Lesson 44. Storage Conditions For Various Fruits & Vegetables

44.1 Introduction

Cold storage of fruits and vegetables was used extensively by our ancestors to keep food after the harvest season. In modern times, the year round availability of fresh produce in the supermarket has reduced the use of home storage. However, even today there are benefits of home storage, which make it a good alternative to buying produce from the store. Most importantly, farmers often have excess fruits and vegetables that cannot be consumed immediately but would store well. Stored fruits and vegetables harvested at peak maturity from the farm usually have better flavor and a higher nutritional value.

When harvesting the produce for storage, or buying it locally in season, there are certain guidelines to follow which assure maximum quality and minimum spoilage of stored food.

1.  Harvest fruits and vegetables at peak maturity or as near as possible.

2.  Only use produce that is free from all visible evidence of disease.

3.  Do not pick any fruit or vegetable that has severe insect damage.

4.  Handle food carefully after harvest so that it is not cut or bruised.

5.  Leave an inch or more of stem on most vegetables to reduce water loss and prevent infection.

6.  Use late-maturing varieties better suited to storage.

Once harvested, fruits and vegetables must be stored under proper conditions, the most important of which are temperature and humidity.  Each fruit or vegetable has its own ideal set of conditions at which it will store most successfully for the maximum length of time. These conditions can be classified into four groups:

1.  Vegetables which require cold & moist conditions

2.  Vegetables which require cool & moist conditions

3.  Vegetables which require cold & dry conditions

4.  Vegetables which require warm & dry conditions

The tables on the following page list temperature and humidity requirements for most vegetables.  In addition to proper temperature and humidity, all fruits and vegetables must be kept in a dark, aerated environment. While most vegetables like moist conditions, standing water must be avoided, as it will quickly lead to rot.  Produce must not be allowed to freeze and should be protected from animal pests such as mice.  It is important to remember that crops held in storage are still living plants, capable of respiration and affected by their environment.  The goal of storage is to keep them in a dormant state.

One other note, fruits and vegetables should always be stored separately.  Fruits release ethylene, which speeds the ripening process of vegetables.  Fruits are also very susceptible to picking up the taste of nearby vegetables.

Table 1. Fruits & Vegetables that require cold, moist conditions

Vegetable

Temperature (oF)

Relative Humidity (%)

Length of Storage

Asparagus

32-36

95

2-3 weeks

Apples

32

90

2-6 months

Beets

32

95

3-5 months

Broccoli

32

95

10-14 days

Brussels Sprouts

32

95

3-5 weeks

Cabbage, Early

32

95

3-6 weeks

Cabbage, Late

32

95

3-4 months

Cabbage, Chinese

32

95

1-2 months

Carrots, mature

32

95

4-5 months

Carrots, immature

32

95

4-6 weeks

Cauliflower

32

95

2-4 weeks

Celeriac

32

95

3-4 months

Celery

32

95

2-3 months

Collards

32

95

10-14 days

Corn, sweet

32

95

4-8 days

Endive, Escarole

32

95

2-3 weeks

Grapes

32

90

4-6 weeks

Kale

32

95

10-14 days

Leeks, green

32

95

1-3 months

Lettuce

32

95

2-3 weeks

Parsley

32

95

1-2 months

Parsnips

32

95

2-6 months

Pears

32

95

2-7 months

Peas, green

32

95

1-3 weeks

Potatoes, early

50

90

1-3 weeks

Potatoes, late

39

90

4-9 months

Radishes, spring

32

95

3-4 weeks

Radishes, winter

32

95

2-4 months

Rhubarb

32

95

2-4 weeks

Rutabagas

32

95

2-4 months

Spinach

32

95

10-14 days

 

Table 2. Vegetables that require cool, moist conditions 

Vegetable

Temperature (oF)

Relative Humidity (%)

Length of Storage

Beans, snap

40-50

95

7-10 days

Cucumbers

45-50

95

10-14 days

Eggplant

45-50

90

1 week

Cantaloupe

40

90

15 days

Watermelon

40-50

80-85

2-3 weeks

Peppers, sweet

45-50

95

2-3 weeks

Potatoes, early

50

90

1-3 weeks

Potatoes, late

40

90

4-9 months

Tomatoes, green

50-70

90

1-3 weeks

Tomatoes, ripe

45-50

90

4-7 days

 

 Table 3. Vegetables that require cool dry conditions.

