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

Monomers, homogeneous nuclei and protofibrils are intermediate products during beta-lactoglobulin (beta-lg) fibril formation, they have different abilities to resist disturbance by other protein agents. The results showed that when beta-lg monomer coassembly with alpha-Lactalbumin (alpha-la)/k-Casein (kappa-CN), it would affect beta-lg self-assembly to fibril. While homogeneous nuclei and protofibrils coassembly with alpha-la/kappa-CN had little effect on fibril formation. Moreover, the result of forming fibril was quite different when beta-lg monomers coassembled with alpha-la and kappa-CN. Notably, alpha-la increased the fibril diameter, and k-CN clearly inhibited fibril formation. The reason for the differences was the different binding sites. alpha-la and kappa-CN had different effects on beta-lg's alpha-helical structure: alpha-la did not destroy the beta-lg's alpha-helical structure thus had little effect on fibril formation. While k-CN especially its hydrophobic area, interacted with beta-lg via -S-S- during the aggregation, it destroyed beta-lg's alpha-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.