[Biological quality of the protein isolated from the leaves of Atriplex numularia]

Plant leaf proteins have acquired great relevance during the last two decades because of their well-balanced amino acid composition. A study was therefore undertaken to evaluate the biological quality of the leaf protein of Atriplex numularia. The protein content of the fresh leaves from this plant was found to be 4.70 g/100, with a dry matter content of 18.70 g/100 g. A protein concentrate (PC) from the same material was then obtained by macerating the leaf in a 2% sodium sulfite solution at a pH of 10 and subjecting it to filtration and pressing. The product thus obtained had a dark greenish color and contained 55.42 g/100 g of protein. The amino acid analysis revealed that its protein has a balance similar to that of animal origin proteins, with a lysine and methionine content of 8.5 g/16 g N and 3.0 g/16 g N, respectively. Biological assays were then carried out to evaluate nitrogen utilization, with the following resulting values: net protein utilization (NPU) = 48.3 +/- 2.7; digestibility (D) = 58.0 +/- 1.4, and biological value (BV) = 83. As inferred from the NPU value, nitrogen utilization was low. Therefore, to improve digestibility values, the action of papain on the PC was assayed. The material thus treated was again submitted to biological trials, obtaining, this time a D of 75.4 +/- 1.05, and thus, an improved new NPU value of 54.8 +/- 1.1 (p less than 0.01).