(105c) Protein Based Aerogels: Preparation, Applications and Potential for Food Engineering

In the last decades the interest toward porous materials based on natural polymers is continuously growing. A promising way to achieve mesoporous materials, having porosity up to 99% and correspondingly a huge internal surface area is the supercritical drying of gels resulting in aerogels. Natural polymer-based aerogels consisting of polysaccharides or proteins are promising for life science and food applications because of their biocompatibility and biodegradability. However, also the area of bio-based insulation could be targeted as well, since very low thermal conductivity is given.

In this work we focus on aerogels based on natural proteins, such as milk and egg white proteins, which are well-known as staple foods. Producing aerogels from natural food sources can open a new market for the aerogel in food, for instance as food additives. In this work mainly an application of protein-based aerogels as carrier material for sensitive and sensorial unpleasant compounds in food products is aimed. The carrier material is produced in different shapes, depending on the targeted application. Primarily, spherical particles are preferred due to simple handling and a later possible coating. The main requirements for such a carrier material are high specific surface areas coupled with high mechanical stability as well as a homogeneous particle size. Protein aerogels exhibit BET surface area up to 390 m²/g depending on pH during the gelation. Aerogels formed at very low and very high pH values are found to have highest surface areas. Since the proteins have positive and negative charges the orientation and arrangement of the proteins vary with pH. Ordered proteins generate more ordered gel structures yielding aerogels with higher BET surface area compare to those gelated at the isoelectric point. The mechanical stability of the protein aerogels depends on the reactivity of S-H-groups. At higher pH more â??S^â?? anions are formed and hence more Sâ??S-bonds lead to stronger gels and aerogels.

The gel particle size distribution is depending on the droplet size distribution in the emulsion before gelation. It was optimized to obtain aerogel particle sizes between 50 to 100 µm.

Further, aerogels with the desired properties were loaded by two compounds, fish oil and ascorbic acid (vitamin C), via adsorption from supercritical CO₂. Remarkably high fish oil loadings were achieved without losing the free-flowing properties of the aerogel particles.

Further, storage and release behavior in simulated gastrointestinal fluids were investigated showing the potential of protein-based aerogels as carrier materials for food applications.