title: The stability of tryptophan, 5-methyl-tryptophan and α-methyl-tryptophan during NaOH hydrolysis of selected foods.
abstract: This study evaluated the use of 5-methyl-tryptophan, α-methyl-tryptophan or synthetic tryptophan to correct for the losses of protein-bound tryptophan in foods during NaOH hydrolysis. Synthetic tryptophan and each protein source was incubated in 4.5M NaOH containing 5-methyl-tryptophan and α-methyl-tryptophan in nitrogen gas-sparged Teflon vials for 0-144 h at 110 °C. The hydrolysis and loss rates of protein-bound tryptophan, 5-methyl-tryptophan, α-methyl-tryptophan and synthetic tryptophan were predicted using least-squares nonlinear regression. Using 5-methyl-tryptophan or synthetic tryptophan to correct for hydrolytic losses of tryptophan overestimated the tryptophan content by 8.2-19% and -0.3-8.8% respectively, while correction using α-methyl-tryptophan underestimated tryptophan by between 0.2% and 8.1% across the protein sources. Correction using α-methyl-tryptophan or synthetic tryptophan was more accurate than using 5-methyl-tryptophan, but when highly accurate tryptophan composition data are required, least-squares nonlinear regression is the best approach as it removes the need for a hydrolysis correction factor.
authors.affiliation: Riddet Institute, Massey University, Palmerston North, New Zealand. Electronic address: S.M.Rutherfurd@massey.ac.nz.
authors.forename: Shane M
authors.initials: SM
authors.lastname: Rutherfurd
authors.affiliation: Riddet Institute, Massey University, Palmerston North, New Zealand.
authors.forename: Russell K
authors.initials: RK
authors.lastname: Richardson
authors.affiliation: Riddet Institute, Massey University, Palmerston North, New Zealand.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Moughan
mesh_terms: D005504:Food Analysis; D006868:Hydrolysis; D016018:Least-Squares Analysis; D017711:Nonlinear Dynamics; D012972:Sodium Hydroxide / Q000737:chemistry*; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C020774:alpha-methyltryptophan; C004182:5-methyltryptophan; D012972:Sodium Hydroxide; D014364:Tryptophan
keywords: Alkali hydrolysis; Food; Stability; Tryptophan