Nutritional Value of Date Fruits and Potential Use in Nutritional Bars for Athletes

The date palm (Phoenix dactylifera L.) is one of the oldest primary staple crops in Southwest Asia and North Africa. Date palms are also grown in Aus-tralia, Mexico, South America, Southern Africa, and the United States, especially in Southern California, Arizona, and Texas. Date fruit is a high nutritional value food that is rich in carbohydrates, dietary fibers, proteins, minerals and vitamin B complex such as thiamine (B1), riboflavin (B2), niacin (B3), pantothenic (B5), pyridoxine (B6), and folate (B9). Carbohydrates comprise 70% of date fruit mainly as fructose and glucose. Minerals in date fruits are calcium, iron, magnesium, selenium, copper, phosphorus, potassium, zinc, sulfur, cobalt, fluorine, and manganese. Date fruits are highly nourishing and may thus confer numerous potential health benefits. In recent years, a huge interest in the abundant health promoting properties of date fruits has led to the need to develop new food products using dates as a source of nutrients. Thus, the aim of this paper is to review the nutritional value of date fruits in the context of the potential use of dates in nutrition bars for athletes.


History and Origin of Dates
The date palm is thought to be one of the oldest plants in the world with a 7000-year history. The planting of this fruit coincided with some of the oldest civilizations that extended from Northeast Africa to northwest of the Tigris and Euphrates plateau [2]. It is believed that the Phoenicians were among the first people to cultivate the date palm around the Mediterranean region in ancient times. The date palm name, Phoenix dactylifera originated with the Greeks when the fruit was transferred from the Phoenicia region to the Mediterranean region [2]. This date palm, has been considered to be one of the most important plants in the arid, desert area of the Middle East, Southern Asia and Northern Africa for over 5000 years [3]. The date palm fruit is also the major staple food and primary source of agricultural wealth in the United Arab Emirates (UAE) region [4].
The date palm (P. dactylifera L.) belongs to the Arecaceae (or palmae) family and structurally consists of three main parts, namely: 1) flesh with thin crust, 2) date pit, and 3) cap as shown in Figure 1. This fruit has been planted for many years in the semi-arid and desert areas of the Middle East, Pakistan, India, in the Canary Islands, and in the northern African countries for fuel, shade, fiber, and as building material [5] [6]. The commercial production of dates in the USA, began in the late 19 th and early 20 th centuries and is still considered to be an important component of desert agriculture in Southern California and Arizona [3].  Date palm trees are very resistant to harsh climatic conditions and can withstand a vast range of temperatures (from −6˚C to 50˚C). They are also resistant to both water and soil salinity, and the most appropriate area for their growth is in arid regions with hot, dry climates and limited rainfall [7]. The total production of date fruits globally was more than 7.5 million tons in 2017 [8].
Five countries provide 54% of the total global production of date fruits globally include; Egypt (1.08 million tons), Iran (0.95 million tons), Saudi Arabia (1.08 million tons), Iraq (1.08 million tons) and the United Arab Emirates (UAE, 1.08 million tons), respectively [9]. Cultivation of the date palm in UAE has increased considerably in the last two decades with over 250 varieties being cultivated in various parts of the country, most notably in Al Ain and Abu Dhabi. The growth of date fruits in the UAE is paralleled by its high consumption rate, with the per capita daily intake being 10 g to 200 g in Abu Dhabi alone [10].

Date Cultivars and Fruit Texture
Globally, there are several thousand known date cultivars of commercial importance. Most of the top cultivars are grown extensively around the world and include the following four important commercial varieties: Deglet Noor, Zahidi, Khadrawy, and Halawy. Deglet Noor is the most popular cultivar and has the highest cultivation rate due to its large fruit size, light color, delicate flavor, and considerable shelf life during storage [7]. Regarding fruit texture, dates are categorized into three groups as soft (e.g. Barhi, Halawy, Khadrawi, and Medjhool), semi-dry (e.g. Dayri, Deglet Nour, and Zahidi), and dry (e.g. Thoory). The texture of dates largely depends on the amount of pectin methylation as the less the methylation amount, the softer the date becomes. The Tamer date is the softest (with 39% methylation) whereas the Kimri date is the toughest (with 72% methylation) [1] [11] [12]. The moisture and fiber content are also expected to play a role in determining whether a date is soft, semi-dry or dry [13].

