A Study On Maillard Reaction In Bovine Serum Albumin And Dextran System

Bovine serum albumin (BSA) and dextran were used to prepare BSA-dextran conjugates (B-D) by dry-heating (D-H) and water- heating (W-H), hydro-thermal method (H-T) and pulsed electric field assisted method (PEF-H). The physicochemical properties, conformational and functional properties of conjugates were investigated in order to study the mechanism of Maillard reaction and provide a theoretical basis for industrial processing, as a result, to be used to meet the need of industrialization.The o-phthalaldehyde (OPA) analysis and high performance liquid chromatography results indicated that the weaker Maillard reaction with high polymerization stage under D-H condition was observed. However, conjugates by D-H had a high degree of graft, and appeared a broad molecular distribution of 3470±300kDa. Compared with D-H condition, the Maillard reactions based on water phase system were prone to higher polymerization stage with a lower degree of graft, and a narrow molecular distribution. W-H and H-T products show a similar molecular weight as the D-H products, however the products by PEF assisted method were 860±100kDa. Moreover, The PAS staining verified that all glycosylation products were covalent binded glycoproteins with different conjugation degrees.Amino acids analysis suggested that the major locus during Maillard reaction contains lysine, tyrosine, cysteine, leucine and phenylalanine, with the first two contributed more. The conclusion that degree of graft calculated from o-phthalaldehyde method had limitatation was arrived. Circular dichroism and infrared spectra results showed that the covalent D-H products appeared little second structures changes, while the products based on water phase system were destroyed seriously, of whichα-helix content decreased accompany withβ-sheet and random coil content increasing. All water phase system products exhibited large disturbances at tyrosine and phenylalanine residues.The study also found BSA-dextran conjugates by D-H increased emulsification with significant decrease in foaming capacity and slight decrease in hydrophobicity. W-H, H-T and PEF-H method significantly improved the foaming capacity and hydrophilic, but with little emulsifying capacity. In addition, the study found Maillard reaction improved heat stability except that the H-T products showed lowest heat stability, and the products posses a weak DPPH radical scavenging ability.The optimal levels of W-H method were obtained after studying the effects of preparation conditions on degree of graft and heat stability. Then, the response surface analysis was applied to optimize the reaction according the degree of graft and heat stability of the products. The quadratic regression equations were obtained respectively, and the optimum conditions were predicted.