ARS | Publication request: Rheological Studies Utilizing Various Lots of Zein in N, N-Dimethylformamide Solutions

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2005
Publication Date: December 1, 2005
Citation: Selling, G.W., Lawton Jr, J.W., Bean, S., Dunlap, C.A., Sessa, D.J., Willett, J.L., Byars, J.A. 2005. Rheological studies utilizing various lots of zein in N, N-dimethylformamide solutions. Journal of Agricultural and Food Chemistry. 2:40.

Interpretive Summary: Each year increased effort is being expended on replacing materials that are based on fossil fuels with those based on renewable resources. One underutilized renewable material that is a co-product of the bioethanol industry is zein. Zein is the principal corn protein. Historically zein has been used in the textile fibers and coatings industries. Due to the development of competitive products based on fossil fuels, the use of zein rapidly declined. In order to re-enter these markets, research must be performed to: reduce the impact of moisture on the properties of a zein article, reduce the cost of zein isolation and develop a cost effective process of producing the zein based products. There are several key factors in developing a commercial process, such as the flow properties (rheology) of the zein solution or melt as it makes its way through the industrial process as well as how lot-to-lot variation in the zein may impact the final product properties or production process. In this work we have developed information on the rheology of zein solutions using N, N-dimethylformamide as solvent. This information will be useful to researchers in industry that are working to optimize chemical processes that take place in solution. We have also found that there are significant rheological differences in zein N, N-dimethylformamide solutions when different lots of zein are used. These differences include: how thick the solution is when prepared in the same fashion and how quickly the solutions thicken with time or at elevated temperature. By using various analytical techniques it was determined that there are some important differences between the three lots of zein tested. This information will be valuable to scientists in industry, academia and government labs who work with renewable materials. Methods have been developed to identify key properties that would influence a commercial process as well as developing a technique to understand what is different in the raw material that gave rise to the different property.

Technical Abstract: Rheological studies were carried out on solutions of zein in N, N-dimethylformamide (DMF), where the specific lot of zein, time and temperature were varied. DMF is a good solvent for zein, giving clear, relatively low viscosity solutions. It was found that all of the zein samples behaved in a non-Newtonian fashion. At high concentration and elevated temperature zein solutions will increase in viscosity with time. A temperature study on the rate of viscosity rise illustrated that at temperatures above 40 deg C, the rate of viscosity rise increased in a non-Arrhenius fashion. There can be significant lot to lot variations in commercially obtained zein that give rise to differences in viscosity and rate of viscosity rise. With the samples studied, as-is viscosity was found to double from one lot of zein to another. Differences were observed after size exclusion chromatography which suggests that compositional differences between the lots drive the observed difference in viscosity.