Production of Zein From Dry Milled Corn by Solvent Extraction and Ultrafiltration
Shukla, Rishi
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https://hdl.handle.net/2142/77467
Description
Title
Production of Zein From Dry Milled Corn by Solvent Extraction and Ultrafiltration
Author(s)
Shukla, Rishi
Issue Date
2000
Doctoral Committee Chair(s)
Cheryan, Munir
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Engineering, Agricultural
Engineering, Chemical
Engineering, Packaging
Language
eng
Abstract
This research focused on developing a process for the production of low cost zein from corn using a combination of solvent extraction and membrane technology. Extraction of zein from dry milled whole corn was optimum with 70% ethanol at 50°C using a solvent-to-solids ratio of 6 ml ethanol per g corn for 45 minutes. Zein concentration in extract was 3--9 g/l. Continuous column extraction was also best at 50°C and 70% ethanol; a solvent ratio of 1 ml/g resulted in zein concentrations of 17 g/l in the extract. Multiple extractions of the same corn with fresh ethanol resulted in a yield of 85% after 4 extractions, while multiple extractions of fresh corn with the same ethanol resulted in high zein concentration in the extract (15 g/l). The zein extracted in our research was comparable in amino acid analysis and SDS-PAGE profiles to commercial samples.
Several commercially available polymeric and inorganic membranes were evaluated for stability, flux and rejection in aqueous ethanol solutions. Regenerated cellulose, surface-modified/cross-linked composite and ceramic membranes had better stability than polysulfone or cellulose acetate membranes.
Three polymeric membranes and one inorganic membrane were selected for further studies with model zein solutions in a cross-flow cell. Flux with the Osmonics-Membrex MX25 was 45 liters per square meter per hour (LMH) at 5 g/l zein and 25 LMH at 150 g/l zein at 20 psi and 50°C. Zein rejections were 88% and the Cg value was 340 g/l. The Membralox 200 A ceramic membrane gave a flux of 70 LMH at 5 g/l zein at 15 psi and 50°C, with a zein rejection of 80%. Pilot scale trials done with real extracts confirmed model solution data.
The process developed here can be easily integrated into any corn processing facility, especially dry-grind ethanol plants. The solvent extraction step involves only mixing and a filtration/centrifugation step. The filtered extract, after further treatment if necessary to improve protein purity, can be concentrated using solvent stable membranes to at least 250 g/l, which results in a recycle of over 97% of the extraction solvent, thus substantially lowering energy requirements.
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