The Limiting Amino Acid Sequence in Raw and Roasted Peanut Protein

Abstract

The limiting amino acid sequence of blanched but unroasted peanut protein was found to be lysine equal to threonine equal to methionine. Tryptophan and histidine do not appear to be limiting in the unroasted protein. In roasted peanut protein the limiting amino acid sequence was lysine, threonine, and methionine. Tryptophan and histidine sometimes produced an increase in feed efficiency when added in the presence of lysine, threonine, and methionine. Roasting under the conditions described caused a decrease in the amount of lysine, threonine, and methionine equal to 15, 11, and 10% of the total, respectively. This decrease was due to an actual destruction of the amino acids. No attempt was made to quantify the loss of biologically available amino acids. Calculations of the limiting amino acids based upon amino acid content and upon the rat amino acid requirements suggest that methionine would be more limiting than lysine and that threonine should not be limiting. The discrepancy between the calculated and determined limiting sequence must be due to alteration of, or a decreased biological availability of, lysine and threonine, or to both. A feed efficiency equal to or better than that of a 15% casein diet can be obtained by supplementing roasted peanut protein with at least 0.31% of L-lysine, 0.19% of DL-threonine, and 0.21% of DL-methionine.