Epigallocatechin-3-gallate enhances sterilization of irradiated whole bovine casein and protects alpha and beta caseins from gamma radiation: Depending on polyphenol/protein ratio

Abstract

The increasing use of milk proteins in medicine requires developing effective processes for sterilizing milk formulations. It was found that epigallocatechin-3-gallate (EGCG) reduce bacterial flora in total casein, depending on the concentration of EGCG. Furthermore, the combination of EGCG and gamma radiation reduced the dose D10 to 0.88 kGy and 0.63 kGy with 250 and 500 μM EGCG, respectively, instead 2.01 kGy without EGCG. The effect of gamma radiation on alpha- and beta-casein in the absence and presence of epigallocatechin-3-gallate (EGCG) was also examined. Milk proteins in solution were exposed to different doses of gamma radiation with and without EGCG. Unirradiated and irradiated samples were analyzed by SDS-PAGE and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-MS). The results suggest that EGCG (10 μM) protects α- and β-casein from degradation and subsequent polymerization, possibly by scavenging oxygen and protein free radicals generated during irradiation. Although it was used a ratio of polyphenols to the protein higher for alpha-casein (1/5) than beta-casein (1/10), beta-casein was better protected with EGCG. According to previous studies, this result could be explained by differences in primary protein structure and its interaction with EGCG. The interaction of EGCG with casein is hydrophobic rather than hydrophilic, so the interaction with β-casein is more robust than with α-casein. In conclusion, the low EGCG concentrations enhance the sterilization of total casein by gamma radiation. It provided an excellent radioprotection of α- and β-casein, especially β-casein, against degradation and aggregation.