Proximate and Nutritive Composition of Dates
Date fruit is very sweet and comprise about 50% -88% of the total weight according to cultivar type, the ripening stage and the total water content. The date flesh is composed of sugars, primarily fructose and glucose. These sugars make up two-thirds of the total date flesh, with one-fifth of the total fleshy composition comprised of water and just a small remaining portion of dietary fiber.
Other rich components of dates include its protein, fat, crude fiber, minerals, vitamins (especially vitamin B) and tannins among others [14] [15]. Dates possess very high nutritive value and can thus play an effective role in providing human nutritional needs. For example, 100 grams of fresh dates contain approximately 157 calories of energy, whereas dry dates contain more than 300 calories of energy per 100 grams [1]. Table 1 summarizes the general proximate composition of the date fruit.
The flesh of dates contains between 0.2% -0.5% oil compared to 7.7% -9.7% in the seed or pit. Date fruit contains unsaturated fatty acids which include palmitoleic, oleic, linoleic and linolenic acids. Date seeds could be used as a potential source of oleic acid as the oleic acid content of the seeds varies between 41.1% and 58.8%. The protein content in dates contains twenty-three (23) different types of amino acids, some of which are non-existent in popular fruits such as oranges, apples and bananas. Date fruit contains at least six vitamins including a small amount of vitamin C plus vitamin B(1) thiamine, B(2) riboflavin, nicotinic acid (niacin) and vitamin A. The pectin content which ranges between 0.5% -3.9% also confers health benefits such as lowering cholesterol levels. The essential nutrients in dates thus make this an ideal food, providing a wide array of beneficial nutrients for human health and development [16].

Carbohydrates (Sugars)
The major chemical constituents of dates are carbohydrates, which include reducing sugars such as glucose and fructose as well as non-reducing sugars such  [16]. According to Shafiei et al., polysaccharides in the date flesh and seeds or pits contain xylose, arabinose, glucose, and galactose [17]. The level of sucrose is higher in dried dates than on soft dates. Soft dates, however, contain reducing sugars, except for a few cultivars that contain sucrose [18] [19]. It is interesting to note that semi-dry dates have nearly 50% each of sucrose and reducing sugars [20]. According to Eltayeb, et al., semi-dry dates contain more sucrose than reducing sugars [18].
However, the cultivar, Deglet Nour which grows mostly in California, contains only sucrose [21]. It has also been observed that dry dates with solid and dry flesh contain relatively more sucrose than reducing sugars [18]. In general, dates can be grouped into two types depending on the type of sugars contained in the dates. These are sucrose containing dates or reducing sugar containing dates [22]. The composition of sugars (sucrose, glucose and fructose) along with the glucose to fructose ratio (G/F) in some selected date fruit varieties in the UAE are summarized in Table 2. The moisture content of the date is indirectly proportional to its sugar content, such that dates with low moisture content always contain high sugar and vice versa. Date varieties in Saudi Arabia contain about 70% reducing sugars with almost equal quantities of both glucose and fructose [19]. The most important commercial characteristics of dates are based on the sugar content which is significant for both fresh consumption and for fruit processing [23].
Because dates contain a relatively high sugar content, they may also have an important agro-industrial future as a potential source of refined sugar [24] [25] [26] [27].

Protein
The protein content of dates ranges from 1% -7% and includes essential amino  [15]. According to Al-Shahib and Marshall, date proteins contain twenty-three (23) types of amino acids, some of which are not present in popular fruits such as oranges, apples and bananas. Most date cultivars contain the following amino acids: lysine, histidine, arginine, aspartic acid, threonine, glutamic acid, serine, proline, glycine, alanine, cystine, valine, methionine, isoleucine, leucine, tyrosine, and phenylalanine [16]. It is worthy to note that glutamic and aspartic acid make up the highest amino acid quantities in dates according to Nour and Magboul [26]. These proteins are rich in acidic amino acids and low in sulphur containing amino acids such as methionine and cysteine [27].
The molecular weight of date proteins varies from 12,000 -72,000 daltons.
Most date proteins are water soluble albumins. Dates grown in Middle Eastern countries such as Saudi Arabia, Jordan, Oman and Iran have very similar protein profiles and contain complex protein mixtures, whereas some varieties grown in the US have very low protein and a simple protein profile as well [27]. During date sugar production, the extracted juice becomes darkened as a result of proteins and thus must be removed [5].

