Used to Make Edible, Water-Resistant Film
By Jim Core
August 2, 2002
An Agricultural Research Service (ARS) scientist has received a patent for
her method to turn a milk protein into water-resistant films that could be used
to coat or package foods.
The method removes the protein, called casein (pronounced kay-seen), from
milk by using carbon dioxide under high pressure. Casein, which solidifies when
milk is acidified, is the chief ingredient in cheese. It is also used as a food
supplement and as an ingredient in nonfood products including adhesives,
finishing materials for paper and textiles, and paints.
Until now, it's been difficult to obtain films, fibers and molded materials
with acceptable mechanical properties from casein. That's because moisture can
The new extraction method takes advantage of casein's natural structure to
form water-resisting films or coatings, according to Peggy Tomasula, the
method's inventor. Tomasula is a chemical engineer at the ARS Eastern Regional
Research Center (ERRC) in Wyndmoor,
Films act as stand-alone sheets, while coatings are thinner and adhere
directly to the product. Both can act as a barrier to outside substances while
protecting a product from damage or contamination. The new material remains
intact when exposed to water, unlike water-soluble, protein-based films
patented in the past.
The film can lock in moisture, according to Tomasula. Edible coatings might
be used to coat dairy food products such as cheese, or could be used as part of
a laminate in packaging for cottage cheese or yogurt. Flavorings, vitamins or
minerals could be added to the coating to enhance the flavor and reinforce
nutrition. The method could also be used to develop biodegradable packaging
materials from casein. Casein may also be combined with plasticizers to soften
and improve the flexibility of casein-containing, nonfood materials.
In pilot plant studies, ERRC researchers are further evaluating the method's
potential. The patent is available for licensing, and ARS is seeking commercial
partners. ARS is the U.S. Department of
Agriculture's chief scientific research agency.