The nutritional value of sweet potato is an important reason why people pay attention to it again. More and more studies show that sweet potato is rich in starch and soluble sugar, and also contains protein, fatty acids, vitamins, amino acids and inorganic salts such as calcium, phosphorus and iron. It is reported that VB 1 and VB2 are twice that of rice flour; VE is 9.5 times that of wheat, and cellulose is 10 times that of rice flour. The content of VA and VC is higher than that of rice flour, while that of rice is zero.
Sweet potato is a "physiological alkaline" food, containing minerals such as calcium, phosphorus and iron, which can neutralize excessive acid produced by eating acidic foods such as meat, eggs, fish, rice and noodles to maintain the acid-base balance in the human body. The cellulose content of sweet potato is as high as 7.8%, which can stimulate intestinal wall, accelerate gastrointestinal peristalsis and absorb water, increase fecal volume and help defecation, thus reducing the chance of self-poisoning caused by constipation, delaying the aging process of people and helping to prevent hemorrhoids and colorectal cancer.
Today, in the pursuit of bodybuilding and longevity, sweet potato is regarded as an ideal health food to lose weight and prolong life, which is popular all over the world. According to the dietary survey of longevity people in Ma Xian County, China, and some Japanese areas, it is found that these longevity people have a common feature, that is, they all have a special hobby, that is, eating sweet potatoes. Because of the high nutritional value of sweet potato, NASA screened sweet potato from many crops as "space food".
People living in cities tend to eat too carefully, and their dietary fiber intake is seriously insufficient, which is easy to induce constipation. Sweet potato contains a variety of cellulose and pectin that are not easily destroyed by digestive enzymes, which can effectively stimulate the secretion of digestive juice and gastrointestinal peristalsis and make the stool smooth.
2 medical use
The health care function of sweet potato has been valued by people since ancient times. Li Shizhen, a famous Chinese doctor in Ming Dynasty, recorded in Compendium of Materia Medica that "steaming, cutting, drying and harvesting sweet potato can make people live longer and have fewer diseases", and pointed out that sweet potato has the functions of nourishing spleen and stomach, nourishing heart and benefiting qi, promoting blood circulation and removing blood stasis, and clearing away heat and toxic materials. From the research of modern Chinese medicine, it is considered that strengthening spleen and benefiting qi is an important method to enhance human immune function; Detoxifying, eliminating dampness and clearing heat are the meanings of "strengthening the body resistance and consolidating the foundation" in treating tumors.
From today's point of view, the most important diseases affecting human life span are cancer and cardiovascular diseases, and sweet potato has a unique role in preventing and treating these two diseases. This is inseparable from the special nutrients it contains.
The biggest feature of sweet potato is its unique dehydroepiandrosterone, which can prevent cancer and prolong life. It is a steroid, similar to the hormone secreted by mammalian adrenal gland. Professor Arthur Schnitz, a biologist in Philadelphia, USA, proposed this substance from sweet potato and called it "fake hormone" or DHEA. He injected "DHEA" into mice inoculated with cancer cells, which could prevent mice from suffering from colon cancer and breast cancer, and the life span of normal mice was extended from 24 months to 36 months.
Japanese scientists also found that sweet potato contains mucin, which is a mixture of polysaccharide and protein, and belongs to collagen and mucopolysaccharide. It has a special protective effect on the mucosa of various organs and tissues of human digestive system, respiratory system and urinary system, such as maintaining arterial elasticity; Maintain the lubrication of articular surface and serosa cavity in articular cavity; Prevent the atrophy of connective tissue of liver and kidney, and prevent the occurrence of collagen disease. Without this mucus, all organs and tissues are prone to inflammation and canceration. This substance is not even available for chicken, duck and fish, but only for sweet potatoes.
According to the publication of Japan Anti-Cancer Association, the residue of sweet potato starch contains a glycolipid, which can inhibit the proliferation of cancer cells to below 1/5 when injected into the culture solution of uterine cancer and skin cancer. This glycolipid is contained in the leaves and tubers of sweet potato. According to the research of Japan National Institute of Prevention, sweet potato ranks first among 12 kinds of vegetables with cancer prevention and health care functions, and is known as the "king of cancer prevention".