Fat
Date fruit typically contains little fat, with most of the fat concentrated in the crust. The fat content in the flesh ranges between 0.1% -0.5%, and fat plays an essential role in the protection of the fruit more than in the nutritional value of the date flesh [13] [16]. For example, eight fatty acids exist in very low concentration in the flesh. The major saturated fatty acids in dates include lauric, myristic, and palmitic acids, while the major unsaturated fatty acid is oleic acid [16]. Other fatty acids in minor quantities include capric, caprylic, stearic, margaric, arachidic, linoleic, and pelargonic [13] [16].

Crude Fiber
The daily consumption of 100 g of dates provides approximately 50% -100% of the recommended daily amount of fiber [16]. The insoluble part of the date flesh is its crude fiber which is comprised of cellulose, hemicellulose, lignin, and lignocellulose. The quantities of cellulose, hemicellulose, and lignin of date flesh are 1.55%, 1.28%, and 2.01%, respectively [5]. The crude fiber in high quality, ripe dates, amounts to 2% -6% of date flesh, whereas in low quality dates, this percentage can be as high as 10% with the fiber being used primarily for industrial purposes [13]. The crude fiber content of dates is, however, not a good indication of its total dietary fiber content since the fiber also contains pectin, he-  [31]. These polysaccharides have a main chain of (1 → 3)-β-D-glucopyranosyl residues with (1 → 6)-linked branched saccharide residues [31]. However, accurate information regarding the exact quantity of glucans in the date fruit is not available at present.
Date crude fiber plays an important role in date processing as it indirectly affects the yield in liquid date sugar production. The higher the crude fiber and moisture content, the less the yield during production of liquid date sugar [14].
During the production of date syrup and its storage, pectin causes gelation, which results in lower liquid sugar yields. However, this situation is eliminated properties such as high water-holding capacity, high oil-holding capacity, emulsifying, pseudoplasticity behavior of their suspensions, and gel formation that are important to the food industry [33]. Dietary fiber could also be used as an ingredient in many food products such as in dairy, soup, meat, bakery products and jam in order to modify their textural properties, avoid syneresis, and stabilize high fat food and emulsions.

Minerals and Vitamins
Dates are rich sources of vitamins and minerals and are known to provide a  [16]. In many date varieties, the potassium content in the flesh can be as high as 0.9%, while some seeds could have as much as 0.5% [16]. Potassium is thus considered to be the predominant microelement in the date flesh, whereas the phosphorous content is less than that of the other macro-elements [27] [36].
The micro-elements zinc and copper are found in low concentrations in dates, and iron is present in higher concentrations [36]. The high potassium and low sodium content in dates are beneficial for people suffering from hypertension.
Boron is very useful in the treatment of brain cancer and, in conjunction with other vitamins, is also used in the treatment of rheumatism [37]. The abundance of fluorine present in dates is useful for the prevention of tooth decay. Moreover, the selenium content of dates has beneficial effects for cancer prevention and strengthening of the human immune system [16] [38]. According to Al-Showiman et al., the amount of selenium is in the range of 1.48 -2.96 μg/g in some date varieties [37]. Dates could be used as iron deficiency supplements without causing side effect such as nausea, headache, and anorexia that may occur with the use of conventional iron supplements.
Dates are a reasonable source of vitamins compared to other dried fruits [39].
In addition, fresh dates contain higher concentrations of vitamins than dried dates as a result of the depletion of vitamins during the drying process. Thiamin, riboflavin, niacin, ascorbic acid, pyridoxin, and vitamin A are six vitamins that have been confirmed to be present in dried dates in relatively low concentrations [16] [40].

Antioxidants
Dates Phenolic compounds and carotenoids (flavonoids and anthocyanins) can contribute to varying degrees of antioxidant and antimutagenic activity. For example, the contribution of total phenolics toward antioxidant activity in dates is greater than that of ascorbic acid [43]. Many research studies have confirmed the free radical scavenging properties of date fruit as well as date juice extracts Most of the antioxidants observed in dates have been reported to be hydrophilic or water soluble [34]. Some of the confirmed and reported data on the antioxidant activity of date fruit from different parts of the world such as Algeria [44], Kuwait [45], Iran [13], Bahrain [46], Oman [34], and the United States [47] has established the dual benefits of dates as providing an unparalleled source of natural antioxidants as well as being a good alternative for the improvement of flavor and color in food products due to their high content of active phenolic acids.

