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Journal of Food and Nutrition Sciences
2014; 2(4): 105-109
Published online June 20, 2014 (http://www.sciencepublishinggroup.com/j/jfns)
doi: 10.11648/j.jfns.20140204.12
Dried fruits – brief characteristics of their nutritional
values. Author’s own data for dietary fibers content
Gyurova, Desislava Krasteva
1
, Enikova, Rositsa Kirilova
2
1
Department “Organic Analysis”, National Center of Public Health and Analysis, 1431 Sofia, Bulgaria
2
Department “Microbiological Analysis”, National Center of Public Health and Analysis, 1431 Sofia, Bulgaria
Email address:
d.k.gyurova@gmail.com (Gyurova D. K.), r.enikova@abv.bg (Enikova R. K.)
To cite this article:
Gyurova, Desislava Krasteva, Enikova, Rositsa Kirilova. Dried Fruits – Brief Characteristics of their Nutritional Values. Author’s Own
Data for Dietary Fibers Content. Journal of Food and Nutrition Sciences. Vol. 2, No. 4, 2014, pp. 105-109.
doi: 10.11648/j.jfns.20140204.12
Abstract:
A review of nutritional and dietetic properties of dried fruits, such as natural and concentrated sources of sugars,
vitamins A, C, niacin, riboflavin and folate, potassium and trace elements of iron and copper, and of organic acids,
phytonutrients with antioxidant properties was made. Many important properties of dry fruits have a low glycemic index and
the content of dietary fiber, including insoluble fiber. The results of insoluble dietary fiber content by enzymatic-gravimetric
method AOAC 991.42 of 18 kinds of different varieties Bulgarian dried fruits were shown. The highest content of fiber was
found in hips (40%), followed by dried quinces, pears, chokeberries, dried apples, and plums (from about 13% to over 23%).
A lower content of insoluble fiber in different varieties of cherries and sour cherries is established. The data are important for
a healthy nutrition of Bulgarian population, but also for a diet-therapeutic practice, and problems related to motility of the
gastrointestinal system, anemia, and atherosclerosis, cardiovascular and metabolic diseases.
Keywords:
Dried Fruits, Insoluble Fibers, Glycemic Index
1. Introduction
Drying is the oldest and most reliable method for storing
food and preserving its properties. Drying does not destroy
the nutritional properties, as fibers, carbohydrates, minerals
and vitamin A, are stable at dehydration. Dehydration, in its
capacity of a basic method for fruit, vegetable and meat
processing, has been used in household conditions since
ancient times, while in industrial conditions it was
implemented in the middle of the 19
th
century. Drying
methods [9] depend on the product type. Currently basic
techniques are known – convective, pulverization (contact),
drum (rotational), and lyophilization technique [1].
Drying is a very old traditional method for fruit and
vegetable preservation. Most frequently dried fruits are
apples, pears, apricots, grapes, plums, cherries, hips and
occasionally – peaches and quinces. Numerous European
populations have centuries-long traditions of using dried
fruits, vegetables and herbs in traditional home diet,
implementing mostly the natural convective method [7].
This method is particularly popular on the Balkans where
there are beneficial climatic conditions for cultivation of
various fruit varieties.
Fresh fruits and vegetables are perishable. They contain
significant amounts of water that is a favorable medium for
development of microorganisms and for the progress of
certain biochemical processes affected by various enzymes
(ferments). Thus the products perish quickly. In order to
achieve their stability the water contained in them should be
reduced to a certain minimum limit. For dried fruits this
value should be from 18 to 23% and for vegetables – from 8
to 12%. The elimination of a substantial portion of water
allows the fruits and vegetables to decrease their volume and
weight and transform into a “concentrated product”, thus
enabling their storage in ordinary conditions.
Fruits and vegetables are dried whole or sliced depending
on their size. Plums, cherries, morello cherries, blueberries,
blackcurrants, figs, peppers, parsley and celery leaves are
dried whole. Apples, pears, quinces, peaches, apricots,
carrots, onions, carrots, celery roots and leafy herbs are dried
sliced. Before drying they have to be washed thoroughly and
rough tissues, stones, skins, and seeds should be discharged.
