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: 765-494-1180; fax: 765-496-1115; email: mmorgan@purdue.edu.
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