Study On Maillard Reaction Of β-lactoglobulin/gum Acacia Seyal

Gum arabic is defined as the airdried exudates from the branch and stem of Acacia. Gum Acacia Senegal(ASG) and Gum Acacia Seyal(ASY)are the two main species of gum Arabic. Gum arabic consists of three mian components: arabinogalactan protein complex(AGP), arabinogalactan(AG) and glycoprotein(GP).AGP is the functional component for emulsification. Comparaed with ASG, ASY contains less protein in AGP, resulting poorer emulsifying properties.This limitsthe wide application of ASY in the food industry.Typically, Maillard reaction could improve the functional properties of proteins by conjugation with polysaccharide. This project aimstoimprove the emulsifying properties of ASY, via the Maillard reaction withβ-lactoglobulin(BLG) at 60 °C and a relative humidity of 79%in dry-heating condition. By analyzing browning index and grafting degree, and using SDS-PAGE and GPC-MALLS, the effect of incubation time on the Maillard reaction of BLG-ASY and its emulsifying properties was studied.By measuring light scattering intensity, hydrodynamic radius and turbidity, the phase diagram of BLG-ASYmixed system was constructed. The impact of different phase regions on the Maillard reaction of BLG-ASYwas investigated.Furthermore, the influence of ionic strength on the Maillard reactionofBLG-ASY and the resultant emulsifying properties wasexamined.Main conclusions are as follows:1) Incubation time had a significant impact on the Maillard reaction of BLG-ASY system. The Maillard reaction between BLG-ASY occurred to a limited extent when the incubation time was less than 12 h.The reaction extent increased significantlyafterward and leveled offaround 36 h. More than 64% of the protein was successfully incorporated into ASY, resulting in a two-fold increase in AGP content. The conjugation with BLG markedly improved the stability of ASY-stabilized emulsions and their resistance against severeconditions(such as low pH and high temperature and high saline conditions).2) Themaximum stoichiometry of BLG-ASYwas found around 1.0. The phase diagram of BLG-ASY was classified into four phase regions:(I) pH > pHIEP, individual soluble polymers;(II) pHc < pH < pHIEP, Intramolecular soluble complexes;(III) pHφ < pH < pHc, intermolecular soluble complexes;(IV) pH < pHφ, intermolecular insoluble complexes. The Maillard reaction between BLG-ASY was largely influenced by the different phase regions. After incubation for 12 h, BLG-ASY showed the maximum Maillard reaction extent in the phase region(I), while in the phase region(III) and(IV), the increase in AGP content was due to the Maillard reaction of ASY itself without incorporation of BLG.3) The effect of ionic strength on the Maillard reaction between BLG-ASY was as follows: When 0mM< C[NaCl] ≤ 30 mM, the Maillard reaction was promoted by increasing NaCl concentration;When 50 mM ≤ C[NaCl] ≤ 200 mM, the Maillard reaction was inhibited with increasing NaCl concentration.