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If produce is to be stored, it is important to begin with a high quality product. The lot of produce must not contain damaged or diseased units, and containers must be well ventilated and strong enough to withstand stacking. In general, proper storage practices include temperature control, relative humidity control, air circulation and maintenance of space between containers for adequate ventilation, and avoiding incompatible product mixes.
Commodities stored together should be capable of tolerating the same temperature, relative humidity and level of ethylene in the storage environment. High ethylene producers (such as ripe bananas, apples, cantaloupe) can stimulate physiological changes in ethylene sensitive commodities (such as lettuce, cucumbers, carrots, potatoes, sweet potatoes) leading to often undesirable color, flavor and texture changes.
Temperature management during storage can be aided by constructing square rather than rectangular buildings. Rectangular buildings have more wall area per square feet of storage space, so more heat is conducted across the walls, making them more expensive to cool. Temperature management can also be aided by shading buildings, painting storehouses white to help reflect the sun's rays, or by using sprinkler systems on the roof of a building for evaporative cooling. The United Nations' Food and Agriculture Organization (FAO) recommends the use of ferro-cement for the construction of storage structures in tropical regions, with thick walls to provide insulation.
Low cost cold rooms can be constructed using concrete for floors and polyurethane foam as insulation materials. Building the storeroom in the shape of a cube will reduce the surface area per unit volume of storage space, also reducing construction and refrigeration costs. All joints should be carefully caulked and the door should have a rubber seal around the edges. While cooling produce, the ventilation system should be set to create an air flow rate of 100 cfm/ton (5 l/sec/ton). Once cooling is completed, air flow rates should be decreased to the lowest speed that will keep produce cool (20 to 40 cfm/ton is usually sufficient, according to Thompson et al. 1998). The greater the refrigerator's evaporator coil area, the less of a temperature difference there will be between the coils and the target room temperature, and the less moisture will be lost from the product as it cools. (See Thompson et al in Kader, 2002 for more information).
Facilities located at higher altitudes can be effective, since air temperature decreases as altitude increases. Increased altitude therefore can make evaporative cooling, night cooling and radiant cooling more feasible. Underground storage for citrus crops is common in Southern China , while in Northwest China , apples are stored in caves (Liu, 1988). This system was widely used in the U.S. during the early 1900s.
Certain commodities, such as onions and garlic, store better in lower relative humidity environments. Curing these crops by allowing the external layers of tissue to dry out prior to handling and storage helps to protect them from decay and further water loss (see Chapter 2).
Commercially constructed cold rooms can be quite expensive, but fortunately the small-scale operator has many choices. Cold rooms can be self-constructed, purchased as prefabricated units (new or used), or made from refrigerated transportation equipment such as railway cars, highway vans or marine containers. For more detailed information about determining the cold room size best suited to your operation, evaluating choices when purchasing or building a cold room, refer to the source below.
Thompson, J.F. and Spinoglio, M. 1994. Small-scale cold rooms for perishable commodities. Family Farm Series, Small Farm Center , University of California , Davis .
The air composition in the storage environment can be manipulated by increasing or decreasing the rate of ventilation (introduction of fresh air) or by using gas absorbers such as potassium permanganate or activated charcoal. Large-scale controlled or modified atmosphere storage requires complex technology and management skills, however, some simple methods are available for handling small volumes of produce.
Recommended Temperature and Relative Humidity, and Approximate Transit and Storage Life for Fruits and Vegetable Crops (see Hardenburg et al, 1986 for more complete information on individual crops).
