Development of coffee residue products by wet extrusion molding

Abstract

Coffee residue (spent coffee grounds) has been unused biomass resources and discarded as food waste in a large amount. In this study, we aimed to develop all-biomass coffee residue products by wet extrusion molding with a natural molding aid. Coffee residue and hydroxypropylmethyl cellulose (HPMC) were mixed at a ratio of 8:2 to 5:5, water of 70 to 200% of the solid weight was added and kneaded, as a result, the coffee residue obtained fluidity. The amount of water has a great influence on the fluidity, and it was successful to extrude coffee residue into a plate or hollow shape with water of 100% of the solid weight. Unlike wood powder, the larger the ratio of HPMC was used, the higher the extrusion resistance, the lower the shrinkage and the Young's modulus of the molded products were. The difference in the components probably affected the characteristics because coffee residue has a low cellulose content and a large amount of oil and protein. It is epoch-making that coffee residue can be molded three-dimensionally without using thermoplastic resins with poor biodegradability. The products are possible to solve both the food waste problems and the serious environmental problems originated from plastics.