What temperature should fresh vegetables be stored and transported at?

Once fruits and vegetables are harvested, they continue to ripen and their freshness and value decreases as time goes by. Proper storage and transport packaging conditions such as temperature and humidity, will lengthen storage life and maintain quality of fruits & vegetables. 10%-40% of fresh fruit and vegetable shipments are lost due to improper storage and handling!

Fresh fruits and vegetables need low temperatures (0 to 12°C) 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.

Fresh Fruit apple

What is Relative Humidity and how does it affect produce?

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 saleable weight, appearance, nutritional quality and flavour, and wilting, softening and juiciness are reduced. Leafy vegetables with high surface-to-volume ratios; like lettuce; and immature fruits and vegetables have higher transpiration rates. External factors affecting transpiration rates are temperature, relative humidity, air velocity and atmospheric pressure. So it’s best to keep fresh fruit and vegetables in low temperatures between 0-12°C with high humidity and to minimise air movement during storage.

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. Using a humidifier in the storage area.
  2. Keeping air movement and ventilation to a minimum in the storage room – keep doors shut as much as possible
  3. Keeping refrigeration temperature consistent within 3°C.
  4. Using moisture barriers in the insulation of the storage room or transport vehicle, and using plastic liners in the packing containers.
  5. Wetting the storage room floor.
  6. Using ice packs to pack produce for shipment.
  7. Sprinkling leafy vegetables, cool-season root vegetables, and immature fruits and vegetables with water.

Fresh Fruit picture

Temperature

Lower storage temperatures slow respiration rates and the ripening processes, which prolongs the life of fruits and vegetables.  The table below contains a list of fruits and vegetables classified by respiration rates. Producers & distributors 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.

Table 1. Fruits and vegetables classified by their respiration rates (at 5°C).

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

 

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 (0 to 2°C), and warm-season crops should be stored at warmer temperatures (8 to 12°C). There are exceptions to this rule, though. Table 2 lists optimum storage temperatures for commonly grown fruits and vegetables.

Temperatures that are too low can be just as damaging as those too high. Freezing will occur in all commodities below 0°C. Some vegetables and fruits can be frozen and thawed with minimal damage, while others are ruined by one freezing. Table 2 shows the highest freezing point for most fruits and vegetables.

Table 2. 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 (°C)

Rel. humidity (percent)

Approximate
storage life

Freezing point (°C)

FRUITS

Apples

1–4

90–95

1–12 months

-1.6

Apricots

0–1

90–95

1–3 weeks

-1.1

Berries

– Raspberries

0–1

90–95

2–3 days

-1.1

– Strawberries

0

90–95

3–7 days

-1

Cherries

0–1

90–95

2–3 weeks

-1.7

Grapes

0–1

85

2–8 weeks

-1.2

Nectarines

0–1

90–95

2–4 weeks

-0.8

Peaches

0–1

90–95

2–4 weeks

-0.8

Pears

-1-1

90–95

2–7 months

-1.5

Plums

0–1

90–95

2–5 weeks

-0.8

VEGETABLES

Asparagus

0-2

95–100

2–3 weeks

-0.6

Beans green or snap

4–7

95

7–10 days

-0.7

Broccoli

0

95–100

10–14 days

-0.6

Brussels, sprouts

0

95–100

3–5 weeks

-0.8

Cabbage, early

0

98–100

3–6 weeks

-0.8

Cabbage, late

0

98–100

5–6 months

-0.8

Carrots, mature

0

98–100

7–9 months

-1.3

Carrots, immature

0

98–100

4–6 weeks

-1.3

Cauliflower

0

95–98

3–4 weeks

-0.7

Celery

0

98–100

2–3 months

-0.5

Corn, sweet

0

95–98

5–8 days

-0.6

Cucumbers

10–12

95

10–14 days

-0.5

Lettuce

0

98–100

2–3 weeks

-0.1

Rockmelon

0–2

95

5–14 days

-1.1

Honey Dew Melon

7

90–95

3 weeks

-0.9

Watermelon

10-15

90

2–3 weeks

-0.3

Mushrooms

0

95

3–4 days

-0.8

Onions, green

0

95–100

3–4 weeks

-0.8

Peas, green

0

95–98

1–2 weeks

-0.6

Peppers, sweet

7-12

90–95

2–3 weeks

-0.7

Radishes, spring

0

95–100

3–4 weeks

-0.7

Spinach

0

95–100

10–14 days

-0.2

Tomatoes mature—green

12-20

90–95

1–3 weeks

-0.5

Tomatoes firm—ripe

12-20

90–95

4–7 days

-0.5

 

 

Frozen Raspberries

Freezing 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. Some fruits & vegetables that are very susceptible to freezing injury: Apricots, asparagus, snap beans, berries, cucumbers, eggplant, lettuce, peaches, plums, potatoes, tomatoes. For more information see https://extension.umaine.edu/publications/4135e/

Chilling Injury
Fruits and vegetables that require warmer storage temperatures (4 to 12°C) can be damaged if they are subjected to near freezing temperatures (0°C). 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.  Some fruits & vegetables that are very susceptible to chilling injury are: cucumbers, Honey Dew Melons, Watermelons, Eggplants, pumpkins, sweet potatoes, tomatoes, capsicum. For more information see https://extension.umaine.edu/publications/4135e/

 

Thermogard for fresh food delivery

Keep your produce chilled during transit
The proper use of Thermogard Ice Packs can keep your fresh produce chilled and in top quality during transport. Thermogard is widely used by grocery delivery and fresh produce companies that deliver their products direct to their customer’s homes. Thermogard packs are easy to use and won’t leak like bagged ice or other products so your customers won’t end up with soggy produce. If packaging a variety of fruits and vegetables into a package we recommend putting fruits and vegetables that are least likely to be damaged by chilling injury closest to the Thermogard Packs. A layer of cardboard can use used between the Thermogard packs and produce if necessary. Thermogard Ice Packs hold a more constant temperature than bagged ice does and it stays frozen for approximately twice as long as ice. Request a free sample pack of Thermogard now >

 

Thermogard Ice Blankets

Thermogard Ice Blankets
Ice blankets are a great way to keep pallets or crates of produce chilled inbetween the chiller and shop shelf or while waiting to be packed. There are a range of sizes available to suit the size of your pallets or crates and they can be refrozen & reused many times. Find out more about Ice Blankets click here >

 

References:

 https://extension.umaine.edu/publications/4135e/

http://www.foodstandards.govt.nz/consumer/safety/faqsafety/pages/foodsafetyfactsheets/charitiesandcommunityorganisationsfactsheets/transportingfoodmay21480.aspx


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