Ethylene is an important, natural plant hormone. It regulates the ripening and senescence (aging) of plants. Ethylene is normally produced in small quantities by most fruits and vegetables. However, climacteric fruits, like bananas, avocados and tomatoes create larger amounts of ethylene and this release of ethylene starts several actions like increased respiration, more ethylene production, and changes in color, aroma, and flavor. Fortunately, the onset of this internal ethylene production can be controlled. The ability of fresh produce companies and distribution centers to apply ethylene allows the promotion of predicable ripening times and more uniform ripening…the result is better quality and consumer eating experience.

We invented and patented the world’s first ethylene generator for fruit ripening in 1973. A small but powerful device for creating ethylene in a ripening room or chamber, the generator allows fruit to be ripened on a demand schedule. By introducing small, controlled amounts of natural ethylene into the room, several types of fruits, like bananas, avocados and mangos will begin a managed ripening process. This allows for perfectly ripened fruit to be delivered to the consumer, ready-to-eat!

Yes, ethylene is very explosive. At concentrations above 27,000 part per million (ppm), just a spark can cause it to explode. There have been several instances of explosions in ripening rooms where cylinders were in use…we have compiled a list of ethylene explosions.

However, the ripening process of most fruits can be initiated by ethylene at concentrations as low as 50 ppm, or less than 1% of the explosive level, and most operators ripen with 1,000 ppm or less. Catalytic Generators are the safest commercial form of ripening; they produce small, controlled amounts of ethylene and when used as directed, they cannot produce explosive amounts of ethylene. That is why so many fresh produce companies use our generators rather than other forms of ethylene application.

When using our generator and Ethy-Gen® II Ripening Concentrate in rooms that are 2000 ft3 (57 m3) or larger, there is NO CHANCE OF ETHYLENE EXPLOSION.

See this page for more safety details.

Ethylene has been found not harmful or toxic to humans or the environment in the concentrations found in ripening rooms (100-150 ppm).

In fact, ethylene was used medically as a anesthetic in concentrations significantly greater than that found in a ripening room. However, ethylene is often targeted as the reason for difficulty in breathing in ripening rooms; what can affect some people is usually either:

• Carbon Dioxide (CO2,) levels: CO2, is produced by the ripening fruit in the room and levels increase over time, or

• Oxygen levels: The oxygen in the room when loaded is taken in by the ripening fruit. This sometimes will make breathing in a ripening room difficult.

The increased CO2, and decreased oxygen levels are the main reasons for venting the ripening room.

Ethylene is Generally Recognized as Safe (GRAS) by the United States Food and Drug Administration (FDA). Given the numerous amounts of food substances, the FDA does not categorize every one. Salt, pepper and vinegar are examples. These, along with ethylene, all are within the category of food substances that, when used for the purposes indicated, in accordance with good manufacturing practice, are regarded by the FDA as generally recognized as safe (GRAS) for such uses.

Not likely, when using our ethylene generators. The International Fire Code exempts ripeners from making special ripening room adaptions for international fire code compliance when using ethylene generators in the correct manner.

See our blog post on this for more details.

We tend to think of solid materials as magical barriers. But at the molecular scale they’re not. They’re strands of molecules or lattices of atoms or both. When you get down to the teeny, tiny realm, solid objects are more like thick jungles than brick walls.

So, ethylene will permeate through fresh produce cardboard shipping boxes, wood and even concrete walls.

Ethylene is a natural plant hormone that regulates the ripening and senescence (aging) of plants. Ethylene is normally produced in small quantities by most fruits and vegetables. However, climacteric fruits, like bananas, avocados and tomatoes create larger amounts of ethylene and this release of ethylene starts several actions like increased respiration, more ethylene production, and changes in color, aroma, and flavor. Fortunately, the onset of this internal ethylene production can be controlled. The ability of fresh produce companies and distribution centers to apply ethylene allows the promotion of predicable ripening times and more uniform ripening…the result is better quality and consumer eating experience.

The additional externally applied ethylene merely accelerates the normal ripening process. There are no important biochemical, chemical, or physiological differences between fruit ripened where the naturally produced ethylene has been the triggering mechanism or where additionally externally applied ethylene has triggered the process in the mature but unripe fruit.

For example, tomato fruit are not and cannot be “artificially reddened” by ethylene. The normal tomato ripening process, which includes pigment changes – the loss of green chlorophyll and conversion of carotenoids into red lycopene pigments – can be accelerated and brought about earlier by externally applied ethylene, but this is a normal process. In fact, some of the components of nutritional quality, such as Vitamin C content, benefit because of the fact that the fruits will be consumed after a shorter time interval from harvest as a result of ethylene treatments and hence, the initial level will not have degraded as far as the longer, un-accelerated process.

Bananas are harvested mature but very green in order to survive the trip from the growing regions to destinations across the world. Along with a rise in pulp temperature and control of relative humidity and ventilation of carbon dioxide, an external ethylene application will trigger the proper ripening process to begin, which includes the fruit producing internal ethylene. This natural process results in uniform, controlled and predictable ripening. Without this exposure to external ethylene, bananas will eventually soften, but the change in color will not be uniform and the peel will be dull, pale yellow, and unattractive, and perhaps inedible.

