[Improvement of protein quality of popped sorghum with soybean grain]

The present study was carried out to evaluate the chemical composition and protein quality of popped sorghum by thermic dry processing. The chemical results indicated losses in the ether extract and increases in crude fiber. Likewise, losses were found in the essential amino acids, lysine and tryptophan, of 26 and 45%, respectively. The loss in these amino acids was confirmed by biological studies in which the protein quality of the raw sorghum, based on a PER was 32% of the casein value and of 8% for the popped sorghum (expanded). It was also found that the apparent and true digestibilities were lower for the popped sorghum than for the raw grain. In order to correct this loss in protein quality, the popped sorghum was supplemented with 5, 10 and 15% of roasted soybeans. Although no increase in quality was observed as evaluated by NPR, an increase in weight was found, as the soybean level in the diet was increased. This was attributed to the fact that the protein in the diet increased with respect to the soybean level. In an additional biological assay carried out with 15% of roasted soybean, a statistical significant increase in PER was found, equivalent to 74% of the casein value, while for the expanded sorghum without supplement, the relative casein value was of 30%. On the basis of these results an "alboroto" was formulated with 36% of popped sorghum, 10.5% whole roasted soybean, 3.5% dehulled sesame grain and 50% brown sugar. This product is superior to the commercial product in protein quality and quantity, as well as in energy content.