Many consumers have experienced the frustration of having to discard a large percentage of the produce they purchased weekly. While the cause is often attributed to forgetting the produce exists, many times improper storage methods are the primary reason. Cucumbers become limp in two days. Many types of berries begin to mold before being half eaten. Fresh herbs at the back of the refrigerator turn to slime. These are not due to bad fortune or poor quality products. They are the inevitable result of consumers' failure to provide proper storage conditions for the various fruits and vegetables. The use of a small number of fundamental concepts such as cold sensitivity, ethylene gas production, moisture content and airflow will help extend the storage life of nearly all purchases made and significantly reduce the volume of discarded product.

How Fruits and Vegetables Spoil – The Basic Science

Fruits and vegetables are biological organisms and therefore continue to respire after they are harvested. During this respiration process, oxygen is consumed and carbon dioxide is produced along with a gradual breakdown of the cells themselves. The speed at which this process occurs is influenced primarily by temperature, moisture content, and exposure to ethylene gas. Ethylene is a natural plant hormone that stimulates ripening and senescence. Some varieties of produce generate considerable amounts of ethylene gas; others are extremely susceptible to its effects. One of the leading causes of premature spoilage in home kitchens is placing ethylene-generating produce adjacent to ethylene-susceptible produce.

Additionally, bacteria and mold contribute to the degradation process. Mold requires moisture to germinate and therefore, wet produce in a closed container decays considerably faster than dry produce with adequate ventilation. The rate of bacterial growth is also affected by temperature. Low temperatures retard bacterial growth, which is why refrigeration extends shelf life. However, cold temperatures do not benefit all produce. There are certain varieties of produce that are damaged by temperatures lower than approximately 10 degrees Celsius (50 degrees Fahrenheit). In fact, storing these items in a refrigerator can accelerate their demise rather than preserve them.

The Ultimate Principle: Not All Produce Is Best Stored in the Refrigerator

While a refrigerator is generally an excellent means of preserving many types of produce, it is not a universal preservative. A sizeable group of fruits and vegetables — mainly those originating from warm climates — experience damage from cold temperatures in a process known as chilling injury. Their cell walls break down under low temperatures resulting in soft spots, off flavors, rapid decay, and diminished nutritional value. Thus, as critical as it is to know which items to store in the refrigerator, it is equally important to know which items to leave at room temperature.

Always Store Produce At Room Temperature

  • Tomatoes — Refrigerating tomatoes causes them to lose the volatile compounds that create their unique taste and texture. As a result, they become mealy. Store them at room temperature with the stem side down in a location that receives indirect sunlight. Consume them within 3–5 days after they reach full ripeness.
  • Bananas — Cold temperatures halt banana ripening and darken the peel. Store bananas at room temperature; if they ripen too quickly to enjoy before they go bad, slice them up, put them on a baking sheet lined with parchment paper and flash-freeze them for later use in smoothies.
  • Avocados — Before avocados can ripen, they must be allowed to ripen at room temperature. Once ripe, move them to the refrigerator to prolong their useful time by 1–2 days.
  • Onions and Garlic — Both onions and garlic require cool, dry, well-ventilated areas for optimal storage. Do not store them in your refrigerator where excessive humidity creates mold. Instead, hang them in a mesh bag or on an open basket in a dark closet. Store them away from potatoes since they give off moisture and gases that promote spoilage in both.
  • Potatoes — Keeping potatoes in the refrigerator converts their starch to sugars resulting in an unacceptable alteration of their taste when cooked. Therefore, store potatoes in a cool, dark area with good airflow — not in your refrigerator nor near onions.
  • Winter Squash and Pumpkins — Whole winter squash may be stored for several weeks or even months at room temperature in a cool, dry area.
  • Stone Fruits (Peaches, Nectarines, Plums) — Allow stone fruits to ripen at room temperature prior to refrigeration; once fully ripe, they may be refrigerated for consumption within 1–2 days.
  • Mangoes, Papayas, Pineapple — Due to chilling injury associated with cold temperatures found in standard refrigerators, tropical fruits such as mangoes, papayas and pineapple should be allowed to ripen at room temperature and then used immediately.

