Table of content A-Z

 

yam

 

Botanical name: Dioscorea sp.


Yams

 

A total of about 250 species belong to the family Dioscorea. Some of these are called yams and originated in various tropical and subtropical regions of the earth. Some stem from Africa, others from China, Indonesia, the Philippines and Malaysia.

A large portion of the area under yam crops is in Africa; Nigeria alone delivers around half of the yams produced in the world. In the regions where it is grown the yam is as important as the potato is for us. Nevertheless, because of the difficulty of harvesting yams, the cultivation is declining.


Availability


It would be possible to have yams available all year round, but owing to the very low demand only small amounts are imported to Germany.


Appearance, taste, characteristics


The two most important of the numerous yam varieties are presented here:

* Water yam (Dioscorea alata)

This is native to Southeast Asia; it is grown in India, the Philippines and Polynesia.

The water yam bush forms roots up to 2 m long underground; these can weigh up to 50 kg. The shape of the fleshy roots varies greatly; it can be cylindrical, with or without branches. Its pulp is white to light yellow and can take on reddish or purple hues. Cooked water yam tastes slightly sweet and develops a mealy texture.

* Potato yam, or hardy yam (Dioscorea batatas)

This yam originated in China, where it is grown today, as well as in Korea, Japan and Taiwan.

Compared with the water yam, this species is considerably smaller and reaches a length of only 40 cm. It is oblong and without branches, resembling a potato. The skin is smooth and usually light to dark-brown. The texture, colour and flavour are comparable to those of the water yam. Further varieties are the yellow yam (Dioscorea cayennensis), which thrives in West Africa and Central America; the lesser yam (Dioscorea esculenta); the white yam (Dioscorea rotundata), that also grows in West Africa; and the bitter yam (Dioscorea dumentorum) from Central Africa. Also known as the potato yam is the variety Dioscorea bulbifera, which stems from tropical Africa and Asia.


Ingredients


The ingredients of the yam are similar to those of the potato.

100 g contain:


Yam, fresh
Energie (kcal)
101
Wasser (g)
69
Eiweiß (g)
2
Fett (g)
< 1
Kohlenhydrate (g)
22
Ballaststoffe (g)
5,6
Vitamin C (mg)
10
Vitamin B1 (μg)
90
Vitamin B6 (μg)
160
Folsäure (μg)
23
Kalium (mg)
393
Calcium (mg)
25
Magnesium (mg)
21
Phosphor (mg)
44
Eisen (mg)
0,7



Harmful substances


Some varieties of yam contain the alkaloid dioscorine, but it is destroyed by cooking and the tubers can be eaten without hesitation. Dioscorine is a spasmogenic; it causes cramps.


Quality criteria, optimal storage conditions


As with potatoes, you should look for firmness and for any possible damage to the tuber. In a cool, but not cold, cellar room yams can be kept for several weeks.


Form of consumption, use, processing, practical tips for preparation


Yams are prepared like potatoes. The peeled roots are cooked for about 40 minutes and are eaten as a side dish. Alternatively, they are mashed and prepared as a purée, known in Africa as "fufu". This is an accompaniment to fish or meat and is eaten with hot, spicy sauces.

Baked in the skin, the yam can be served like a jacket potato. It is usual to season it with salt and pepper and to put a pat of butter on the hot tuber. Yams can also be filled with the most varied ingredients and baked with a cheese topping, or they can be made into casseroles, gratins and soups.

The yam root is used industrially to obtain starch, called dioscorea starch or arrowroot starch.


Miscellaneous


The offering by the greengrocer or the supermarket is often confusing, because sweet potatoes, taro and the arrowleaf elephant ear tuber are also frequently sold as "yams", and vice versa.

 

 

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