Premium
Specific limited hydrolysis and phosphorylation of food proteins for improvement of functional and nutritional properties
Author(s) -
Chobert JeanMarc,
Sitohy Mahmoud,
Whitaker John R.
Publication year - 1987
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02542507
Subject(s) - chemistry , casein , isoelectric point , hydrolysis , solubility , emulsion , hydrolysate , chromatography , lysine , amino acid , tryptophan , biochemistry , organic chemistry , enzyme
Limited specific hydrolysis of casein by Staphylococcus aureus V8 protease was used to produce 2% and 6.7% hydrolysates (2 and 6.7% of the peptide bonds hydrolyzed), each containing five polypeptides (by gel filtration) ranging in size from ∼ 16,000 to ∼1,000 daltons. The mixtures of polypeptides had substantially increased solubilities at pH 4.0–4.5, near the isoelectric point of casein. In general, the emulsifying activity index was less for the hydrolysates than for casein; the emulsion stability was higher for the 2% hydrolysate than was the emulsion from casein. Phosphorylation of zein markedly increased the water solubility of zein above and below pH 4. When the free amino acids tryptophan and/or lysine were added to zein in the presence of POC1 3 , some amino acids were covalently bound to zein, in addition to covalent attachment of phosphate groups. Threonine did not become incorporated into zein by this method. These derivatives were much more soluble than zein above and below pH 4, the minimum solubility point. A derivative containing 0.98 mol P/mol of zein, along with 1.05% tryptophan and 0.24% lysine, had a relative growth effect on Tetrahymena thermophili of 49% that of casein, in comparison to 4.5% for unmodified zein. All the modified zeins had improved emulsifying activity indices.