The effects of whey protein and oleogel interactions on mechanical properties of oleocolloids and hydro-oleocolloids matrices

Abstract

The objective of this study was to examine mechanical properties of oleocolloid (OC) and hydro-oleocolloid (HOC) networks formulated with different whey protein concentrations (2.5, 5, and 7.5% w/w), high oleic soybean oil (HOSO), rice bran wax (RBW), and water. Temperature sweep tests documented that the oleogelation time (determined as the time at which tan δ = 1) was delayed about 4 min in HOC when compared to OC due to the whey protein gelation in the water phase. While OC showed significantly larger storage and complex moduli at higher protein concentrations, the moduli of HOC decreased with increasing protein content. Additionally, strain at the limit of linearity in OC samples was linearly dependent on protein and wax contents while HOC systems exhibited an opposite trend. Similar trends were observed from large deformation penetration tests by using texture profile analysis. Creep-recovery tests, based on a fractional calculus analysis, confirmed that OC gel networks had higher strength than HOC gels, but the latter displayed a greater degree of gel elasticity. Using the viscoelastic properties of gel systems, a fractal analysis was performed using scaling theory. In particular, OC samples were characterized by a weak-link regime in which the macroscopic behavior was primarily governed by hydrophobic interactions among proteins and oleogels. Conversely, HOC samples indicated the presence of complex interactions in the presence of water. The observed differences among the mechanical properties of OC and HOC matrices are clearly originated by the different protein-oleogel interactions in oil (OC) and in emulsion (HOC).