Protein Quality of Opaque-2 Corn Evaluation in Rats

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Abstract
A study was made on the protein quality of opaque-2 corn as tested in rats. Opaque-2 corn showed a protein efficiency ratio (PER) of 2.79 as compared with 2.88 for casein at comparable levels of protein in the diet. The results also indicate that processing the corn into corn-masa or tortilla does not alter its high protein quality, although slightly lower PER values were found. Amino acid-supplementation studies indicated that lysine is the first limiting amino acid in opaque-2 corn when it provides less than 10% protein in the diet. Results are presented on the significant improvement obtained when common corn is supplemented with lysine and tryptophan, added together. Evidence that niacin from opaque-2 corn is available to the niacindepleted rat, as opposed to its low availability for rats in the same condition in common corn, is also provided. Furthermore, the data show that opaque-2 corn has more niacin than common corn. Because of the high quality of opaque-2 corn proteins, efforts should be made to introduce the gene causing high lysine content into local varieties, especially in areas where corn is the most important staple food.