[Amaranthus cruentus protein concentrate. Extraction methods. Functional properties]. / Concentrado proteico de Amaranthus cruentus. Métodos de extracción. Propiedades funcionales.

The most favorable conditions of pH, temperature ratio for the yielding of a protein concentrate (PC) of seed flour from Amaranthus cruentus was determined. The optimal values were: extraction pH 11, stirring time 1 h 30 min, precipitation pH 4.5 and a flour/ solvent ratio of 1:15. Obtained the PC, its functional properties were assayed. The PC chemical composition expressed in g/100 g was: protein 50.9: humidity 3.3; ethereal extract 5.8; raw fiber 6.4; ashes 3.8; total carbohydrates 29.9. The following PC functional properties were found: a maximal solubility value of 94.3 at pH 1); emulsification activity (EA) 47.90 +/- 4.9, water absorption capacity (WAC) 2.0 +/- 0.3; and oil absorption capacity (OAC) of 0.7 +/- 0.8. The use of this product as supplement for cereals and for others foods with poor lysine content is considered possible. Despite of the functional properties which show the hydrophilic character of the protein from the Amaranthus cruentus PC, great expectancies are inferred for its future utilization in bread products.

[Biologic value of the protein concentrate of Atripex lampa and its value as a complement to wheat flour]. / Valor biológico y complementario a la harina de trigo, del concentrado proteínico de Atriplex lampa.

The Atriplex lampa, chenopodiáceae, is a very abundant bush in the arid and semiarid regions of our Province. This work was undertaken to characterize from the chemical point of view, both the fresh leaves and the protein concentrate (PC) obtained from them. A second purpose was to determine the biological value of the protein, and to evaluate its capacity as a complement to wheat flour (WF). Through this study, the leaf was shown to have a high content of ashes, sodium, potassium and silica, what accounts for its low palatability. The PC obtained has a protein concentration of 59.37 g/100 g and its biological value is limited by the sulfur amino acids, with a chemical score of 85.70. Since the protein is poorly utilized, this results in a relatively low value of its net protein utilization (NPU), a fact which may be attributed to its low true digestibility. The studies on the complementary effects of PC on WF were made at three levels, i.e., 30, 50 and 60%, respectively. The results revealed that the best complementation, measured by the nitrogen utilization, happened to be when 50% of the protein contribution was provided by the A. lampa protein concentrate.

[Effects of treatment with polyvinylpyrrolidone on nutritional quality of sorghum]. / Efectos del tratamiento con polivinilpirrolidona (PVP) sobre la calidad nutricional del sorgo.

The purpose of this paper was to show that a high polyphenolic compound content in the sorghum grain (Sorghum saccharatum, var sugar drip) has an unfavorable influence on the nitrogen absorption. In order to arrive at this conclusion, the tannin content in sorghum flour was reduced by means of a treatment with polyvinylpyrrolidone (PVP) as a complexing agent. Several biological experiments were performed with non-treated flour (S) and with PVP-treated flour (S + PVP). Treatment improved true digestibility (D), having obtained the following values: for S = 31 +/- 2.67, and for S + PVP = 55.8 +/- 3.48 (significance P less than 0.001). The tannin evaluation yielded the following results: S = 1.90 g/100 g, and S + PVP = 0.85 g/100 g reported as tannic acid. The digestibility increase induced a better nitrogenous utilization, the net protein utilization (NPU) values being from 19 +/- 1.58 to 37 +/- 3.36 for S, and S + PVP, respectively.

[Biological quality of the protein isolated from the leaves of Atriplex numularia]. / Calidad biológica del aislado proteínico de hojas de 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).