Oat protein-shellac beads: Superior protection and delivery carriers for sensitive bioactive compounds

The purpose of this work was to better understand the interactions between oat protein (OPI) and shellac to form oat protein-shellac based gels at near neutral pH as carrier to protect and deliver sensitive bioactive compounds. There were moderate interactions between OPI and shellac with a binding constant (K-a) of 2.088 x 10(3) M-1 via hydrophobic interactions and hydrogen bonding as revealed by Isothermal Titration Calorimeter (ITC) and Fourier Transform Infrared Spectroscopy (FTIR). Such interactions allowed the formation of a gel-like mixture with good compatibility that only one endothermic peak and T-g value for OPI-shellac mixture as demonstrated by differential scanning calorimetry (DSC) analysis. Novel core (OPI)-shell (OPI-shellac mixture) beads were then developed by a cold-gelation method at near neural pH and ambient temperature. The optimized samples possessed a homogeneous, smooth and integrated shell structure. This structure could effectively restrict the swelling of the shell and prevent premature diffusion of the contained riboflavin. Also, this structure could efficiently protect the survival of L. acidophilus as 85.5% and the activity of amylase as 80.0% in the harsh environment of simulated gastric fluids after 1 h. When transferred to a simulated intestinal tract, riboflavin and L. acidophilus were sustainably released. Since the beads are easily prepared using a simple extrusion method at near neutral pH and ambient temperature, they are excellent candidates for natural delivery systems for sensitive bioactive compounds in the food and biomedical industries. (C) 2017 Elsevier Ltd. All rights reserved.