Skip Navigation

Bulletin #4135, Storage Conditions: Fruits & Vegetables

Print Friendly

Storage Conditions: Fruits & Vegetables

tomatoes in wooden crates; photo by Edwin Remsberg, USDAThis bulletin was reprinted with permission from Kansas State University Cooperative Extension Service, Manhattan, KS. Written by Karen L. B. Gast, Extension specialist, Post Harvest and Marketing.

For information about UMaine Extension programs and resources, visit extension.umaine.edu.
Find more of our publications and books at extensionpubs.umext.maine.edu.

Once a crop is harvested, it is almost impossible to improve its quality. Losses of horticultural crops due to improper storage and handling can range from 10 to 40 percent. Proper storage conditions—temperature and humidity—are needed to lengthen storage life and maintain quality once the crop has been cooled to the optimum storage temperature.

Fresh fruits and vegetables are living tissues, although they are no longer attached to the plant. They breathe, just as humans do, and their composition and physiology continue to change after harvest. They continue to ripen and, finally, they begin to die. Cellular breakdown and death (senescence) are inevitable, but can be slowed with optimal storage conditions. Fresh fruits and vegetables need low temperatures (32 to 55°F) and high relative humidities (80 to 95 percent) to lower respiration and to slow metabolic and transpiration rates. By slowing these processes, water loss is reduced and food value, quality and energy reserves are maintained.

Relative Humidity

Transpiration rates (water loss from produce) are determined by the moisture content of the air, which is usually expressed as relative humidity. At high relative humidity, produce maintains salable weight, appearance, nutritional quality and flavor, while wilting, softening and juiciness are reduced. Leafy vegetables with high surface-to-volume ratios; injured produce; and immature fruits and vegetables have higher transpiration rates. External factors affecting transpiration rates are temperature, relative humidity, air velocity and atmospheric pressure. High temperatures, low relative humidity and high air velocity increase transpiration rates.

Relative humidity needs to be monitored and controlled in storage. A hygrometer or a sling psychrometer, not the appearance of the produce, should be used to monitor humidity. Control can be achieved by a variety of methods:

  1. Operating a humidifier in the storage area.
  2. Regulating air movement and ventilation in relation to storage room load.
  3. Maintaining refrigeration coil temperature within 2°F of the storage room air temperature.
  4. Using moisture barriers in the insulation of the storage room or transport vehicle, and in the lining of the packing containers.
  5. Wetting the storage room floor.
  6. Using crushed ice to pack produce for shipment.
  7. Sprinkling leafy vegetables, cool-season root vegetables, and immature fruits and vegetables with water.

Table 1 lists the optimum relative humidity for the storage of several fruits and vegetables.

Temperature

Respiration and metabolic rates are directly related to room temperatures within a given range. The higher the rate of respiration, the faster the produce deteriorates. Lower temperatures slow respiration rates and the ripening and senescence processes, which prolongs the storage life of fruits and vegetables. Low temperatures also slow the growth of pathogenic fungi which cause spoilage of fruits and vegetables in storage. Table 2 contains a list of fruits and vegetables classified by respiration rates. Producers should give special care and attention to proper storage conditions for produce with high to extremely high respiration rates—those crops will deteriorate much more quickly.

It is impossible to make a single recommendation for cool storage of all fruits and vegetables. Climate of the area where the crop originated, the plant part, the season of harvest and crop maturity at harvest are important factors in determining the optimum temperature. A general rule for vegetables is that cool-season crops should be stored at cooler temperatures (32 to 35°F), and warm-season crops should be stored at warmer temperatures (45 to 55°F). There are exceptions to this rule, though. Table 1 lists optimum storage temperatures for commonly grown Kansas fruits and vegetables.

Freezing Injury. Temperatures that are too low can be just as damaging as those too high. Freezing will occur in all commodities below 32°F. Whether injury occurs depends on the commodity. Some can be repeatedly frozen and thawed without damage, while others are ruined by one freezing. Table 1 shows the highest freezing point for most fruits and vegetables. Table 3 lists susceptibility to freezing injury. Produce that is likely to be injured by one freezing is classified as “most susceptible.” The “moderately susceptible” produce will recover from one or two freezings. Produce which is “least susceptible” can survive several freezings without injury.

Injury from freezing temperatures can appear in plant tissues as loss of rigidity, softening and water soaking. Injury can be reduced if the produce is allowed to warm up slowly to optimum storage temperatures, and if it is not handled during the thawing period. Injured produce should be marketed immediately, as freezing shortens its storage life.

Chilling Injury. Fruits and vegetables that require warmer storage temperatures (40 to 55°F) can be damaged if they are subjected to near freezing temperatures (32°F). Cooler temperatures interfere with normal metabolic processes. Injury symptoms are varied and often do not develop until the produce has been returned to warmer temperatures for several days. Besides physical damage, chilled produce is often more susceptible to disease infection. Table 4 lists susceptible fruits and vegetables, and characteristic symptoms of chilling injury.

Storage Facilities

Crops that require different storage conditions will need three different storage facilities.

Cold storage (temperatures 32 to 36°F).

