Wheat gluten amino acid composition analysis by high-performance anion-exchange chromatography with integrated pulsed amperometric detection.
A simple accurate method for determining amino acid composition of wheat gluten proteins and their gliadin and glutenin fractions using high-performance anion-exchange chromatography with integrated pulsed amperometric detection is described. In contrast to most conventional methods, the analysis requires neither pre- or post-column derivatization, nor oxidation of the sample. It consists of hydrolysis (6.0M hydrochloric acid solution at 110 degrees C for 24h), evaporation of hydrolyzates (110 degrees C), and chromatographic separation of the liberated amino acids. Correction factors (f) accounted for incomplete cleavage of peptide bonds involving Val (f=1.07) and Ile (f=1.13) after hydrolysis for 24h and for Ser (f=1.32) losses during evaporation. Gradient conditions including an extra eluent (0.1M acetic acid solution) allowed multiple sequential sample analyses without risk of Glu contamination on the anion-exchange column. While gluten amino acid compositions by the present method were mostly comparable to those obtained by a conventional method involving oxidation, acid hydrolysis and post-column ninhydrin derivatization, the latter method underestimated Tyr, Val and Ile levels. Results for the other amino acids obtained by the different methods were linearly correlated (r>0.99, slope=1.03).
Rombouts
Ine
I
Laboratory of Food Chemistry and Biochemistry and Leuven Food Science and Nutrition Research Center, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium. Ine.Rombouts@biw.kuleuven.be
Lamberts
Lieve
L
Celus
Inge
I
Lagrain
Bert
B
Brijs
Kristof
K
Delcour
Jan A
JA
D000596:Amino Acids / Q000032:analysis* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D002852:Chromatography, Ion Exchange / Q000295:instrumentation / Q000379:methods*; D005983:Glutens / Q000032:analysis* / Q000302:isolation & purification; D006868:Hydrolysis; D014908:Triticum / Q000737:chemistry*
D000596:Amino Acids; D005983:Glutens