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Biodegradable protein film begins to form. Link to photo information
A continuous biodegradable protein film begins to form using the new ARS film-making process. Click the image for more information about it.

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Edible Films Made From Dairy, Biofuel Byproducts

By Linda Tokarz
June 5, 2007

Got film? A method developed by Agricultural Research Service (ARS) scientists uses byproducts—not only from dairy processing, but also from biofuel production—to create biodegradable protective films.

The technology was developed by research leader Peggy M. Tomasula and her colleagues at the ARS Eastern Regional Research Center's Dairy Processing and Products Research Unit in Wyndmoor, Pa. They found that combining the milk protein casein with water and glycerol, a byproduct of biofuel production, produces a water-resistant film that can be used as an edible coating for food products.

The scientists used carbon dioxide as an environmentally friendly solvent to isolate dairy proteins from milk, instead of harsh chemicals or acids that can be difficult to dispose of, according to Tomasula. Carbon dioxide (CO2) is another byproduct of the glucose fermentation that is used to make ethanol. Using CO2 makes the edible film more water-resistant and biodegradable.

The resulting food coatings are glossy, transparent and completely edible. Like conventional food packaging, edible films can extend the shelf life of many foods, protect products from damage, prevent exposure to moisture and oxygen and improve appearance. By using renewable resources instead of petrochemicals, the scientists can create more biodegradable products and reduce waste.

Tomasula has been working with food technologist Kirsten L. Dangaran and chemist Phoebe X. Qi to improve the appearance and protective properties of the casein films.

At one point in the production process, CO2 dissolves into the milk, decreasing its pH level and causing casein to form particles of a substance known as CO2-casein. The researchers found that decreasing the size of the CO2-casein particles improved the films' ability to block moisture and increased their glossiness.

They also found that coating a low-density polyethylene film with the CO2-casein increased the film's ability to block oxygen permeation. Adjustments like these could make the films more competitive with existing, less eco-friendly products.

Read more about the research in the May/June 2007 issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.