Product |
Temperature |
Relative Humidity (percent) |
Approximate storage life |
||
°C |
°F |
||||
Amaranth |
0-2 |
32-36 |
95-100 |
10-14 days |
|
Anise |
0-2 |
32-36 |
90-95 |
2-3 weeks |
|
Apples |
-1-4 |
30-40 |
90-95 |
1-12 months |
|
Apricots |
-0.5-0 |
31-32 |
90-95 |
1-3 weeks |
|
Artichokes, globe |
0 |
32 |
95-100 |
2-3 weeks |
|
Asian pear |
1 |
34 |
90-95 |
5-6 months |
|
Asparagus |
0-2 |
32-35 |
95-100 |
2-3 weeks |
|
Atemoya |
13 |
55 |
85-90 |
4-6 weeks |
|
Avocados, Fuerte, Hass |
7 |
45 |
85-90 |
2 weeks |
|
Avocados, Lula, Booth-1 |
4 |
40 |
90-95 |
4-8 weeks |
|
Avocados, Fuchs, Pollock |
13 |
55 |
85-90 |
2 weeks |
|
Babaco |
7 |
45 |
85-90 |
1-3 weeks |
|
Bananas, green |
13-14 |
56-58 |
90-95 |
14 weeks |
|
Barbados cherry |
0 |
32 |
85-90 |
7-8 weeks |
|
Bean sprouts |
0 |
32 |
95-100 |
7-9 days |
|
Beans, dry |
4-10 |
40-50 |
40-50 |
6-10 months |
|
Beans, green or snap |
4-7 |
40-45 |
95 |
7-10 days |
|
Beans, lima , in pods |
5-6 |
41-43 |
95 |
5 days |
|
Beets, bunched |
0 |
32 |
98-100 |
10-14 days |
|
Beets, topped |
0 |
32 |
98-100 |
4-6 months |
|
Belgian endive |
2-3 |
36-38 |
95-98 |
24 weeks |
|
Bitter melon |
12-13 |
53-55 |
85-90 |
2-3 weeks |
|
Black sapote |
13-15 |
55-60 |
85-90 |
2-3 weeks |
|
Blackberries |
-0.5-0 |
31-32 |
90-95 |
2-3 days |
|
Blood orange |
4-7 |
40-44 |
90-95 |
3-8 weeks |
|
Blueberries |
-0.5-0 |
31-32 |
90-95 |
2 weeks |
|
Bok choy |
0 |
32 |
95-100 |
3 weeks |
|
Boniato |
13-15 |
55-60 |
85-90 |
4-5 months |
|
Breadfruit |
13-15 |
55-60 |
85-90 |
2-6 weeks |
|
Broccoli |
0 |
32 |
95-100 |
10-14 days |
|
Brussels sprouts |
0 |
32 |
95-100 |
3-5 weeks |
|
Cabbage, early |
0 |
32 |
98-100 |
3-6 weeks |
|
Cabbage, late |
0 |
32 |
98-100 |
5-6 months |
|
Cactus Leaves |
2-4 |
36-40 |
90-95 |
3 weeks |
|
Cactus Pear |
2-4 |
36-40 |
90-95 |
3 weeks |
|
Caimito |
3 |
38 |
90 |
3 weeks |
|
Calabaza |
10-13 |
50-55 |
50-70 |
2-3 months |
|
Calamondin |
9-10 |
48-50 |
90 |
2 weeks |
|
Canistel |
13-15 |
55-60 |
85-90 |
3 weeks |
|
Cantaloupes (3/4-slip) |
2-5 |
36-41 |
95 |
15 days |
|
Cantaloupes (full-slip) |
0-2 |
32-36 |
95 |
5-14 days |
|
Carambola |
9-10 |
48-50 |
85-90 |
3-4 weeks |
|
Carrots, bunched |
0 |
32 |
95-100 |
2 weeks |
|
Carrots, mature |
0 |
32 |
98-100 |
7-9 months |
|
Carrots, immature |
0 |
