Nutritional composition of jujube fruit

The jujube, also known as ziziphus, is grown and cultivated in India, Russia southern Europe, China and the Middle East. The fruit has been used in Chinese medicine for over 4,000 years. In India, the jujube is grown for just a few niche markets. Jujube contains potassium, phosphorus, manganese and calcium as the major minerals. There are also high amounts of sodium, zinc, iron and copper. Jujube also contains vitamin C, riboflavin and thiamine. The vitamin and mineral content of the fruit helps to support cardiovascular health and enhance metabolism. This brief review provides information on nutritional composition, changes in nutritional components with maturity and its maturity indices of Indian (Ziziphus mauritiana Lamk.) and Chinese (Zizyphus jujuba Mill.) jujube.


Introduction
Indian jujube (Ziziphus mauritiana Lamk.) is also known as ber, desert apple or Indian plum.It belongs to family Rhamnaceae.It is a tropical/subtropical fruit native to the northern hemisphere (Lyrene, 1979).The genus Ziziphus has 135 to 170 species (Islam and Simmons, 2006), of which 17 are native of India (Watt, 1883;Bailey, 1947;Singh et al., 2000).Z. mauritiana is cultivable ber in drier parts of the Indian subcontinent (Sebastian and Bhandari, 1990).Ber is also cultivated on marginal lands in some African countries (Johnston, 1972).The Ziziphus species are distributed throughout the tropical, subtropical and temperate regions of both the hemispheres (Rendle, 1959).Small or large plantations of ber exist in Afghanistan, Iran, Syria, Burma, Australia (Nijjar, 1975), France (Evreinoff, 1949;Munier, 1973), the United States of America (Thomas, 1924;Lanham, 1926;Riley, 1970) and the Russia (Mukherjee, 1967).Ber fruit is a drupe, globose to ovoid in shape, up to 6 x 4 cm in size; skin smooth or rough, glossy, thin but tough, yellowish to reddish or blackish; flesh white, crisp, and juicy, sub acid to sweet, becoming mealy in fully ripe fruit (Figure 1, 2).Irregular furrowed stones are found in tuberculate seed which contains 6 mm long brown kernels of elliptic shape.Ber fruit is generally eaten fresh and is a rich source of ascorbic acid, essential minerals and carbohydrates (Pareek, 1983;Abbas et al., 1988;Pareek et al., 2002).Colour of fruit is changed from green to yellow to chocolate brown with the maturity and ripening (Figure 3).
Jujube (Zizyphus jujuba Mill.) is cultivated from ancient time in China and reported that cultivated for last 5000 years.Chinese jujube is found in subtropics of Asia and largely in China.Sixty lakh quintals of fruits were produced from 30,000 ha area in 2009 in China (Cui, 2009).China alone contributed 90% of world production of jujube (Li et al., 2005;Su and Liu, 2005).'Chinese Winter Jujube', a new jujube cultivar, is known as "the king of jujube in China".This cultivar characterized with thin peel, crisp flesh and rich in nutritional components (Sun et al., 2007).Jujube fruit contains flavonoids, vitamins, amino acids, organic acids, polysaccharides, and microelements (Li et al., 2007) and found useful in spleen diseases and nourishment of blood in Chinese system of medicine (Shen et al., 2009).
Correlation studies suggest that there were no correlation found between antioxidants and phenolics or with ascorbic acid in Chinese jujube (Li et al., 2007).Pareek (2001) gave details of the composition of Chinese jujube pulp.They include 9.6 -33% sugar, 0.3-2.5% acids (Ahmedov and Halmatov, 1969), 2.9% protein and 136-363 mg/100g of vitamin C (Tasmatov, 1963;Baratov et al., 1975;Ristevski et al., 1982;Ciressa et al., 1984).The average dried Z. jujuba sugar content is 50.3 -86.9 g/kg, while the protein content is 3.3 -4.0 g/kg, and fat content is 0.2 -0.4 g/kg.Chinese jujube also contains 18 kinds of amino acids, including eight essential amino acids, and is rich in vitamins and minerals (Annon., 1989).Z. jujube fruits are very rich in vitamin C, thiamin and riboflavin (Troyan and Kruglyakov, 1972;Kuliev and Guseinova, 1974).Consumption of one ber fruit in a day would meet the diet requirements for vitamin C and vitamin B complex of an adult man recommended by WHO.It is also known to have high vitamin P (bioflavonoid) content.

Fruit growth and development
Jujube fruit showed double sigmoid growth (Bal and Singh, 1978;Abbas et al., 1994;Abbas and Fandi, 2002).On the basis of diameter and weight, it has been confirmed that jujube fruit having double sigmoid growth from 40 to 88 days after petal fall (Lu et al., 2012).Cultivar differences were found for days taken to maturity e.g., 'Changhong' Jujube fruit matures in 80 days (Lu et al., 2011), whereas 'Zaytoni' took 124 days (Abbas and Fandi, 2002).Due to the rapid cell elongation and cell division (Bollard, 1970) as well as high levels of growth hormons particularly auxins, gibberellins, and cytokinins (Fandi, 1999) the first rapid growth was observed between 40 to 48 days after petal fall (Lu et al., 2012).A lag phase was observed after first rapid growth.The lag phase period was also different for different cultivars and it was more than two weeks in Indian jujube (Bal and Singh, 1978;Abbas et al., 1994) and less than two weeks in 'Zaytoni' (Abbas and Fandi, 2002) and 'Changhong' (Lu et al., 2012) jujube fruit.The occurrence of a short lag phase of growth resulting in early maturity.The fruit then entered a second period of rapid growth.This stage of fruit growth is mainly due to cell enlargement and is associated with high levels of gibberellins, whereas cytokinins are no longer detectable (Fandi, 1999).Source: (Li et al., 2007) Figure 3. Changes in color with maturity and ripening of Indian jujube fruits.

