Impact of calcium on the interactions between epigallocatechin-3-gallate and α_S1-casein

Recently, much attention has been given to the interactions between caseins and green tea catechins, such as epigallocatechin-3-gallate (EGCG). However, no study has determined the impact of other important milk components such as calcium on the interactions between α_S1-CN and EGCG. Thus, in this work, four different EGCG concentrations were tested (0, 1.0, 1.5, and 2.0 mg mL⁻¹) both in the presence and absence of calcium. When EGCG was present, ζ-potential increased in negative surface charges and particle size was also influenced by the polyphenol, particularly in the presence of calcium. The increase in EGCG concentration also caused changes in protein secondary structure with a decrease in all structures, except the β-sheets increased. This study demonstrates for the first time, to the best of our knowledge, that the presence of calcium influences the interactions between α_S1-CN and EGCG and consequently the physicochemical characteristics of the resulting complexes.