Dairy Byproducts Can Supplement Plastic

The average American consumes more than 30 pounds of cheese every year, and each pound produced creates an estimated nine pounds of the liquid byproducts known as whey.

Disposing of whey isn't difficult—in fact, it can be profitable, thanks, in part, to Agricultural Research Service (ARS) scientists in Wyndmoor, Pa. Researchers at the ARS Eastern Regional Research Center's (ERRC) Dairy Processing and Products Research Unit have helped create uses for more than one billion pounds of whey every year in products such as candy, pasta, animal feeds and even eco-friendly plastics.

Now, food technologist Charles I. Onwulata is using a process called reactive extrusion to supplement polyethylene—a common nonbiodegradable plastic—with whey proteins.

Reactive extrusion involves forcing plastic material through a heating chamber, where it melts and combines with a chemical agent that strengthens it before it's molded into a new shape. Onwulata showed that by combining dairy proteins with starch during this process, it's possible to create a biodegradable plastic product that can be mixed with polyethylene and molded into plastic utensils.

Working with Seiichiro Isobe, a laboratory chief at the Japanese National Food Research Institute, Onwulata created a bioplastic blend. They combined whey protein isolate, cornstarch, glycerol, cellulose fiber, acetic acid and the milk protein casein and molded the material into cups. The dairy-based bioplastics proved to be more pliable than other bioplastics, which made them easier to mold.

Bioplastic blends can only replace about 20 percent of the polyethylene in a product, so resulting materials would be only partially biodegradable. However, Onwulata and his colleagues are currently applying this process to polylactide (PLA), a biodegradable polymer. This research could someday result in completely biodegradable bioplastics.

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.