Optimizing Your Banana Ripening Room for Ethylene Application

As the go-to potassium source, breakfast item, or quick energy supply, bananas are beloved to consumers worldwide. As a ripener, providing customers with the highest quality, perfectly ripened bananas available should be a goal across the entire fresh produce industry. The first step in providing customers with exceptional quality bananas is preparing and optimizing banana ripening rooms for ethylene application.

Preparing Your Ripening Room

Bananas bruise easily, green or ripe. Careful handling at all stages will reduce bruising and enable you to sell the bananas for more money. Beyond this, the following recommendations are suggested within banana ripening rooms:

• The room must be as airtight as possible to prevent too much of the ethylene from leaking out.
• Must be sufficiently insulated to be able to properly maintain the room temperature
• Must have adequate refrigeration; the refrigeration equipment must have the capacity to accurately control the pulp temperature.
• May need heating equipment to maintain proper room temperature in cold weather.
• Rooms should be constructed so that the airflow path from the refrigeration system, through the load, and back to the refrigeration system is unobstructed.
• Refrigerated air in the room must always circulate uniformly throughout the load.
• To ensure the best quality ripened fruit, we recommend consulting with room design & build experts.

Pressurized Ripening Rooms

Perhaps the most important advancement in fruit ripening since the advent of the banana box is the development of Pressurized Ripening Rooms. The key feature of these rooms is that conditioned air is forced through the product rather than the product just being stored in a temperature-controlled room. The system passes air through each box or series of boxes before returning to the evaporator. Therefore, any “air-stacking” or “cross-stacking” of boxes is not necessary, and the result is less handling of the fruit and improved product quality. For non-pressurized rooms, the boxes of bananas should be “air stacked”. That is, the boxes should be arranged in an offset pattern to allow the air to circulate among all the boxes since a non-pressurized room design will not pass air through boxes but around them.

Airflow throughout the produce is incredibly important as bananas are extremely sensitive to temperature. “Chilling” or “cooking” damage can occur if the fruit is subject to temperatures below 56° F or excessively high temperatures for several hours. Irregular temperature exposure can be identified by external coloring. Chilled fruit causes the peel to have a smoky, dull gray appearance (this may not show up for 18 to 24 hours after chilling occurs). Cooked bananas will result in a peel that has a brown to orange appearance, may be soft, and have a short shelf life.

Ethylene Application Recommendations

Once proper quality control checks are done for the load of bananas, the amount of time ethylene is applied to bananas will vary based on the fruit maturity. Initially, ethylene should be applied for a minimum of 24 hours during the early phase of the ripening cycle (we recommend 100-150 PPM).

To achieve this, the ethylene generator settings will depend on the size of the ripening room. It should be noted that all rooms vary in terms of how air-tight they are, so if more precise PPM determination is required, air testing for ethylene PPM levels is recommended.

Ripeners can follow banana ripening guidelines listed in the “Suggested Guide for Banana Ripening” chart which includes additional pulp temperature, color index, and ventilation recommendations. When bananas 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 bananas release ethylene 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, or by automatic control. More detailed information regarding the importance of room ventilation can be found here.

UC Davis. Suggested Guide for Banana Ripening.

The University of California, Division of Agriculture and Natural Resources. “Postharvest Center Publications.” UC Postharvest Technology Center, 2021, postharvest.ucdavis.edu/Library/Postharvest_Center_Publications/.

The University of California, Division of Agriculture and Natural Resources. “Postharvest Center Publications.” UC Postharvest Technology Center, 2021, postharvest.ucdavis.edu/Library/Postharvest_Center_Publications/.

Catalytic Generators’ Products Exempted From Fire Codes in Ripening Rooms

Catalytic Generators’ unique ethylene systems comply with the international fire safety testing standards of TÜV (TÜV SÜD America) which exempts ripeners from making special room adaptions for international fire code compliance within ripening rooms. 

According to Section 2506.1 “Ethylene Generators” of the International Fire Code: 

“Ethylene generators shall be listed and labeled by an approved testing laboratory, approved by the fire code official; and used only in approved rooms in accordance with the ethylene generator manufacturer’s instructions. The listing evaluation shall include documentation that the concentration of ethylene gas does not exceed 25 percent of the lower explosive limit (LEL).” 

Per manufacturer instructions for use on the Easy-Ripe® and other generators from the company, the minimum ripening room size used with these generators must be 1,600 ft3 (45 m3). “As long as the ripener follows our easy-to-use directions, there is no way that our generators can produce enough ethylene to reach an explosive level.  It is a peace of mind for ripeners and an easier installation for ripening room engineers and builders,” stated Greg Akins, President & CEO of Catalytic Generators.

