Tuning the mechanical properties of starch-based cryogels with the aid of additives

Starch cryogel is a strong, yet light and porous material with various applications. Neat starch cryogel often suffers from suboptimal mechanical properties. In this study, we investigate the effects of additives on the material properties of starch-based cryogels. Cellulose fibre and glycerol were selected as reinforcing agent and plasticizer, respectively, to formulate starch-based hydrogels, which were freeze-dried into cryogels. Cryogels were characterized in terms of moisture content, density, microstructure, and mechanical properties. Our results show that adding cellulose fibres improves the Young's modulus and structural stability of composite materials. Conversely, adding glycerol significantly enhanced the ductility of the composite materials (i.e., higher maximum flexural strain) without compromising on their Young's modulus. We attributed these results to the impact of the additives on ice formation in the hydrogels during freezing and the structural stability of the matrix during freeze drying, which yielded in distinct microstructures of glycerol-containing samples. This study shows edible composite materials with a large range of material properties can be obtained with the aid of additives, to substitute engineering materials with equivalent properties for various applications.