Structure and tribology of κ-carrageenan gels filled with natural oil bodies

摘要

Natural oil bodies (OBs) are micron-sized oil droplets found in parts of plants. Due to their nutritional value and characteristic that they are naturally emulsified, OBs have potential applications in food industry. In this study, kappa-carrageenan (KC, 1.0 wt %) gels filled with soybean OBs (up to 10 wt % oil content) bound or unbound with the matrix were constructed. Their structure, rheological and tribological properties were characterized. It was found that in the boundary lubrication regime, the lubrication properties of the OB cream and OB emulsion-gels were significantly improved compared with pure water and the KC gels, and are better than the emulsion-gels with medium chain triglycerides (MCT) droplets stabilized by Tween 80. An ultralow boundary friction coefficient (mu) of 0.038 was achieved. The viscosity of the OB cream, the elasticity of the OB emulsion-gels, as well as the ball-bearing and rolling effect of the OBs in and out the gel fragments under shear were believed to contribute to the promising lubrication properties. It was also found that there was no significant difference in mu between the bound and unbound emulsion-gels, although mu of both types of emulsion-gels decreased with increase of oil concentration. The fragmentation and structure failure of the emulsion-gels under shear were believed to weaken the difference.