Sweetpotato Facts
Of the many, many applications of sweetpotatoes, perhaps none is so exciting as their potential role in space. Sweetpotatoes are attracting considerable attention as a crop suitable for space stations, where they would help to allow humans to remain in space over long periods while attaining food self-sufficiency. Among their benefits for space use, sweetpotatoes produce edible foliage, contain well-balanced nutrients, and can be cultivated hydroponically. And just as importantly, they are easy to cook and can be eaten repeatedly without becoming tiresome. Tuskegee University in the U.S. is now working under commission from NASA to breed new sweetpotatoes suitable for the space environment.
The Miyazaki Prefecture Beverage Agricultural Association (Kawaminami-cho, Miyazaki) began marketing beverages and yogurt using sweetpotatoes in April 1997, through A Corp stores and automatic vending machines in the prefecture. These products use the J-Red sweetpotato, which is a carotene-rich variety developed for juicing by the Sweetpotato Breeding Laboratory, part of the Ministry of Agriculture Forestry and Fisheries' Kyushu National Agricultural Experiment Station. The beverage contains 35% sweetpotato extract, along with carrot and apple juices, with no added sweeteners. The yogurt contains 10% sweetpotato juice, along with milk and fermented milk, and has a faint flavor of baked sweetpotato.
J-Red was developed through an R & D effort initiated by the Association in 1995 under a contract with farmers in the prefecture. While sweetpotatoes are generally rich in vitamins and dietary fiber, this variety contains more beta-carotene than carrots do. The company regards beauty and health as the products' selling points, and is targeting women and children. They have high expectations for both products, which are priced at 110 yen for a 195 g container. According to the Yamaichi Securities Economic Research Institute, demand for tea-based drinks such as barley or green tea, and for vegetable drinks is predicted to increase. Under these conditions, sweetpotato beverage and yogurt can be expected to receive a favorable market reception.
Since the deregulation of local beer production, locally produced beer has played an important role in activating local economies in Japan. Since April, 1996, micro brews have been created by the "Koedo Brewery Kawagoe," of Kawagoe. The brewery's leading product is sweetpotato lager, produced from roast local sweetpotatoes. It contains 7% alcohol and tastes like something between beer and wine, with a faint sweetness. Visitors to the brewery can enjoy food as well as sparkling liquor in the brewery's restaurant while observing brewery operations. The introduction of more such attractive facilities will have positive benefits for sweetpotato demand.
4) A full course of sweetpotatoes
There is a famous Japanese saying that implies the most delicious sweetpotatoes come from Kawagoe. Indeed, in Kawagoe, there is a restaurant that provides an entire dinner organized around the sweetpotato. "Imozen," the restaurant in question, opened in 1982 and has established itself as an expert in preparation of Kawagoe's local specialty. Many guests order the restaurant's "Imokaiseki" sweetpotato meal which is offered year round. Mr. Kamiyama, the restaurant's owner, had a hard time opening the restaurant and setting the business on its way. In April 1989, he established the Sweetpotato Museum to spread the message of "Sweetpotato Culture," and it now serves as a major reference source for information on the history of sweetpotatoes in Kawagoe and around the world.
Home page: http://www.kawagoe.com/imo_idx.html
5) A general-purpose potato harvester
Less than half as much land worldwide is devoted to sweetpotatoes as to conventional potatoes. One reason is that key farming systems for sweetpotatoes cannot be easily mechanized. According to data on production costs, it takes 67.1 hours to bring 10 ares of sweetpotatoes to harvest, vs. 9.3 hours for potatoes (or 720% longer). The sprout transplantation and harvest phases are particularly time-consuming. In an effort to reduce the time required for harvesting, the Biological Specific Industrial Technology Research Promotion Organization (formerly the Agricultural Mechanization Research Institute) developed a general-purpose potato harvester in 1996.
This harvester, developed by improving the conventional-potato harvester, is capable of harvesting, foliage processing, sorting and storing sweetpotatoes, potatoes and taro. At present, it is difficult to use the harvester to collect sweetpotatoes for fresh consumption, because it tends to peel off the potato's skin, but it can be used for sweetpotatoes intended for processed foods. Before long, the harvester should be employed in large-scale sweetpotato cultivation areas.
