COMPRESSION-FORMED STARCH-BASED PLASTIC

Alternatives to synthetic plastics used in ovenable trays for frozen f oods are of interest because of environmental and food safety concerns . A new technique for making a compression molded starch-based plastic is described that uses starch foams rather than starch powders as a f eedstock. Starch foams were compressed between polished, unheated plat ens into plastic sheets from which tensile bars were cut. The starch p lastic had the highest tensile strength when compressed greater than 6 9 MPa. Starch powders that were compressed under identical conditions did not form a cohesive starch plastic. Initially, the tensile strengt h of the starch plastic derived from starch foams was comparable to th at of polypropylene. However, tensile and flexural strength decreased with time for starch plastics stored at room temperature or -20 degree s C. The functional properties of samples that were baked in contact w ith three different food types (low moisture, high moisture, oily) wer e studied. The tensile and flexural strength of polypropylene samples were not affected by baking treatments. However, the starch plastic sa mples lost both tensile and flexural strength and formed numerous blis ters in some treatments. Maltose was blended into the starch plastic i n efforts to reduce the hygroscopicity of the starch and decrease blis ter formation. While maltose significantly reduced the hygroscopicity of the starch plastic, it did not prevent blister formation. (C) 1997 Elsevier Science B.V.