Cool storage (temperatures 40 to 55°F).

Warmer storage (temperatures 55 to 60°F for sweet potatoes, squash, pumpkins or similar crops).

A recording thermometer can be helpful in determining whether storage facilities are maintaining ideal conditions and are not fluctuating. A maximum/minimum thermometer could be substituted. The thermometer should not be the same as the thermostat controlling the refrigeration equipment. Relative humidity also should be monitored with a hygrometer or a sling psychrometer.

Controlling and monitoring temperature and relative humidity will enable a grower to maintain optimum conditions for maximum storage life of the crop, and to minimize crop damage from chilling, freezing and/or too-high temperatures and water loss from the crop. Close attention to storage conditions will yield returns through greater customer satisfaction, less waste and spoilage, and in the flexibility to hold a crop without significant storage losses to wait for better markets.

References

Hardenburg, R.E., A.E. Watada and C.Y. Wang. 1986. The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks. USDA-ARS Agriculture Handbook Number 66 (revised) 136p.

Table 1. Commonly grown fruits and vegetables with recommended storage conditions for temperature and relative humidity  approximate storage life under optimum conditions and highest freezing points.
Commodity Temperature (°F) Rel. humidity (percent) Approximate
storage life
Freezing point (°F)
FRUITS
Apples 30–40 90–95 1–12 months 29.3
Apricots 31–32 90–95 1–3 weeks 30.1
Berries
- Blackberries 31–32 90–95 2–3 days 30.5
- Currants 31–32 90–95 1–4 weeks 30.2
- Elderberries 31–32 90–95 1–2 weeks
- Gooseberries 31–32 90–95 3–4 weeks 30.0
- Raspberries 31–32 90–95 2–3 days 30.0
- Strawberries 32 90–95 3–7 days 30.6
- Cherries, sour 32 90–95 3–7 days 29.0
Cherries, sweet 30–31 90–95 2–3 weeks 28.8
Grapes, American 31–32 85 2–8 weeks 29.7
Nectarines 31–32 90–95 2–4 weeks 30.4
Peaches 31–32 90–95 2–4 weeks 30.3
Pears 29–31 90–95 2–7 months 29.2
Plums and prunes 31–32 90–95 2–5 weeks 30.5
Quinces 31–32 90 2–3 months 28.4
VEGETABLES
Artichokes, Jerusalem 31–32 90–95 4–5 months 28.0
Asparagus 32–35 95–100 2–3 weeks 30.9
Beans, dry 40–50 40–50 6–10 months
Beans green or snap 40–45 95 7–10 days 30.7
Beans, lima 37–41 95 5–7 days 31.0
Beans, sprouts 32 95–100 7–9 days
Beets, bunched 32 98–100 10–14 days 31.3
Beets, topped 32 98–100 4–6 months 30.3
Broccoli 32 95–100 10–14 days 30.9
Brussels, sprouts 32 95–100 3–5 weeks 30.5
Cabbage, early 32 98–100 3–6 weeks 30.4
Cabbage, late 32 98–100 5–6 months 30.4
Cabbage, Chinese 32 95–100 2–3 months
Carrots, bunched 32 95–100 2 weeks
Carrots, mature 32 98–100 7–9 months 29.5
Carrots, immature 32 98–100 4–6 weeks 29.5
Cauliflower 32 95–98 3–4 weeks 30.6
Celeriac 32 97–99 6–8 months 30.3
Celery 32 98–100 2–3 months 31.1
Chard 32 95–100 10–14 days
Chicory, witloof 32 95–100 2–4 weeks
Collards 32 95–100 10–14 days 30.6
Corn, sweet 32 95–98 5–8 days 30.9
Cucumbers 50–55 95 10–14 days 31.1
Eggplant 46–54 90–95 1 week 30.6
Endive and escarole 32 95–100 2–3 weeks 31.9
Garlic 32 65–70 6–7 months 30.5
Greens, leafy 32 95–100 10–14 days
Horseradish 30–32 98–100 10–12 months 28.7
Jicama 55–65 65–70 1–2 months
Kale 32 95–100 2–3 weeks 31.1
Kohlrabi 32 98–100 2–3 months 30.2
Leeks 32 95–100 2–3 months 30.7
Lettuce 32 98–100 2–3 weeks 31.7
Melons
- Cantaloupe (3/4 slip) 36–41 95 15 days 29.9
- Cantaloupe (full slip) 32–36 95 5–14 days 29.9
- Casaba 50 90–95 3 weeks 30.1
- Crenshaw 45 90–95 2 weeks 30.1
- Honey Dew 45 90–95 3 weeks 30.3
- Persian 45 90–95 2 weeks 30.5
- Watermelon 50–60 90 2–3 weeks 31.3
Mushrooms 32 95 3–4 days 30.4
Okra 45–50 90–95 7–10 days 28.7
Onions, green 32 95–100 3–4 weeks 30.4
Onion, dry 32 65–70 1–8 months 30.6
Onion sets 32 65–70 6–8 months 30.6
Parsley 32 95–100 2–2.5 months 30.0
Parsnips 32 98–100 4–6 months 30.4
Peas, green 32 95–98 1–2 weeks 30.9
Peas, southern 40–41 95 6–8 days
Peppers, chili (dry) 32–50 60–70 6 months
Peppers, sweet 45–55 90–95 2–3 weeks 30.7
Potatoes, early crop 40 90–95 4–5 months 30.9
Potatoes, late crop 38–40 90–95 5–10 months 30.9
Pumpkins 50–55 50–70 2–3 months 30.5
Radishes, spring 32 95–100 3–4 weeks 30.7
Radishes, winter 32 95–100 2–4 months
Rhubarb 32 95–100 2–4 weeks 30.3
Rutabagas 32 98–100 4–6 months 30.0
Salsify 32 95–98 2–4 months 30.0
Spinach 32 95–100 10–14 days 31.5
Squashes, summer 41–50 95 1–2 weeks 31.1
Squashes, winter 50 50–70 1–6 months 30.5
Sweet potatoes 55–60 85–90 4–7 months 29.7
Tomatoes mature—green 55–70 90–95 1–3 weeks 31.0
Tomatoes firm—ripe 55–70 90–95 4–7 days 31.1
Turnips 32 95 4–5 months 30.1
Turnip greens 32 95–100 10–14 days 31.7
Watercress 32 95–100 2–3 weeks 31.4


