Effect of succinylation on physicochemical and functional properties of milk protein concentrate

• Highest degree of succinylation of milk proteins was obtained at 4 mol of succinic anhydride/mole of lysine.
• Succinylation of milk proteins increased intrinsic tryptophan intensity of native MPC.
• Succinylation of MPC significantly increased solubility, which in turn increased different functional properties of the native MPC.

Milk protein concentrate (MPC) is a complete dairy protein ingredient (containing both caseins and whey proteins) available with protein concentrations ranging from 40 to 90%. However, MPC powders are poorly soluble which thus, restricts their potential use for food application. Succinylation involves chemical derivatisation of ϵ-amino group of lysine in proteins and enhances solubility of less soluble proteins. In the present investigation, highest degree of succinylation was achieved at the level of 4 mol of succinic anhydride/mole of lysine in MPC. Findings from intrinsic tryptophan intensities stated that succinylation of milk proteins showed structural modification and increase in hydrophobicity. Further, the effects of succinylation on the functional properties (solubility, water- and oil-binding capacities, viscosity, foaming capacity and stability, emulsion activity and stability) of MPC were evaluated. Succinylation of proteins significantly (P < 0.05) increased solubility as a result of altered charge on protein and reduced particle size of native MPC, which in turn improved other functional properties of native MPC. The microstructure of succinylated MPC at different degrees of succinylation by scanning electron microscopy revealed that the size and number of white patch like structures present on protein increased with degree of succinylation.