Have you ever wondered why the green bananas you buy in the grocery store turn yellow and then soon get brown spots and change texture from firm to soft? This is all a part of the normal ripening process. Considering that bananas travel a long distance from harvest to our local food markets, there has to be a method of controlling the ripening process so that the consumer can purchase a quality product. The same ripening process occurs with locally grown produce. Large commercial produce vendors have storage rooms where they regulate the amount of an odorless, colorless gas called ethylene that controls the ripening process.

Ethylene is a natural plant hormone which regulates the plant’s growth and development as well as the speed at which these occur. You take advantage of this natural, colorless gas when you put a ripe apple in a bag of unripe pears to hasten the ripening process.

Eventually, ethylene causes plant cells to degrade — fruit softens and becomes sweeter, and vegetable leaves yellow and drop. Think of the saying “one rotten apple spoils the whole barrel.”

Some foods are more sensitive to ethylene than others. Many vegetables are especially sensitive to this gas, which is why we store refrigerated vegetables separate from some fruits — perhaps in a different crisper drawer or in an airtight plastic container. There are no hard and fast rules for identifying ethylene-sensitive produce, but many vegetables are ethylene sensitive such as asparagus, broccoli, Brussels sprouts, cabbage, cauliflower, corn, cucumbers, eggplant, green beans, kale, lettuce and greens, mushrooms, onions, parsley and herbs, peas, peppers, summer squash, and sweet potatoes.

Fruits differ in their sensitivity to ethylene. Some fruits ripen after harvest and emit a greater amount of ethylene as they ripen. These are called climacteric fruits and include apples, apricots, avocado, bananas, mango, cantaloupe and honeydew, pears, peaches and nectarines, plums, and tomatoes. You want to keep them away from produce that is ripe when it is harvested. Fruits that do not ripen after harvest are sensitive to ethylene and are called non-climacteric. These include blueberries, blackberries, raspberries, cherries, grapes, strawberries and watermelon. Citrus fruits vary somewhat. Most ethylene-sensitive fruits are best stored away from ethylene-producing fruits.

Take advantage of the divided produce drawers in your refrigerator, designating one for vegetables and the other for fruits that produce ethylene. Store ethylene-sensitive fruits separately from those that produce ethylene — since many of these are delicate to start with, they may be left in a perforated basket until they are ready to be washed and used.

You may have seen products advertised to remove ethylene from produce in the refrigerator. They are sold under various names — removers, blockers, scavengers, absorbers and scrubbers. No doubt you have purchased food in boxes that have been treated to absorb ethylene gas. Products available in stores include granules in boxes, balls or sachets as well as produce bags called “green bags.” The mention of these products here is not an endorsement of them, but to make you aware of them if you choose to use them as another method of controlling ethylene and slowing the ripening process.

If you have a food preservation question, contact your local Penn State Extension office and they will forward it to the proper educator.

The Well Preserved news column is prepared by Penn State Extension.

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