Changes in nutritional composition during growth and maturation Ascorbic acid and phenolics
The ascorbic acid content of ber fruits was initially low, and continued to increase till the fruit reached physiological maturity (Abbas, 1997).The increase in ascorbic acid with the advancement of ripening was noticed in ber fruit and reached peak value i.e., 559 mg/100g on 15 th day of storage (Kader et al., 1984).Bal et al. (1995) also noted the increase in vitamin C content as the maturity advanced in 'Umran' ber fruits.Highest content of ascorbic acid was observed at 56 days after petal fall and after this period it continuously decreased up to maturity (Lu et al., 2012).A significant difference in ascorbic acid was reported by various workers.Comparatively lesser amount (250-600 mg/g fresh weight) was reported by Wu et al. (2010) whereas it was as high as 721 mg/g fresh weight at 88 days after petal fall (Lu et al., 2012).Total phenols increased from 40 to 48 days after petal fall, decreased from 48 to 56 days after petal fall, again increased between 56 and 64 days after petal fall and decreased steadily after 64 days to maturity (Lu et al., 2012).

Sugars
Reducing sugars were increased from 40 days to 72 days after petal fall and then decreased until maturity and ripening (Lu et al., 2012).However, in some Indian jujube cultivars ('Zaytoni', 'Umran', 'Sanaur', and 'Kaithli') reverse trend was reported (Bal and Singh, 1978;Bal et al., 1979;Jawanda and Bal, 1980;Abbas and Fandi, 2002).Reducing sugars tended to accumulate over most of the growth period in jujube fruit cvs.'Bambawi' and 'Mallacy' (Abbas et al., 1994).Soluble sugars content continuously increased throughout growth and development of fruit and highest increase was noticed between 40 and 48 days and 80 to 88 days after petal fall.The soluble sugars content in ripe jujube fruit was 121.58 mg/g (Lu et al., 2012) and Indian jujube was in the range 85-145 mg/g (Teotia et al., 1974).It was found as low as 58-79 mg/g in 'Mallacy' and 'Bambawi' (Zizyphus spina-christi L. Willd) jujube fruit (Abbas et al., 1994) and as high as 179 mg/g was found in 'Zaytoni' jujube fruits (Abbas and Fandi, 2002).Reducing and nonreducing sugars increased up to maturity (Bal and Man, 1978;Bal et al., 1979;Jawanda and Bal, 1980).Total sugars increased gradually up to certain period of growth and then increased rapidly (Bal and Singh, 1978;Bal and Man, 1978;Jawanda and Bal, 1980;Gupta et al., 1984;Bhatia and Gupta, 1985;Pandey et al., 1990;Kadam et al., 1993).In 'Umran' ber, sucrose and fructose continued to increase whereas glucose decreased slightly with advancement of ripening.The stages of harvest had a significant effect on total sugars (Kudachikar et al., 2000).Delaying the picking of fruits to later maturity stages resulted in higher sugars after ripening (Bal and Chauhan, 1981;Bal, 1986).While working on four Indian jujube cultivars ('Gaolangyihao', 'Xinshiji', 'Mizao', 'Miandianchangguo') in China, Ling et al. (2008) reported that the soluble sugar mainly consisted of sucrose, glucose and fructose.The rate of increase in sucrose accumulation was highest during midlate growth period to ripening in all cultivars studied, however the rate of sucrose accumulation in 'Gaolangyihao' was faster than that of the other three cultivars.The cultivar difference was found in glucose and fructose content of total sugars and fructose was significantly higher than that of the glucose in 'Mizao' and 'Miandianchangguo' fruit while fructose and glucose was almost equal in'Gaolangyihao' and 'Xinshiji' (Ling et al., 2008).

Carotenoids, pH and phenols
In 'Changhong' jujube fruit, carotenoid content increased from 40 to 56 days after petal fall and staying more or less unchanged until 72 days after petal fall.At the later fruit development stage, the carotenoid content rose again (Lu et al., 2012).The pH increased at early stage and decreased at middle stage of jujube fruit development, and at maturity stage, the pH increased again (Lu et al., 2012).
The total phenols decreased with the advancement of maturity (Bal and Singh, 1978;Bal, 1981;Bal et al., 1995;Al-Niami et al., 1992).This reduction in phenolics during the ripening could be due to its hydrolysis into sugars, acids or any other compounds or owing to their transformation from a soluble into an insoluble form (Singh et al., 1981).Both on tree as well as stored 'Umran' ber fruits showed decrease in total phenols with the advancement of ripening (Sharma, 1996) and tannins also decreased (Kadam et al., 1993).Total phenolics were decreased in Chinese ber after 3 days at 20ºC and again increased on 15 days of storage period (Kader et al., 1982).

Conclusions and direction for future research
Chinese jujube is grown in temperate regions while Indian jujube is cultivated in hot arid regions of India.Both the fruits are rich in nutritive value.Vitamin C content is very high in Chinese jujube and it is fairly high in Indian jujube fruits.More than 300 varieties are available in Indian jujube but very few are in cultivation.The complete nutritional profile is not known for both these fruits.Proximate composition, fraction of sugars, vitamins, carotenoids, minerals, amino acids, volatiles etc. should be studied in both jujube fruits for particular cultivars.Nutritional changes with the advancement of growth, maturation and ripening should be measured.

Figure 1 .
Figure 1.External and internal of Indian jujube fruit.

Table 1 .
Nutritional composition of Indian jujube fruit (on fresh weight basis).

Table 2 .
Nutritional composition of five cultivars of Chinese jujube (on dry weight basis).