The nutritive value of leaf protein concentrates determined in biological tests with rats and by microbiological methods

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Abstract
The biological values and true digestibilities of a number of leaf protein concentrates have been determined by the balance‐sheet method at an 8% level of protein intake on young growing rats. Determinations were made on preparations from the leaves of 14 different species of plants. The effects of several methods of drying the concentrates and of the maturity of the leaves at harvesting were studied. The availability of some essential amino‐acids was determined microbiologically in selected samples; in all of them methionine was less available than in whole egg proteins. The microbiological results were consistent with the biological findings. In general biological values of the proteins in the leaf concentrates were of the order found for good quality plant proteins such as those of legume and cereal seeds and of yeast but true digestibilities were lower. Freeze‐drying, drying by acetone extraction and drying on starch in a current of air proved satisfactory but oven‐drying at 100° caused a significant decrease in biological value and a more marked loss of true digestibility. Biological values and true digestibility increased with the maturity of the leaves at harvesting because of increased availability of methionine. A possible explanation of the results is suggested.