Bovine serum albumin (BSA) was phosphorylated by 2 methods. One is dry-heating in the presence of pyrophosphate, and the other is conjugation with maltopentaose through the Maillard reaction and subsequent dry-heating in the presence of pyrophosphate. The phosphorus content of BSA was increased to approximately 0.45% by dry-heating at pH 4.0 and 85 degrees C for 5 d in the presence of pyrophosphate, and approximately 0.91% by glycation and subsequent phosphorylation. The circular dichroism spectra showed that the change of secondary structure in the BSA molecule by phosphorylation was mild. However, tryptophan fluorescence intensity of BSA decreased by phosphorylation. The differential scanning calorimetry thermograms of BSA showed a disappearing of the 1st peak and a lowering of the 2nd peak denaturation temperature by phosphorylation. These results indicated molten (partially unfolded) conformations of BSA formed by both phosphorylation methods. The functional properties of BSA such as heat stability and calcium phosphate solubilizing ability were improved by phosphorylation alone and further by phosphorylation after glycation. Transparent gels of BSA with relatively high water-holding capacity were obtained by phosphorylation alone, and the immunogenicity of BSA was reduced significantly by glycation and phosphorylation, respectively.
