Dragonfruit, also known as pitaya or pitahaya, belongs to the Hylocereus genus of theCactaceae family. It is recognized as leathery,slightly leafy – skinned sweet fruit of many cactus species rooted from Mexico,which was believed to be then brought to Central America by the European.Nowadays, dragon fruits are widely cultivated in the United States, the SouthEast Asia region, Israel, Australia, Cyprus, as well as the Canary Islands (Morton, 1987). The term “dragonfruit” is used in English to express the vernacular Asian name.
There are varioustypes of dragon fruit derived from three main species of white – fleshed fruit(H. undatus), red – fleshed fruit (H. polyrhizus), and yellow – skinnedfruit (H. megalanthus). In thisresearch, only white – fleshed and red – fleshed dragon fruits are considered.
White– fleshed dragon fruits (Hylocereusundatus) are the most popular kind in the genus, which are widely grown inthe tropical regions. They are lithophytic or hemiepiphytic species that sprawlby using aerial root on rocks or tree with the reaching height up to 10 metersor more (Staples & Herbst, 2005). The fruit is oblongor oval with various sizes from 6 – 12 cm long and 4 – 9 cm thick. It hasedible white pulp and small black seeds that contain high amount of essentialoils (Anderson, 2001). Likewise, red – fleshed dragon fruits(Hylocereus polyrhizus) are alsohemiepiphyte plants with impressive ornamental vine and huge flowers. They areeasy to cultivate and fast growing in the regions of dry or deciduous coastalforests (Hammel, 2013). As called, they have bright magentapulp with pear – shaped seeds and ovate or globous shape.InVietnam, there are more than 40 varieties of dragon fruit grown, 95% of whichbelong to H.
undatus species whilethe remaining 5% derive from H.polyrhizus. They are grown mainly in Red River Delta and Southern part ofVietnam. According to Vietnam Trade’s report in 2017, the cultivated areas of dragonfruits have increased from 5,000 hectares in 2000 to 25,000 hectares with theproduction mass of 614.346 tons in 2014 (http://vietnamtradeoffice.
net/).Due to the increasing rate in production for the past few years, the price ofdragon fruits also tends to rise. The season of dragon fruits is from April to Octoberand depending on the harvest, one kilogram of dragon fruit may range from 8,000to 20,000 VND, though the red – fleshed dragon fruit may cost higher. Besideinternal trading, dragon fruit production also plays an important role inexportation to China, the United States, and South East Asia regions, etc.Therefore, the cultivation of dragon fruits can be considered as a resolutionto raise the living standard of poor farmers in Vietnam. For the physiological properties, previous studies have found thatdragon fruits are rich in phytonutrients and antioxidant compounds.
The highestamount of antioxidant content present in dragon fruits is vitamin C, whichaccounts for 10% of the daily value (Mercola, 2017). Along with vitaminC, dragon fruits are also known as a good source for thiamin vitamin and otherB vitamins that help in breaking down of foods in the body. The phytochemicalcaptin present in the fruit is used in medication to treat heart problems.Dragon fruits have no complex carbohydrate.
The carbohydrate source comes fromfructose and glucose, which are the main sugar component in the fruits (Liaotrakoon, 2013).Besides, they also contain other nutrients such as polyunsaturated (good) fattyacids, carotene, and protein. Lycopene pigment, a carotene responsible for thered color in red – fleshed dragon fruit, is believed to help in lowering the oxidativeDNA damage, thus preventing the prostate cancer risk (Shahar, et al.
, 2011). The mineral contentin dragon fruit includes calcium, which is believed to be beneficial for strongbones and teeth, iron and phosphorous that help in tissue formation and bloodcirculation. These positive effects from the fruits can be realized in numerousways from consolidated immune system to fewer respiratory problems. For theseeds, dragon fruits’ seeds are high in polyunsaturated fats (omega-3 andomega-6 fatty acids) that reduce triglycerides and lower the risk ofcardiovascular diseases. The seeds oil is also used in medication as mildlaxative. Frequent consumption of dragon fruit can help in maintaining normalbody function such as removing from the body toxic heavy metals and improvingeyesight (Mercola, 2017).
oSaccharomyces cerevisiae is a species of yeast that is widely used in the making ofalcoholic beverages and baking goods. It is a eukaryotic microbe that hasglobular shape, yellow-green color and belongs to the Fungi kingdom. In nature,S.
cerevisiae is mainly found on thesurfaces of plants and ripe fruits such as grapes, the gastrointestinal tractsand body surfaces of insects and warm-blooded animals, soils from all regionsof the world and even in aquatic environments (Martini, 1992). Scerevisiae can live in both aerobic as well as anaerobic conditions. Underaerobic condition, the yeast undergoes respiration that uses oxygen to breakdown glucose into carbon dioxide to produce ATP. In the absence of oxygen, it feedson carbohydrate sources such as glucose, maltose, fructose, galactose, etc.
,however, they cannot grow on lactose and cellobiose (Bekatorou, Psarianos, & Koutinas, 2006). In the foodindustry, S. cerevisiae is used toanaerobically convert sugars from their substrate into ethanol in alcoholicbeverages. Depending on different types of beverages, different ways of thisyeast fermentation is applied. In baking industry, S.
cerevisiae acts as a leavening agent by releasing gases thatform holes and create soft structure of the baked goods. The yeast also worksas a probiotic that helps eliminate the potentially pathogenic bacteriaresiding since it does not colonize the GI tract permanently.