Serum release: The hidden quality in fracturing composites

Release of serum is important for many food systems such as meat products and its replacers, gels, vegetables and fruit, where serum release plays a clear role in the perception of juiciness. Nevertheless, this phenomenon and its consequences for large deformation and fracture behaviour have not been studied extensively for semi-solid food systems. It has been avoided in the experimental setup or it even has been neglected in analysis of the data. In this study mixed whey protein isolate/gellan gum gels were used as model systems. Gels were subjected to uniaxial compression and evaluated sensorically by a quantitative descriptive analysis panel. The latter showed that serum release was a dominant factor in sensory perception of the gels regarding mouthfeel attributes as slippery and watery. Compression experiments showed that serum release is related to microstructural characteristics of the gels. The serum release can be described by flow through a porous medium, starting from the Darcy's equation. It was demonstrated that the large deformation mechanical properties of the gels can be described better by correcting for the effect of serum release. Moreover, a relation between serum release, gel microstructure and sensory evaluation was established.