I I Aprrl 1977 RAIN P"g LEAF-EATING: Moving on Down the Food Chain -Franklin Martin and Ruth Rubert6 Green leaves are one of the most important elements of the food chain which sustains ail animal and human life. Nevertheless, because we lack enzymes to digest leaves well, green leaves are used by people chiefly in indirect forms as other plant products (fruits, seeds, roots) or through animals that have themselves used the leaves as food. Much of the food value is lost to us in these conversion processes. Techniques for removing protein from leaves have been developed, and the process is commercial or on the verge of commercialization in various places. The production of protein concentrates useful as feed and as food for humans appears entirely feasible. Unfortunately, these processes presently depend on large and complex techniques which place leaf protein concentrate out of direct reach of the people who most need protein supplementation. Many tropical plants such as the edible legumes, species of of the Euphorbiaceae, and some tropical grasses appear to be especially suitable for leaf protein concentration. Because some of these plants can produce foliage on a year-round basis, selection of the appropriate plant as a crop could iead to high froduction per hectire of ihe protein so badly needed in the tropics. Because reliance on large commerciai ventures would negate some of the advantagis of leaves, especially the fact that they are readily available, we have worked out small scale techniques that can be used in the home without the use of electrical or expensive apparatus. We focused experiments on Auropis, a plant called katuk in Indonesia. This plant is a tail, spindly, slightly woody shrub which produces very dark green leaves. The tender shoots are eaten raw, while older leaves need cooking. Katuk can be easily grown from seeds or from cuttings and is widely adaptable throughout the tropics. Leaves were hand-picked and then passed through a small hand mill used for grinding grain. The iron burrs of the mill were adjusted as close as possible for fine grinding, but comfortable turning of the crank. Two volumes of water were added to the mixture of ground leaves, and after thorough mixing, this was filtered through a lady's nylon mesh stocking. When filtration of juice stopped, the stocking was kneaded with the hands to press out more of the liquid. The liquid was then heated 'o 8O degrees C., where precipitation began. The Species Sauropis (S aur opis an dro g3t nus) Sorghum (S orgbum bic ol or) Chay a (Cnid o sc o lu s c b ay am ansa) Cassava (Ma nih ot esculenta) Whole leaves 4.9t A COMPARISON OF 5 PLANT SPECIES FOR EXTRACTABILITY AND RECOVERABILITY OF PROTEIN AND RECOVERABILITY OF PROTEIN FROM LEAVES GRAMS PROTEIN IN lOO G. LEAF AND EXTRACTS Non-precipitant Fibrous residue Precipitated protein soluble residue liquid was removed from the heat, and a green precipitate formed, Ieaving a yellowish whey. The whey and precipitate were filtered through a cotton cloth filter, and the curd remaining was rinsed twice by adding warer ro the filter. This washing is very important in removing strong flavored substances from the curd. The filter cloth containing the precipitate was squeezed to remove more liquid, and the resultant green protein concentrate was removed and kept in the refrigerator until used. With some practice , it was found possible to prepare a one kiiogram batch of leaves in abour one hour, nor including time to heat the liquid extract on the stove. The protein curd was a very dark green color, had a leaflike smell and an oily texture. The hardness of the curd depended on the degree to which water was pressed out, and the curd varied from a consistency of cottage cheese to that of soft cheese. The amount of protein recovered in preliminary trials varied from 1 1 to 45 percent. These vaiues depended chiefly on rhe amounr of protein extracted from the leaf by grinding and filtering technique. In the case of Sauropis, almost half of the leaf protein was recovered in the final protein concentrate. This protein concentate was used as a food in the following ways, by itself, as a spread with bread, cooked inro a soup with meat stock, mixed with white yams, used a a ten percent mixture for making pancakes, and sciambled with eggs as one third of an omelette. In Pakistan and India leaf proteins are extracted with sugarcane extracting apparerus. Fleat is used to coagulate the protein, which is then incorporated into various foods. In India, the protein concentrate is made into candy and distributed to school chiidren, where it is readily accepted and has become a valuable source of calories and protein. Leaf protein concentrates generally have strong color and flavor, and development of recipes to complement them with suitable spices and other ingredients will go far to placing home leaf protein concentrating alongside tofu-making from soybeans and cheese-making from milk as valuable culinary and dietary contributions. Frank Martin and Rutb Rubertl are uith tbe Mayagi)ez Institute of Tropical Agriculture, P.O. Box 70, Maiagi)ez, Puerto Rico OO708. 2.21 2.24 FROM LEAVES Percent protein extracted and precipitated 45.6 11.3 9.9 s 13.3 25.3 3.92 2.83 2.82 0.32 1.48 0.39 6.01 5.01 0.80 o.46 0.70 2.O5 0.20 Winged bean (Psopbocarpus tetragonolobus) 3.2O |.26 0.81 1.13
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