Interaction of flavan-3-ol derivatives and different caseins is determined by more than proline content and number of proline repeats

•Galloylation has a larger impact on binding affinity for proteins than dimerization of flavan-3-ols.•Procyanidin dimer A1 has a higher affinity for α-casein than B-type procyanidin dimers.•β-Casein does not bind procyanidin dimer A1 despite its proline content higher than in α-casein.