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In this project, study of application of food by products (Spent coffee – wheat bran) in order to producing fiber solid foam using extrusion was carried out. Central composite design was used for evaluation of variables containing spent coffee: wheat bran ratio (75:25, 50:50, 25:75), feed moisture content (14, 17, and 20) and screw speed (120, 160, 200 RPM) on moisture, water activity, expansion index, hardness and microstructure of extrudates. Results showed that by increasing spent coffee and moisture, water activity and humidity of solid foams were increased significantly. However screw speed had no effects on both properties. Improvement of spent coffee: wheat bran concentration in formulations in order to higher concentration of nonsalable fiber caused an increase in hardness and decrease in expansion index significantly. Increasing feed moisture content (14, 17, and 20) and screw speed simultaneously, showed an increase in expansion index and decrease in hardness. Microstructure survey of solid foams illusterated that increasing spent coffee: wheat bran ratio leaded porosity reduction and improvement of cell wall size and reducing in air buble diameter. Based on optimization results, in order to production of solid foam with appropriate characteristics such as final moisture content (4.73%), wateractivity (0.29), expansion index (1.23), hardness (68.51 N), the process conditiond were determined at spent coffee: wheat bran ratio (69:31), feed moisture content (14.1) and screw speed (190 RPM) [ABSTRACT FROM AUTHOR]