Sweet Cassava.

By Harvey W. Wiley.

(Abstracted from Bulletin No. 44, U. S. Department of Agriculture, Division of Chemistry.)

In the southern peninsula of Florida, and growing well up into the frost belt, is found in many localities a cultivated plant known as cassava, or sweet cassava. From a careful study of the climatic conditions under which the plant flourishes, it is safe to assume that it may also be grown with success in southern Alabama, Mississippi, Louisiana and Texas. Cassava is a name which should properly apply only to the purified starch derived from the roots of the plant, but it has passed into general use to designate the plant itself. Botanically, the plant is known as Janipha manihot, Manihot utilissima, Jatropha manihot, Manihot aipi, Manihot loeflingii, and Manihot palmata. One of its common names is manioc plant.

There is properly only one variety of the plant growing in Florida, while that variety which grows in the tropics contains so much hydrocyanic acid as to render it poisonous. The variety grown in the subtropical region of Florida, however, contains only a small quantity of hydrocyanic acid, and is, therefore, commonly known as sweet cassava. It is quite probable that after the tropical variety has grown for some time in a subtropical climate, it would lose largely its poisonous properties.

The attention of the Division of Chemistry was first called to the cassava plant as an article of food and a possible source of starch, in 1888, in a letter received from Mr. R. H. Burr, of Bartow, Fla., who also sent a package of the roots. These roots were long, slender and of various sizes, some of them two feet long and weighing several pounds. The analysis of the substance, exclusive of the bark, calculated to dry substance, is given in the following table:

The amount of starch compares fairly well with the best varieties of potatoes. On account of the large quantities of sugars present, the cassava root could be more economically used for the manufacture of glucose than for starch.

A larger quantity of the root was obtained from Florida, the bark separated from the root, and each subjected to analysis, with the following results:

With the starch in the analysis given above is reckoned also the soluble carbohydrates, consisting almost exclusively of cane sugar, and of which, in an analysis of another portion of the dry substance, as high as 17 per cent. was found. In the laboratory it is not difficult to prepare crystallized cane sugar from the aqueous extract of the fresh pulp. The percentage of sugar in the plant, however, is too low to excite any reasonable hope of the preparation of this article on a commercial scale. The most promising way to save it is by conversion into glucose, as indicated in another place. The undetermined portion consists of the digestible fibre and carbohydrates of the pentose series. The pentosans in the fibre were determined by the furfurol process, as modified by Krug, and the amount in the air-dried material was found to be 3.92 per cent., and in the material after the removal of the starch, 5.33 per cent

The amount of mineral matter taken from the soil by the 100 kilos of the fresh root is approximately only one-half a kilo. The albuminous matters are also present in small quantities, being only slightly more in amount than the ash itself. The plant, therefore, is one which seems particularly suited to feed almost exclusively from the air and water, and hence is one which could be recommended on the sandy soils of Florida as a crop which would require the minimum of fertilization.

The ash was found to consist of silica, ferric oxide, calcium oxide, magnesium oxide, sodium oxide, potassium oxide, phosphoric acid, sulphuric acid, carbonic acid, and chlorine. The calcium, potassium and phosphoric acid made up three-fourths of the ash in the peeled root, while silica and potassium predominated in the bark from the root.

Quite a number of preparations are made from the starch of the root, and among them maybe mentioned: (1) Tapioca; the first portions of starch washed out, especially, produce an excellent article of tapioca when treated in the usual way. (2) Glucose; both the fresh root and the extracted root yield full theoretical amounts of glucose, and samples of this article were made by the conversion of the starch both by sulphuric acid and by diastase. The samples of glucose made from the starch were exceptionally good, especially when diastase was used, the glucose in this case containing large quantities of maltase. (3) Alcohol; the glucose on fermentation affords the usual quantity of alcohol. (4) Cane sugar; a beautiful preparation of cane sugar was made from the water used in washing out the starch. The amount of cane sugar, however, is not large enough to warrant its extraction on a commercial scale from the waters used in washing. It is, however, present in such quantity as to indicate that in making glucose it is better to use the whole root, and so obtain the product from both the cane sugar and the starch, rather than to make it from the starch alone.

The general result of the investigation is to establish the fact that the cassava is a plant of high economic value, and worthy of the attention of those interested in the carbohydrate products of the country.

Cassava has been grown for one year on the department experiment station at Runnymede (post-office, Narcoossee), Osceola County, Florida. The field in which the crop was grown is high pine sand, with almost no other ingredient.

Attempts were also made to grow cassava in a piece of very wet muck land on the station, in which sugar cane would not grow to any advantage. An immense development of tips was secured, some of the plants reaching a height of 10 feet, and resembling young trees. The root development was fair, but not commensurately increased with the top growth.

The profits which the farmer may make from growing this crop, and the manufacturer from using it, should be based upon a yield of 4 or 5 tons per acre. If it be desired to make starch from the plant, we may suppose, as a minimum rate of yield, that 20 per cent. of the weight of the fresh root may be obtained as a merchantable starch of a high grade. On a yield of 4 tons per acre, this would amount to 1,600 pounds. Compare this with the weight of starch obtained from Indian corn producing 40 bushels per acre. The yield of merchantable starch of a high grade may be placed 35 pounds per bushel, which for 40 bushels would amount to 1,400 pounds. It is thus seen that the yield per acre in the matter of starch from cassava would be fully equal, if not superior, to that from Indian corn. If the manufacture of glucose be considered, the estimate is even more favorable.

Conclusions.

(1) Cassava can be cultivated with safety and profit in the greater part of the peninsula of Florida, and probably also in southern Alabama, Mississippi, Louisiana and Texas.

(2) It will yield, with fair treatment, on sand soils, from 4 to 5 tons per acre.

(3) It will give, when properly manufactured, from 20 to 25 per cent. of the weight of the fresh root in starch of high grade.

(4) The starch is naturally in a pure state, and no chemicals of any kind are necessary in its manufacture.

(5) The starch resembles, in its physical properties, that of maize, and can be used as a substitute therefor in all cases.

(6) An excellent article of tapioca can be prepared from the starch of the cassava plant.

(7) Glucose can be prepared directly from the starch, or more profitably from the pulp of the peeled root.

(8) The plant furnishes an excellent human and cattle food, deficient, however, in nitrogen. It would make a well-balanced ration for cattle when mixed with one-fourth its weight of cotton-seed oilcake.

The American Journal of Pharmacy, Vol. 67, 1895, was edited by Henry Trimble.