“We contract with third-party testing labs to ensure that our equipment meets international electrical and safety standards, and fire officials recognize this fact with TÜV listing and International Fire Code compliance.”

Greg Akins, President & CEO of Catalytic Generators

The need for safer ethylene application systems for ripening was one of the driving forces behind the research and development of the original Catalytic Generator.  Over the years, the generators produced by the company have evolved, and there are different types that offer various benefits for any ripening operation. But one thing hasn’t changed; ethylene generators are the safest form of ethylene application and have the added benefit of third-party accreditation and international fire code compliance.

From this, produce professionals do not need to worry about ripening room safety, expensive fireproofing adjustments, warning signs, and more. 

Overview of Tools That Help Determine the Quality of Fresh Produce

The bar is set high when it comes to the quality of fresh produce and continues to be gradually lifted.

Pre-harvest: Measuring Brix and Firmness

Quality testing starts before the produce is even harvested. By measuring Brix and fruit firmness, fruit maturity can be determined, indicating when the fruit is ready to be harvested. Digital refractometers and handheld penetrometers help with gauging fruit maturity. When testing fruit firmness, the penetrometers automatically freeze the peak firmness reading. With this added convenience, users don’t need to watch the gauge while correctly inserting the plunge tip into fresh fruit. Once the measurement has been taken, the penetrometer can be pulled out of the fruit and the peak reading can easily be read on the dial.

Our sister company, QA Supplies, offers different types of penetrometers for a variety of fruit, but the ones from the FT-series are unique as they can be handheld, portable units, or mounted using a manual test stand for firmness. Alongside these tools, produce knives are also being used during this stage of quality checks.

“To meet today’s expectations of buyers and consumers, it is important for quality checks to be done throughout all stages of the supply chain.”

Greg Akins, President of Catalytic Generators

Post-harvest: Transportation

The next quality check takes place when produce is transported to a warehouse or distribution center. During the transportation phase, we recommend utilizing data loggers that monitor temperature, which is key to maintaining quality and preventing defects. Below recommended levels, chill damage could occur and a temperature that’s on the high side could result in an accelerated ripening and decreased shelf life. Keeping the transport temperature within an acceptable range is critical for shippers and receivers.

In the Warehouse

Once the fruit has been accepted by the warehouse, one of the first quality control checks is to measure pulp temperature as it may differ from air temperature. This is especially true when the product is not in forced air storage, but temperature variation can occur in any controlled storage environment. As some produce ages during transport and storage, the heat of respiration may cause the internal temperature to rise above the room air temperature. Knowing this difference allows facilities to make adjustments and maintain the best quality; a great example are banana ripening charts as the temperature recommendations on the charts are based on pulp, not air temperatures.

The internal temperature can be checked with a digital probe thermometer, available in economy and premium options. The premium alternative offers a greater range and tends to have a better degree of accuracy. Because of the higher price point, usually, one or two are purchased for a warehouse whereas the economy option is being made available to everyone in the warehouse or field.

Ripening Operations

Once the internal temperature has been determined, the shipper/ripener has a better idea of exactly how ripe or mature the produce is. This helps to make decisions on what type of storage conditions will maximize the quality and shelf life of the fruit. If ethylene exposure is needed, we recommend ripening via ethylene application with our generators and Ethy-Gen® II Ripening Concentrate.

These are the only generators with certifications by both UL and TÜV and they produce no harmful byproducts when converted into ethylene. Because safety matters, we make sure our generators are certified by third-party recognized testing laboratories. The ripening concentrate’s active ingredient is all-natural as well as GMO-free and is the only ‘ripening fluid’ approved by both the US EPA and the UK Chemicals Regulation Directorate (CRD).

Ripening Concentrate

Naturally, ethylene is odorless and without measuring the level in the room, there is no way to know it is present in the ripening room. For optimal safety, the ethylene created from Catalytic’s concentrate has a slight sweet smell. That way, customers know it is present in the ripening room. An additional benefit of Catalytic’s generators is that ethylene levels need to only be checked initially as opposed to continuously.

The initial levels need to be checked to determine the appropriate ethylene production level of the generator for each ripening room. Thereafter, only occasional ethylene level checks are needed as a ‘confirmation’ that levels remain in the correct range. The generator consistently and dependably creates small amounts of ethylene and is great at maintaining a set level. Ethylene levels can be measured with ethylene testing tubes that can be used with an Air Sampling Kit, or the F-960 Ripen IT! Gas Analyzer, or F-940 Store It! Gas Analyzer.

By consistently using these post-harvest tools, perfectly ripened pallets of fruit can be delivered to customers all over the world.

