a b s t r a c tThe pretreatment operations (drying, cell disruption and oil extraction) of microalgae biomass to the lipids extraction are important steps to the product quality and production cost. In this study, the lipids from Spirulina were obtained by different methods of biomass drying (tray and spouted bed), cell disruption (microwave, autoclaving and milling) and solvent extraction (hot and cold). The average content of lipids extracted by the cold method, using polar solvents, was of 5.8 ± 0.6 g 100 g À1 . The spouted bed drying with cell disruption by milling achieved the best performance with the hot extraction method. Under these conditions, the TBA value was of 0.57 ± 0.09 mg MDA kg À1 . FT-IR spectra and thermal analysis indicated that the hot extraction resulted in a more purified lipid extract than the cold extraction. The Brimberg model showed the best fit to the lipid extraction kinetics and the activation energy in the best conditions was of 6.11 ± 1.41 kJ mol À1 .

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This study aimed to examine the impact of the combination of acoustic energy at the nominal powers of 100, 200, 300, and 400 W with moderate heat processing at 40, 50, and 60 °C on the extraction of phytochemical compounds from Foeniculum vulgare. Thermosonication processing, based on high-intensity ultrasound combined with an external heat source, can potentialize the extraction of soluble solids from plant material. However, the excessive temperature increase generated by the two energy sources during thermosonication treatment may degrade the thermolabile bioactive compounds. Regardless of the temperature condition, fennel extracts obtained at 400 W presented lower total phenolic content (TPC) than those obtained at 300 W. The cavitation heat and mechanical stress provided at 400 W may have degraded the phenolic compounds. Thereby, the best extraction condition was 300 W and 60 °C. The fennel extract presented the highest content of TPC (3670 ± 67 µg GAE/g) and antioxidant activity determined by DPPH and ABTS methods (1195 ± 16 µg TE/g and 2543.12 ± 0.00 µg TE/g, respectively) using this treatment. Thermosonication can be an innovative technique for extracting phytochemicals because it provides good results in shorter processing times, with 73% and 88% less energy consumption than Percolation and Soxhlet techniques, respectively.

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