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Evauation of lysinoalanine determinations in food proteins

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Author: Haagsma, N. · Slump, P. · Gortemaker, B. · Schreuder, R.
Institution: Centraal instituut voor voedingsonderzoek TNO
Source:Zeitschrift für Lebensmittel-Untersuchung und -Forschung, 4, 167, 238-240
Identifier: 228382
doi: doi:10.1007/BF01135594
Keywords: drug derivative · comparative study · densitometry · food analysis · hydrolysis · methodology · protein intake · thin layer chromatography · Chromatography, Thin Layer · Comparative Study · Densitometry · Dietary Proteins · Food Analysis · Hydrolysis · Lysine · Lysinoalanine


A comparison is made between lysinoalanine (LAL) determinations both with an automatic amino acid analyzer (AAA) and with thin layer chromatography-densitometry (TLC) in different types of food and food ingredients, taken from the Dutch market. Generally there is a reasonable agreement between the LAL content obtained by both methods. However, some results indicate that a single technique is not always conclusive about the real identity of the ninhydrin-positive compound at the same position as LAL on the chromatogram. By TLC for instance, in yeast a content of about 800 mg of LAL/kg in protein is found, but according to the AAA method no LAL is present. In heated milk and milk products the LAL content determined by the TLC method is also higher than that found by the AAA method. This is caused by a preceding unknown ninhydrinpositive compound in TLC, occurring in all heated milk products and practically coinciding with LAL. In the AAA technique similar interferences of unknown ninhydrin-positive compounds could be avoided by choosing a suitable elution temperature; however, application of this temperature modification to foaming agents gave no satisfactory results. © 1978 J. F. Bergmann Verlag. Chemicals/CAS: lysine, 56-87-1, 6899-06-5, 70-54-2; lysinoalanine, 18810-04-3, 23250-50-2; Dietary Proteins; Lysine, 56-87-1; Lysinoalanine, 18810-04-3