Development and characterization of brewers’ spent grain-based materials

Brewers’ spent grain (BSG) is the main by-product of brewing processes. As a lignocellulosic material, BSG is suitable for producing disintegrable composite materials and packaging. Our research aimed to develop BSG-based formulations with and without corn starch that are suitable for producing objects through thermomoulding. The thermomoulding temperature was fixed at 200 °C, and the thermomoulding time ranged from 4 to 30 min. The effects of the thickness (2, 5 and 10 mm), addition of corn starch and BSG type (W (wet), U (dried and unground), P (dried, unground and hot-water treated before use) and M (dried and milled)) on the physical and mechanical properties, absorption capacity, disintegration degree and solubility of the tray materials were investigated. All formulations were characterized by high water absorption (>71.73%), weight loss (46.73%–67.58%) and solubility (30.78%–44.68%). The density, breaking strength and resistance to penetration decreased as the thickness increased, whereas no differences in the flexural strength were detected. The addition of starch reduced both the density and water absorption percentage and increased the penetration strength. With respect to the BSG state, the use of W-BSG resulted in the highest resistance to flexion (0.11 N/mm²) and the lowest resistance to penetration (2.15 N/mm); the use of M-BSG resulted in the highest resistance to penetration (6.36 N/mm). Principal component analysis highlighted that most of the materials developed had physical and mechanical characteristics that made them different from each other and therefore suitable for different uses.