Pest-Proofing Food Packaging
Entomologist Mike Mullen checks seals for
signs of infestation after a 3-month test of
No one wants to open their breakfast cereal or pancake mix and find it
infested with bugs. Even if these occurrences represent one in a million, they
make a lasting impression.
Manufacturers of food, feed, and other processed grain products want to
avoid these incidents and provide consumers with high-quality products. That's
why Agricultural Research Service's
entomologist Michael A. Mullen at the U.S. Grain Marketing and Production
Research Center in Manhattan, Kansas, has been working with food and feed
manufacturers since 1989 to help design insect-proof packaging.
"Packaging should protect the commodity from the point of manufacture
to the point of consumption," says Mullen. Nine times out of 10, an insect
infestation isn't the manufacturer's fault. Often, insects get into packages
during transportation or storage in a warehouse.
Like people who fall into two basic personality types--uptight A or laidback
B--stored product insects are one of two types. They're either invaders or
"The invaders look for opportunities to get inside food containers by
searching for cracks, crevices, and holes," says Mullen. "The
penetrators simply chew holes in the packages."
Invaders include the red flour beetle, confused flour beetle, sawtoothed
grain beetle, Indianmeal moth, and almond moth. Penetrators like the lesser
grain borer, cigarette beetle, warehouse beetle, and rice moth can bore through
one or more layers of packaging materials.
"There is no perfect package," says Mullen. "Packages are
usually tailored to fit the product and designed to last throughout its shelf
life. Often, this means that the package will have to provide this protection
for more than a year."
Although packages can become infested anywhere along the marketing chain,
they are most likely to become infested during long-term storage. Inside
warehouses, insects start by attacking vulnerable packaging and later jump to
Most stored-product insects are invaders, entering food and feed packages
through seams and closures. They lay their eggs in the tight spaces formed when
packages are folded. These spaces give the newly hatched larvae an ideal
starting spot to invade. Dry pet foods are usually packaged in bags like these.
Mullen has been working with several companies that make dry pet food and
with others that produce paper bags used for its packaging. In November 1997,
ARS and Mullen initiated a cooperative research and development agreement
(CRADA) with International Paper of Loveland, Ohio, to improve existing
packaging or develop alternative packaging to protect dry pet foods from insect
Dry pet food is a favorite food of insect pests such as these flour beetles.
Other companies that Mullen has had formal CRADAs with include Ralston
Purina in St. Louis, Missouri, and Continental Extrusion Company in New Jersey.
Seals and closures can often be improved by changing the type or pattern of
sealant glue. A pattern that forms a barrier is usually the most insect
resistant. Recently, paper bag manufacturers discovered through working with
Mullen that closures on bag bottoms were prone to insect entry and needed
reinforcement as much as top closures. Mullen is helping one bag manufacturer
expand its customer base from nonfood agricultural products to food products.
Another packaging problem involves smell. Insects are attracted to packages
that allow food odors to escape. Certain plastic film overwraps that fit
tightly around a package can help prevent insects from smelling its contents.
Interior plastic liners like those used in breakfast cereal boxes can be
effective, blocking air from carrying aromas outside to hungry insects.
In 1991, Mullen helped to develop an odor neutralizer that can be
incorporated into packaging materials. He devised a laboratory choice test
allowing insects to choose between a food protected by the odor neutralizer or
by only untreated packaging. They chose the food in untreated paper.
"There's really no one thing that makes a package insect proof,"
says Mullen. "Each additional improvement added to the package design
helps keep insects out. All packages provide some protection against invasion.
But tightening up the seals and adding a repellent adds even more," he
Mullen has developed scientifically proven methods to evaluate packaging
materials against insects in the laboratory. He places 32 to 40 of each package
type in an environmentally controlled room for about 3 months. These packages
are exposed to five species of insects. Each month, the researchers examine
packages for holes and flaws in seams and closures. Finally, they open the
packages and examine the contents for insect infestations.
Manufacturers rely on these findings to improve future package designs or to
conduct larger packaging studies. Test results have led to insect-resistant,
pesticide-free packages for dry pet foods, raisins, baby cereals, pancake
mixes, and breakfast cereals for domestic consumption and export. One company
has reported a 75-percent reduction in consumer complaints from insect-related
The food industry is facing increasing restrictions on pesticide use.
Insect-resistant packaging can help reduce dependence on insecticidal
treatments. This research helps assure consumers of insect-free food and
protects manufacturers against loss of goodwill arising from insect-infested
packaging. By Linda
Cooke, Agricultural Research Service Information Staff, 1815 North
University Street, Peoria, IL 61604, phone (309) 681-6530.
Michael A. Mullen is in the
USDA-ARS Biological Research Unit,
U.S. Grain Marketing and Production Research Center, 1515 College Ave.,
Manhattan, KS 66502; (785) 776-2782, fax (785) 537-5584.
"Pest-Proofing Food Packaging " was published in the March
1998 issue of Agricultural Research magazine. Click here to see this
issue's table of contents.