Table of content A-Z

 

dried fruit and vegetables

 

 

Drying is the oldest method of preserving food.

There are various ways for food to spoil, depending on its water content. A low water content favours the oxidation of fat, a medium water content favours non-enzymatic browning. With an increasing amount of water first the intrinsic enzyme activity of the fruit increases, which leads to the degradation of ingredients; this is followed by the growth of moulds, yeasts and bacteria.

One method of inhibiting spoilage is therefore dehydration. This largely stops the microbiological spoilage of the food and reduces enzymatic and non-enzymatic spoilage reactions. As plant foods are low in fat, there is no danger of fat oxidation.

Dehydration is accompanied by a loss of weight, and this makes it possible to transport more products in the same amount of space.

1) Dried fruit

Fruits that are dried include apples, pears, apricots, peaches, plums, grapes (currants, sultanas, raisins), pineapple, figs, dates, bananas and mangos. Dried cranberries, sour cherries and wild fruits and berries can also be found.

The basic raw material for dried fruit is healthy, whole fruits. They are prepared in the typical manner: e.g. apples are peeled, cored and cut into rings; plums are only pitted. The drying itself takes place in the countries of origin in the sun or with hot air, and the length of time for drying varies with the type of fruit.

Unfortunately, quality is also lost in with the drying process. According to the kind of fruit there may be changes in texture and flavour, as well as loss of aroma and active substances. However, in the processes employed and with an exact, controlled temperature geared to the given product it is attempted to limit these losses as far as possible.
To protect already dried fruits from changes in colour that take place later (through reactions with oxygen apples, apricots, etc. turn brown), they are treated with sulphur dioxide or sulphites. This must be declared on the package label if there is at least 10 mg/kg dried fruit, because some people are allergic to these substances (the terms ‘sulphurized’ or ‘sulphur dioxide’ or E220, and for sulphites E221–E227 appear in the list of ingredients). Sorbic acid may also be added to some kinds of fruit to improve their shelf life; this appears in the list of ingredients as E200.


To keep the fruits from sticking together, so-called surface treatment products may also be used. These are waxes or oil. The latter increases the fat content of the fruits considerably.

Ingredients

Dried fruits contain only about 14–24% water. The other ingredients are largely the same as they were in the fresh fruit. Therefore, the sugar content is greater compared with that in fresh fruit, and the energy density (kcal per 100 g or per fruit) is higher. The fibre content is also high. However, the heat required for crisp drying and the length of storage deplete the vitamin content.

100 g contain:

 

Apple, fresh

Apple, dried

Apricot, fresh

Apricot, dried

Banana, fresh

Banana, dried

Date, fresh

Date, dried

Energy (kcal)

52

248

43

240

88

326

114

176

Water (g)

85

26.7

86.3

17

73.9

7.6

n.a.*

20.2

Protein (g)

<1

1.4

0.9

5

1.2

4.4

1

1.9

Fat (g)

<1

1.7

0

n.a.*

0.2

0.8

n.a.*

0.5

Carbohydrates (g)

11

55.4

8.5

47.9

20

75.2

27

65.1

Fibre (g)

2

11.2

1.5

17.3

1.8

12

3

8.7

Vitamin C (mg)

12

12

10

12

11

7

58

3

Vitamin A (RE) (µg)

8

32

136

5800

5

13

2

25

Folic acid (µg)

7

21

4

5

20

49

21

21

Potassium (mg)

144

541

280

1370

382

1477

350

650

Sodium (mg)

3

16

2

11

1

4

6

35

Calcium (mg)

7

38

17

82

8

32

21

63

Magnesium (mg)

6

32

9

50

32

n.a.*

21

50

Iron (mg)

0.5

1.2

0.6

4.4

0.3

2.8

0.8

1.9

n.a.* = no data available

Shelf life and storage

The shelf life of dried fruits varies with the storage conditions. Unopened packages can usually be stored for 6 or 12 months, but in some cases for up to 2 years. Opened packages should be reclosed as airtight as possible. The fruits should also be protected from moisture, light and heat.


Moisture, including that absorbed from the surrounding air, shortens the shelf life, as it provides the basis of existence for micro-organisms. Light facilitates changes in colour and aroma caused by the food itself, i.e. through the enzymes it contains and through reactions by the substances in it. Heat and fresh air cause the fruit to dry out, which makes it brittle and robs it of flavour.

