THERMOTROPIC GELATION OF FOOD PROTEINS

This review paper is an attempt to summarize the results of investigations over several years in the field of thermotropic gelation of proteins which have been carried out in the Laboratory of Novel Food Forms of the A.N.Nesmeyanov Institute of Organo-Element Compounds in Moscow. The gelling behavior of food proteins [soybean globulin fraction, 11S globulin from broad beans (legumin) and ovalbumin] is studied. Heat-setting mechanisms and general physical approaches for the phenomenological description of gel formation from globular proteins are discussed. Behavior of gelling systems with protein concentrations below and above the gelation threshold (the gel-point) is analysed in detail. The classical and modern theories of gelation, and their use in the description of concentration dependences of the average size of finite clusters in the sol-fraction, and gel equilibrium elasticity modulus are compared. The modern theory of gelation based on the 3d percolation model has been shown to reflect more correctly the main features of the thermotropic gelation of proteins. Detailed consideration is given to viscoelasticity of protein thermotropic gels under small deformations. It is shown that, due to microheterogeneity of the structure, protein gels display some characteristic features of the rheological behavior of both amorphous and crystalline polymer solids.