The extent of drying is also important for the good
qualities of dried fruits and vegetables. Overdried fruits
containing lower water percentage rate are hard and cannot
be eaten unless boiled; underdried ones with more humidity
106 Gyurova, Desislava Krasteva and Enikova, Rositsa Kirilova: Dried Fruits – Brief Characteristics of their Nutritional
Values. Author’s Own Data for Dietary Fibers Content
perish quickly.
The convective drying method [2] can be implemented in
domestic and semi-industrial conditions – drying in the sun
or in an oven at temperature not exceeding 55 – 60ºC in
order to preserve the best biological and nutritional
properties as well as the plant pigments of the fruits and
vegetables. Rotational or drum drying is implemented in
industry where the mashed fruits and vegetables are spread
on a heated rotating drum. They lose humidity in seconds
and are scrubbed with a proper knife in the form of flakes.
This is the way to produce potato [23] and maize dehydrated
squash, mash and cornflakes. The pulverization contact
thermal drying is applied for the production of products that
are more sensitive to high temperatures such as powdered
milk and eggs. This technique is also appropriate for drying
fruit and vegetable juices.
The lyophilization process is the most expensive method.
This technique consists of pre-freezing of the products to
-38ºC and releasing the liquid phase by vacuum sublimation.
This is the best currently implemented drying technique.
Dried fruits are among the healthiest dietary alternatives
of foods containing refined sugar (sweets, candies, jams,
fruit preserves) and are an excellent means to satisfy the
desire to eat sweet things. Moderate fruit consumption is an
excellent way to supply the necessary sugars and vitamins to
the organism. Many manufacturers input fructose, naturally
present in fruits, to sweeten their products.
While the fruit itself is very rich in natural sugars, many
dried fruits [15] are additionally saccharified for taste
modeling. Such products should rather be called “candies”
and should be avoided in healthy diets. Some examples for
additionally sugar coated dried fruits that should be avoided
are listed below:
Pineapple: Usually coated with refined saccharose;
Banana chips: Usually fried and sweetened. It is
recommended to consume dried bananas without
added sugar.
Blueberry: Added sweeteners are almost always
applied due to the acerbity of the fruit.
Plums: Usually the fruits are dipped in concentrated
saccharose solution to improve the sour taste before
drying.
Watermelon: The combination of low content of
nutrients and high sugar content is not beneficial.
Dried fruits can be purchased in bulk at most shops for
healthy foods and/or pre-packed at customary food shops. It
is necessary to check always the list of ingredients for added
sugar or input food additives [15]. A list of traditionally
consumed dried fruits by the Bulgarian population is
presented below:
1. Apple. Apples are a marvelous source of fibers and
contain many phytonutrients (natural plant components
with nutritional value) with antioxidant effect.
2. Apricot. Drying is the healthiest way to preserve and
have apricots available for consumption during all
seasons. Dried apricots are a good source of fibers,
vitamins A and C, as well as iron.
3. Cherry. Cherries are called “the new antioxidant
superfruit”. Compared to other fruits they have
substantially greater content of antioxidants as well as
of important nutrients, such as beta-carotenes, folic
acid and fibers.
4. Raisins. Raisins are often called “nature’s candy”.
They contain low amounts of sodium and many fibers.
5. Plum. Dried plums are called prunes. Prunes are an
excellent source of vitamins and contribute
substantially to regulation of assimilation functions.
6. Pear. Pears are a good source of vitamin C and copper
and are rich in dietary fibers.
7. Proper drying depends on temperature [22], low air
humidity and good air circulation. Similarly to all
preservation methods drying cause certain loss of some
nutrients [19]. The nutrient changes occurring in the
drying process involve:
Energy content: it is not altered but is concentrated in
smaller mass/volume as the humidity is eliminated.
Fibers: not changed.
