Controlled Self-Organization of Zein Nanostructures for Encapsulation of Food Ingredients

Micro/nano-encapsulation technologies have the potential to meet food industry challenges concerning the effective delivery of health functional ingredients and controlled release of flavor compounds. The inherent complexity of food systems has translated into an intensive search for novel functional shell materials. Understanding their structure has become critical for the design of effective carriers. Nanotechnology methods may prove useful in the construction of food delivery systems. Zein, the prolamine in corn endosperm, has long being recognized for its coating ability. Zein has a marked amphiphilic character. It is soluble in alcohol-water mixtures. It contains more than 50% nonpolar amino acids arranged in unique spatial disposition consisting of tandem repeats of a-helix segments aligned parallel to each other forming a ribbon or prism. This structure gives rise to well defined hydrophobic and hydrophilic domains at the protein surface. Zein can bind and enrobe lipids, keeping them from deteriorative changes. Zein has been shown to adsorb fatty acids and produce periodic structures, most interestingly, nanoscale layers of cooperatively assembled fatty acid and zein sheets. Other experiments have detected the formation of nanoscale "tubes" of zein formed upon adsorption of the protein on hydrophilic surfaces. Lamellar structures detected by x-ray diffraction, formation of zein "tubes" observed by AFM, and the long rod-like structures observed by SEM may be explained in terms of the formation of liquid crystalline phases. Effort has been invested in tracking the self-organization and characterizing resulting tertiary structures formed by zein. The goal is to produce nanostructures of controlled geometry, useful as microencapsulation materials for fatty acids, flavors, oleoresins, vitamins, and peptides.