Novel enzyme immobilization technique uses energy-curable materials for bioactive packaging.

Enzymes improve the quality, performance and appearance of food. Incorporating enzymes within a packaging material, sometimes referred to as bioactive packaging, is a niche area in the field of active food packaging.

However, commercial examples of bioactive packaging are scarce due to technical and economic limitations, since complex immobilization steps can only be performed in a laboratory-like setting. The practical commercialization of such packaging systems would require rapid and effective immobilization techniques.

Scientists at Purdue University wanted to determine if ultraviolet (UV) polymerization could be used as a quick, feasible and inexpensive way to immobilize an enzyme--glucose oxidase--on food contact surfaces. Their research indicates that UV polymerization may effectively bind the enzymes, with retained activity, to a food contact surface to act as bioactive packaging.

UV polymerization is used for curing acrylic monomers and oligomers. The technique involves the use of a photo-initiator (PI). PIs trigger free radical generation under appropriate UV wavelengths, causing complete polymerization in a fraction of a second.

Introducing enzymes in oligomer and PI matrices before curing embeds them permanently to the cured polymer, providing the polymer surface with bioactive properties. Two oligomers were used separately to immobilize glucose oxidase (GOx) on corona-treated low-density polyethylene (LDPE) at 254 nm for 1 min in an [N.sub.2] atmosphere using a UV lamp with intensity of 6400 W per [cm.sup.2].

The activity and orientation of the immobilized GOx was tested using a standard protocol. The scientists tested the technique in food samples by testing the efficiency of GOx as an oxygen scavenger in apple juice at 25 C and 4 C. The results show that the retained activity of immobilized GOx was 85% to 89% with a percentage orientation of 90% to 95%. Immobilized glucose oxidase was effective in reducing oxygen concentration levels in apple juice from 4.6 ppm to 0.0 ppm in 30 min at 25 C and in 70 min at 4 C when tested in a glass reaction vessel.

Further information. Mark Morgan, Purdue University, Department of Food Science, FS 1161, 745 Agriculture Mall, West Lafayette, IN 47907; phone: [phone]; fax: [phone]; email: [e-mail].