Microalgae biscuits – Sensory, physical and chemical properties, antioxidant capacity and in-vitro digestibility

Microalgae use as food is still poorly developed in Europe due to high cost, low demand and strict Novel Foods legislation. The aim of this work was to evaluate biscuits, a food consumed on a daily basis, as microalgae vehicle. Arthrospira platensis F&M-C256, Chlorella vulgaris Allma, Tetraselmis suecica F&M-M33 and Phaeodactylum tricornutum F&M-M40 were studied. Two content levels were tested: 2%(w/w) typically used in algal-based products and a significantly higher content, 6%(w/w), to provide additional algal-bioactives. The biscuits sensory and physical properties were evaluated during 8 weeks and no significant differences among the algae were found (p<0.05). A. platensis biscuits presented the highest sensory scores. Besides, this alga provided a significant structuring effect. Phycocyanin content was 0.56 and 0.87 mg/g for 2% and 6% A. platensis biscuits. No differences were found in fatty acid content. All microalgae-based biscuits showed significantly higher total phenolic content (TPC) compared to the control. P. tricornutum biscuits exhibited the highest TPC (0.31 and 0.62 mgGAE/g for 2 and 6% biscuits). Microalgae biscuits presented significantly higher in vitro antioxidant capacity (AC) compared to the control (from +45% to +307%). 6% T. suecica biscuits presented the highest AC (25 mmolTEAC/kg). The microalgal biscuits in vitro digestibility (IVD) was also assessed. No significant difference in IVD between microalgae biscuits and the control (IVD 95%) was found, although, as expected, biscuits added with 6% Chlorophyceae biomass exhibited the lowest digestibility (87%). In general, increasing microalgae content from 2% to 6% resulted in a significant increase in the biscuits TPC (on average +115%) and AC (on average +69%), while digestibility was slightly lower (-5.9% on average).