Guanidination of lysine in cottonseed protein
1996
Ravindran, V. | Imbeah, M. | Angkanaporn, K. | Bryden, W.L.
The conversion of lysine residues to homoarginine was determined for 11 feed protein sources by incubating the proteins in 0.4 M O-methylisourea (OMIU) solution at pH 10.5 and at room temperature. The conversion efficiency in these protein sources was found to vary from 36.1 to 74.5%. Proteins from soybean meal, lupin, and fish meal had moderately high conversions (69.0-74.5%), while the conversion of lysine in cottonseed protein was very low (36.1%). For this reason, studies were undertaken to determine the optimum conditions for the maximum guanidination of cottonseed protein. Effects of different incubation times (24 to 144 h), lysine:OMIU ratios (1:8 to 1:32), and pH (9.5 to 13.0) on the guanidination of lysine in cottonseed protein were studied in separate experiments. On the basis of this monofactorial approach, optimum conditions for the maximum guanidination of cottonseed protein were determined to be as follows: lysine:OMIU ratio 1:12; pH, 12.5; and incubation time, 72 h. Potential protein racemization during guanidination under strong alkaline conditions can be avoided by incubating at 4 degrees C, but this will be associated with significant losses in conversion efficiency.
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