Date Processing
Dates contain a plethora of nutritive elements that are highly medicinal making dates a suitable product in many food applications. Dates are consumed either in their fresh or dried state, however, value addition through processing of the date fruit leads to an array of high end assorted products such as date juice concen- According to Ahmed et al., the general process includes steaming the dates, de-pitting, and macerating which transforms dates into a semi-solid form known as paste with an approximately 20% -23% moisture content and a water activity below 0.6 [51]. Date paste has thus become a sugar substitute in many food product formulations, and many confectioneries utilize it as an ingredient [52].
In the date syrup industry however, date processing involves mixing the fruit with water and applying heat at a temperature of 50˚C for an hour. The liquid extract which primarily contains sugars is then filtered and concentrated in order to achieve the finished product. This process could be easily performed at home and in village settings by simple boiling and extraction of date juice. Date syrup processing can therefore be achieved on a small to medium scale or in a fully industrialized context [53]. It is also worthy to note that mature date fruit could also be processed into date bars [54].

Date Bars as a Potential in Sports Nutrition
Energy bars can be classified as dietary supplements that are often consumed by athletes and other physically active people to maintain their calorie needs. These bars provide the strength and vitality for sustained physical and mental activity and are typically high in carbohydrates and moderate in protein content [55].
Energy bars are globally known to be a convenient ready-to-eat food which does not require any preparation and can be easily stored at room temperature. These bars are uniquely made to fit a specific purpose and are consumed by all age groups in order to enhance daily energy values. Energy bars come in various sizes and shapes, and they are a nutritiously dense alternative to food. In addition, energy bars are uniquely aligned to various objectives or diets (i.e. low carb, organic, kosher, etc.) and exercise needs (i.e. pre-workout, during workout or post-workout) [56]. Moreover, they have a balanced nutritional profile meeting both macro and micronutrients requirements for enhanced body metabolism [57]. Fruit based bars can serve the purpose of an energy bar as they are an exceptional source of superior nutritive and bioactive elements that provide energy required to meet the recommended daily nutritional intake [58].
Date fruit is a good source of carbohydrates in the form of sugars that constitute about 78% of the whole fruit. This reservoir of natural sugars is readily pro-Food and Nutrition Sciences vided to the human body as a source of energy [42]. Date fruit consumption also provides consumers with therapeutic benefits and nutrition that are vital for the proper functioning of the human body. The fruit is either consumed directly (fresh or in dried form) or is converted into products such as date paste and syrup, among others [59]. According to Tang et al., date fruit provides inherent antioxidant, anti-inflammatory, gastrointestinal-protection, and anticancer properties that are vital for human health [59]. In addition, these properties may help reduce and control diabetes mellitus and other cardio-and cerebrovascular diseases (CCVD) [59]. Fruit bars are a better alternative to direct consumption of dates, as fruit bars are especially geared towards energy provision for active individuals [58]. It is important for athletes to consider natural food sources that provide a canister of energy at any point in time in order to replenish their strength after strenuous activities.
An excellent food source that contains appropriate amounts of both macroand micronutrients is therefore essential in order to provide for the energy and nutrition needs of athletes, sportspeople, and others with active lifestyles. Date bars could fulfil this requirement under sports nutrition, as such bars may enhance athletic performance by reducing fatigue and the risk of disease and injury as well as enable athletes to optimize training and recover faster [60]. The centrepiece goal of virtually all athletes is to balance energy intake with energy expenditure in order to prevent an energy deficit or an excess of it [61].

