Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2011
Publication Date: 7/11/2011
Citation: Sessa, D.J., Woods, K.K. 2011. Purity assessment of commercial zein products after purification. Journal of the American Oil Chemists' Society. 88(7):1037-1043.
Interpretive Summary: Commercial corn zein from co-products of the ethanol industry, possessing about 90% protein, has an off-odor and yellow color that are deterrents to its usage in certain food, pharmaceutical, medical and cosmetic applications. Column filtration of ethanolic zein solutions through Zeolite 5A and activated carbon columns yields zein products that can have a variety of purities from 96-100% dependent on its applied uses. In this research, methodologies to define degree of odor and color removals and to characterize composition of protein in the product were developed. Since a high purity zein product possesses a high degree of a-proteins, additional methodologies were designed to measure a-helical content and validate findings. Combinations of all these methodologies can be used to define zein products for specific applications. Lot-to-lot and batch-to-batch differences from a commercial operation, that play havoc with zein protein users, are now defined. These findings are of great importance to industrial users of zein and will open the door for zein’s use in high-end products.
Technical Abstract: Successful utilization of commercial zein products for certain food, pharmaceutical, cosmetic and medical applications requires a decolorized/deodorized zein of high purity. A zein protein product with those qualifications can be achieved by column filtration of commercial yellow zein solutions through Zeolite 5A and activated carbon where recycling of column eluents will yield zein products of varying purity. The objective of this investigation was to devise a combination of methodologies to assess those attributes. Off-odor removal is defined by a UV spectroscopic ratio of 280nm:325nm where diferuloylputrescine is the major contributor. Removal of yellow color, attributed to xanthophylls in zein, was followed by visible spectroscopic assay of a series of dilutions at 448nm. Zein purity was assessed by FTIR of commercial zein before and after column filtration. Spectral differences were observed in the amide I (1650cm-1) peak, amide II region (1530 and 1550cm-1) and the amide III peak at 1240cm-1, where ratio of the dominant peaks were strongly dependent on purity of sample. Circular dichroism (CD) analyses validated FTIR results by showing increased '-helical content for the column purified zeins. Combinations of these methodologies can be used to define zein products with different degrees of purity required for specific applications.