Table 2. Fruits and vegetables classified by their respiration rates (at 41°F).
Class Respiration rate
Btu/ton/24 hrs
Commodity
Very low
<5 Nuts, Dates, Dried Fruits and Vegetables
Low 5–10 Apple, Grape, Garlic, Onion, Potato (mature), Sweet Potato
Moderate 10–20 Apricot, Cherry, Peach, Pear, Nectarine, Plum, Cabbage, Carrot, Lettuce, Pepper, Tomato, Potato (immature)
High 20–40 Strawberry, Blackberry, Lima Bean, Raspberry, Cauliflower
Very high 40–60 Artichoke, Snap Bean, Green Onion, Brussels Sprouts
Extremely high >60 Asparagus, Broccoli, Sweet Corn, Mushroom, Spinach, Pea


Table 3. Fruits and vegetables classified by susceptibility to injury by temperatures below 32°F.
Group 1, Most susceptible Group 2, Moderately  susceptible Group 3, Least susceptible
Apricots Apples Beets1
Asparagus Broccoli, sprouting Brussels Sprouts
Beans, snap Cabbage, new Cabbage, mature and savoy
Berries (except cranberries) Carrots1 Kale
Cucumbers Cauliflower Kohlrabi
Eggplant Celery Parsnips
Lettuce Cranberries Rutabagas
Okra Grapes Salsify
Peaches Onions (dry) Turnips1
Peppers, sweet Parsley
Plums Pears
Potatoes Peas
Squash, summer Radishes1
Sweet Potatoes Spinach
Tomatoes Squash, winter
1Without tops


Table 4. Fruits and vegetables susceptible to chilling injury when exposed to temperatures below their optimum range and above 32°F.
Commodity
Approx. lowest safe temperature (°F)
Symptoms of injury from below – optimum temperatures
Apples-certain cultivars
36–38
Internal browning, brown core, soggy breakdown, soft scald
Asparagus
32–36
Dull, gray-green, limp tips
Beans (lima)
34–40
Rusty brown specks, spots, or areas
Beans (snap)
45
Pitting and russeting
Cucumbers
45
Pitting, water-soaked spots, decay
Eggplants
45
Surface scald, alternaria rot, blackening of seeds
Melons
- Cantaloupe
36–41
Pitting, surface decay
- Honey Dew
45–50
Reddish-tan discoloration, pitting, surface decay, failure to ripen
- Casaba
45–50
Same as above, but no discoloration
- Crenshaw and Persian
45–50
Same as above, but no discoloration
- Watermelons
40
Pitting, objectionable flavor
Okra
45
Discoloration, water-soaked areas, pitting, decay
Peppers, sweet
45
Sheet pitting, alternaria rot on pods and calyxes, darkening of seed
Potatoes
38
Sweetening
Pumpkins and hardshell squashes
50
Decay, especially alternaria rot
Sweet Potatoes
55
Decay, pitting, internal discoloration; hard core when cooked
Tomatoes
- Ripe
45–50
Water soaking and softening decay
- Mature-green
55
Poor color when ripe, alternaria rot

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 2001
Published and distributed in furtherance of Cooperative Extension work, Acts of Congress of May 8 and June 30, 1914, by the University of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the USDA provide equal opportunities in programs and employment.

Call 800-287-0274 or TDD 800-287-8957 (in Maine), or 207-581-3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit extension.umaine.edu.

The University of Maine does not discriminate on the grounds of race, color, religion, sex, sexual orientation, including transgender status and gender expression, national origin, citizenship status, age, disability, genetic information or veteran’s status in employment, education, and all other programs and activities. The following person has been designated to handle inquiries regarding non-discrimination policies: Director, Office of Equal Opportunity, 101 North Stevens Hall, 581-1226.