Air bubbles in calcium caseinate ﬁbrous material enhances anisotropy
Dense calcium caseinate dispersions can be transformed into hierarchically ﬁbrous structures by shear deformation. This transformation can be attributed to the intrinsic properties of calcium caseinate. Depending on the dispersion preparation method, a certain amount of air gets entrapped in the sheared protein matrix. Although anisotropy is obtained in the absence of entrapped air, the ﬁbrous appearance and mechanical anisotropy of the calcium caseinate materials are more pronounced with dispersed air present. The presence of air induces the protein ﬁbers to be arranged in microscale bundles, and the fracture strain and stress in the parallel direction are larger compared with the material without air. The eﬀects can be understood from the alignment of the ﬁbers in the parallel direction, providing strain energy dissipation. This study shows that creation of anisotropy is the result of interactions between multiple phases.