Ethylene and Produce: Friends or Foes?

Buying a lot of fresh fruits and vegetables these days?  Then it's well worth knowing something about ethylene. "What's ethylene?" some may ask.  It's a plant hormone that fruits and vegetables produce naturally as they ripen.  Reducing exposure to ethylene slows the natural ripening, thereby extending produce shelf life.  The problem is that, like many gases, it's sneaky--invisible and odorless.  Nevertheless, you can infer its presence and control it to some extent.

You can slow down or speed up the ripening of fruits and vegetables if you know which ones are sensitive to (respond to) exposure to it. To find out, check out this article, and consult the chart it refers you to.

How to Control Ethylene to Prevent Quick Spoilage

- Be careful to keep ethylene-sensitive produce away from ethylene-producing produce.  How do you know which is which?  Simple. Click on the link to the ethylene chart given near the end of this article.  Print out the chart to keep handy in your kitchen.

- Fruits and vegetables that produce large amounts of ethylene gas should be wrapped loosely so that the gas can escape. This will slow the ripening process of the ethylene producers.  (Note: berries, which give off a lot of moisture, should also be loosely wrapped to prevent mold-causing moisture build-up.)

- Apples ripen quickly when kept at room temperature. Keep them on the counter only if you plan to eat them within the next few days.  Otherwise, place them in a perforated plastic bag and refrigerate them toward the back of the fridge.  Handled that way, they should last 3-6 months!

- Keep apples away from other produce (unless you want to speed up the ripening of your other fruits or vegetables).  Apples give off large amounts of ethylene, so they hasten the ripening of many other fruits and vegetables.

- Bananas also give off a significant amount of ethylene, so don't keep them near already-ripe produce that is sensitive to ethylene.

- Here's a tip from the Vegetarian Times website: don't put spinach or kale in the same bin as apples or peaches.  If you do, the greens will turn yellow and limp within a day or two. 

- Can you control ethylene with coated bags?  According to food scientist Dr. Karin Allen, coated bags (such as the Debbie Meyer Green Bags) work some of the time, depending upon the type of produce that is put into it.  “These bags have a clay-like material deposited on them. That material causes them to absorb ethylene gas. Whether the bag will work or not depends upon these two factors: 1) how much ethylene the produce gives off; and 2) whether the product is responsive to ethylene or not.   Given either one or both of these conditions, putting the produce into one of these bags should extend the shelf life of, for example, apples, bananas, and tomatoes. For strawberries, the bags provide no benefit.”  Allen says she's found that the bags work better on bananas when bananas are wrapped individually than when they're wrapped in bunches. She points out that, since apples are cheap and last a long time, it may not be worthwhile to place apples in these bags. 

How to Use Ethylene to Speed up Ripening

Suppose your bananas are green, and your nectarines are hard, and you want to eat them in a day or two.  Ethylene can come to the rescue.

- Apples, bananas, and avocados all give off a lot of ethylene, so, if you've got some ethylene- sensitive fruit that you want to ripen quickly, place it in a paper bag, close it tightly, and let ethylene speed up ripening. Why does this work? When placed in a paper bag, fruits are exposed to less oxygen and more ethylene.

- Use the link to the ethylene chart (given below). Consult the chart to identify ethylene producers and ethylene-sensitive produce. Presto!  You're empowered to control your produce, at least to some extent.

Ethylene Chart

To consult an extensive chart listing produce that gives off ethylene and produce that responds to it, click here. (Note: It sometimes takes a little while for this long chart to open.)  This chart also lists the shelf life and optimal temperature and humidity for many fruits and vegetables, so it can help you decide which ones to refrigerate and which to store in a cool basement or crawl space. It also tells which products can be sprinkled with water and which should not be. The right storage conditions help to lengthen the life and maintain good quality of harvested produce. To quote the site, "Fresh fruits need low temperature and high relative humidity to reduce the respiration and slow down the metabolic process."

On the chart, the following fruits are listed as high ethylene producers: apples, apricots, avocados (ripe), bananas (ripe), kiwi, peaches, pears, plums, and prunes.  (This is not a complete list of high producers.) Note:  bananas and avocados that are NOT ripe are low producers.  The chart also indicates which types of produce are medium or low producers of ethylene.

Produce that is sensitive to ethylene (that will ripen faster when exposed to it) are also listed on this chart.  This list includes apples, apricots, avocados (very sensitive) bananas, leafy greens, cabbage, cauliflower, celery, cucumbers, mangos, mushrooms, tomatoes, and many more.  What does all this mean?  You can ripen your avocado faster by bagging it with an apple or banana. However, to avoid shortening shelf life, keep your mushrooms away from apples and other high ethylene producers.

Ethylene, an International Concern

Believe it or not, controlling ethylene is an international economic matter. Nowadays, many of the fruits and vegetables in our neighborhood grocery stores have traveled from faraway countries to get there.  When fruits and vegetables are packaged for long trips, the air in the container circulates and speeds up ripening.  As a result, ethylene-related problems make up a significant portion of postharvest losses in developing countries. A sensor to monitor ethylene production was developed in 2009. Scientists continue to work on technologically sophisticated ways to monitor and control ethylene production and thereby keep fruits, vegetables, and flowers fresh longer.

For more Shelf Life Advice information on extending the shelf life of produce and many other foods, click here and here.

Sources:

www.engineeringtoolbox.com "Fruits and Vegetable - Optimal Storage Conditions"

http://www.engineeringtoolbox.com/fruits-vegetables-storage-conditions-d_710.html

vegetariantimes.com “Spoiled Rotten—How to Store Fruits and Vegetables”

http://www.vegetariantimes.com/article/spoiled-rotten-how-to-store-fruits-and-vegetables/

Karin E. Allen, Ph.D., Utah State University, Dept. of Nutrition, Dietetics, and Food Sciences

ShelfLifeadvice.com "From Purchase to Storage, Tips on Extending Shelf Life"

http://shelflifeadvice.com/content/purchase-storage-tips-extending-shelf-life

www.csrees.usda.gov "New Technology Prolongs Produce Freshness"

http://192.73.224.129/newsroom/impact/2009/sbir/08212_fresh_produce.html

ShelfLifeAdvice.com "FAQs on Raw Fruits and Veggies--the Answers Can Protect Your Wallet and Your Health"

http://shelflifeadvice.com/content/faqs-raw-fruits-and-veggies—-answers-can-protect-your-wallet-and-your-health