For centuries, the date (Phoenix dactylifera L.) has been
an important crop in the desert regions of Arabian countries and has formed
the basis of survival for many ancient nomads, this continues to be true
today (Mohammed et al., 1983). It is extremely useful in controlling
desertification by creating a microclimate which prevents long-term degradation
of ecologically weak environments (Rhouma, 1995). At present, 2000 or
more different cultivars of date palm are known to exist all over the
world, but only a few important ones have been evaluated for their agronomic
performance and fruit quality (Al-Hooti et al., 1997). Rygg (1975)
gave a detailed description of the date-growing regions of the world,
varieties and general cultural practices. On the other hand fruits exploitation
of date palm trees represents an important economical support for indigenous
populations (Reynes et al., 1994).
Actually, the mean yield of date production is important as it varies
between 18 and 50 kg of dates per tree. Tunisia is considered to be one
of the date-producing countries; the number of date trees is estimated
to be over 4 million and around 100,000 tons of dates are produced annually.
The fruit of the date palm is composed of a fleshy pericarp and seed.
Considering the food importance of the flesh date fruit, numerous studies
have been reported on the characterization of it chemical composition
particularly, polysaccharides, minerals, carbohydrates and Vitamins identification
(Al-Shahib and Marshal, 2002; Al-Hooti et al., 1995; Fayadah and
Al-Showiman, 1990; Sawaya et al., 1983; Vandercook et al.,
1980; Youssef et al., 1982). The date is a one-seeded fruit, usually
oblong. It has been the staple food and chief source of wealth in the
irrigable desert from ancient times. Dates are rich in certain nutrients
and provide a good source of rapid energy due to their high carbohydrate
content (70-80%). Most of the carbohydrates in dates are in the form of
fructose and glucose, which are easily absorbed by the human body (Al-Farsi
et al., 2005; Myhara et al., 1999). According to Sawaya
et al. (1983), the moisture, total nitrogen, fat, fiber, ash,
tannins, vitamin C, β-carotene and ten nutritionally important minerals
were highest in the early stages of development and decreased during maturation.
Date fruit, being exceptionally rich in potassium and extremely low in
sodium, is a desirable food for hypertensive persons who are advised to
consume low sodium diets. Increase in date fruit production will, therefore,
play an extremely significant role in worldwide improvement of the nutritional
status of people, with special reference to calories and important minerals
(Ahmed et al., 1995).
Although the date is a popular human food, very little is known about
the chemical composition (minerals, carbohydrates) and the moisture of
fruit date in Tunisia. Therefore, the objective of this study was to analyze
various physicochemical characteristics of ten extensively grown littoral
cultivars obtained from Gabes oases during the 2003-2004 crop year that
would be used for subsequent processing. The chemical composition of date
fruits from these cultivars was compared to the one of Deglet Nour, grown
in the continental Oases and the most exploited and commercial culivar
MATERIALS AND METHODS
Plant material: Ten Tunisian date varieties were used in the setting of this work.
Samples were collected at maturity stage Tamar at the end of 2003-2004
cropping year. Ten feet of each cultivar were used for all analysis. The
Deglet Nour variety, the most exploited in Tunisia, was taken as reference
for all analysis.
Water content: The water content was determined by desiccation of 2 g of pulp.
The sample, weighed is spread out in a tared stainless capsule and then
dried at a temperature of 70°C for 48 h. These conditions permit to
avoid the sugars caramelization.
Chemical analysis Sugar contents: Sugars were extracted from 3 g of broyat by a 100 mL ethanol solution
(ethanol 80 mL and water 20 mL). Surnagent was analyzed by HPLC, using
a chromatograph of the type Knauer model Wellchrom. The separation was
carried out on a Eurospher column 100°C 18, 17 μm, 250x4.6 mm.
Sugar quantifications were made, by comparison to the standards sugars
(external standard method). These standards (fructose, gluctose and saccharose)
were mixed to obtain a synthetic solution of 10 g L-1. The
peak surfaces were determined by the software Eurochrome 2000.
Vitamin C analysis: Vitamin C was extracted starting from 5 g of broyat by a metaphosphoric
acid solution (80%). Extracts were homogenized during 1 min at a maximum
speed. After centrifugation at 1740 t/15 min at 20°C, the extracts
were filtered through a 0.45 μm filter micropore and were diluted
with 25 mL of metaphosphoric acid. Twenty microlitres of filtrate were
injected into the injector. The quantification was made by comparison
to vitamin C standards. All manipulations were quickly carried out to
avoid vitamin C degradation.
Mineral analysis: Plant material was dried at 70°C. One gram of sample (date pulp), placed in a porcelain capsule, was calcined then by the muffle furnace at 550°C/4 h. After cooling, ashes were attacked by 5 mL of deionized water and 1 mL of hydrochloric acid and were subjected in boiling. The capsule content was filtered.
