This week's editorial takes a look at edible polymers
in food packaging and adhesive applications. In these unique applications
a food product is considered to be the substrate, and the adhesive must
meet the ultimate food standard - the digestive process of the formulator.
I was surprised recently to see significant development activity in edible
films. Edible films have been around for a long time. Sausage casing made
from animal intestines, and more recently collagen, allow meat batters
to be held in a form until hard set. Wax coatings on fruits and vegetables
prevent moisture loss, and these have been in use since the 1800s. Probably
the most recognizable edible coating is a carbohydrate and gum based coating
used to protect M&M chocolate candies from moisture and body heat
until eaten. It also protects one's self from a messy chocolate covering
One of the most useful functions of edible films is their ability to
act as barriers, either to gas, oil, or more often moisture. Water-dispersible
forms of corn protein (Zein) can be applied as a film for meats or fruits.
One such application is the coating on raisins for use in dry ready-to-eat
breakfast cereals. Edible films can also be used as a barrier to oil absorption
in battered and fried foods. Methyl cellulose and hydroxypropyl cellulose
have been used for these purposes.
An edible polymer will be generally recognized as safe ("GRAS")
for use in edible films if the material has previously been determined
safe, and its use in edible film is in accordance with current good manufacturing
practices for food and used in amounts no greater than necessary to perform
its function. In the U.S., if the edible polymer is not currently GRAS
but the manufacturer can demonstrate safety, the manufacturer may either
file a GRAS Affirmation Petition to the FDA or precede to make the material
without FDA concurrence.
With all this going on in the area of edible polymers, I became interested
in the possibility of edible adhesives and did a quick search. What I
found is that sugar apparently isn't for sweetening anymore. Now it is
the main ingredient in a new edible adhesive developed by Agricultural
Research Service (ARS, Peoria, IL, USA) scientists. They developed a flavorless,
food grade adhesive that could be used for an assembly line operation
that inserts drinking straws into beverage cans, cartons, and bottles.
Specifically, the company needed a strong, fast curing adhesive that could
bond the straws to a special holder that's lowered into the containers
before they are filled and sealed. At that point, the adhesive is to dissolve
in the bottled liquid in an even and controlled manner; otherwise the
straws would remain fixed to the holders instead of rising freely out
of the container when consumers opened them.
The formulation and processes to form the sugar-based adhesives is described
in a recent publication1and has been patented.2 Tests show that the resulting
adhesive bond to substrates including wood, metal, cloth, leather, glass,
plastic and paper. Besides holding the straws, the adhesives have potential
applications in binding food items, utensil packaging, and manufacture
of drug capsule layers.
Many foods we consume every day take advantage of edible coatings, and
now edible adhesives are providing functionality as well. It remains,
however, for food scientists to apply edible films and adhesives in other
settings to fully utilize some of the properties of these unique packaging
- "How Sweet It Is", Adhesives and Sealants Industry, June
- US Patent No. 6,613,378.
Should you have any comments or feedback, please contact
Edward M. Petrie