Purity Assessment of Commercial Zein Products After Purification

Successful utilization of commercial zein products for certain food, pharmaceutical, cosmetic and medical applications requires a decolorized/deodorized zein of high purity that can be achieved by column filtration of commercial yellow zein solutions through Zeolite 5A and activated carbon. The objective of this investigation was to devise a combination of methodologies to assess purity and degree of deodorization and decolorization. Off-odor removal is defined by a UV spectroscopic ratio of 280:325 nm where diferuloylputrescine is the major contributor. Removal of yellow color, attributed to xanthophylls in zein, was followed by visible spectroscopic assays of a series of dilutions at 448 nm. SDS-PAGE analysis demonstrated removal of beta-zein in combination with diminished sulfur content by sulfur analysis. Zein purity was assessed by Dumas nitrogen and FTIR of commercial zein before and after column filtration. Spectral differences were observed in the amide I (1,650 cm(-1)) peak, amide II region (1,530 and 1,550 cm(-1)) and the amide III peak at 1,240 cm(-1), where ratio of the dominant peaks were strongly dependent on purity of sample. Circular dichroism (CD) analyses validated the FTIR results by showing increased alpha-helical content for the column purified zeins. Combinations of these methodologies can be used to define zein products as a quality control measure for a commercial operation.