30C-23 |
The effect of extrusion on protein aggregation in partially defatted peanut flour |
A. SHAH1, L. Chen, M. Corredig, and R. D. Phillips. (1) Dept. of Food Science and Technology, University of Georgia, Food Science Building, Athens, GA 30605-7610 Extrusion cooking of peanut flour provides unique processing features because of the high pressure in combination with severe shear forces and high temperature the peanut flour is subjected to. However, it is difficult to understand the behavior and conformational changes the proteins undergo upon extrusion. By determining solubility of proteins with different buffers and their chromatographic elution depending on their aggregation state, protein-protein interactions have been examined. Focus of the present work was to determine the effect of extrusion on peanut protein interactions. Unextruded peanut flour and two samples of 50% peanut flour/50% corn starch, extruded at 500 rpm, 20% moisture, 135„aC and 500 rpm, 40% moisture, 115„aC were sequentially extracted with 20mM Na-Phosphate buffer pH 7.9 with 0.5M NaCl (stage 1), 6M Urea (stage 2), and, 6M Urea-0.01M DTT (stage 3). Electrophoretic analysis (SDS-Page, Bio-Rad, CA), Size-Exclusion chromatography (Superdex 200, Pharmacia, NJ), and, Ion-Exchange chromatography (HiTrap Q, Pharmacia, NJ) were conducted to determine the differences in aggregation and protein composition of the various aggregates. Our results showed a marked difference in the solubility of the samples. SDS-Page of the soluble extracts showed the presence of a high amount of disulfide interactions. This was reconfirmed by size-exclusion chromatography of the extracts. However, non-covalent interactions were predominant in high moisture-lower temperature extruded sample as compared to lower moisture-high temperature extruded sample. Ion-exchange chromatography indicated the elution of three main peaks along with a large amount of unbound protein. Extrusion strongly affects the solubility of peanut proteins and moisture conditions and temperature conditions play a major role in protein-protein interactions. These conditions can have significance in optimizing extrusion parameters.
Session 30C, Food Chemistry: Proteins
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