Addressing the role of structural features of proteins in cereal processing

Several novel methodologies have been recently proposed to investigate the significance of structural features of proteins in the processing of cereals and pseudo-cereals. Some of them address features of the proteins in the starting materials, whereas others were designed to analyze structural changes occurring upon processing, and their relevance to the textural and sensory properties of the product. Proteins in cereal-based products are unfolded and insoluble, but their structure is sensitive to the addition of water. Solvation of cereal proteins occurs with stoichiometries and time courses typical for individual grains and flours, and can be monitored by spectroscopic techniques such as fluorescence and NMR. In later stages of processing, protein networks may be formed through covalent (disulfide) and non covalent interactions, among which hydrophobic bonds are the most common. Cysteine thiols on proteins are relevant to the disulfide exchange events involved in network formation, and their role and occurrence has been studied on the original materials by developing a so-called "thiolomics" approach, that also offers information on the accessibility of thiols. Evaluation of thiol accessibility in the presence/absence of denaturants has been proposed as a way of discriminating the compactness of the protein network in various products and the nature of the forces that ensure their stability. As for the role of hydrophobic bonds in these protein networks, basic information has been derived from solubility studies in the absence/presence of denaturants and disulfide reductants. Fluorescent hydrophobic probes have been used to monitor either the number of hydrophobic regions exposed on the protein surface in the starting material(s), as well as process-induced changes in accessibility of these same areas. These approaches may represent a useful tool also for investigating the relationship between molecular and textural/sensory properties in cereal-based materials and products even when proteins other than gluten ensure the solidity of the macromolecular network.