Vitamin A: vitamin A levels are preserved very well at
implementing controlled thermal methods.
Vitamin C: pre-treatment with ascorbic acid [18] or lemon
juice elevates vitamin C levels although certain losses are to
be expected during drying.
Thiamin, riboflavin, niacin: their levels are relatively well
preserved.
Minerals: their levels are relatively well preserved.
The best method to preserve the nutrients in dried foods
[20] is to store the foods in a cool, dark and dry place and to
consume them within one year.
Dried fruits are a very rich source of minerals and nuts are
also rich in proteins. They have numerous healing properties
because of the sufficient amount of nutrient components.
Each dietologist recommends “a handful” of dried fruits in
the diet with a view to healthy nutrition. Among the ten top
health benefits [21] of dried fruits consumption are the
following items:
-
Pistachio, almonds and raisins are referred to as very
effective in controlling cholesterol blood levels and
blood circulation stimulation.
-
Raisins and dates are recommended to individuals with
anemia as they help in weight gaining and supply
vitamins and minerals to the organism.
-
Dried fruits are very adequate for treatment of
cardiovascular problems.
-
Almonds help in reducing the chronic coronary heart
risk, affect favorably blood hemoglobin levels as well
as support the hemopoiesis.
-
Dates are very beneficial for cardiac health and prevent
atherosclerosis, which is one of the causes for stroke
and myocardial infarction.
-
Prunes are a good source of potassium, vitamin A,
fibers and copper and support high energy levels in the
organism during the whole day.
In fact, dried fruits consumption supplies an immediate
energy surge and causes improvement of the memory.
Journal of Food and Nutrition Sciences 2014; 2(4): 105-109 107
As a whole, fresh fruits are healthy foods, good sources of
vitamins, minerals, phytonutrients and dietary fibers. Fruits
cultivated in gardens and farms are in most cases greater in
size, sweeter and contain less dietary fibers compared to
their “wild” analogues. According to Dr. Cordein dried fruits
contain significantly more sugar than fresh ones. Some
exceptions are avocado, lemons and limes that have low
sugar content [16] and their consumption should not be
restricted.
The majority of dried fruits preserves the nutrition value
of the fresh ones and, together with them is included in the
USA dietary guidelines [14] and the recommendations of the
international health agencies. In principle, all dried fruits
supply the main nutrients and a set of preventive bioactive
ingredients that makes them valuable resources for
improving food quality and reducing the risk for chronic
diseases. The combination of nutritional value and pleasant
taste has been a real prerequisite for dried fruits popularity
and approval as healthy food for millenniums. They are
naturally resistant to decay easy-to-store and transport and
require relatively small expenditures.
1.1. Nutritional Facts
The main nutritional facts for them reveal:
1. Dried fruits, like fresh ones, have very low sodium
content;
2. They are a source of dietary fibers and potassium;
3. Traditional dried fruits do not contain added sugar [13].
The sugar in them is in the form of glucose and
fructose;
4. The drying process eliminates some of the water in the
fruits, thus their natural sugars are concentrated [11].
That is why the total sugar content as well as the energy
value is similar to those in fresh fruits but is in higher
concentrations.
Traditional dried fruits have a low glycemic index (GI),
which expresses the food impact on sugar blood levels in the
organism.The value of GI reflects the capacity of the
organism to assimilate carbohydrate foods (usually 50 g of
available carbohydrates0 compared to the individual´s
response to the same amount of carbohydrates, supplied by
white bread or glucose. The foods are classified as
high-carbohydrate (GI>70), moderate-carbohydrate (GI
56-69), or low- carbohydrate (GI0-55) [12].
Table 1 presents GI values as listed by [12]. Foods with
high fiber content usually have low GI. Nevertheless it is
considered that other factors also contribute to the glycemic
response of the organism, namely: viscous texture of dried
fruits (especially when chewed); their food matrix; available
phenols and organic acids as well as the type of contained
sugar (approximately 50% of fructose in traditional dried
fruits) [27]. Dietary fibers [24] are found only in plant foods
like fruits, vegetables, cereals and pulses. Two fiber types are
distinguished – soluble and insoluble. Soluble fibers are
dissolved in water and insoluble ones cannot be dissolved in
water. Both types are important for health in different aspects.