Ethylene Gas — The Unseen Ripening Factor

One of the least recognized yet most influential elements in managing the storage of fruits and vegetables is ethylene gas generation. If ethylene-generating items are stored proximate to ethylene-sensitive items, it will stimulate an accelerated ripening response in the sensitive items. This is not theory; it has been demonstrated and proven consistent.

High-Ethylene Producing Items

Items that emit significant quantities of ethylene gas should be kept separate from sensitive produce:

  • Apples
  • Pears
  • Bananas
  • Avocado (when ripe)
  • Kiwis
  • Mangoes
  • Peaches
  • Plums
  • Tomatoes

Particularly problematic are apples as they are prolific ethylene generators. In fact, a single apple placed in a fruit bowl can visibly induce an acceleration of ripening in all surrounding items within days.

Sensitive to Ethylene Gas

These items are damaged by ethylene exposure and thus should be stored apart from high-ethylene generating items:

  • Broccoli
  • Cabbage
  • Leafy Greens
  • Carrots
  • Cucumber
  • Peppers
  • Eggplant
  • Watermelon
  • Most Fresh Herbs

Thus, do not store apples near broccoli or leafy greens in the refrigerator crisper drawer. Store high-ethylene producing items in one drawer; store sensitive items in another.

Refrigerator Moisture Control

As previously mentioned, moisture is a dual-edged sword when it comes to produce stored in the refrigerator. Excessive moisture fosters mold growth. Deficient moisture contributes to dehydration/wilting. Most modern refrigerators contain crisper drawers equipped with adjustable humidity vents. By utilizing these vents correctly during storage can make a major positive impact regarding how long produce remains viable.

High-Moisture Drawer

Close the humidity vent to maintain moisture inside the drawer. Store produce in this drawer that is prone to drying out or dehydrating; include items that do not generate ethylene gas:

  • Leafy Greens
  • Fresh Herbs
  • Broccoli
  • Cauliflower
  • Brussels Sprouts
  • Green Beans
  • Cucumbers
  • Peppers

Inadequate airflow within these containers can lead to accumulation of condensation/moisture on the surfaces of these water-dense vegetables.

Low-Moisture Drawer

Leave the humidity vent open allowing ethylene gas and some moisture to escape. Store high-ethylene producing items/produce that continues to ripen post-refrigeration:

  • Apples
  • Pears
  • Grapes
  • Stone Fruits

Airflow helps dissipate ethylene gas; prevents buildup of moisture that leads to mold formation.

Paper Towel Technique

To lengthen the shelf-life of berries, mushrooms and washed salads, line their storage containers with paper towels prior to adding the produce. The paper towels absorb moisture that would otherwise collect at the base of each container and foster mold development. Replace paper towels when saturated. This simple technique can increase the refrigerator life of strawberries by 8–10 days.

Storage Methods For Various Types Of Produce

Leafy Greens And Fresh Herbs

Leafy greens — lettuces, spinach, arugula, kale — deteriorate rapidly when stored moist/wet/sealed. Following cleaning, spin all leafy greens thoroughly using a salad spinner prior to storing loosely wrapped in clean kitchen towels/paper towels within an open/loose bag containing them. Absorbed moisture reduces dehydration/wilting; loose seal provides minimum airflow necessary for maintaining viability. Leafy greens typically retain viability for 5–7 days rather than 2–3.

Herbs fall into two distinct categories dependent upon their preferred storage methodologies. Tender herbs (basil, cilantro, parsley, mint) should be handled similar to flowers: trim stems, stand upright in glass jar with approximately 1 cm water depth and store at room temperature (for basil); store all other tender herbs loosely wrapped in fridge.

Hardy herbs (rosemary, thyme, oregano, sage) prefer storage in loose wrapping in slightly moistened paper towels within a zip lock bag in the refrigerator. When properly stored, tender herbs will retain viability for 1–2 weeks whereas hardy herbs will retain viability for 2–3 weeks.

