Studies On Sweet Potato Leaves For Vegetable Use

In this paper we determine chemical components of seven kinds of sweet potato leaves and compare their nutritive values with three common leafy vegetables. We select sweet potato breeds with high nutritive values, this provides academic foundation for sweet potato quality breeding and hygienical food exploitation. As we known that sweet potato leaves are rich in flavonoids, we investigate extraction technics of flavonoids from sweet potato leaves systemically, and analyze the flavonoids content with selected vegetables.Edibleness, total sugar, reductive sugar, protein and vitamin C are more credible among the indexes. "Japan" is rich in all nutritive components, low in water, prone to store and transportation, so it is the most suitable for vegetable use. Content of seven essential mineral elements for human body in sweet potato leaves is K>Mg>P>Na>Fe>Zn>Cu, this natural distributing trend accord with human needs. So sweet potato leaves are edible as vegetables and it is better for human body's growth and development and physical robustness. Three factors (alcohol concentration, solid-liquid ratio, ultrasonic time) affect the extracting efficiency obviously during the extraction of flavonoids by ultrasonic. Basing on the experiment of single factor, the optimum extraction conditions of flavonoids from the leaves of sweet potato using ultrasonic method is studied according to the orthogonal design. The optimum extracting conditions are as following: 80% alcohol, treating with ultrasonic for 45 min, 40 times volumes. Different alcohol concentration takes more effect on the extraction ratio, while different ultrasonic time and solid-liquid ratio take little effect on the extraction ratio. Certain variation in the flavonoid contents has been found under the optimum extracting condition among the breeds tested with change range between 7.06% and 10.74%, average 8.71%. The result shows the flavonoids content in sweet potato leaves is higher than the selected vegetable, which is always considered as high in flavonoids content.Analysis of nutritive content in kinds of sweet potato leaves enriches the food database, provides academic foundation of sweet potato leaves for vegetable use, and it provides a theoretics basis and technologic parameters for the industrialization of flavonoids in sweet potato leaves.