To anyone who has ever wondered why some of their fruits and vegetables spoil faster than they can eat them, the secret may be something that these foods naturally produce—ethylene.
Ethylene is a gas and natural plant hormone that triggers ripening. Once a fruit or vegetable begins producing ethylene, it initiates a series of biological changes—which include an increase in sweetness, a reduction in acid levels, and aroma development—signaling to us that it’s ready to eat.
Ethylene has other functions beyond growth and development, Macarena Farcuh, an assistant professor of plant science and landscape architecture at the University of Maryland, told The Epoch Times. Ethylene triggers flower aging, controls the shedding of leaves and fruits, and helps plants respond to stress.
Not all fruits and vegetables produce the same amount of ethylene, however, according to Lynette Johnston, an assistant professor and food safety extension specialist at North Carolina State University.
“Fruits such as bananas, apples, tomatoes, and avocados are high producers, while crops like carrots, broccoli, and leafy greens produce very little,” she told The Epoch Times.
Fruit also ripens differently depending on when it’s harvested. Some fruit is picked before it’s ripe—called climacteric—and ripens because of exposure to ethylene. Examples include apples, bananas, mangoes, and avocados. Others are non-climacteric and picked when fully ripe, such as grapes, strawberries, and cherries. Most vegetables are harvested when ripe and don’t rely on ethylene, although exposure can cause them to spoil more quickly.
“Ethylene production rates will vary with fruit maturity as well as even between cultivars of the same fruit species,” Farcuh said.
Cultivars, or cultivated varieties, are specific varieties of fruit that humans have created based on desired traits—such as better flavor, texture, appearance, drought resistance, or increased yield.
In addition to ethylene, multiple other factors affect ripening:
- Species and cultivar, for example, some apple varieties, such as McIntosh, release far more ethylene than others
- Stage of maturity and ripeness
- Temperature
- Light
- Physiological stress, such as bruising or damage
- Oxygen and carbon dioxide levels
- Relative humidity
Ethylene Producers, Ethylene Sensitive and Non-Sensitive Foods
Some types of produce release high amounts of ethylene, while others are highly sensitive to it. Storing the two together can speed spoilage.
Below are lists of each to help you distinguish between them. For a more comprehensive list, you can visit US Foods’ produce-ethylene sensitivity chart.
Foods That Produce Ethylene
- Apples
- Avocados
- Bananas
- Cantaloupe
- Kiwi
- Peaches
- Pears
- Peppers
- Tomatoes
Foods Sensitive to Ethylene
- Apples
- Asparagus
- Avocados
- Bananas
- Broccoli
- Cantaloupe
- Collard Greens
- Cucumber
- Eggplant
- Grapes
- Honeydew
- Kiwi
- Lemons
- Lettuce
- Limes
- Mangos
- Onions
- Peaches
- Pears
- Peppers
- Squash
- Sweet Potatoes
- Watermelon
Foods Not Sensitive to Ethylene
- Blueberries
- Cherries
- Beans (Snap)
- Garlic
- Grapefruit
- Oranges
- Pineapple
- Potatoes
- Raspberries
- Strawberries
- Tomatoes
- Yucca
How You Store Your Produce Matters
We no longer have to be at the mercy of our produce and can change how we store it to yield the results we want and need.
Slow Down Ripening
Placing fruits and vegetables in the fridge can keep them fresh longer, as the cold temperature slows down the ripening process. However, some produce should never be stored in the refrigerator, such as potatoes, onions, and garlic—the exception is when they are cooked, cut, or crushed.
To help your fruits and veggies last a little longer, avoid storing high-ethylene-producing foods, such as apples and bananas, near those that are sensitive to it, such as cucumbers and eggplant.
Another way to slow down ripening is to remove both producers and sensitive foods from any packaging, such as bags or containers covered with plastic wrap, which can trap gas and accelerate the process.
Speed Up Ripening
There are times when you might have a hankering for a tasty guacamole, but all your avocados feel like they are weeks away from cooperating.
To expedite ripening, place unripe fruit near an ethylene producer, particularly prolific producers such as apples or bananas. To accelerate the process further, put them together in a paper bag, and you will be enjoying guac in no time.
“Paper bags facilitate air exchange, avoid excessive moisture buildup, and are still able to keep ethylene in order to accelerate ripening. Plastic bags are going to create a highly humid environment, which can enhance rot development, as well as prevent an even air exchange,” Farcuh said.
Leaving cut fruit or vegetables exposed to air, and storing food in warm or sunny places, can also increase ripening, according to Johnston.
Keeping Food Fresh
Vegetables don’t rely on ethylene for ripening because they are harvested when they are mature and ready to eat. However, some items we think of as vegetables are, botanically speaking, considered fruit and affected by ethylene. Particularly sensitive examples include peppers, eggplant, and cucumbers.
In other instances, exposing vegetables to ethylene is problematic, and exposure does not increase ripening but accelerates aging and leads to spoilage.
Because many vegetables are also sensitive to ethylene and can spoil more quickly when exposed to ethylene, they should be stored away from fruit that produces abundant amounts of ethylene, such as apples, bananas, and avocados, to ensure that they stay fresh.
“For example, broccoli and cauliflower may yellow, leafy greens like lettuce and spinach can develop russet spotting, carrots may become bitter, and cucumbers or zucchini can yellow and soften,” Johnston said.
Ultimately, she said, there are numerous things we can do to ensure that our produce lasts:
- Wash fruits and vegetables only just before eating—except for berries, which benefit from a vinegar-water rinse and thorough drying.
- Dry produce thoroughly before storing.
- Monitor humidity levels and keep them appropriate—high for leafy greens, low for onions and garlic.
- Move ripened fruit from the counter to the refrigerator if more time is needed before you eat it.
By using the above tips, all your future produce should thrive, elevate your recipes with their freshness, and make it through the week until your next grocery run.