Catalytic Generators

A Smarter Approach to Monitoring & Management of Fruit Storage Facilities

Environmental factors in fruit storage play an extraordinarily important role in determining post-harvest fruit quality and shelf-life. Storage facilities, as the name suggests, store fruit after it is harvested and before it is shipped to stores. Ripening rooms, which are often a part of larger storage facilities, have the specialized task of ripening unripe fruit. While their processes differ, the goals of storage and ripening facilities are similar – to control the environmental factors that affect fruit ripening and shelf-life.

Bananas in Ripening Room

The primary environmental factors crucial to fruit ripening are temperature, relative humidity, ethylene gas (C2H4), carbon dioxide (CO2), and oxygen (O2). The levels of all five factors will vary based on the commodity being stored and whether the goal is storage or ripening. Fruit is alive, and it continues to respire and transpire even post-harvest. As a result, the fruit actively modifies its own environment through its own physiological changes. The 3 ways it does this are:

Respiration: Fruit uses oxygen during respiration to break down sugars and produce heat, water, and carbon dioxide. During storage, keeping the temperature low reduces the rate of respiration, ripening, and senescence. Similarly, the concentrations of CO2 and O2 can also influence the respiration rate.

Transpiration: When there is a difference in the water vapor pressure between fruit and its environment, the fruit loses water. As a result of transpiration, fruit shrivels, and its quality and flavor can be spoiled. Respiration increases transpiration. Less than desired RH% also causes weight loss, which is a big deal since fruit is most often sold by weight. Keeping moisture in the fruit keeps up the weight and profits; therefore, high relative humidity is maintained in the storage room during storage.

Ripening: Ethylene is a phytohormone produced by climacteric fruit. Climacteric fruit responds positively to external ethylene. Many non-climacteric fruits, which are sensitive to ethylene, will also respond by to the presence of ethylene by the shortening of storage life and hastening senescence. For predictable and repeatable ripening, ethylene application must be regulated under optimal temperature for a specified number of days. On the other hand, during storage, ethylene accumulation must be controlled and often suppressed. The level of ethylene in the air is reduced by “scrubbing” to prevent early deterioration.

Monitoring & Management

Due to continuous fluctuations in the five environmental factors in ripening and storage rooms, it is necessary to constantly monitor and control the environment. Any change can reduce storage time, or spoil fruit, and interfere with the ripening process. As a result, it is essential to take accurate measurements and then make rapid modifications based on these measurements.

An ideal monitoring and management system integrates with all of the storage facilities’ or ripening rooms’ current processes. As many of our site’s readers know, we carry ethylene generators produced by Catalytic Generators, LLC. These generators, with the use of Ethy-Gen® II Concentrate, can safely produce the ethylene gas needed for ripening. In addition, our long time partner, Felix Instruments, produces two programmable monitoring and management systems – the F-901R AccuRipe and the F-901D10 AccuRipe (customized for ethylene levels of 10-1000 ppm and 0-10 ppm, respectively), that integrate directly with the Catalytic Generators ethylene generators, ensuring desired ethylene levels are maintained inside the facility.

Ripening Room Controller

While the ethylene generator does its work from inside the ripening room, the Felix systems enable the user to monitor and manage ethylene, temperature, humidity, CO2, and O2 from the outside, without ever leaving the comfort of the office. The systems are engineered to “bolt-on” to any ripening or storage room and tap into existing systems, giving precise and real-time control and regulation of the ripening/storage facility’s environment for a broad range of fruits.

Additionally, both Felix systems are programmable, so users can enter a ripening or storage “recipe”, which the system then automatically executes, ensuring consistent fruit quality with every new load. Through close collaboration, Felix Instruments and Catalytic Generators have developed the perfect ripening room management solution for fruit producers.


Becker, B.R., & Fricke, B. A. Transpiration and Respiration of Fruits and Vegetables. Retrieved from https://b.web.umkc.edu/beckerb/publications/chapters/trans_resp.pdf  (June 6, 2020)

FAO. 5. Post-harvest Treatments Designed to Manipulate the Environment around Produce in Order to Enhance Quality. Retrieved from http://www.fao.org/3/y5431e/y5431e06.htm (June 6, 2020)

Tamil Nadu Agricultural University. Fruit Ripening. Retrieved from http://agritech.tnau.ac.in/horticulture/fruit_ripening.pdf (June 6, 2020)

Sylvia Blankenship, S. [Sylvia Blankenship]. (2000, Mar 15).  Ethylene: The ripening hormone. Retrieved from http://postharvest.tfrec.wsu.edu/pages/PC2000F (June 6, 2020)