PROTEIN SOURCE. Ν. W. Pirie (shown at news conference) has worked on a scheme for extracting the protein from leafy plants to aid the protein shortage
Leafy plants can bridge protein gap AG&FOOD Agricultural and food chemists at the ACS national meeting pulled together hunger-oriented chemistry and tech nology in a symposium on synthetics and substitutes for the food industry. Concentrating mainly on proteins and carbohydrates, the speakers ran through possibilities all the way from volume use of soybeans and production of carbohydrates from basic elements to ton-lot protein production by pulp ing leafy crops and even weeds. A critical perspective on new sources of protein, given from the view of those needing it most, came from the first speaker on the program. N. W. Pirie, head of biochemistry at Rothamsted Experimental Station, Harpenden, Herts, U.K., opened by observing, of the session, "Half the papers deal with themes that will seem rather remote to anyone who is, or expects to be, hungry." Mr. Pirie then spread caution on several western approaches to the food crisis, etched the magnitude of the problem, and suggested a different lineup of development priorities to make the maximum amount of food. Mr. Pirie includes in this lineup a scheme which he and others have worked on for extracting protein from leafy plants. "We have made equipment," the biochemist states, "in which 1 ton of fresh crop can be pulped in an hour and the juice pressed out. This brings with it half to three quarters of the protein. The protein is coag ulated, filtered off, and washed."
"When properly made, dry leaf protein contains 60 to 70% protein and 20 to 30% liquid." The liquid can diminish the plant's nutritive value and brings up the problem of stabilizing the product. Mr. Pirie notes that solvent extraction is possible but too expensive for developing coun tries. He cites possible preservation in malt or pickling. Mr. Pirie singles out leafy protein as a high-potential food source "be cause the yield is large, the methods are sufficiently simple to be used by any community technically competent to handle a tractor, and leaf crops grow well in parts of the tropics where rain is so frequent that it is difficult to ripen a seed crop. It is in these regions that the protein shortage tends to be most acute." As to other avenues for filling the enormous protein need, Mr. Pirie advises caution on present develop ments and sketches the vastness of the problem. Future protein supply cannot come from affluent countries, he states. "The protein could not be paid for, and, in spite of encouraging instances of personal and national generosity, charity cannot be relied on indefinitely. "Not only must protein be produced within a country, it should also be produced near the places where it is needed. . . . Attention is too often con fined to the needs of the city dweller; those who live 50 miles up a dirt track should not be neglected." "The world shortage of protein in the forms traditionally eaten by people is at present 20 million tons a year. Another 20 million tons would be needed to give everyone a further 15
grams a day, and the population is expected to double by the end of the century. The need therefore is great and growing, and it is very unlikely that it can be met by any single source." Spotlighting reduced forms of car bon and not nitrogen as the crucial factor in food production, Mr. Pirie concludes, "clearly, there is no shortage of carbon; but the more abundant the carbon source, the more difficult the process of converting it into food. The immediate problem for those now in need is therefore to ensure that photo synthesis is organized in a manner that will produce the maximum amount of human food." With this criterion in mind, the speaker finds many current and future food production methods wanting. In the sector of edible plants, he notes that most of the 100 or so important species were chosen thousands of years ago. "It is possible that prim itive people were not invariably the best judges of biological potentialities, and it may now be advantageous to enlarge the favored group." He notes encouraging development of high-protein cereal crops for par ticular parts of the world. However, he warns, "more effort is put into attempts to grow familiar crops in in creasingly improbable environments than into attempts to use those species that already grow exuberantly in the region." Extraction of leafy protein from in digenous plants has yielded 2 tons of protein per hectare (2.5 acres) per year in the U.K. and 3 tons in India, Mr. Pirie says. "These yields of pro tein greatly exceed those attained by any other system of husbandry." Aside from plants, Mr. Pirie finds use of animals for future protein limited. Calling cattle raising methods in affluent countries a "pleasant ex travagance," he states that ruminant and nonruminant animals in food-short countries should be raised only on nonarable land and fed on agricultural by-products. Microorganisms, he concludes, are "a complement to agriculture and not an alternative to it because, except for the algae and a few photosynthetic bacteria, microorganisms depend on fermentable material from another source." Mr. Pirie sees "obvious potentialities" in growing microor ganisms on certain fractions of crude oil, a development much publicized by U.S. oil companies. However, he states again that the project has to be kept in perspective. "Oil is simply a carbon source, and its value should be assessed in com parison with other possible substrates such as molasses, sulfite liquor, straw, sawdust, and so on." SEPT. 22, 1969 C&EN
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