contains about 400 ppm of ethylene. So opening doors to vent out ethylene in urban, air-polluted areas could let high concentrations back into the storage area.
Plants respond to external ethylene by producing more themselves, a process called autocatalytic ethylene production. Just a small amount of the gas, when added to a produce or floral storage area, can result in extremely high levels. Cleaning as much ethylene out of the air as possible is the best way to cut down on premature ageing and ripening and prolong the post-harvest of life of fruits, vegetables, and flowers.
The quality of produce kept in storage may suffer in many aspects due to improper storage conditions. Mold, rot, premature ripening, shrivel, and weight loss are among the undesirable effects. While high relative humidity helps to eliminate shrivel and weight loss, the challenges caused by airborne bacteria and ethylene (a natural ripening hormone) require a special treatment.
This is when the positive effects of Miatech’s Bio Turbo are most beneficial. It uses a patented four stage process to eliminate ethylene gas, airborne bacteria and mold spores. It successfully prevents mold growth, eliminates unpleasant odors, and reduces unnecessary losses while preserving natural freshness and quality.
Unlike some methods, the performance of the Bio Turbo is not affected by the high humidity levels associated with perishable storage.
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