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)

Catalytic Generators Describes Best Practices For Ripening Papayas

Papayas can be found year-round at your local grocer, thanks to strategic ethylene application.  Ethylene generators from Catalytic Generators will help to turn dark green papayas to a golden yellow color when ripened. To perfect the papaya ripening process by ethylene application, ripeners should follow the suggested protocols listed below:

Determine the fruit maturity when received.  The degree of maturity in papayas is related to external color development and will indicate whether the papaya should be exposed to ethylene. Papayas that are fully mature at harvest should not be ripened with ethylene if they are to be stored for an extended period. Papayas of ¼ to ½ yellow color minimum will benefit from a treatment of ethylene with an improvement in texture and color. Papayas that are immature (green) can ripen but will never develop good flavor. Other physical changes that are associated with papaya ripening include a decrease in flesh firmness, increased juiciness, and increased aroma volatiles.

Strategically place papayas within ripening rooms. If not using pressurized ripening rooms, then air stack the boxes (at least 2″ between boxes) to ensure proper air circulation. Leave 1½ feet between walls and pallets and about 6″ between pallets.

Utilize temperature and humidity management. Fruit temperature is the most important factor in papaya ripening.Ripening occurs faster when papayas have been previously held at low temperatures. Depending upon desired shipping time, bring the pulp temperature to the range of 72 to 82°F (22 to 27.5°C) for the best color development. The temperature within the room during ethylene application should be between 20 to 25°C (68 to 77°F); if the temperature goes above 86°F (30°C), ripening will be stalled.

Once ripened, papayas can be kept at 50 to 55°F (10 to 13°C) and 90 to 95% relative humidity for up to 1 week. The optimal relative humidity range to prevent excessive water loss and shrivel is at least 90% relative humidity.

Apply ethylene and vent ripening rooms. Apply 100 ppm ethylene for 24-48 hours (actual time of exposure to ethylene is determined by the maturity of the fruit; a yellowing of fruit color indicates that the papayas are producing ethylene and the generator is no longer needed) to induce faster and more uniform ripening, provided that carbon dioxide is kept below 1% by ventilating the rooms with outside air once per day. Rooms should be vented by opening doors or controlled fan exhaust ventilation for 20 minutes every 12 hours to flush out carbon dioxide and bring in oxygen.

To achieve 100 ppm, the generator setting[1] will depend on the size of the ripening room:

  • Setting 1 for rooms 1600 – 2500 cubic feet (45-70 m3 )
  • Setting 2 for rooms 2500 – 5000 cubic feet (70-142 m3)
  • Setting 3 for rooms 5000 – 7500 cubic feet (142-212 m3)
  • Setting 4 for rooms 7500 – 10000+ cubic feet (212-283+ m3)

Following these best practices will result in better papaya color, texture, and overall quality. Papayas have been ripened successfully for some time by using Catalytic Generators and Ethy-Gen® II Ripening Concentrate to produce ethylene in the ripening room. For more information regarding ethylene application, contact Catalytic Generators here.

[1] Please note 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.


Brecht, Jeff. “Ripening Mangos & Papayas.” UC Davis Postharvest Technology Center, UC Davis Postharvest Technology Center, 19 Apr. 2017, postharvest.ucdavis.edu/files/261290.pdf (Accessed May 28, 2020).

University of California. “Fruit English.” Fruit English – UC Postharvest Technology Center, 2014, postharvest.ucdavis.edu/Commodity_Resources/Fact_Sheets/Datastores/Fruit_English/?uid=42&ds=798 (Accessed May 28, 2020).

Best Practices for Washing Fruit & Vegetables During COVID-19

Protect your well-being by following these

best practices for washing fruit and vegetables.

It is common knowledge that fresh produce should be cleaned before eating to prevent illness caused by contamination; however, many do not know the best practices for washing their fruit or vegetables.

According to Glenda Lewis, an expert on foodborne illness with the Food and Drug Administration:
“Fresh produce can become contaminated in many ways. During the growing phase, produce may be contaminated by animals, harmful substances in the soil or water, and poor hygiene among workers. After produce is harvested, it passes through many hands, increasing the contamination risk. Contamination can even occur after the produce has been purchased, during food preparation, or through inadequate storage.”

The best solution to clean your fresh produce is amazingly simple: water. That is right, only plain water! All produce should be washed under running water while gently rubbing with clean hands. A clean vegetable brush can be used to scrub firm produce such as melons or cucumbers. For produce with leaves or outer layers, such as cabbage or lettuce, the outermost leaves should be removed. After rinsing, the fresh produce should then be dried with a clean cloth or paper towel to further reduce bacteria that may be present.

The FDA states, “Nearly 8 million people are sickened by food contaminated with harmful germs each year.” During this global pandemic, Catalytic Generators wants to ensure the public is aware of these practices to lessen the spread of germs and illness.


U.S Food & Drug Administration, Office of the. “7 Tips for Cleaning Fruits, Vegetables.” U.S. Food and Drug Administration, FDA, 10 June 2018, www.fda.gov/consumers/consumer-updates/7-tips-cleaning-fruits-vegetables.