Confocal Laser Scanning Microscopy (CLSM) has been used to follow the dynamic structure evolution of two protein/polysaccharide mixed biopolymer gel systems during large strain deformation. Gelatin/maltodextrin composites exhibited a ‘;pseudo-yielding’ stress-strain response in both tension and compression, when the gelatin-rich phase is continuous, which was attributed to debonding of the particle/matrix interface. This behaviour was significantly less apparent for gelatin/agarose mixed gels. The interfacial fracture energy of the two systems was determined using an elastomer composite debonding model. The gelatin/maltodextrin interfacial fracture energy (∼0.2 J.m-2) was found to be an order of magnitude less than for gelatin/agarose, leading to the observed variation for the two systems.