[The protein quality of commercial products of texturized soybean protein and meat mixtures].

The purpose of the present study was to evaluate the protein quality of eight commercial samples of texturized soybean protein (TSP) collected in the food markets of various Latin American countries. The study also included experiments designed to establish the limiting amino acids in those products, and studies to evaluate the process of texturization by extrusion cooking. Finally, experiments were also carried out to evaluate the effect of replacement of meat by TSP as well as the supplementary value of the latter to tortilla flour. The eight samples were characterized for their functional properties and protein quality. The results obtained indicate that all samples were different in density, water absorption, and nitrogen solubility. Likewise, all samples were different in their lysine, methionine and threonine content, with PER values ranging from 1.75 to 2.31. Protein quality standard value is 2.3. The amino acid supplementation studies showed a positive significant response to methionine addition, particularly in those products exhibiting low PER values. The addition of both lysine and threonine to the methionine-supplemented product, increased PER significantly. The data also demonstrated that replacement of more than 25% of meat protein by TSP protein decreased protein quality of the product, even when a TSP with an accepted protein quality value was used. This product was also found to supplement the quality of tortilla protein. Finally, it was established that the texturization process did not reduce the protein quality of soybean protein. Based on these results, it is concluded that the variability in the protein quality measured in the eight TSP samples was due to the initial quality of the soy flour texturized, which was already damaged before texturization. For this reason, it is recommended that Latin American countries establish TSP quality standards when this product is used as a protein extender for meat, and that appropriate systems be implemented for the quality control of such products.