32 |
98-100 |
4-6 weeks |
|
Cashew apple |
0-2 |
32-36 |
85-90 |
5 weeks |
|
Cauliflower |
0 |
32 |
95-98 |
34 weeks |
|
Celeriac |
0 |
32 |
97-99 |
6-8 months |
|
Celery |
0 |
32 |
98-100 |
2-3 months |
|
Chard |
0 |
32 |
95-100 |
10-14 days |
|
Chayote squash |
7 |
45 |
85-90 |
4-6 weeks |
|
Cherimoya |
13 |
55 |
90-95 |
2-4 weeks |
|
Cherries, sour |
0 |
32 |
90-95 |
3-7 days |
|
Cherries, sweet |
-1 to -0.5 |
30-31 |
90-95 |
2-3 weeks |
|
Chinese broccoli |
0 |
32 |
95-100 |
10-14 days |
|
Chinese cabbage |
0 |
32 |
95-100 |
2-3 months |
|
Chinese long bean |
4-7 |
40-45 |
90-95 |
7-10 days |
|
Clementine |
4 |
40 |
90-95 |
24 weeks |
|
Coconuts |
0-1.5 |
32-35 |
80-85 |
1-2 months |
|
Collards |
0 |
32 |
95-100 |
10-14 days |
|
Corn, sweet |
0 |
32 |
95-98 |
5-8 days |
|
Cranberries |
2-4 |
36-40 |
90-95 |
24 months |
|
Cucumbers |
10-13 |
50-55 |
95 |
10-14 days |
|
Currants |
-0.5-0 |
31-32 |
90-95 |
1-4 weeks |
|
Custard apples |
5-7 |
41-45 |
85-90 |
4-6 weeks |
|
Daikon |
0-1 |
32-34 |
95-100 |
4 months |
|
Dates |
-18 or 0 |
0 or 32 |
75 |
6-12 months |
|
Dewberries |
-0.5-0 |
31-32 |
90-95 |
2-3 days |
|
Durian |
4-6 |
39-42 |
85-90 |
6-8 weeks |
|
Eggplants |
12 |
54 |
90-95 |
1 week |
|
Elderberries |
-0.5-0 |
31-32 |
90-95 |
1-2 weeks |
|
Endive and escarole |
0 |
32 |
95-100 |
2-3 weeks |
|
Feijoa |
5-10 |
41-50 |
90 |
2-3 weeks |
|
Figs fresh |
-0.5-0 |
31-32 |
85-90 |
7-10 days |
|
Garlic |
0 |
32 |
65-70 |
6-7 months |
|
Ginger root |
13 |
55 |
65 |
6 months |
|
Gooseberries |
-0.5-0 |
31-32 |
90-95 |
34 weeks |
|
Granadilla |
10 |
50 |
85-90 |
3-4 weeks |
|
Grapefruit, Calif. & Ariz. |
14-15 |
58-60 |
85-90 |
6-8 weeks |
|
Grapefruit, Fla. & Texas |
10-15 |
50-60 |
85-90 |
6-8 weeks |
|
Grapes, Vinifera |
-1 to -0.5 |
30-31 |
90-95 |
1-6 months |
|
Grapes, American |
-0.5-0 |
31-32 |
85 |
2-8 weeks |
|
Greens, leafy |
0 |
32 |
95-100 |
10-14 days |
|
Guavas |
5-10 |
41-50 |
90 |
2-3 weeks |
|
Haricot vert (fine beans) |
4-7 |
40-45 |
95 |
7-10 days |
|
Horseradish |
-1-0 |
30-32 |
98-100 |
10-12 months |
|
Jaboticaba |
13-15 |
55-60 |
90-95 |
2-3 days |
|
Jackfruit |
13 |
55 |
85-90 |
2-6 weeks |
|
Jaffa orange |
8-10 |
46-50 |
85-90 |
8-12 weeks |
|
Japanese eggplant |
8-12 |
46-54 |
90-95 |
1 week |
|
Jerusalem Artichoke |
-0.5-0 |
31-32 |
90-95 |