Sweet potato is also rich in anti-cancer substances such as carotene (1.31mg/100g), vitamin C(30 mg/100 g) and lysine (25mg/100g). Carotene can be converted into vitamin A when it enters the human body. VA can prevent and inhibit the proliferation of cancer cells and restore the function of normal tissues. The synergistic effect of VA, VC and VE can make the chemical oxidants that cause cancer in the body fail, thus playing a role in preventing cancer. VC can promote the growth of fibrous tissue, form a dense "encirclement" around the tumor and prevent the tumor from spreading. The antiviral effect of VC can prevent some tumors originating from viruses.
Animal experiments have proved that the simultaneous use of lysine and anticancer drugs can alleviate gastrointestinal discomfort and avoid the obvious decline of white blood cells and red blood cells. Lysine can prevent cancer cells from absorbing nutrients, thus inhibiting the crazy reproduction of tumor cells. The experiment of medicinal sweet potato "Simon 1" proves that it has anticancer effect.
Sweet potato is also an ideal diet food. Why? First of all, sweet potatoes are low in calories; Secondly, sweet potatoes have a strong satiety and tend to swell up, so it is generally not easy to eat more. Therefore, eating sweet potatoes often will not be obese, but can maintain a moderate body shape. Therefore, sweet potato is known as the food with the most balanced nutrition.
3 the use of vegetables
In recent years, sweet potato leaves and sweet potato tips have gradually stepped onto the dining table of urbanites and even become a special dish in hotels. Especially after being confirmed by experts and reported by domestic and foreign media, its value has doubled and it has been favored by more and more families.
Sweet potato stems and tender tips of vines are nutritious and healthy vegetables. According to the determination of fresh stems and leaves of sweet potato, the content of protein is 2.74%, carotene is 5580 international units/100g, vitamin B2 is 35mg/kg, vitamin C is 4 1.07mg/kg, iron is 3.9mg/ 100g, and calcium is 74. According to the research, compared with spinach, leek and other 14 vegetables, the contents of protein, carotene, calcium, phosphorus, iron and vitamin C in sweet potato leaves are the first. The contents of VB 1, VB2, VB6, calcium and iron in sweet potato leaves are more than twice that of spinach, but oxalic acid is only half that of spinach. Therefore, the United States listed sweet potato as one of the healthy and longevity dishes with great development prospects. Japan, the United States, Taiwan Province Province and other places list sweet potato as "longevity food", while Hongkong, France and other places call sweet potato leaves and tips "the queen of vegetables".
According to medical and nutritional experts, sweet potato leaves and potato tips have the functions of enhancing immune function, promoting metabolism, delaying aging, lowering blood sugar, relaxing bowels and diuresis, especially effectively preventing arteriosclerosis and various tumors, and have good health care functions and medical effects in preventing cell canceration. Sweet potato leaves are not only nutritious food for people, but also "functional food" for patients. Therefore, the price of sweet potato leaves per 1000 gram in Hong Kong food market is about 100 Hong Kong dollars. Centenarians in Changshou Township, China like to eat sweet potatoes, which shows that eating sweet potatoes is beneficial to longevity.
4 feed
The tuberous roots, stems and leaves of sweet potato are all feed with high nutritional value. Stems and leaves are rich in protein, carbohydrates and fat. By-products of sweet potato processing, such as powder residue, sugar residue, wine residue, etc. It is also rich in nutrients and is a good feed for livestock and poultry. The abandonment of sweet potato tubers, stems and leaves or by-products not only further improves its nutritional value, but also prolongs the supply period of feed.
5 industrial raw materials
Sweet potato can be used in agricultural and sideline products, food, medicine, daily chemicals, packaging materials and other deep processing production fields. In particular, starch and its derivatives, such as whole sugar, anhydrous glucose, high concentration glucose, oligosaccharides, sorbitol, sweet potato alcohol and so on, have been widely used in food, medicine, daily chemical and other industries, with considerable economic benefits and broad market prospects.
Using sweet potato starch as the base material, it can be made into fully decomposed, nontoxic and harmless green packaging materials and agricultural films; Disposable tableware produced by fully degradable starch foaming technology can be made into fertilizer or feed after recycling, and can be completely degraded within 60 days after being discarded. Therefore, eliminating "white pollution" is a promising industry supported by environmental protection at present.
The crude starch produced by sweet potato can be directly transformed into single-cell protein by mixed culture of two strains without hydrolysis or enzymolysis, and its feeding effect is close to that of imported high-quality fish meal. Sweet potato refined starch can produce 100 kinds of valuable chemical products through deep processing of different processes, and the added value reaches about 30 times.