Refrigeration: Crispers: Keep that crunch
By The Vann’s Editorial Team
Last revised October 12th, 2009
Here’s something you may remember from your high school science class: most living organisms are composed primarily of water. Whether you’re a human or a carrot, dehydration is bad news. You guzzle water when you’re thirsty, but how do you keep your veggies and fruit well watered? Refrigerators now come with adjustable-humidity (and sometimes adjustable-temperature) crispers to help preserve your produce. The trick is knowing what kind of conditions are ideal for which items. There are three key elements that will influence your decision: relative humidity, temperature, and ethylene production.
Relative humidity is key for keeping produce hydrated. This is basically a measure of water vapor in the air. Air may contain a lot or very little water vapor (think Florida versus Arizona). For example, at a temperature of 68° F, a cubic meter of air can hold a total of 18 grams of water. If the air only contains 10 grams of water, the relative humidity is about 55%. (10 grams actual water vapor divided by 18 grams possible water vapor). Relative humidity is expressed as a percentage. So a relative humidity of 100% means that the air contains 18 grams at 68° F.
Fruits and vegetables generally require three different levels of relative humidity. Items requiring high relative humidity (90-100%) include leafy greens, beans, cucumber, asparagus, broccoli, celery, avocado, berries, green onions, and pears. A medium relative humidity (80-90%) is best for things like melon, sweet potatoes, tomatoes, and citrus. Low relative humidity (below 80%) works best for dried garlic and onions, pumpkin, and squash.
Adjusting the humidity on a crisper is easy. There is usually a sliding tab on the front of the drawer. Sliding to the “high” end closes a vent in the drawer, keeping the drier refrigerator air out and the moisture in. Sliding to the “low” end opens the vent allowing more circulation and decreasing the amount of water vapor in the air. However, crisper drawers on some models of refrigerators are not adjustable; the relative humidity stays constant at a fairly high level, which is where most of your produce will be happiest. The GE Profile has a drawer that will determine the best temperature and relative humidity after you tell it what kind of item you’re placing in the drawer.
Temperature, although separate from relative humidity, is a related factor. There are three main optimum temperature ranges for storing fresh produce. First, there is the coolest temperature range, from about 32° F to about 40° F. Your refrigerator is the ideal storage space for these items. Leafy greens are included in this category along with asparagus, broccoli, cabbage, celery, onions, peas, and berries. The second group requires slightly higher temperatures (40°-55° F) and includes beans, melons, sweet peppers, summer squash, avocado, and grapefruit. Items such as sweet potatoes, potatoes, ripe tomatoes, and hard-rind squashes and pumpkins can be stored at temperatures of 50°-60° F. Dry garlic and onions, unripe or partly ripe melons, and tomatoes can also be stored at room temperature.
Even after fruits and vegetables are harvested and stored, they continue to ripen. Many fruits and some vegetables produce ethylene during this process. Ethylene is a gas that can adversely affect other items in storage. For example, it will cause yellowing in green vegetables, russet spotting on lettuce, sprouting of potatoes, toughening of asparagus, and bitter-tasting carrots. Ethylene-producing fruits and vegetables should be separated from items that don’t produce the gas. Some common ethylene offenders are apples, cantaloupes, peaches, plums, and pears. Other tips for making the most of your crisper include keeping it at least 2/3 full and storing produce in perforated plastic bags.
Don’t let your fresh produce become the latest science experiment in your refrigerator. By taking advantage of the optimum storage conditions in your crisper, you can enjoy your fruits and vegetables at their peak ripeness.