Starch, fiber and CaCO 3 effects on the physical properties of foams made by a baking process

Abstract

Single-use food containers with a self-closing hinged lid made of extruded polystyrene (EPS) or coated paperboard (PB) are used to serve a variety of food products. Food containers made of materials that are inexpensive and can be composted into a useful mulch would be of commercial interest as a replacement for EPS or PB. In this report, a baking process was used to study the functional properties of foams made of starch or starch composites containing fiber and/or CaCO 3. Baked foams made of formulations containing only starch had a lower flexural strain to break ( e b) and elongation to break ( Elmax) than EPS or PB foams. The e b was increased by lowering the starch concentration in the formulations, using potato starch versus wheat, corn or tapioca starch and by increasing the moisture content. Nevertheless, the e b and Elmax values remained lower than in the EPS and PB samples. Calcium carbonate did not improve the mechanical properties of the foams. Foams containing starch and CaCO 3 were more dense with lower e b and Elmax compared to foams containing only starch. Foam density decreased and e b markedly increased by including softwood fiber in the dough formulations. Formulations with a starch/fiber ratio of approximately 5:1 or less made baked foams with e b values greater than 5% and Elmax values nearly double those of foams containing only starch. The addition of CaCO 3 to starch/fiber foam composites did not improve foam properties. The CaCO 3 increased density and decreased e b and Elmax values compared to foams made of starch and fiber.