The filtrate was adjusted by deionized water to 100 mL. This solution
will be used for mineral analysis such as potassium, sodium, calcium,
magnesium and phosphorus.
Statistical analysis:Data were subjected to statistical analysis. Results were expressed in dendrogram form using the order TREE. This technique was founded on the Euclidean distance. The classification of the varieties is based on
their affinities for the studied variables. All analysis was carried out
by software SPSS 12.5 version.
RESULTS AND DISCUSSION
Dates moisture: Moisture is one of the essential components of the fruit which imports
basically on its quality and acts on its conservation. The moisture content
of the fruit vary from 60% at the mature to about 25% at the dried stage
(Barreveld, 1993), safe moisture content for storage of date is between
24 and 25%. Results showed that this parameter vary from 14 to 47% (Fig.
1). The highest rate was observed at the Mattata variety (47%). The
low one was recorded at the Garn Ghazel variety (14%). Toutain (1976)
considered dates as soft if they present a water content more than 30%,
dry if this rate is less than 10% and half-soft if the rate is between
10 and 30%. This nomenclature permits us to classify the littoral dates
as soft dates.
Sugar contents: Results showed that the majority of the littoral varieties were
rich in reducing sugars (glucose + fructose) (Fig. 2
and 3). Whereas, they presented a weak rate of saccharose;
only the two varieties Garn Ghazel and Korkobbi presented the highest
content. The values were respectively about 24.05 g/100 g MF and 17.75
g/100 g MF for the two previous varieties.
Results corroborate those obtained by Bouabidi et al. (1996) and
Cance and Widdowson (1993) which suggested that the soft dates are rich
in reducing sugar and poor in saccharose. These results are also in agreement
with Ben Salah and Hellali (2003) for littoral dates. Similar rates of
reducing sugar were shown by Youssef et al. (1982) and Sawaya et
al. (1983) for Iraqi and Saoudi varieties, respectively.
Comparison of the littoral varieties according to their sugar content: Results of date sugar varieties analysis separated four groups (Fig.
||Water content (TE) of the different date cultivars
||Reducing sugar content (%) of the different date cultivars
||Saccharose content (%) of the different date cultivars
Group 1: It contains six varieties (Lemsi, Kenta, Rochdi, Korkobbi,
Garn Gazel, Mermella) this group is characterized by:
||A high content of total sugar (> 50%);
||A mean content of reducing sugar (39 to 46%);
||A mean content of saccharose (10 to 24%).
Group 2: This group consists of three varieties (Bouhattam, Eguwa,
Mattata) which is characterized by:
||A weak content of reducing sugar (< 30%);
||A mean content of total sugar (> 30%);
Group 3: Contain one variety (Ksseba) which is characterized by:
||Absence of saccharose;
||A high content of reducing sugar (> 50%).
Group 4: Contain the Deglet Nour variety which is characterized
||A high content of saccharose (> 60%);
||A weak content of reducing sugar (< 20%).
Several reports were interested in the sugar date compositions. Myhara
et al. (1999) considered the percentage of reducing sugar as criteria
for date qualities. In the aim of the quality improvement of the Deglet
Nour variety, these authors proposed to add the invertase in order to
convert saccharose into reducing sugar.
By comparing the sugar content of the Deglet Nour variety with the one
of littoral varieties, results showed a fundamental difference in the
composition of the glucidic fraction (absence of saccharose in the littoral
varieties). This saccharose underwent a complete hydrolysis into reducing
sugar at stage tamar.
Although the littoral varieties were composed of high percentage of reducing
sugar (glucose and fructose), which are the most important as energy calories
(Al-Farsi et al., 2005; Myhara et al., 1996), easily digestible
and hydrolysables. The farmer and consumer attentions were already directed
towards the Deglet Nour variety with saccharose. Indeed, the principal
reason of the Deglet Nour popularity is the high content in saccharose
(34% more sweetened than glucose) which confers consequently a more pleasant
taste (Reynes, 1994). It is important however to note that the high energy
capacity of date and their easy assimilability thanks to their high content
in reducing sugars permit to advise them with a large variety of public.
It is thus the case of littoral varieties.
Vitamin C contents of: Results showed that vitamin C content vary according to varieties
(Fig. 5). This content reached 45 mg/100 g MF for Ksebba
variety, was only 23 mg/100 g MF for Korkobbi. In previous report, Youssef
et al. (1982) showed in Iraqi dates a weak rate in vitamin C varying
from 2.41 to 17.51 mg/100 g MF. Rates of 2 mg/100 g MF were recorded by
Cance and Widdowson (1993).
