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Influence of isoelectric precipitation on the solubility of soya bean proteins
Author(s) -
Lillford Peter J.,
Wright David J.
Publication year - 1981
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.2740320402
Subject(s) - chemistry , isoelectric point , solubility , precipitation , titration , ionic strength , soya bean , phosphate , reducing agent , chromatography , isoelectric focusing , globulin , food science , biochemistry , inorganic chemistry , aqueous solution , organic chemistry , physics , meteorology , immunology , biology , enzyme
The factors controlling the solubility characteristics of soya bean proteins consequent upon acid precipitation were investigated. Two processes of protein insolubilisation, fundamentally different in their effects, were identified. One, termed ‚pH sensitivity’, involved principally haemagglutinin and low molecular weight (2S) proteins, and was affected by exposure to low pH (4.5) in the presence of reducing agents; resolubilisation could be achieved by adjusting the pH to 7.6, but only at low ionic strength. The second process concerned a precipitation‐induced aggregation of the globulins which was produced in the absence of, and largely eliminated in the presence of, reducing agent. In this case, complete resolubilisation was afforded by readjustment of the pH to 7.6, either by back titration or dialysis against a phosphate buffer, but was not dependent upon the presence of reducing agent. The mechanisms underlying these insolubilisation processes were concluded to be mainly of an electrostatic nature, rather than ones involving disulphide exchange reactions.