α-Lactalbumin/к-casein coassembly with different intermediates of β-lactoglobulin during heat-induced fibril formation

Abstract

Monomers, homogeneous nuclei and protofibrils are intermediate products during β-lactoglobulin (β-lg) fibril formation, they have different abilities to resist disturbance by other protein agents. The results showed that when β-lg monomer coassembly with α-Lactalbumin (α-la)/к-Casein (к-CN), it would affect β-lg self-assembly to fibril. While homogeneous nuclei and protofibrils coassembly with α-la/к-CN had little effect on fibril formation. Moreover, the result of forming fibril was quite different when β-lg monomers coassembled with α-la and к-CN. Notably, α-la increased the fibril diameter, and к-CN clearly inhibited fibril formation. The reason for the differences was the different binding sites. α-la and к-CN had different effects on β-lg's α-helical structure: α-la did not destroy the β-lg's α-helical structure thus had little effect on fibril formation. While к-CN especially its hydrophobic area, interacted with β-lg via –S-S- during the aggregation, it destroyed β-lg's α-helical structure thus resulted in an inability to form fibrils. This study would expand the application value of dairy protein-based products aggregated at low pH.