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18 Yambean
Pages 322-344

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From page 323...
... Part of Thailand's large yambean output, for instance, is now shipped to many Asian stores in major European cities. This American crop has even entered production trials in Portugal, where, under conditions seemingly so different from its native tropical habitat, it has demonstrated very impressive yields: 54 tons per hectare, with up to 24 percent dry matter containing 10 percent crude protein.5 1Several Pachyrhizus species go by this name, but the best known and best developed yambean is Pachyrhizus erosus.
From page 324...
... 6 Both the Mexican yambean (Pachyrhizus erosus) and the Amazon yambean (Pachyrhizus tuberosus)
From page 325...
... Its tubers, however, are elongated and look more like sweet potatoes than yams. In nutritional terms, they are a class above the mainline root crops, containing more than twice the protein of sweet potatoes, yams, or potatoes and more than ten times that of cassava.
From page 326...
... Part of the reason for this adaptability to bad substrates is that like other members of the legume family, the African yambean enjoys a symbiosis with bacteria that fix nitrogen from the air. The invisible bacterial microbes inhabiting its roots relieve the farmer of the necessity to supply additional nitrogenous fertilizer.
From page 327...
... Any root crop even vaguely capable of delivering record quantities of protein from soils normally considered marginal would seem to deserve intense global attention. For all its potential, though, African yambean remains a neglected, even primitive, resource.
From page 328...
... Moreover, it grows easily and is well suited to the difficult environment of the hot wet tropics where the climate and conditions now constrain local diets to far less nutritious foods. And the tubers, with their succulence and crunchy texture, could appeal to millions of palates.
From page 329...
... 2005. Nutritional value of African yambean (Sphenostylis stenocarpa L)
From page 330...
... Roots The tubers are eaten either raw or cooked. The exact details are still unclear, but some idea of their eventual utility can be inferred from the yambean in Mexico, where: · Raw tubers are cut into sticks and sprinkled with lime juice and chili;13 · Fresh tuber slices are added to salads of both the dinner and dessert kinds; · Cooked tubers are used on their own or with other vegetables to prepare soup; · Chopped tuber is added to Oriental stirfries; · Tubers are grated and boiled in milk to create a tasty drink; · Sliced or diced tubers are pickled with onion and chili to form a popular snack food; or · Tuber segments and green beans are preserved in vinegar as a sort of three-bean salad.
From page 331...
... In a protein, quality is judged by the incidence of a few amino acids, and many plant proteins, being deficient in lysine and methionine, are low in nutritional quality. On the other hand, Africanyambean seed protein contains those two in abundance: lysine 7-8 percent and methionine 1-2 percent.
From page 332...
... In nutritional terms, they are a class above the mainline root crops, containing more than twice the protein of sweet potatoes, yams, or potatoes and more than ten times that of cassava. Moreover, the protein is of exceptional nutritional quality, superbly complementing the proteins of maize, sorghum and the other staples.
From page 333...
... When that happens their bodies stop producing all protein -- brain, muscle, hair, antibodies, enzymes, blood cells, skin, and the rest. In such situations, the addition of even a small amount of the missing essential amino acid from, say, yambean raises the overall protein effectiveness out of all proportion and restores the bodily processes to normal operation.
From page 334...
... . An alternate route suggested by the authors was Rhizopus- and lactic-acid fermentation, as used with soybean, which greatly reduces most of these antinutritional factors with much less energy cost, while yielding additional fermented foods for this part of the world, where such delicacies are already 18Alternatively, they are loaded straight into trucks and whisked to a local market, to Mexico City, or to the northern border for cleaning and repackaging, and onward shipment to US supermarkets.
From page 335...
... Southern Nigerians, for instance, like darker types, while northerners want brightly colored seeds. · High moisture content makes yambeans shrivel and lose condition more quickly than the mainstream root crops.
From page 336...
... In particular, the presence and fate of potential cyanogenic glycosides in both raw and cooked portions should be traced from plant to plate, just as they have been in soybean, cassava, sorghum, and other staples carrying these compounds. · Culinary Issues The long cooking time is a barrier to the plant's wider use as a bean crop.
From page 337...
... Yambean tubers, for example, may well prove an attractive addition to various traditional dishes, as well as a popular snack. · Pods In India, young American yambean pods are eaten like French beans.
From page 338...
... Early maturing cultivars are known in yambean, and likely exist in the African form as well; · Quick-cooking seeds; · Lower levels of potential antinutritional factors; · Thick-skinned tubers that don't bruise during shipping and have a long shelf life; and · Tubers of good size and taste for consumer acceptance.28 26In the Mexican species there is said to be a strong positive correlation between seed size and yield. 27Although unreported in African yambean, this alkaloid is found in the leaves and pods of New World yambeans.
From page 339...
... With all the emphasis on tuber production, there has been little work on optimizing seed production. Means that have successfully increased seed yield of better-known bean crops deserve to be also applied to this species With any viney crop the issue of plant support is paramount.
From page 340...
... Whether any possess practical quantities of sugar is unknown, but their cousin from the Andes (Pachyrhizus ahipa) has proven to contain more than twice the sugar found in sugar beet.29 · Protein Even though the protein content of the tuber is lower than that of grain-legume seeds, the total protein yield per hectare for the tubers exceeds that of soybean, the world's premier protein crop.
From page 341...
... Synonyms Dolichos stenocarpus, Vigna katangensis, Vigna ornata,Vigna ornata var. latifolia, Sphenostylis congensis, Sphenostylis ornata, Sphenostylis stenocarpa var.
From page 342...
... Distribution Within Africa Although African yambean is obscure in a general sense, it exists in a number of countries. In broad terms, the cultivation area extends from tropical West Africa to Sudan, Eritrea and northern Ethiopia.
From page 343...
... Fertile sandy soils are said to be "highly suitable."31 Related Species The African yambean is so closely related to Vigna species that a botanist once classified it as Vigna ornata. This genus -- an important one for food in the tropics -- includes moth bean, mung bean, bambara bean, rice bean, cowpea, and adzuki bean.


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