Functionality of the storage proteins in gluten-free cereals and pseudocereals in dough systems

Abstract

The dough functionality of the storage proteins in “gluten-free” grains has been studied for almost 25 years. Zein, maize prolamin, when isolated as a-zein can form a wheat gluten-like visco-elastic dough when mixed with water above its glass transition temperature. There is good evidence that its doughforming properties are related to a change in protein conformation from a-helix to b-sheet and association of the molecules into fibrils. Stabilisation of b-sheet structure and visco-elasticity can be enhanced by inclusion of a co-protein. No other isolated cereal or pseudocereal storage protein has been shown to form a visco-elastic dough. Many treatments have been applied to improve “gluten-free” storage protein functionality, including acid/base, deamidation, cross-linking by oxidising agents and transglutaminase, proteolysis, disulphide bond reduction and high pressure treatment. Such treatments have some limited positive benefits on batter-type dough functionality, but none is universally effective and the effects seem to be dependent on the composition and structure of the particular storage protein. Research into mutants where prolamin synthesis is altered appears to be promising in terms of improved dough functionality and scientific understanding. Research into how treatments affect the functionality and structure of isolated storage proteins from “gluten-free” grains other than maize is required.