6) A Chinese sweetpotato, "Shori No. 100"
"Okinawa No. 100" supported the Japanese during and after World War II. Bred in Okinawa in 1934, this variety was originally suitable for early cultivation and had a notably good taste; when raised in other areas of Japan, however, it tasted far less good. However, its yield was extremely high and it was easy to cultivate, so "Okinawa No. 100" was cultivated throughout Japan and went on to save the lives of many people during the food shortage of the war era. At the same time, though, it gave many people cause to dislike sweetpotatoes. After the end of World War II, samples of "Okinawa No. 100" were brought to the Xuzhou Sweetpotato Research Institute, China. There, the variety was renamed "Shori No. 100" and utilized as a breeding material, a role that continues today.
7) The unique purple sweetpotato
More than 40 varieties of sweetpotatoes are now cultivated in Japan, some of which are unique. For instance, one variety looks like a common sweetpotato from the outside but has purple flesh. "Yamakawa murasaki," a traditional variety, contains relatively little saccharide and tastes bad, making it unsuitable for fresh consumption. However, since its flesh is dark purple, it can be processed into paste and/or flakes, then used for ice cream and imoame [sweetpotato candy]. By contrast, the "Tanegashima murasaki," a traditional variety from Tanegashima, is very sweet, and when steamed, becomes quite tasty without becoming soggy. These features make it a popular choice for fresh consumption. "Beniimo," produced in Okinawa, resembles the above variety.
"Ayamurasaki," which was bred from "Yamakawa murasaki," was released in 1995. It offers unsurpassed yields and anthocyan pigment levels, and is promising both for pigment-related and processing applications.
8) Functional components of sweetpotatoes
[Dietary fiber to decrease blood cholesterol]
Sweetpotatoes contains more dietary fiber than many other vegetables. Dietary fiber has two well-known functions: eliminating constipation and decreasing blood cholesterol. It also controls blood sugar levels, and can make an important contribution to modern dietary needs. Excessive intake of dietary fiber inhibits the absorption of minerals such as iron and calcium, however, so it is important to consume only appropriate amounts.
[The anticancer effects of beta-carotene]
Yellow-fleshed sweetpotatoes like "Benihayato" contain abundant beta-carotene, which functions in the body as vitamin A. Beta-carotene protects the biomembranes as a lipid antioxidant, and may also inhibit cancer cell growth. Dark green and yellow vegetables, including carrots, have a cancer-preventive effect by immunologically inhibiting cancer-promoting factors.
[Potassium - effective for lowering blood pressure]
Among the minerals in sweetpotatoes, potassium is present in the highest levels. The potassium content of boiled rice is 27 mg/100 g, but that of roast sweetpotatoes is 490 mg, or 18 times higher. Since potassium causes sodium to be excreted, it is effective for lowering blood pressure. In addition, since sweetpotatoes provide sodium-adsorbing and constipation-preventing effects through their dietary fiber, they can be essential to preventing hypertension.
[Sweetpotato vitamins make you more beautiful]
|
Vitamin A Promotes growth, prevents the skin from drying and leaves it healthy. Also helps in the treatment of acne and wrinkles. Vitamin B1 One of the vitamins contained in sweetpotato in large quantity. Helps saccharide utilization, and worsens fatigue when present in insufficient levels. Vitamin B2 Promotes growth, making the skin and mucous membranes healthy. However, it is not present in sweetpotatoes in high levels, and it is necessary to ingest animal products as well to maintain sufficient dietary levels. Vitamin C Present in sweetpotatoes at 10 times the level of apples. Plays an important role in forming collagen necessary to keep the skin healthy and is effective for preventing acne and healing scars. Vitamin E Inhibits the formation of peroxide lipid in the body, regarded as a cause of aging. Also defers cell aging and keeps the skin young, as part of the same function. |
9) Edible leaf petioles of sweetpotatoes
References to sweetpotato petioles may bring back gloomy memories to those who experienced the food shortages in Japan after World War II, but they remain a useful vegetable. In fact, in neighboring Korea and some Southeast Asian countries, they are used as a vegetable. In Japan, JA (agricutural cooperative) Toba-shima of Mie Prefecture ships sweetpotato petioles under the trade name "Green Stalk." Petioles are also marketed as a vegetable in Fukuoka and Okinawa Prefectures.
