Alkali induced gelation behavior of low-density lipoprotein and high-density lipoprotein isolated from duck eggs

Changes in the gelation behavior and mechanism were investigated in low-density lipoprotein (LDL) and high-density lipoprotein (HDL) under the treatment of alkali. Three textural parameters of two kinds of alkali-induced lipoprotein increased, especially the springiness of LDL and the hardness of HDL. Alkaline treatment contributes to the sulfhydryl (SH) oxidation and SH-disulfide bonds (SS) exchange reactions to produce SS, promoting the aggregation of proteins and the formation of lipoprotein gels. For LDL gels, the increased hydrophobic interaction improves its thermal stability. HDL underwent deep unfolding and reassemble to form a network structure with high thermal stability and uniform density. Continuously alkaline treatment destroyed less SS and exposed more buried SH. The decrease of beta-structures in both lipoproteins was observed by Fourier Transform Infrared (FTIR). These results suggested that alkali-induced LDL and HDL gelation behavior highly related to the protein structure, SS and hydrophobic interactions.