Protein from Tropical Plants

s of Workshop Papers Abstracts of Workshop Paperss of Workshop Papers TOBACCO LEAF PROTEIN Pilot-scale technology that extracts high-quality protein from young tobacco leaves has been developed. Soluble proteins extracted from tobacco plants might be added to foods as nutritional supplements or for functional properties (e.g., gelling, thickening). Although not fully tested, they might have a specialized medicinal use as a pure protein source for kidney patients. Insoluble proteins might be suitable as a supplemental livestock feed. The leaf material left after protein extraction might be used in the manufacture of safer cigarettes with lower concentrations of toxic substances. Several important constraints to the development of this technology make its future uncertain. Because a stigma is attached to tobacco by a large segment of society, there is a strong likelihood that food products developed from tobacco would not be readily accepted by the general public. Tobacco would face strong competition from alternate sources of protein. Before this technology could be economically viable, the residual deproteinized tobacco would have to be marketed successfully for the manufacture of smoking products, such as cigarettes. Significant flavor changes and associated characteristics of the deproteinized tobacco may not satisfy consumer tastes. Lastly, expanding the technology from the pilot scale to commercial scale will require the solution to certain technical and economic problems. PROTEIN FROM TROPICAL PLANTS The leaves of some 500 tropical plants have been screened by the U.S. Department of Agriculture (USDA) as potential sources of highprotein animal and human foods. Leaf protein fractionation for livestock feed is based on the principle that nitrogen-fixing plants contain higher levels of protein than ruminant animals can use, and nonruminants can assimilate only a portion of the total plant protein but cannot consume the volume of leaves necessary to meet their protein needs. The high-protein content of these plants allows partial removal of protein for nonruminant use and subsequent use of the remainder of the plant and its protein by ruminants. An appropriate combination of animals for the dual-use of leaf protein would be hogs and dairy cattle. The plants with the greatest potential for commercial LPC (leaf protein concentrate) production are herbaceous nitrogen-fixers. Tropical grasses are naturally too low in nitrogen to be adequate sources of LPC. Fertilization with nitrogen increases the protein content, but the expense of commercial fertilizer is too great to make LPC production economical. Many tropical tree leaves contain toxic and antinutritional compounds which limit their use as livestock feed. Processing of the leaves might rid them of these harmful compounds, but the additional cost and technology requirements to do so might be prohibitive. Work on alfalfa in the United States, Europe, and Japan has demonstrated the potential for dualwse of plant protein and has provided techniques and machinery that may be adapted to tropical plants. Although extraction and use of leaf protein in tropical regions seems promising, especially as livestock feed, a number of areas need additional research, including extraction methods, energy needs, acceptance of products, year-round vegetation supply, plant protein content, plant substances that adversely affect animal and human nutrition, environmental impacts, and cost. The feasibility of