The cooking methods available for sweetpotato petioles are diverse. They can be used freely for aemono (dishes seasoned with various kinds of sauce), sunomono (dishes seasoned with vinegar), tempura (Japanese deep-fat fried food), nibitashi (stewed vegetables) and frying in oil. Varieties having petioles that are thicker, longer and less bitter are suited for salad. When chopped fine, such petioles can be added to misoshiru (miso soup) to create a tasty variation. High nutrient levels are a key selling point of sweetpotato petioles. They have three times the protein content of lettuce, and about twice the dietary fiber of cabbage. "Elegant Summer," released in 1996, features excellent petioles and is expected to be cultivated more widely for this purpose.
10) Sweetpotatoes and black pigs
Kagoshima Prefecture raises more pigs than any other prefecture in Japan. The prefecture's black pigs, Kagoshima's particular pride, are well-known throughout Japan for their delicious meat. Black pigs are smaller than Landrace, a white pig, and have a total of six white patches on their legs, nose and tail. Their flesh is good, their muscle fibers fine and elastic, and their meat, when cooked, has a crisp feeling in the mouth. According to historical records, the black pig was introduced from Ryukyu to Satsuma in about 1600. Meanwhile, sweetpotatoes were introduced from China to Rhyukyu in 1605, and reached Satsuma in 1705. It was at this point, some 380 years ago, that these two imports - the sweetpotato and the pig - became destined to meet.
Empirical findings indicate that sweetpotato feed improves the taste of pork. Black pigs raised on sweetpotatoes produce a meat generally light in color, which is delicious in both its lean and fatty portions. And deliciousness is a factor difficult to measure scientifically, studies thus far have revealed that meat from black pigs contains fat with a higher melting point. When cooked, the result is a slightly chewier meat with a higher fat content.
11) How to make a delicious roast sweetpotato
Many people prefer roast sweetpotatoes to other sweetpotato dishes, owing to their simple and delicious taste. Although there are fewer street stalls selling ishiyakiimo (sweetpotatoes roasted in hot pebbles) than was once the case, the roast sweetpotato continues to play a special role in the Japanese winter. But why is the ishiyakiimo made by professionals so delicious? There are three points to consider.
The first is the roasting. Sweetpotatoes contain amylase, an enzyme which decomposes starch into sugar and which becomes active at about 50 degrees C. Therefore, by heating sweetpotatoes using far infrared radiation or putting them into the ashes of an open-air fire, their sweetness is increased.
The second is water content. Sweetpotatoes roasted quickly are moist and sticky, while those roasted for an extremely long time become drier. According to professionals, the tastiest roast sweetpotato is obtained by roasting in a jet oven at 200-250 degrees C for about 40 minutes, keeping water content at about 65%.
The third is time since harvest. Once harvested, the sweetpotatoes should be matured for about 2 months. Maturation allows sweetness to increase; and when the potato is roasted, sweetness increases further. No special maturation method is required; ordinary preservation is sufficient. If possible, though, store the potatoes in a styrofoam container or wrap them in newspaper.
<<A simple, easy way of roasting "ishiyakiimo">>
|
Though most nonprofessionals consider it very difficult to make "ishiyakiimo," it is actually easier than you think. First, prepare a kettle and some pebbles. A used, damaged kettle will do, but an enameled kettle is better. Place the pebbles in the kettle, followed by the sweetpotatoes, then put the kettle on the fire. After about 40 minutes of roasting over a weak fire, your hot and tasty "ishiyakiimo" will be ready to eat. |
12) "Kansho Hyakuchin," a 1789 guide to sweetpotato cuisine
As sweetpotatoes gained a greater place in the public's eating consciousness, the number of cooking methods for them increased. The "Kansho Hyakuchin," written by a leading epicure of the day and published in 1789, is a unique text that introduces a number of popular and innovative sweetpotato dishes. In all, it provides 123 different recipes. This book is said to have been published as a companion volume to the earlier "Tofu Hyakuchin." The dishes introduced in the "Kansho Hyakuchin" can be classified into four types:
Unique dishes: 63Ordinary dishes. 21
Rare dishes (offering both excellent taste and appearance): 21
Exquisite dishes: 11 dishes
While the cooking utensils and seasonings available two centuries ago were likely simpler than those available now, the ideas, originality and ingenuity of the era remain impressive today. This unique book shows that sweetpotatoes played a key role in improving Japanese living standards and eating habits, and in extending Japanese cuisine in new directions.