Cellulose, lignin, and the other hemicellulose compounds
belong to the group of insoluble fibers. Skins and peels of
fruits and vegetables are good sources of insoluble fibers.
Most foods contain a mixture of soluble and insoluble fibers.
Many fruit types are rich in insoluble fibers [1]. They
contain soluble and insoluble fibers although in some
species the levels of insoluble fibers are higher. Insoluble
fibers are an important part of human diet [4]. They are
essential for stimulation of the gastrointestinal motility,
regulation and acceleration of the intestinal passage and
evacuation of intestinal content, and for reducing obstipation
risk [5]. Dried fruits are an adequate source for intake of
insoluble fibers. Thus, for example, 100g of raisins contain
more than 3g of total fibers of which more than 70% (2.2 g)
are insoluble. The same portion of prunes contains more
than 8g of total fibers with some 50% of them insoluble.
Traditionally the Bulgarian population consumes large
amounts of dried fruits, especially in winter. A popular
practice is to dry plums, apricots, apples, pears, cherries,
morello cherries, hips, quinces and other fruits at home and
in industrial conditions.
This fact determined the AIM of this study: to present the
content of insoluble dietary fibers in some typical Bulgarian
dried fruits, widely consumed by the population and to
inform consumers, nutritionists and dietologists about their
content with a view to compiling adequate diets and
determination of nutritional benefits.
Table 1. Glycemic index of various dried fruits
Type of dried foods Glycemic index
Dates 62
Dried apples 29
Dried apricots 30
Dried peaches 35
Prunes 29
Figs 61
Raisins 54
2. Material and Methods
The study was conducted in the period 2010-2012.
Eighteen market samples of Bulgarian dried fruits consumed
by the Bulgarian population were analyzed for content of
insoluble fibers by enzymatic-gravimetric АОАС method
991.42. Three parallel samples of each fruit were analyzed.
In the end of 2010 three samples from one and the same
lots of dried fruits produced by a single manufacturer were
selected and delivered to the laboratory:
- Dried white cherries I,
- Dried black cherries I,
- Dried pears I,
- Dried hips I and
- Dried chokeberry I.
In mid-2011 the same approach was applied for the
selection of identical samples of the same fruits from other
lots of the same manufacturer:
- Dried white cherries II,
- Dried black cherries II,
- Dried pears II,
108 Gyurova, Desislava Krasteva and Enikova, Rositsa Kirilova: Dried Fruits – Brief Characteristics of their Nutritional
Values. Author’s Own Data for Dietary Fibers Content
- Dried hips II and
- Dried chokeberry II.
The remaining samples were purchased from the same
manufacturer who modified the assortment of his production
and placed new types of dried fruits on the market, and the
samples were also analyzed.
The samples were analyzed for content of insoluble fibers
by the enzymatic-gravimetric method 991.42 immediately
after the preparation of the analytical sample at the
laboratory. Three parallel samples for each fruit were
analyzed. The differences in the values for insoluble fibers
are discussed below.
3. Results and Discussion
Table 2 presents the results of the tests for insoluble fibers
content in dried fruits with listed standard uncertainty of the
implemented method. Those data would be particularly
important to evaluate the real intake of dietary fibers.
In principle dried fruits are very rich natural concentrates
– sources of dietary fibers. Dried hips rank first and we could
outline pears, quinces, followed by chokeberries and apples
among the species with wider implementation in the diet.
The amount of insoluble fibers in drupes – cherries,
morello cherries - was lower. Plums presented much greater
differences, due obviously to multiple varieties.
Differences were observed in the values of insoluble
fibers also in the differing between themselves types of
white, black cherries, hips, pears and chokeberries when
comparing the evidence for the different lots of analogous
fruits harvested in two different years - 2010 and 2011. The
most possible differences in the content of insoluble fibers
could be explained by a complex of causes, such as fruit
ripeness, cultivation and farming conditions, and climatic
conditions; and last but not least – variety differences of the
analyzed fruits.
