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Relationship between total N, total S and the s‐containing amino acids in extracted leaf protein
Author(s) -
Byers Marjorie
Publication year - 1976
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.2740270208
Subject(s) - methionine , cystine , amino acid , chemistry , total synthesis , hydrolysis , biochemistry , chromatography , food science , biology , stereochemistry , cysteine , enzyme
The total S:total N ratio in both unfractionated and fractionated proteins extracted from the leaves of lucerne and lupin has been determined. The results were similar to those found with 80% ethanol‐insoluble residues from leaves of lucerne and some other species. Methionine‐S accounted for 38–43% of the total S. If methionine‐S is deducted from the total S content, and the difference expressed as cystine, it appears that all preparations contained from 2.1–2.8 (as % of protein content)—more than had been previously supposed. When compared with the FAO reference protein none of the preparations are deficient in total S‐containing amino acids, although the problems associated with unavailability remain. Calculating cystine by this method is not suggested as a substitute for direct determination, where this is practicable, but may be a useful approach when cyst(e)ine is present only in small amounts in a complex protein concentrate and is liable to be destroyed during acid hydrolysis.