MINI WHITE PAPER ON SWEET POTATOES

I Special Features of Sweetpotatoes

While sweetpotatoes are a familiar crop to most, they often suffer from a negative reputation as an emergency food source. Also, more than a few people firmly believe that sweetpotatoes cause obesity. In reality, however, sweetpotatoes are a highly functional, low-calorie food that contain various key nutrients. They're even effective in beauty care! To learn more about sweetpotatoes, read on below:

1. A healthy and nutritious crop

With growing concern among consumers about health and nature, the nutritional strengths of sweetpotatoes are again attracting attention. Every sweetpotato contains high levels of starch, along with abundant vitamins, minerals and dietary fiber (such as cellulose and pectin). Indeed, sweetpotatoes can be considered at least a "semi-perfect" food because they can provide an ideal meal when consumed in conjunction with proteins and fats.

　○ Main nutrients of sweetpotatoes

[Vitamins]　

Beta-carotene

Changes to vitamin A in the body, functions as a lipid antioxidant, protects biological membranes, and may inhibit the growth of cancer cells.

Vitamin B1

One of the vitamins contained in large quantities in sweetpotatoes. It promotes saccharide utilization; B1 deficiencies can worsen fatigue.

Vitamin C

Found in sweetpotatoes at 10 times the concentration in apples. Promotes collagen formation which strengthens cellular bonds. Also, vitamin-C levels in sweetpotatoes are barely affected by cooking, due to the effects of starch paste.

Vitamin E

Inhibits the internal formation of peroxide lipids, said to cause aging.

[Minerals and dietary fiber]

Potassium

Discharges sodium from the kidneys, and is effective for lowering blood pressure. Sweetpotatoes have 18 times the potassium content of boiled rice, and possess far more potassium than most vegetables as well.

Dietary fiber

Sweetpotatoes contain much more dietary fiber than many other vegetables. This fiber not only helps avoid constipation but also reduces blood cholesterol and controls blood sugar levels.

2. Versatile processing use

Sweetpotatoes are characterized by great versatility: they can be processed for an extremely wide range of purposes. In addition to common household uses, sweetpotatoes are employed in a number of well-known Japanese delicacies including yakiimo (roast sweetpotatoes) and daigakuimo (fried sweetpotatoes coated with sugar syrup and sesame seed); starches and confectioneries; and imojochu (a spirit distilled from sweetpotatoes). Recently, uses of sweetpotato has expanded into new fields including semi-processed foods (frozen foods utilizing diced and other forms of sweetpotato, flakes, juice, and powder), and beer.

　○ Uses of processed sweetpotato

From starches

Sweeteners in soft drinks, harusame (clear noodles), kuzukiri, and citric acid

For foods

For confectionery

Dried sweetpotatoes (mushikiriboshi -- dried slices of steamed sweetpotatoes), "imoyokan (sweetpotato paste)", "imosenbei" (Japanese crackers made of sweetpotatoes), imokarinto (fried sweetpotato sticks), imoamanatto (sugar-glazed sweetpotatoes), imoame (sweetpotato candy), kintsuba, sweetpotato cakes, cookies, cakes, and ice creams

For delicatessens

Daigakuimo, salad

Semi-processed food

Frozen diced sweetpotatoes, flakes, paste, juice, powder

For brewing

Class A and B "Imojochu" (a spirit distilled from sweetpotato), beer, and wine

3. An upland crop offering superior environmental performance

Sweetpotatoes are a mainstay crop essential for the planting systems used in upland regions of Kanto and southern Kyushu. In fact, during Japan's years of food shortage during and after World War II, the Kanto area and the lands to the west were planted almost exclusively in sweetpotatoes during the summer season. From a farm management perspective, sweetpotatoes offer the following characteristics:

○ Characteristics as an upland field crop

Extensive growth

When cultivated in dense patches, sweetpotatoes shield the field from weeds because of their vigorous vine growth, thereby reducing the amount of labor needed to maintain the fields until harvest time. In addition, sweetpotatoes can be harvested over an extended period, using flexible labor distribution. Fields used for sweetpotatoes can be planted with a variety of other crops in alternate growing seasons.