Use and practical tips

Its sweetness, long shelf life and moistness make dried fruit a versatile food. It is a good component of muesli and an ingredient in sweetened breads, sauces and dips. It is also a popular snack for between meals. But watch out: It contains quite a lot of calories and should be eaten only in moderation. The high energy and nutrient density are advantageous if one wants to fortify oneself following a longer period of physical stress (e.g. hiking). The mass of fibre stimulates digestion, frequently in combination with flatulence. Sensitive people should therefore mostly do without dried fruits. However, the flatulent effect often wears off, the more the digestive tract becomes used to dried fruit, because the intestinal flora adapt to it.

2) Dried vegetables

Synonyms: dehydrated vegetables, freeze-dried vegetables

Dried vegetables are used mostly to prepare ready-made meals and instant products, less often for direct human consumption.


In the shops consumers can buy dried legumes/pulses above all, but also dried tomatoes and mushrooms, for instance, which are soaked in water again prior to being eaten. Freeze-dried herbs and potato products also count as dried vegetables, however.

Prior to being dried, vegetables are prepared according to the variety and, in contrast to fruits, blanched. The drying takes place by the effect of indirect heat, by freeze-drying (see below), or by vacuum freeze-drying (see below). With the conventional method a water content of 4–18% is aimed for; following freeze-drying only 4% moisture may remain in the food. With freeze- or vacuum-freeze drying the deep-frozen vegetables are dried at continuing low temperatures and under vacuum, i.e. reduced pressure. The water that has frozen to ice is thus vaporized directly, without an intermediate step in the liquid state. This is known as sublimation.


This process is gentler for the ingredients. Changes in colour and aroma, as well as the loss of vitamins, are largely avoided. The texture is also better preserved. The disadvantage to this process, however, is that it requires a considerable use of energy and is therefore comparatively expensive. Primarily herbs and instant coffee are preserved by freeze-drying, but also carrots, cauliflower and peas. The process is not suited for some types of vegetables. The important thing is that the subsequent packaging of the products is moisture-proof.

Ingredients

To ensure a good microbial shelf life, the remaining moisture, i.e. the water content in dried vegetables, may not be more than 8%. There are some products with up to 15% water, however.


Drying increases the energy and nutrition densities; this means that 100 g of dried vegetables contain more calories, protein and minerals, and, depending on the type of process used for drying, more vitamins than fresh vegetables.


With freeze-dried vegetables the shape, colour, vitamin content and flavour are to a great extent the same as they were in the fresh state. As with fruits, there is less degradation of the valuable ingredients through drying with heat. Also like fruits, dried vegetables can be treated with sulphur compounds to prevent enzymatic browning and must be labelled accordingly.

100 g contain:

 

Carrot, raw

Carrot, dried

Onion, raw

Onion, dried

Chanterelle, raw

Chanterelle, dried

Boletus mushroom, raw

Boletus mushroom, dried

Energy (kcal)

25

194

27

198

15

126

21

124

Water (g)

86.2

9.4

88

10.8

91.5

10

88.6

11.6

Protein (g)

1

6.8

1.2

10.8

2.4

24.7

5.4

29.5

Fat (g)

0.2

1.5

0.3

0.9

0.5

2.2

0.4

3.2

Carbohydrates (g)

4.8

36.8

4.9

35.3

0.2

1.8

0.53

4.11

Fibre (g)

3.6

38

1.8

36.5

4.7

46.5

6.02

55.3

Vitamin C (mg)

7

19

10

42

6

2

2.5

n.a.*

Vitamin A (RE) (µg)

1700

16 000

1

43

217

n.a.*

n.a.*

n.a.*

Folic acid (µg)

12

n.a.*

n.a.*

n.a.*

n.a.*

n.a.*

n.a.*

n.a.*

Potassium (mg)

320

2640

162

1040

367

5370

327

2000

Sodium (mg)

60

495

3

105

3

32

6

14

Calcium (mg)

41

25

31

31

4

85

42

34

Magnesium (mg)

17

n.a.*

11

11

14

n.a.*

12

n.a.*

Iron (mg)

0.4

4.7

0.3

3.3

6.5

17.2

1

8.4

*n.a. = no data available

Shelf life and storage

Dried vegetables can be stored for up to several years in a cool, dark, dry and well-ventilated place

 

 


 

  With the website www.the-green-pantry.com the Fritz Terfloth Foundation of Münster offers consumers independent and competent information about plant foods and their health effects. All texts are subject to German copyright law. Information about the conditions for use of the texts by third parties can be found here.


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