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Zein Batch Extraction from Dry-Milled Corn: Cereal Disintegration by Dissolving Fluid Shear

¹U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038-8598. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Corresponding author. Phone: 215/233-6640. Fax: 215/233-6795. E-mail: Ldickey@arserrc.gov

Corn particles were extracted in an agitated vessel with a 4:1 mass ratio of 70% ethanol to corn for periods of 1–6 hr at ambient temperature. The extract solution was filtered and centrifuged to remove suspended particles after extraction and then diluted to 40% ethanol to precipitate extracted solute. Measurements of the mass of suspended particles separated by centrifugation indicate that mixing the corn particles with the ethanol dissolves and weakens the protein between cells and between starch granules within cells near the particles' surface. Under the conditions of this study, corn particles release starch granules more rapidly than the protein bodies dissolve, as indicated by analysis of the centrifuged particles. The diffusion coefficient for ethanol solution in corn was estimated and compared with a coefficent derived from a fit of the trend in the rate of release of fine particles from the milled corn. The diffusion coefficient of pure zein in a stagnant 70% ethanol solution was estimated from the measurement of weight loss by a ball of zein. Analysis of the ambient temperature protein extraction rate indicates that 2-mm particles exhibit more convective mass transfer than 20-μm particles.