Hybrid aerogels of spirulin and whey proteins as novel cellular solids

This work proposes a new strategy to obtain cellular solids of spirulin (SP) cells and whey protein (WP) using the aerogel production process. To this aim, aqueous suspensions containing 20 g/100g of a mixture of WP and SP in different ratios, were submitted to thermal gelation. The obtained hydrogels were characterised by an intense green colour and the typical unpleasant fishy odour of spirulin. Hydrogels were then submitted to ethanol solvent exchange and supercritical-CO₂ drying, leading to hybrid aerogels, which were analysed for physical properties (color, density, volume contraction, firmness, microstructure). The conversion of hydrogels into aerogels partially reduced their green colour. The increase in SP in the aerogel progressively decreased its firmness, so that the aerogels obtained from suspensions containing more than 10 g/100g spirulin were not able to maintain the continuity of the aerogel network. The latter was demonstrated by SEM to consist of dried WP microgels organised in a tri-dimensional architecture embedding SP cells. The aerogel obtained from 10 g/100g SP suspension, did not swell or disintegrate upon absorption of both water and oil. Sensory analysis also showed this sample to have negligible SP odour. These results open new possibilities in the development of hybrid cellular solids with neutral sensory properties, posing the basis for a new approach to the engineering of food tissue analogues.