CHAMPAIGN, Ill. - A mix of zein and fatty acids, coated in flax oil, has created
water-resistant, plastic-like food containers that potentially could be discarded as naturally decaying compost in the backyard.
Don't look for the products on store shelves yet, however. University of Illinois food scientists are just looking ahead for when zein, which is extracted from a corn refiner's byproduct, becomes more available through efficient membrane processing.
Zein is extracted from corn gluten meal left over after ethanol manufacture and also from dry milling waste. Only a small portion of the zein currently available is used commercially in the formulation of specialty coatings for candies, rice, dried fruits and pharmaceutical tablets. U. of I. researchers think their process could give zein -- and corn -- a new market at a time when there is a worldwide demand for biodegradable containers.
In a paper published in the January-February issue of the journal Cereal Chemistry, the U. of I. scientists reported on their success in turning zein into plasticized resins that can be molded into plates, sandwich containers, sealing material and trays.
"There are growing environmental demands, especially in places such as Europe and Japan, for solving a lack of landfill space," said food scientist Graciela Wild Padua. "Part of the problem in using zein before now has been its price. If you try to develop products out of commercial zein that is available, it wouldn't make financial sense. We need to be able to obtain zein in a greater quantity."
As part of the overall effort, U. of I. food scientists have developed a process to manufacture biodegradable plastics from corn gluten meal. The process involves melting the zein with fatty acids to produce moldable resins. When disposed of, the plasticized zein will degrade naturally, acting as a slow-release nitrogen source for soil, Padua said.
In the Cereal Chemistry report, Padua, Huey-Min Lai, who has since earned her doctorate in food science, and Lun Shin Wei, now an emeritus professor of food science, turned the zein into thin plastic-like sheets by mixing it with palmitic or stearic acids at varying weight ratios. While the structure of the sheets changed according to the ratios, the sheets with the zein-palmitic acid mixture showed a substantially stronger tensile strength.
Without the plasticizing acids, zein sheets were brittle and had higher water-absorption qualities. Zein sheets without the fatty acids lacked a definitive structure and showed cracking and voids under a microscope. The strongest, most watertight zein sheets were those containing a mixture of palmitic acid and fatty acids and coated with heated flax oil.
The researchers -- whose work is funded by the Illinois Council on Food and Agricultural Research and the Illinois Corn Marketing Board -- now are creating zein-based wrapping films with varied flexibility.