Table 2. Content of insoluble fibers in dried fruits
Number Tested samples Content of insoluble fibers, % ± SU* (АОАС 991.42)
1 Dried white cherries I 5,02 ± 0,13
2 Dried white cherries II 3,50 ± 0,09
3 Dried black cherries I 3,94 ± 0,10
4 Dried black cherries II 4,70 ± 0,12
5 Dried pears I 23,30 ± 0,59
6 Dried pears II 16,10 ± 0,41
7 Dried hips I 49,20 ± 1,24
8 Dried hips II 44,50 ± 1,12
9 Dried quinces 22,80 ± 0,57
10 Dried mix-white cherries, apples and pears 9,50 ± 0,24
11 Dried mix-black cherries, apples and prunes 8,90 ± 0,22
12 Dried morello cherries 6,90 ± 0,17
13 Prunes 8,60 ± 0,22
14 Ground prunes 13,86 ± 0,35
15 Dried apples 14,50 ± 0,37
16 Dried chokeberries I 17,70 ± 0,45
17 Dried chokeberries II 23,84 ± 0,61
18 Dried chokeberries powder 22,96 ± 0,58
* SU – standard uncertainty
The content of insoluble fibers presented in Table 2 was
provided by the enzymatic-gravimetric AOAC method
991.42 [3]. The gravimetric method [17] for insoluble fibers
(such as cellulose) used in compiling the Bulgarian Food
Composition Tables [26] obviously lists substantially lower
values for the fibers in some analogous fruit types,
respectively:
- For dried hips – 2,9 %
- For dried pears – 5,5 %
- For prunes – 1,5 %.
According to the Danish Food Composition Database
using the enzymatic-gravimetric method, the content of
fibers in prunes is 7,6%; in dried apples – 8,7% and in dried
hips – 43,0% [6]. According to the Norwegian Tables [25]
the rate of dietary fibers in dried apples is 9,5 %.
The publications of Russian researchers and scientists
reported insoluble fibers amounts (such as cellulose) in
prunes in the range 9 - 30% [8], in dried apples - 48%, and in
dried pears - approximately 20 % [10]. The principle of the
implemented analytical method for determination of
insoluble fibers was not reported.
Doubtlessly the differences in the values of insoluble
fibers could be explained, together with intervariety
differences of the tested fruits, with the principle of the
implemented analytical method. In the particular food
composition databases the application of the
enzymatic-gravimetric method leads to similar results.
According to WHO recommendations the consumption of
dietary fibers should be not less than 25 g daily. The
dietologists recommend a daily intake of 30 to 50 g of
dietary fibers. This is the optimal amount that does not harm
the organism and the beneficial effect is perceived very
quickly.
Certain other dried fruits are also a good source of
insoluble fibers – raisins, dried apricots, figs, etc., thus
presenting a challenge for further comprehensive scientific
research.
Journal of Food and Nutrition Sciences 2014; 2(4): 105-109 109
4. Conclusion
Dried fruits of Bulgarian origin are a significant source of
insoluble dietary fibers. Hips, quinces, prunes, apples, pears
and chokeberry (recently introduced and cultivated in Bulgaria)
are the fruits that are the richest in this fibers type and are
reasonably consumed by the population, especially in winter.
The implementation of the current enzymatic-gravimetric
method enables the more objective determination of the
content of insoluble dietary fibers like cellulose,
hemicelluloses and lignin in dried fruits. This outlines the
necessity of revising and completing the Bulgarian Food
Composition Tables with more precise recent data for that
type of products, adequate and necessary for the targets of
dietetic therapy practice.
The improvement of the information for the specialists in
dietetics and the goals of the policy focused on healthy
nutrition require more comprehensive survey on the content
of fibers in dried fruits and vegetables belonging to varieties
cultivated in our geographic region.
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