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Caseinophosphopeptide enrichment and identification

Zhu, Yi‐Shen, FitzGerald, Richard J.
International journal of food science & technology 2012 v.47 no.10 pp. 2235-2242
affinity chromatography, calcium, caseinates, ethanol, gallium, heat treatment, hydrolysis, manufacturing, mass spectrometry, oxidation, pH, quality control
Caseinophosphopeptides (CPPs) were generated via tryptic hydrolysis of sodium caseinate followed by heat treatment (75 °C) at pH 6.0, 7.0 and 8.0. Calcium aggregation, ethanol precipitation and gallium immobilised metal affinity chromatography (IMAC) were applied to enrich the CPPs. Nano‐liquid chromatography electrospray ionisation‐quadrupole time‐of‐flight tandem mass spectrometry was used for phosphopeptide separation and identification. The combination of gallium IMAC isolation with calcium and ethanol precipitation appears to be a useful tool in characterising the fate of CPPs in CN hydrolysates during thermal processing. CPPs appeared to be less susceptible to thermal modification when heat‐treated at pH 7.0 than at pH 6.0 and 8.0. Different extents of methionine oxidation occurred in the CPPs depending on heat‐treatment pH. The results herein may have important implications for the manufacture of CPPs and for the quality control of CPP products.