License process for making edible, water-resistant film.

A new process for continuously producing films from a milk protein could lead to edible, water-resistant coatings on several products commonly found in grocery store dairy aisles. The technique harnesses the characteristics of casein, whose natural structure gives it the ability to form water-resistant and biodegradable films or coatings.

Casein films could be produced as stand-alone sheets or as thin coatings that could adhere directly to a product. Either form would act as a barrier to outside substances while protecting a product from damage or contamination. The edible film locks in moisture, so it may be used to coat dairy products, such as cheese, or it could find use as part of a laminate in packaging for cottage cheese or yogurt. Flavorings, vitamins, or minerals could also be added to the coatings.

The process uses high-pressure carbon dioxide to separate casein from milk. Researchers found that if this casein is mixed with water and glycerol and left undisturbed to dry, it forms a water-resistant, flexible, film-like material. It's been difficult to obtain films, fibers and molded materials with acceptable mechanical properties from casein. That's because moisture can dissolve it. The new material remains intact when exposed to water, unlike other protein-based films patented in the past.

The researchers determined which feeding mechanism would spread the casein solution uniformly and which belt material would allow easiest removal of the dried films. They use a Meier rod to spread the feed over the belt. They have found that the best belt materials to use are polyethylene and Mylar. They've also had some success with polyurethane. The researchers have specified drying conditions and temperatures for making the films in three hours.

This process makes the films continuously, and it can be modified for other proteins. It establishes the feasibility of commercial production of biodegradable polymer coatings made from dairy products. Up to 20% of the casein can be substituted with nonfat dry milk, which reduces the cost of the films with little loss in physical properties.

ARS has filed a patent application on the continuous-production process and is interested in finding business partners to move it to market.

Further information. Peggy Tomasula, USDA-ARS Dairy Processing and Products Research Unit, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038; phone: [phone]; fax: [phone]; email: [e-mail].