Use of Dates in Nutritional Bars for Athletes
Dates are naturally sweet due to their high content of sugars such as sucrose,

Probiotic Nutritional Bar for Athletes
The word, probiotics, was derived from the Greek words "for life" and has had many definitions over the years [63]. Huis Int Veld and Havenaar broadened the definition of probiotics as being "a mono-or mixed culture" of live microorganisms which, when consumed by man or animal (e.g. as dried cells or as a fermented product), beneficially affect the host by improving the properties of the indigenous microflora [64]. According to the Food and Agricultural Organisation (FAO)/World Health Organisation [65], probiotics are defined as "live microorganisms, which, when administered in adequate amounts, confer a health benefit on the host." Additionally, according to the International Olympic Committee (IOC), "Probiotics are defined as live micro-organisms that, when administered orally for several weeks, can increase the number of beneficial bacteria in the gut. Probiotics have been associated with a range of potential benefits to gut health as well as modulation of immune function" [66].
Strenuous, extensive exercise induces stress on the gastrointestinal (GI) tract that increases the probability of multiple symptoms linked to a disturbed gut microbiota and a decrease in performance [67]. These symptoms include abdominal cramps, acid reflux, nausea, vomiting, diarrhea, and permeability of the gut that may lead to systemic endotoxemia [68]. Consumption of date bars fortified with probiotic bacteria will ultimately provide a dual benefit to the athlete by releasing enough calories for performance and holistically protecting the athlete's gastrointestinal tract effectively. The immune system readily and heavily protects the GI tract, as the GI tract is the major pathway for pathogen entry.
Consequently, a boost in the immune system to heighten its defenses against pathogens in the GI tract is the sole objective and potential benefit of probiotics for athletes [67]. Date fruit nutritional bars as a vehicle for probiotic bacteria will effectively provide athletes with a stronger immune system via healthy gut bacteria.
Probiotics will thus serve as a functional modulator of the microbiome in athletes and will potentially enhance health, exercise adaptation and performance.
A healthy, enriched and well protected microbiome may also impart an indirect functional influence on various indices of exercise performance and recovery in athletes [69].

Date Nutritional Bar for Athletics
Our research team in the food microbiology laboratory developed a new nutritional bar that supports the health of athletes. The bar consisted of pitted soft dates, gluten free rolled oats, protein powder, probiotic mix, chokeberry powder, palatinose and other additives such as chocolate, milk, vanilla, salt and maple sy-Food and Nutrition Sciences rup. The standard recipe for the nutritional bar was derived after series of test trials to attain the best product formulation.
The steps involved in the development of this novel product included processing the oats in a food processor fitted with a steel blade and till finely ground into a flour. The protein powder mixture, pitted dates, maple syrup (optional), vanilla, salt, milk and (optional) melted unsweetened chocolate were all added afterwards. The mixture was then processed until all ingredients were well-combined and tacky (but not sticky) to the touch. More milk, probiotic mixture, palatinose and chokeberry powder was added and further processed till the mixture reached the appropriate and expected consistency.
In the event of not using the melted unsweetened chocolate, more milk, will have to be added which will result in the bars not holding together as firmly when shaped. The mixture was transferred to the prepared pan and firmly pressed into an even layer, with the top being smoothed as much as possible.
The pan was then covered with parchment paper and placed in the refrigerator or the freezer to chill until firm (about 1 hour in the refrigerator, or 20 minutes in the freezer). The bars were removed from the pan and sliced into 10 or 12 equal-sized rectangular bars. The rectangular bars were then dipped in the optional melted bittersweet chocolate to coat and allowed to sit at room temperature until set. The bars were stored in a sealed container in the refrigerator and were readily available to be consumed. The formulated date bar is as shown in

Conclusion
Dates have been underutilized in food product development, especially in energy bars, although they are highly nutritious and contain an array of natural sugars that could enhance athletic performance by providing energy. In addition, the *Original source is Food Preparation and Meal Management Laboratory at North Carolina A&T State University. with probiotic bacteria with dates as a medium superimpose that, its high natural sugars provide an ambient environment for it to effectively thrive. Probiotic bacteria incorporated in the formulated date bar product, will therefore provide beneficial support to the gastrointestinal guts of athletes. The addition of probiotic bacteria to dates in the formulation of nutritional or energy bars will also support the needed energy levels of athletes and active individuals. Research has confirmed the impact of probiotic bacteria on the health of athletes; hence its application in date nutritional bars will go a long way to address energy deficits before, during and after high and low intensity activities. We formulated a probiotic date nutritional bar for athletes and found that dates in conjunction with probiotic bacteria could serve as a highly sought-after nutritional energy bar for the purpose of athletic performance and endurance. However, with further research, dates energy bars could always serve as a super healthy functional food for athletes and individuals with various objectives of exercising and staying healthy and active.