Influence of hydrothermal processing conditions on the functionality of Phaeodactylum tricornutum extracts

Microalgae are an underutilized biomass source of nutritionally valuable extracts with promising texturizing capacities that can be used for food applications. This also requires the development of environmentally friendly extraction technologies. Hydrothermal processing was used in this study to investigate the effects of temperature (up to 225 °C) on the extracts from the diatom Phaeodactylum tricornutum. The relationship between protein and polysaccharides' presence and functionality was assessed, based on structure, composition, bioactivity, and rheological behavior. An optimal condition of non-isothermal processing at 120 °C resulted in the extract with gelling capacity (at 20 % w/w extract concentration). This extract is rich in carbohydrates in oligosaccharide form (9 g per 100 g extract) and protein (16 g per 100 g extract), which indicates nutritional relevance and possible prebiotic effects. Moreover, after an additional purification step with food-grade solvents, this extract was able to gel at 5 % w/w concentration. These combined with its significant antioxidant activity (over 100 μmol Trolox equivalents per gram of extract in all studied conditions, using the ABTS method) point towards new possibilities for the application of Phaeodactylum tricornutum extracts in novel clean-label vegan foods. Overall, these findings suggest that the novel approach proposed in this work, based on hydrothermal processing, is feasible and compatible with the need for the application of simple purification steps with food-grade solvents. Furthermore, it reinforced the relevance of the carbohydrate fractions and carbohydrate-protein interactions from microalgae.