Uneven ripening can be caused by many things:

Insufficient amount of ethylene, caused any of these situations:
- Generator setting too low for room size
- Not applying ethylene long enough to trigger the fruit to ripen on its own
- An air leak, large enough to considerably reduce ethylene levels, has developed somewhere in the ripening room

Elevated Carbon Dioxide (CO2) levels. When bananas and some other fruits are ripening, they release carbon dioxide which will build up in a ripening room. The CO2 production begins as the fruit ripens enters the “climacteric” phase, or the period when certain fruits release ethylene and and have an elevated rate of respiration (along with a great deal of other physiological changes). Respiration involves the uptake of oxygen, the release of carbon dioxide, and the breakdown of starches. Carbon dioxide concentrations above 1% (10,000 ppm) will retard ripening, delay the effects of ethylene and cause quality problems. Therefore, it is recommended to vent rooms by opening the doors for 20 minutes every 12 hours, after the first 24 hours of ripening. Other venting methods are by automatic fan (either timed or sensor-based) or “flow-though” (constant) ventilation.

Immature fruit: When harvested, the fruit had not yet reached a mature stage. In order for fruit to ripen properly, it must be picked when fully developed and mature

Mixed lots: a room of fruit that contains various grades, comes from different origins, or is not uniform in characteristics will usually not ripen evenly

Old fruit: When ripening fruit that has been “held” for an extended period of time after harvest, the ripening results will inevitably vary and will usually involve uneven ripening, as some of the fruit will begin to ripen before others. As a general rule with most types of fruit, it is best to apply ethylene as soon as possible to mature green fruit; this ensures that all fruit within the room will ripen even and uniformly.

Yes! Ethylene is allowed for use on various organic fruits and the regulations vary by country. See our Organic Page for details.

Typically 5 years. The product should be tightly sealed and stored in a dry, out-of-traffic area at temperatures of less than 125°F / 52°C, and in accordance with local fire codes and federal/state regulations.

For the first few days of a ripening cycle, fruit takes in a large amount of oxygen and produces carbon dioxide. This CO2 must be vented from the room. Lack of ventilation can make it difficult to breathe. Venting of the ripening room replaces CO2 with fresh oxygen not only makes it easier for people to breathe in the room but also gives the fruit the fresh air it needs to properly ripen. CO2 inhibits the ripening process and, when not vented out, can cause uneven and delayed ripening, and, while not very likely, but possibly a difficult breathing environment.

Many ripening rooms are vented manually, by opening the room door for several minutes every 12 hours. Some rooms have automatic ventilation, either timed or controlled by a CO2 detector.

Ethylene can promote ripening in tomatoes, bananas, citrus, pineapples, dates, persimmons, pears, apples, melons, mangos, avocados, papayas and jujubes – a clear indication that the action of ethylene is general and widespread amongst a number of fruits. It is clear that ethylene is a ripening hormone – a chemical substance produced by fruits with the specific biological phenomenon of accelerating the normal process of fruit maturation and senescence.

Using tomatoes as an example, the life of a tomato fruit begins with fertilization of the flower ovules. After fertilization, the young fruit goes through a short period of cell division which is then followed by a rapid period of growth as these cells enlarge. During the final stages of growth and development, the tomato fruit reaches its full size and is now mature. This period of growth and development, from fertilization to development of the mature fruit, requires about 45-55 days, depending on the cultivar and the season. During the growth and development period, there are many chemical and physical changes occurring that have an impact on fruit quality and ripening behavior after harvest. Ripening is the final stage of the maturation process when the fruit changes color, and develops the flavor, texture and aroma that makes up what we define as optimum eating quality. The biological agent that initiates this ripening process after the fruit is mature is naturally produced ethylene – this simple plant hormone described and understood over 40 years ago. While there are other factors involved in this “triggering” of the ripening process by ethylene, it is essentially a universal ripening hormone. When this internal concentration of naturally produced ethylene increases to about 0.1 – 1.0 ppm, the ripening process is irreversibly initiated. The process may be slowed, but it cannot be reversed once it is truly under way. So, here is the key point: additional and externally applied ethylene, provided prior to the time that the naturally produced internal concentration reaches the required 0.1 – 1.0 ppm level, will trigger or initiate – “promote” if you will – this natural ripening process at an earlier time.

Let’s use tomatoes as an example…

Although many factors could be listed, there are four which play the dominant role in determining the quality of tomato fruits presented to the customer in the retail store:

— Variety

— Maturity at time of harvest

— Storage temperature during shipping and handling (this is probably the most common cause; tomatoes are often shipped or stored at improper temperatures, which causes severe taste loss…never allow tomato pulp temperature to go below 55°F!)

— Physical damage

Ethylene is harmful to many fruits, vegetables, and floral items.

While ethylene is invaluable due to its ability to initiate the ripening process in several fruits, it can also be very harmful to many fruits, vegetables, flowers, and plants by accelerating the aging process and decreasing the product quality and shelf life. The degree of damage depends upon the concentration of ethylene, length of exposure time, and product temperature. If ethylene damage is suspected, testing for ethylene levels should be performed (here are some ways to test). This will indicate if one of the steps below should be followed:

1. Ethylene producing items (such as apples, avocados, bananas, melons, peaches, pears, and tomatoes) should be stored separately from ethylene-sensitive ones (broccoli, cabbage, cauliflower, leafy greens, lettuce, etc.). Also, ethylene is emitted by engines. Propane, diesel, and gasoline powered engines all produce ethylene in amounts large enough to cause damage to the ethylene-sensitive produce items mentioned

2. Ventilate the storage area, preferably to the outside of the warehouse, on a continuous or regular basis to purge the air of any ethylene

3. Remove ethylene with ethylene absorbing filters. These have been proven in reducing and maintaining low ethylene levels

While we only serve commercial, professional fruit ripening companies, we have a web page set up to help those who would like to perform science projects with the effects of ethylene on fruit. Click here!