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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Plant Polymer Research » Research » Publications at this Location » Publication #96573
Title: EFFECT OF SPECIFIC MECHANICAL ENERGY ON PROTEIN BODIES AND ALPHA-ZEINS IN CORN FLOUR

Author
item BATTERMAN-AZCONA, SHERI - PURDUE UNIVERSITY
item Lawton Jr, John
item HAMAKER, BRUCE - PURDUE UNIVERSITY

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Corn is one of the major cereals used in the production of ready-to-eat (RTE) breakfast cereals. Most research has been focused on the effect starch has regarding the texture of RTE breakfast cereals. No research has been done which addresses the effect of protein on the texture of RTE breakfast cereals. The main protein in corn is zein. In uncooked corn, the structure of zein is spherical and made up of protein bodies. For zein to affect the texture of RTE breakfast cereals, the protein bodies need to be ruptured so that the zein can be released. The purpose of this research is to determine the amount of energy needed to rupture the protein bodies and release the zein. Corn meal was extruded under different conditions so as to cook the corn under different energy conditions. Mild cooking was insufficient to rupture the protein bodies. Intermediate cooking did rupture the bodies, but did not fully rupture them beyond recognition. Higher cooking energies are needed to fully release the zein. This information will be used by corn processors , showing them the mimimum amount of energy needed to disrupt protein bodies.

Technical Abstract: Zeins, the storage proteins of corn, are located in spherical entities called protein bodies. The disruption of protein bodies and zein released during extrusion may influence the texture of ready-to-eat (RTE) corn-based extruded foods. In this work, chemical and microscopic studies were conducted on corn flour, that had been extruded under mild to extreme conditions, to determine the specific mechanical energy (SME) required to break apart protein bodies and release alpha-zein and to assess changes in protein-protein interactions. Transmission electron microscopy with immunolocalization of alpha-zein revealed that starch granules and protein bodies remained intact under mild processing conditions (SME 35-40 kJ/kg), but under harsher conditions, protein bodies were disrupted and alpha-zein released. At SME 100 kJ/kg, protein bodies appeared highly deformed and fused together with the alpha-zein released, whereas at higher SME, protein nbodies were completely disrupted and alpha-zein was dispersed and may form protein fibrils. Protein in extrudates was less soluble in urea/SDS than in unprocessed corn flour, but was readily extracted with urea/SDS/2-ME. This was likely due to protein aggregation upon processing due to a prevalence of hydrophobic interactions and disulfide bonds. This research directly relates SME during extrusion to chemical and structural changes in corn proteins, which may affect the texture of corn-based, ready-to-eat (RTE) food products.