Exploring the Potentialities of Cellulose Aerogels and Cryogels as Food Ingredients

Aerogels are unique nanostructured solid materials, showing extremely low density (0.01-0.2 g/cm3), high specific surface area (200-400 m2/g) and high porosity (>90%). Aerogels can be prepared from different biopolymers, such as proteins and carbohydrates. In this context, cellulose, produced from agro-industrial vegetable waste by closed-loop technologies, is a good candidate for developing food-grade aerogels. The latter could represent novel fiber-rich ingredients able to exert peculiar functionalities in foods. Nevertheless, up to now, no studies have investigated the possible development of cellulose aerogels intended as novel food ingredients. In this work, food-grade cellulose aerogels were developed and characterized to explore their potential as food ingredients. To this aim, monolithic cellulose hydrogels (3, 4, 5% w/w) were prepared and further converted into aerogels by freeze-drying (FD) or supercritical-CO2-drying (SCD). Samples were analyzed for density, BET internal surface area, porosity, pore size, glass transition temperature (Tg), microstructure by SEM and firmness. Additionally, water and oil compatibility was assessed by monitoring absorption kinetics, maximum solvent uptake, and solvent retention ability. SCD aerogels presented higher firmness and lower pore size as compared to FD ones. Water and oil uptake kinetics were dependent on aerogel density, with FD aerogels showing a faster and 2-times higher solvent uptake than SCD aerogels. While water absorption caused SCD and FD aerogel swelling, the oil-loaded aerogels well retained their structure. This work demonstrates the feasibility of converting cellulose into aerogels with tailored functionalities depending on cellulose concentration and drying technique. This structural approach can be regarded as an innovative strategy to turn valuable components from plant-food side streams into novel ingredients for food applications. This work is based upon work from COST Action "Advanced Engineering of aeroGels for Environment and Life Sciences" (AERoGELS, ref. CA18125), supported by COST (European Cooperation in Science and Technology).