pitaya, also known as red dragon fruit, is a fruit cultivated variety of Hylocereus undatus, a genus of Cactaceae, which is native to tropical Central America such as Brazil and Mexico. The fruit of pitaya is oval, with a diameter of 1~12cm. The skin color is purple, gorgeous and charming, while the pulp color is white, yellow and red. Pitaya is widely cultivated in Taiwan Province, China, with a history of 178 years. At present, it has risen in Hainan, Guangxi, Guangdong, Fujian and other provinces, and sporadic cultivation is also seen in Chaoshan area. It is one of the famous tropical and subtropical fruits, and the research on Pitaya has been paid more and more attention.

1. nutritional value of pitaya

in August p>2, we determined some nutritional qualities of pitaya. The test material pitaya is a red-skinned and white-fleshed variety, which was purchased from Chaozhou fruit and vegetable market and cultivated locally. Determination method: The content of soluble solids (TSS) was determined by Abbe refractometer. Vitamin C(VitC) was titrated with 2,6-dichlorophenol indophenol [1]; The content of protein was determined by Coomassie brilliant blue staining, and bovine serum protein was the blank control [2]. The moisture content was determined by a rapid moisture analyzer. The determination was carried out in the laboratory at room temperature, repeated three times and averaged. The determination results are shown in Table 1.

The determination results are consistent with those reported by Chen Zhendong and others. In addition, according to Chen Zhendong and others, every 1g of pitaya fresh fruit also contains .21~.61g of fat, .7~.9 mg of fiber, .5~.12mg of carotene, 6.3 ~ 8.8mg of Ca, 2.2 ~ 26.1mg of P and .5F. It can be seen that pitaya is a kind of low-calorie and high-fiber fruit with rich nutrition. Besides, during the cultivation process, its fruit has not been damaged by pests and diseases, so it is a non-toxic and pollution-free green food.

2. the health function of pitaya

because pitaya has the above components, it determines the dietotherapy and medicinal function of pitaya. according to literature [4], the flowers of Hylocereus undatus are medicinal, sweet, light, cool and fragrant. Clearing heat, moistening lung and relieving cough. Treat cough due to dryness and heat, hemoptysis, and cervical lymph node tuberculosis. Stem cures parotitis, hernia and carbuncle. Pitaya is a fruit cultivation variety with a measuring ruler, so its flowers and stems should have the same curative effect as the measuring ruler in medicine. As we know, dietary fiber is called the seventh nutritional element of human body, which has the functions of lowering plasma cholesterol, improving blood sugar production reaction, preventing constipation and colon cancer, controlling weight, reducing estrogen level and detoxifying [5]. As a low-calorie and high-fiber fruit, the dietotherapy effect of pitaya is self-evident. Regular consumption of pitaya can lower blood pressure, reduce blood fat, moisten the lungs, detoxify, maintain beauty and improve eyesight, and has an auxiliary treatment effect on constipation and diabetes. Low-calorie and high-fiber pitaya is also the most ideal food for people who want to lose weight and maintain beauty, which can prevent the spread of "urban rich diseases".