Glycosylated peptides isolated from cheese whey have antifreezing activity

The glycomacropeptide (GMP) present in the cheese whey byproduct can be an excellent antifreezing agent due to its unique molecular structure. The objective of this study was to concentrate this peptide and investigate its ice recrystallization inhibition (IRI) ability. Heat denaturation of the non-GMP proteins and preparative liquid chromatography were used to create fraction 1 (F1) and fraction 2 (F2) and these were tested using the splat assay and a modified sucrose sandwich assay to investigate their IRI activity. Both F1 and F2 showed moderate IRI activity, but this activity was strongest under low salt and low pH conditions as indicated by the regression trends. F1 demonstrated an ice shaping ability similar to that of antifreeze glycoproteins. Molecular dynamic simulations of GMP, de-glycosylated GMP, and alpha-lactalbumin were performed and confirmed substantial differences of GMP when compared to the others in its high degree of conformational diversity and flexibility, as shown by the combination of radius of gyration, solvent accessible surface area, secondary structure, and hydrogen-bonding measurements together. Thus, GMP was shown for the first time as an effective IRI agent and its concentrate can be feasibly obtained from dairy processing byproduct.