A bottom-up approach for encapsulation of sour cherries anthocyanins by using β-lactoglobulin as matrices

Sour cherries (Prunus cerasus L) anthocyanins were encapsulated with bovine beta-lactoglobulin by freeze drying. Three experimental states of protein were in depth characterized: un-treated protein, heat treated protein and cross-linked protein-anthocyanins complex. The encapsulation efficiency was significantly higher for the cross-linked complex. The docking procedure indicated that beta-lactoglobulin has three different ligand binding sites, namely an internal cavity defined by the beta-barrel, a hydrophobic pocket located on the protein surface in a groove between the alpha-helix and the beta-barrel, and a patch close to Trp(19)-Arg(124) residues. FT-IR analysis showed higher contribution of beta-sheet structures in anthocyanins binding with respect to the alpha-helix, in particular in the case of cross-linked samples. The distribution of anthocyanin inside the protein molecules was highlighted by confocal laser scanning microscopy. Preliminary processing through thermal treatment and cross-linking allowed obtaining twofold larger protein aggregates as encapsulating matrices compared to untreated samples. The highest antioxidant activity was observed for the pre-heat treated samples. The in vitro digestibility results suggested that beta-lactoglobulin protects anthocyanins from the gastric digestion, their release being facilitated in the intestine. (C) 2017 Elsevier Ltd. All rights reserved.