CHANGES OCCURRING IN PROTEIN BODY STRUCTURE AND ALPHA-ZEIN DURING CORNFLAKE PROCESSING

Zeins, which comprise the majority of proteins in corn, are located in spherical organelles called protein bodies. Changes in protein body s hape and release of encapsulated alpha-zeins as a result of cornflake processing (conventional pressed or extrusion flaking) were investigat ed. Size-exclusion chromatography, SDS-PAGE, and protein solubility te sts showed that, upon cooking, zein proteins form large, disulfide-bou nd polymers, many of which were insoluble in nonreducing solvents. Tra nsmission electron microscopy with immunogold staining revealed that c ooking had no effect on protein body structure in corn, but after proc essing to cornflakes, protein body structure was altered. In conventio nal pressed cornflakes, the protein bodies were flattened, partially f used together, and alpha-zeins were to some degree released, whereas i n the extruded flakes, protein bodies were completely disrupted and al pha-zeins dispersed. These results suggest that zeins in cornflakes, p articularly extruded ones, are not confined to rigid protein bodies bu t can interact with each other and other components in the system. The disruption of protein bodies, zein release, and the chemical changes that proteins undergo during processing are speculated to be determina nts of texture in ready-to-eat corn-based breakfast cereals.