Proteomic characterisation of heat-induced hydrolysis of sodium caseinate

The hydrolysis of sodium caseinate during heating for up to 120 min at pH 7.0 and 130 °C was investigated. The formation of 2% trichloroacetic acid (TCA)-soluble peptides was studied using spectrofluorimetry and high resolution liquid chromatography-mass spectrometry (LC-MS), whereas sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) was used to study hydrolysis of the caseins. LC-MS and spectrofluorimetry showed an increase in 2% TCA-soluble peptides over time, confirming that proteolysis had occurred, whereas SDS-PAGE showed a decrease in band intensity for the main caseins over time. In total, 1023 casein-derived peptides were identified. For eleven of the most abundant peptides, release and breakdown were modelled. Peptide bonds containing Pro, Ser, Asn and/or Asp were preferentially hydrolysed during heating. The production of peptides in this manner may represent a novel alternative to enzymatic hydrolysis strategies.