+5 months |
|
Jicama |
13-18 |
55-65 |
65-70 |
1-2 months |
|
Kale |
0 |
32 |
95-100 |
2-3 weeks |
|
Kiwano |
10-15 |
50-60 |
90 |
6 months |
|
Kiwifruit |
0 |
32 |
90-95 |
3-5 months |
|
Kohlrabi |
0 |
32 |
98-100 |
2-3 months |
|
Kumquats |
4 |
40 |
90-95 |
2-4 weeks |
|
Langsat |
11-14 |
52-58 |
85-90 |
2 weeks |
|
Leeks |
0 |
32 |
95-100 |
2-3 months |
|
Lemons |
10-13 |
50-55 |
85-90 |
1-6 months |
|
Lettuce |
0 |
32 |
98-100 |
2-3 weeks |
|
Limes |
9-10 |
48-50 |
85-90 |
6-8 weeks |
|
Lo bok |
0-1.5 |
32-35 |
95-100 |
24 months |
|
Loganberries |
-0.5-0 |
31-32 |
90-95 |
2-3 days |
|
Longan |
1.5 |
35 |
90-95 |
3-5 weeks |
|
Loquats |
0 |
32 |
90 |
3 weeks |
|
Lychees |
1.5 |
35 |
90-95 |
3-5 weeks |
|
Malanga |
7 |
45 |
70-80 |
3 months |
|
Mamey |
13-15 |
55-60 |
90-95 |
2-6 weeks |
|
Mangoes |
13 |
55 |
85-90 |
2-3 weeks |
|
Mangosteen |
13 |
55 |
85-90 |
2-4 weeks |
|
Melons: |
|||||
|
Casaba |
10 |
50 |
90-95 |
3 weeks |
|
Crenshaw |
7 |
45 |
90-95 |
2 weeks |
|
Honeydew |
7 |
45 |
90-95 |
3 weeks |
|
Persian |
7 |
45 |
90-95 |
2 weeks |
Mushrooms |
0 |
32 |
95 |
34 days |
|
Nectarines |
-0.5-0 |
31-32 |
90-95 |
2-4 weeks |
|
Okra |
7-10 |
45-50 |
90-95 |
7-10 days |
|
Olives, fresh |
5-10 |
41-50 |
85-90 |
+6 weeks |
|
Onions, green |
0 |
32 |
95-100 |
34 weeks |
|
Onions, dry |
0 |
32 |
65-70 |
1-8 months |
|
Onion sets |
0 |
32 |
65-70 |
6-8 months |
|
Oranges , Calif. & Ariz. |
3-9 |
38-48 |
85-90 |
3-8 weeks |
|
Oranges , Fla. & Texas |
0-1 |
32-34 |
85-90 |
8-12 weeks |
|
Papayas |
7-13 |
45-55 |
85-90 |
1-3 weeks |
|
Passionfruit |
7-10 |
45-50 |
85-90 |
3-5 weeks |
|
Parsley |
0 |
32 |
95-100 |
2-2.5 months |
|
Parsnips |
0 |
32 |
95-100 |
+6 months |
|
Peaches |
-0.5-0 |
31-32 |
90-95 |
2-4 weeks |
|
Pears |
-1.5 to -0.5 |
29-31 |
90-95 |
2-7 months |
|
Peas, green |
0 |
32 |
95-98 |
1-2 weeks |
|
Peas, southern |
4-5 |
40-41 |
95 |
6-8 days |
|
Pepino |
4 |
40 |
85-90 |
1 month |
|
Peppers, Chili (dry) |
0-10 |
32-50 |
60-70 |
6 months |
|
Peppers, sweet |
7-13 |
45-55 |
90-95 |
2-3 weeks |
|
Persimmons, Japanese |
-1 |
30 |
90 |
34 months |
|
Pineapples |
7-13 |
45-55 |
85-90 |
24 weeks |
|
Plantain |
13-14 |
55-58 |
90-95 |
1-5 weeks |
|
Plums and prunes |
-0.5-0 |
31-32 |
90-95 |
2-5 weeks |
|
Pomegranates |
5 |
41 |
90-95 |
2-3 months |
|