Vitamins are essential micro-nutrient for organisms. It intervenes in
multiple biochemical reactions such as:
||Dendrogram obtained in the basis of sugar content of
the different date cultivars
||Vitamin C content (%) of the different date cultivars
||Hormonal, adrenal and sexual functions;
||Metabolisms of iron (activates its absorption by the intestinal
membrane), of glucids, lipids and proteins (the collagen formation
which intervenes in the skin tonicity);
||Muscular and cerebral metabolisms (activates certain neuro-transmitters);
||Defence immunizing mechanisms;
||Anti-oxidant activity: plays with vitamin E, carotenes, vitamin
A and other substances an important antioxidant role.
Comparison of the littoral varieties according to their vitamin C content: Results of vitamin C analysis permit to separated two groups
Group 1: Contains the majority of varieties (Bouhattam, Kenta,
Mattata, Korkobbi, Eguiwa, Mermella) which is characterized by a high
content of vitamin C (23 to 35 mg).
Group 2: Contain the Deglet Nour variety which is characterized
by a very low content of vitamin C (< 5 mg).
Mineral analysis: Results showed that dates are particularly rich in mineral (Table
1). Some minerals are well represented in dates and are used for their
characterization such as potassium (K). Others are present only in traces.
The potassium, phosphorus and iron percentages in dates are higher than
in other fruits; three to five times higher than in the grapes, apples
and oranges Al-Showiman (1998).
Booij et al. (1992) classified dates on three groups thanks to
their composition in potassium (K), calcium (Ca), magnesium (Mg) and phosphorus
(P) with percentages of 0.6, 0.05, 0.04 and 0.045%, respectively. This
classification seems to be validate for littoral varieties (Table
1). For instance, the Lemsi and Mattata varieties presented however
according to the previous values a high content of K reached the 0.73%.
They exceed the one of Deglet Nour. The Eguiwa variety was characterized
by low mineral contents.
Comparison of the studied varieties according to their mineral contents: Results of date mineral composition permit to discuss three groups
Group 1: Contains the majority of the varieties (Bouhattam, Kenta,
Rochdi, Korkobbi and Ksebba) which is characterized by:
||A mean content of potassium (0.41 to 0.48%);
||A high content of calcium (0.07 to 0.10%);
||A high content of phosphorus (0.6 to 0.8%);
||A mean content of magnesium (0.4 to 0.6%).
Group 2: this group contains only one variety (Eguiwa) which is
characterized by a low content for all minerals.
Group 3: contain four varieties (Lemsi, Mattata, Mermella and
Deglet Nour) which is characterized by:
||A high content of potassium (> 0.7%);
||A high content of phosphorus (< 0.6%);
||A low content of sodium.
||Dendrogram obtained in the basis of vitamin C content
of the different date varieties
||Dendrogram obtained in the basis of mineral content
of the different date cultivars
||Mineral content of the different date cultivars (g/100
According to Booij et al. (1992), the mineral composition of the
different dates varieties vary accordingly with their geographical origin.
Indeed, the dates of the littoral varieties present as similar mineral
contents as the ones of the continental varieties. The current results
seems to confirm those mentioned by Youssef et al. (1982) which
showed that the mineral variations in fruits can in general show considerable
variations not only between the species and the varieties but also within
the same varieties cultivated under different agroclimatic conditions.
However, the abundance of the minerals in dates, like that of all the
fruits, leaves an alkaline surplus. This alkalinity reached 10 meq/100
g for dates, was only 4 to 8 meq/100 g for other fruits (Levine et
al., 2003). It is thanks to their high contribution in minerals that
dates take part in the good food balance (rich in potassium) in particular
for sportsmen and old people.
It is interest to note through this study that the Deglet Nour variety,
considered as reference for the studied dates, did not have a high content
of minerals. It was however the Lemsi, Mattata and Mermella varieties
which presented the important contents.
The little or not exploited common dates varieties can be considered
as an important nutritional and energy values. A laboratory experiment
was carried out to characterize the food and the energy values of certain
common date varieties in the littoral oases of Tunisia. For all analysis,
the variety Deglet Nour was taken as reference.
Results showed that, generally, the common dates were very rich in reducing
sugar (Fructose and glucose; 26 to 51%) by comparison to the Deglet Nour
variety (high content of saccharose; 60%). This result confers consequently
to the common varieties good food and medical values (easily assimilable
and high energy capacity).
Concerning the vitamins C, present study affirms, contrary to previous
reports neglecting these compounds that the common varieties are especially
very rich in vitamin C (24 to 46 mg/100 g) which is absent in Deglet Nour
The mineral composition results showed that the littoral dates are characterized
by their similar mineral contents as the ones of the continental varieties.
The Deglet Nour variety, considered as reference, did not have a high
minerals content. It was however the Lemsi, Mattata and Mermella varieties
which presented the important contents.
It arises from the present report that the littoral dates could present
a particular interest and are able to compete the most marketed varieties
(Deglet Nour). The few source data, results of this study, may permit
to the industrialists to take certain measurements for the date treatments
in the chain of conditioning (humidification, drying) and on the storage