13) History of imojochu (distilled sweetpotato liquor)
When did people begin drinking imojochu? The oldest existing reference to shochu in Japan can be found on a wood plate displaying the characters for shochu, which was written in 1559 at the Gunzan Hachiman shrine, Ooguchi city, Kagoshima Prefecture. Historical records also indicate that shochu was presented from Ryukyu to the Shimazu clan in Satsuma under the name of "raochu" and "toshoshu" in 1573.
Another early reference to shochu comes by way of St. Francis Xavier, famous for having introduced European culture into Japan. Acting on Xavier's advice, the Portuguese captain Jorje Alvares, who stayed at Yamakawa port in Satsuma in 1546, wrote his "Japan Report." Alvares' book cites shochu as oraka (a distilled spirit) commonly produced in Kagoshima, and imbibed by all people of all social standings.
In Japan, sake has long been made from the staple crop of the district. In the 17th century, when sweetpotatoes were grown all over Kagoshima, "imojochu" production was likely a well-established part of shochu culture. Later, Nariakira Shimazu, the noted 28th lord of Satsuma, encouraged imojochu production, and developed imojochu from a drink distributed mainly within the clan into an industry of Satsuma.
14) The best method of drinking imojochu
As a Class B spirit, imjochu is disliked by some due to its peculiar smell; however, it offers a deep taste and flavor that cannot be obtained from Class A shochu or spirits. Generally, imojochu is drunk after diluting it with hot water, but this step requires careful attention. First, use only good water, without exception. Use water treated by a water purifier or mineral water, if possible. Otherwise, pour hot water in a tea cup beforehand. Pour shochu into the cup after the hot water so that the shochu may be warmed from below by the hot water. Using this method, you can enjoy the unique flavor of imojochu most effectively. This drinking method is commonly adopted in Kagoshima, but it is a matter of regret that more than a few persons elsewhere are unacquainted with it.
15) Unusual root and tubers crops
[Polymnia sonchifolia Poeppig & Endlicher]
Polymnia sonchifolia Poeppig & Endlicher, an underground crop from a composite family menamomi polymnia genus, is native to the Andes highlands of South America. The plant has storage roots that resemble dahlias and sweetpotatoes in appearance. These tubers contain much moisture, and have a faint sweetness. If eaten raw (after peeling), the storage root has much the same texture and sweetness as a pear. Through frying or stewing they provide a taste similar to lotus roots. In fact, the tuber combines many of the characteristics of other fruits and vegetables.
The polymnia was first cultivated in Japan in 1985, when a seed/sprout company introduced rooted cuttings from New Zealand. Subsequently, the main components of the polymnia's storage root were found to be saccharides, over 80% of which were fructooligosaccharide. With this, the polymnia began to attract considerable attention for its potential as a low-calorie and functional root crop. Among composite plant family crops specifically containing inulin and fructooligosaccharide, it contains unsurpassed levels of fructooligosaccharide. It is thus expected to see widespread cultivation over the next few years, both as a source for fructooligosaccharide or as a raw material for producing fructose and, in Japan, as a low-calorie and functional root vegetable that can be eaten raw.
[Apios]
Apios americana has a necklace-shaped tuber, swollen from its underground stem. In the wild, the Apios is about the size of a fingertip. Through research and development by the Agriculture Faculty at Tohoku University, however, an improved version which is almost potato-sized has been developed. In North America, the Indians traditionally used the Apios as a source of food and medicine. In terms of taste, the Apios combines the flavors of the potato, sweetpotato and taro.
