Microscopic structure, viscoelastic behaviour and 3D printing potential of milk protein concentrate‐hydrocolloid complex coacervates

Summary To prepare a milk protein‐enriched ink for extrusion‐based 3D food printing, this study investigated the effects of a wide range of hydrocolloids on the microstructures, viscoelastic characteristics and 3D printing performance of milk protein concentrate (MPC). The distributions of hydrocolloids and milk protein in mixed coacervates were characterised by fluorescent covalent labelling and confocal laser scanning microscope (CLSM), and the microstructure of the coacervates was observed by scanning electron microscopy (SEM). In addition, the rheological properties of prepared protein coacervates, including steady shear test, dynamic oscillatory test, thixotropy and creep recovery were investigated. Meanwhile, Burger’s model was fitted to the creep behaviour to further study their viscoelastic properties. The results showed that κ‐carrageenan, pectin, guar gum and sodium alginate significantly increased the zero‐shear viscosity, thixotropy and solid‐like behaviour while xanthan showed an opposite phenomenon. Results showed that the presence of hydrocolloids improved the 3D printability of MPC by forming a complex network between protein particles and hydrocolloids, and guar gum, pectin and κ‐carrageenan better help maintain the deposited 3D structures of MPC ink than xanthan.