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The differential determination of lysine in heated milk. I.— In vitro methods
Author(s) -
Bujard E.,
Handwerck V.,
Mauron J.
Publication year - 1967
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740180204
Subject(s) - lysine , hydrolysis , chemistry , food science , chromatography , amino acid , biochemistry
Abstract Lysine content and availability were determined in a set of milk samples which had sustained increasing heat treatments. Lysine content was measured after acid hydrolysis of the sample (TLV or x‐value), lysine availability by an enzymic digestion procedure (ALV‐e or y‐value) and by two modifications of the fluorodinitrobenzene method: the direct method (ALV‐f I or z‐value) and Carpenter's corrected straight acid procedure (ALV‐f II or v‐value). The four procedures gave strongly correlated, but numerically quite different results. The enzymic procedure and Carpenter's chemical method produced very similar results for lysine availability. In all heated samples, lysine content was much higher than lysine availability. The direct fluorodinitrobenzene method yielded values intermediate between those for lysine content and ‘true’ lysine availability. A nomograph is presented which accounts for the different conditions of lysine in heated milk and allows the interconversion of the x, y, z and v‐values.