 

Vegetable

Temperature (oF)

Relative Humidity (%)

Length of Storage

Garlic

32

65-70

6-7 months

Onions

32

65-70

6-7 months

 

 Table 4. Vegetables that require warm dry conditions.

 

Vegetable

Temperature (oF)

Relative Humidity (%)

Length of Storage

Peppers, hot

50

60-65

6 months

Pumpkins

50-55

70-75

2-3 months

Squash, winter

50-55

50-60

2-6 months

Sweet Potato

55-60

80-85

4-6 months

 

44.2 Indoor Storage

There are many areas in dwellings that naturally provide, or can be adapted to provide, a variety of temperature and moisture conditions for storage. Assess specific situation; if possible, use a thermometer to monitor temperatures in various areas of your building during the fall and winter to find locations that are convenient and most readily adaptable for food storage.

Fig. 44.1 Indoor Storage

Fig. 44.1 Indoor Storage

Any spot that is sufficiently and evenly cool (32-60 oF) can be adapted for some type of food storage.  The relative humidity of these locations will also affect what can be stored there.  Basements are generally the most logical place to adapt. Older homes are often less well-insulated, and have pantries, back halls, enclosed porches, sheds and bulkheads which are adaptable to storage. 

 44.3 Outdoor Storage

In areas with cold winters, vegetables requiring cool to cold, moist conditions can be stored in any of several types of outdoor storage areas. Earthen storages, from simple mounds to more elaborate root cellars, naturally provide cool, moist, dark and even conditions for a fairly long time.  All outdoor storages have the disadvantage of sometimes being inaccessible, as well as being subject to damage by rodents and other vermin. To be successful, any outdoor storage must have thorough drainage.

A storage into which water settles will not keep produce and may result in total loss.

 44.4 Timing of Storage

 Placing fruits and vegetables in storage, either in pits or in basement rooms, before cold weather starts in the fall is a frequent cause of early spoilage. One of the most difficult steps in successful storage is to keep the produce in prime condition from the time of optimum maturity until the night temperature is low enough to cool the storage area. The length of storage and retention of nutrients will be maximized if the produce can be stored under the proper conditions immediately after harvest.

4.5 Refrigerator Storage

One of the best ways to store small quantities of vegetables requiring cold or cool moist conditions is to use an old or extra refrigerator. The amount of current required to run a storage refrigerator is usually low because they are opened infrequently and can be located in an out of the way, cool location.  For best storage, produce should be washed free of soil and placed into plastic bags with 2 to 4 ¼” holes for ventilation.  The 5 or 10 pound bag size is usually most convenient for the average family. Vegetables in plastic bags do not wilt nearly so rapidly as those stored openly in the refrigerator.

 44.6 Outdoor Sheds

Sheds, breezeways, enclosed porches, and garages can be used to store insulated containers.  An insulated container stored in an unheated area should have 6-8” of insulation on the bottom, sides, and top, with 2-3” between layers of produce.  Additional blankets or other coverings may be necessary depending on how cold the outside temperature reaches. Remember that produce must not be allowed to freeze.

 44. 7 Basement Storage Room

Modern basements with furnaces are generally at least 50-60 0F and dry.  While this is appropriate for some types of food storage, in order to achieve the cool, moist conditions necessary for most fruit and vegetables it may be necessary to construct a separate room. This separate storage area should be located in the coldest part of the basement, away from the furnace.  The north and the east sides of the house are preferred.  Avoid heat ducts and hot water pipes that generate heat.  The room should have an outside window for ventilation.

 While the exterior walls do not need to be insulated, the inside partitions should have 3½” thick fiberglass insulation. Faced insulation should have the vapor barrier closest to the warm side of the storage.  If unfaced insulation is used, a vapor barrier such as 6-mil thick polyethylene can be used.  The ceiling also requires insulation and a vapor barrier. Temperature can be controlled in this storage room by opening and closing the outside window. Humidity can be kept high by pouring water on the floor or by keeping wet burlap sacks or some similar material in the room.

References:

  • Isenberg, F. M. R. Storage of Home Grown Vegetables. Cornell University Department of Vegetable Crops, Master Gardener Reference.

  • MacKay, Susan. Home Storage of Fruits and Vegetables. Northeast Regional Agricultural Engineering Service Bulletin 7. 1984.

Last modified: Monday, 30 September 2013, 5:09 AM