The effect of extrusion conditions on aggregation of peanut proteins
Shah, Abhay Arvind
MetadataShow full item record
This study was aimed at understanding a) the major changes occurring to the spectrum of proteins comprised in peanut flour at conformational and aggregation levels as a result of extrusion; b) the influence of extruder operating conditions on the protein scaffold of peanut flour. Protein was isolated from the extrudate using three buffer systems namely phosphate buffer saline (stage 1); phosphate buffer with urea (stage 2) and phosphate buffer with urea and DTT (stage 3). A high protein content in the stage 2 and stage 3 extracts of extruded peanutflour samples indicated that the process of extrusion results in the formation of aggregates which are stabilized by non-covalent and disulfide linkages. These aggregates are insoluble in nondenaturing buffers. This observation was further confirmed by Agarose gel electrophoreses. SDS-PAGE analyses showed negligible difference in the overall migration patterns of the proteins in the un-extruded and extruded samples. However, there was a variation in the relative amounts of proteins in various samples. Also, size exclusion and ion-exchange chromatography revealed that during extrusion, the proteins undergo various interactions involving non-covalent and disulfide linkages resulting in the formation of aggregates of positive charge or moderately negative charge. Further, these studies showed that formation of these aggregates is more favored by less severe conditions of extrusion. Extrudates obtained with 25, 30, and 35% feed moisture content at 125, 150, and 175 ºC temperatures were also analyzed similarly. Extrusion conditions of 25% moisture and 175 ºC (most severe condition) had the most profound effect on native peanut proteins. The highest Specific Mechanical Energy (SME) was observed under low temperature and low moisture extrusion condition. The mean residence time peaked during extrusion performed under 175 °C temperature and 35% moisture content.