Environmental consciousness

Since a sweetpotato's roots absorb nutrients better than those of other crops, adequate yields can be expected - as long as temperature conditions are satisfied - even in poor volcanic ash soil and acidic soil. Sweetpotatoes also require relatively little nitrogen fertilizer, giving them positive environmental properties: fewer agrochemicals used means less contamination of underground water supplies.

Tolerance to environmental extremes

Sweetpotatoes are tolerant to wind damage due to their creeping nature. And since their vines and leaves completely cover the ground surface, they prevent soil erosion and runoff. They also prevent soil moisture from evaporating and help to mitigate potential damage during drought. In fact, low temperature is the only threat to sweetpotato production; otherwise, harvests are quite stable from year to year.

[Vitamins]
Beta-carotene	Changes to vitamin A in the body, functions as a lipid antioxidant, protects biological membranes, and may inhibit the growth of cancer cells.
Vitamin B1	One of the vitamins contained in large quantities in sweetpotatoes. It promotes saccharide utilization; B1 deficiencies can worsen fatigue.
Vitamin C	Found in sweetpotatoes at 10 times the concentration in apples. Promotes collagen formation which strengthens cellular bonds. Also, vitamin-C levels in sweetpotatoes are barely affected by cooking, due to the effects of starch paste.
Vitamin E	Inhibits the internal formation of peroxide lipids, said to cause aging.
[Minerals and dietary fiber]
Potassium	Discharges sodium from the kidneys, and is effective for lowering blood pressure. Sweetpotatoes have 18 times the potassium content of boiled rice, and possess far more potassium than most vegetables as well.
Dietary fiber	Sweetpotatoes contain much more dietary fiber than many other vegetables. This fiber not only helps avoid constipation but also reduces blood cholesterol and controls blood sugar levels.

From starches		Sweeteners in soft drinks, harusame (clear noodles), kuzukiri, and citric acid
For foods	For confectionery	Dried sweetpotatoes (mushikiriboshi -- dried slices of steamed sweetpotatoes), "imoyokan (sweetpotato paste)", "imosenbei" (Japanese crackers made of sweetpotatoes), imokarinto (fried sweetpotato sticks), imoamanatto (sugar-glazed sweetpotatoes), imoame (sweetpotato candy), kintsuba, sweetpotato cakes, cookies, cakes, and ice creams
	For delicatessens	Daigakuimo, salad
	Semi-processed food	Frozen diced sweetpotatoes, flakes, paste, juice, powder
For brewing		Class A and B "Imojochu" (a spirit distilled from sweetpotato), beer, and wine

Extensive growth	When cultivated in dense patches, sweetpotatoes shield the field from weeds because of their vigorous vine growth, thereby reducing the amount of labor needed to maintain the fields until harvest time. In addition, sweetpotatoes can be harvested over an extended period, using flexible labor distribution. Fields used for sweetpotatoes can be planted with a variety of other crops in alternate growing seasons.
Environmental consciousness	Since a sweetpotato's roots absorb nutrients better than those of other crops, adequate yields can be expected - as long as temperature conditions are satisfied - even in poor volcanic ash soil and acidic soil. Sweetpotatoes also require relatively little nitrogen fertilizer, giving them positive environmental properties: fewer agrochemicals used means less contamination of underground water supplies.
Tolerance to environmental extremes	Sweetpotatoes are tolerant to wind damage due to their creeping nature. And since their vines and leaves completely cover the ground surface, they prevent soil erosion and runoff. They also prevent soil moisture from evaporating and help to mitigate potential damage during drought. In fact, low temperature is the only threat to sweetpotato production; otherwise, harvests are quite stable from year to year.