Potatoes, early crop |
10-16 |
50-60 |
90-95 |
10-14 days |
|
Potatoes, late crop |
4.5-13 |
40-55 |
90-95 |
5-10 months |
|
Pummelo |
7-9 |
45-48 |
85-90 |
12 weeks |
|
Pumpkins |
10-13 |
50-55 |
50-70 |
2-3 months |
|
Quinces |
-0.5-0 |
31-32 |
90 |
2-3 months |
|
Raddichio |
0-1 |
32-34 |
95-100 |
2-3 weeks |
|
Radishes, spring |
0 |
32 |
95-100 |
34 weeks |
|
Radishes, winter |
0 |
32 |
95-100 |
24 months |
|
Rambutan |
12 |
54 |
90-95 |
1-3 weeks |
|
Raspberries |
-0.5-0 |
31-32 |
90-95 |
2-3 days |
|
Rhubarb |
0 |
32 |
95-100 |
24 weeks |
|
Rutabagas |
0 |
32 |
98-100 |
+6 months |
|
Salsify |
0 |
32 |
95-98 |
2-4 months |
|
Santol |
7-9 |
45-48 |
85-90 |
3 weeks |
|
Sapodilla |
16-20 |
60-68 |
85-90 |
2-3 weeks |
|
Scorzonera |
0-1 |
32-34 |
95-98 |
6 months |
|
Seedless cucumbers |
10-13 |
50-55 |
85-90 |
10-14 days |
|
Snow peas |
0-1 |
32-34 |
90-95 |
1-2 weeks |
|
Soursop |
13 |
55 |
85-90 |
1-2 weeks |
|
Spinach |
0 |
32 |
95-100 |
10-14 days |
|
Squashes, summer |
5-10 |
41-50 |
95 |
1-2 weeks |
|
Squashes, winter |
10 |
50 |
50-70 |
2-3 months |
|
Strawberries |
0 |
32 |
90-95 |
5-7 days |
|
Sugar apples |
7 |
45 |
85-90 |
4 weeks |
|
Sweetpotatoes |
13-15 |
55-60 |
85-90 |
4-7 months |
|
Tamarillos |
3-4 |
37-40 |
85-95 |
10 weeks |
|
Tamarinds |
7 |
45 |
90-95 |
3-4 weeks |
|
Tangerines, mandarins, and related citrus fruits |
4 |
40 |
90-95 |
24 weeks |
|
Taro root |
7-10 |
45-50 |
85-90 |
4-5 months |
|
Tomatillos |
13-15 |
55-60 |
85-90 |
3 weeks |
|
Tomatoes, mature-green |
18-22 |
65-72 |
90-95 |
1-3 weeks |
|
Tomatoes, firm-ripe |
13-15 |
55-60 |
90-95 |
4-7 days |
|
Turnips |
0 |
32 |
95 |
4-5 months |
|
Turnip greens |
0 |
32 |
95-100 |
10-14 days |
|
Ugli fruit |
4 |
40 |
90-95 |
2-3 weeks |
|
Waterchestnuts |
0-2 |
32-36 |
98-100 |
1-2 months |
|
Watercress |
0 |
32 |
95-100 |
2-3 weeks |
|
Watermelons |
10-15 |
50-60 |
90 |
2-3 weeks |
|
White sapote |
19-21 |
67-70 |
85-90 |
2-3 weeks |
|
White asparagus |
0-2 |
32-36 |
95-100 |
2-3 weeks |
|
Winged bean |
10 |
50 |
90 |
4 weeks |
|
Yams |
16 |
61 |
70-80 |
6-7 months |
|
Yucca root |
0-5 |
32-41 |
85-90 |
1-2 months |
|
Source: McGregor, B.M. 1989. Tropical Products Transport Handbook. USDA Office of Transportation, Agricultural Handbook 668.
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