Apios contains a large quantity of B-group saponin (the main component of ginseng), and is also rich in calcium, iron, fiber, and protein. It contains vitamin E as well, which is present in potatoes in only low levels. As such, the Apios is a promising source of nutrition and health. Among other indications, it can be effective as a supplement of natural calcium, as a source of relief for intestinal disorders (by virtue of its abundant fiber) and food-based allergic reaction (atopy), and as a treatment for lumbago and arthralgia.
This tuber can be prepared in a number of ways, including boiled (just add salt and butter), sliced and fried, french-fried, stewed, or mashed.
16) Kawagoe Sweetpotato Museum (Kawagoe Satsumaimo Shiryokan)
Kawagoe City in Saitama Prefecture, sometimes known as "Little Edo," has had a reputation as a source of good sweetpotatoes since the Edo period. The "Sweetpotato Museum" is located in Kawagoe's Komuro district, toward the edge of the city. The Museum was opened in 1989 by Masahisa Kamiyama, owner of the local "Imozen" restaurant, which specializes in - what else? - sweetpotato dishes. Funded entirely by Mr. Kamiyama, the Museum is run by volunteers and is open without charge to the public. Housed in a two-story wooden building, the Museum is not particularly large (120 m2), but is the only facility of its type in Japan. It attracts around 100 visitors daily from districts around Japan.
Within the Museum, easy-to-understand exhibits cover themes such as "The history of sweetpotatoes," "Sweetpotatoes around the world" and "Why are sweetpotatoes healthy to eat?" An exhibit of fresh sweetpotatoes includes some twenty varieties, from traditional ones like "Beniaka" and "Taihaku" to just-developed varieties.
<Location>
18-5 Komuro, Kawagoe-shi, Saitama Prefecture 350-1106[TEL] 0492-43-8243, [FAX] 0492-41-7050
Home page: http://www.kawagoe.com/imo_shi.html
(Hours)
10 AM - 5 PMClosed Tuesdays
17) Kagoshima Information Center (Kagoshima Yurakukan), a new place of interest in Tokyo
If you want to learn more about sweetpotatoes and Japan's Kagoshima district, the place to visit is the "Kagoshima Information Center" (Kagoshima Yurakukan), opened in May 1995 in Tokyo's Yurakucho district. The Center gives visitors a chance to experience the atmosphere of Kagoshima - right in central Tokyo. It is also home to the Tokyo branch of "Sweetpotato House (Satsumaimo no yakata)," which sells processed foods made from sweetpotatoes produced in Kagoshima as well as specialty products made in Kagoshima. Actual varieties for sale include "Beniazuma," "Benisatsuma," and "Koganesengan" as well as the rare "Tanegashima murasaki," "Annoimo" and "Benihayato."
<Location>
Chiyoda Building 1-3F, 1-6-4 Yurakucho, Chiyoda-ku, Tokyo 100-0006[TEL] 03-3506-9177, [FAX] 03-3506-9178
(Sweetpotato House (Satsumaimo no yakata), Tokyo store, [TEL] 03-3580-8821)
(Traffic access)
Two minutes on foot from JR Yurakucho station; also, directly in front of the A4 exit of the Yurakucho stop on the Hibiya line (subway)
18) Sweetpotato House (Satsumaimo no yakata)
Sweetpotato House (Satsumaimo no yakata) is a clearing house for information on sweetpotatoes. Located on one corner of a gourmet shopping street in Kagoshima's bustling Tenmonkan district, Sweetpotato House (Satsumaimo no yakata) is intended to help raise the profile of Kagoshima-grown sweetpotatoes. Freshly harvested sweetpotatoes are available from the shop in-season, as are some 600 different processed products such as confectioneries and shochu. Very much the place to go if you're ready to learn more about sweetpotatoes.
<Location>
6-28 Higashi-Sengokumachi, Kagoshima-shi 892-0842[TEL] 0992-39-4865, [FAX] 0992-39-4862
<Opening hours>
10 AM - 7 PMClosed most Tuesdays