Formic acid addition also seems to exert a clear and pronounced influence on broadening the temperature interval over which the rubbery-like plateau extends, and consequently, on decreasing the bioplastic temperature susceptibility. This plateau region has been extensively described in polymer rheology in terms of an entanglement network formed by the simple topological interaction of polymer chains. It arises at frequencies higher (timescale shorter) than the lifetime of the topological entanglements (Ferry, 1980). However, for these protein-based systems, it may be attributed to a situation that falls between a temporary entangled network and covalent crosslinking (Ross-Murphy, 1995), as hydrophobic interactions usually act not at a point on the chain as covalent crosslinks do, but involve more extended ‘‘junction zones’’.