Berries

Berries represent one of the most perishable commodities available throughout the year and therefore one of the most frequently wasted. There are four key storage directives applicable to berries: do not wash until ready-to-eat; store unwashed berries either individually layered or separated by layers if possible; store berries in a container lined with paper towels; monitor strawberries for any evidence of mold/damage. If a strawberry shows signs of mold/damage remove it immediately from storage as mold grows very rapidly from berry-to-berry via direct contact/spore dispersal.

An acidic bath will help extend berry life: submerge berries in a solution composed of one part white vinegar per three parts water for a brief period of time; rinse thoroughly; pat dry completely; refrigerate. Vinegar's acidity destroys mold spores present on berry surfaces without negatively impacting flavor/taste. Strawberries treated in this manner regularly retain viability for 10–14 days versus 3–5 days without treatment.

Cruciferous Vegetables

Broccoli, cauliflower, Brussels sprouts and cabbage are both high-moisture/sensitive-to-ethylene producing commodities. To maximize shelf life store these items unwashed in the high-humidity drawer loosely wrapped/opened/bagged. Avoid tightly sealing cruciferous vegetables as they continue to respire; some airflow is required to prevent build-up of moisture condensing inside sealed bags. Broccoli stored according to this methodology retains viability for 5–7 days vs 2–3 days when improperly stored tightly sealed.

Roots

Carrots, parsnips and beets retain optimal quality when stored in the refrigerator with their leaves removed. Leaves draw moisture from the roots thereby promoting dehydration/limpness. Immediately remove leaves from roots after purchase; store roots individually in a perforated bag/loosely sealed container; roots will retain optimal quality for 2–3 weeks. Radishes follow identical procedure — remove greens; store radish roots individually in water; replace water every few days; radish roots retain optimal quality for up to two weeks.

Citrus

Whole citrus fruits retain optimal quality for approximately one week at room temperature or 3–4 weeks stored in the refrigerator. Unless there is imminent intention to consume citrus fruits within a short period of time (i.e., less than 3–5 days), it is usually preferable to store citrus fruits in the refrigerator.

Preparation/Cutting Produce — Special Storage Requirements Exist

After cutting/fresh preparation, produce's shelf life is severely reduced due to exposure of cut surfaces to oxygen (thereby triggering enzymatic browning processes) and increased susceptibility to bacterial growth. Utilization of several methods can effectively minimize these detrimental effects:

  • Rub cut avocado/apple/potato surfaces with lemon/juice/lime juice: Citric acids inhibit oxidation enzyme activity responsible for browning color changes.
  • Store cut vegetable submerged in cold water: Dehydration/browning prevention simultaneous (e.g., celery sticks/carrot sticks/cucumber slices).
  • Seal cut surface with plastic wrap applied directly onto flesh (not loosely over top): Minimize air exposure.

Auditing Your Produce — A Daily Habit

Regardless of perfect storage technique application does not negate necessity for ongoing awareness. The most effective habit for reducing waste generated from produce consumption is conducting regular audits (daily/every other day) of contents contained within your refrigerator and on countertops. Allocate 60 seconds reviewing what items approaching peak maturity are present; develop meal plans around identified produce items. A cucumber nearing three days old does not need discarded — it needs incorporated into your next evening meal. Combining adherence to storage technique fundamentals with incorporation of regular auditing habits will enable households successfully achieve balance between purchasing fresh produce and consuming all of it before it spoils.

The cumulative benefits achievable through application of these produce storage fundamentals are substantial. Households adhering strictly to these guidelines will discover that weekly purchases remain usable throughout their intended week rather than becoming unusable mid-week; food waste generated through weekly purchases decreases substantially; quality remaining toward end-of-week is similar to quality existing at commencement-of-week. No specialized equipment nor additional labor requirements exist relative to implementing these techniques — simply knowledge regarding requirements of specific types of produce and establishment/continuation of consistency related thereto.