Spray Drying of Stevia Rebaudiana Bertoni Aqueous Extract: Effect on Polyphenolic Compounds

The Stevia rebaudiana Bertoni is the raw material of a family of low caloric index sweeteners, the steviol glycosides. Stevia rebaudiana also has other compounds with the desired biological effect on human health, the polyphenols. The spray drying process is a physicochemical and microbiological stabilization process widely used for aqueous vegetables extracts. The effect of the spray drying process variables, the inlet air temperature (160-180 °C) and the feed flow rate (2-3 kg h^-1); on the total polyphenolic concentration/profile from Stevia rebaudiana aqueous extract was evaluated. The polyphenolic profile evaluation was performed by liquid chromatography coupled to time-of-flight mass spectrometer (UHPLC-qTOF-MS); the total polyphenolic concentration, total flavonoids concentration and their antioxidant capacity were evaluated by spectrophotometric method. The concentration of polyphenolic and its associated antioxidant capacity was reduced by all the evaluated spray drying process conditions. At 160 °C - 2 kg h^-1 the lower phenolic concentration and antioxidant reduction were reached (38.69 % and 3.76 % respectively) referred to the fresh aqueous extract. The polyphenolic profile change from 14 compounds (phenolic acids, flavonols, flavones, dihydroflavones and isoflavones) in the fresh aqueous extract to the one phenolic acid at 200 °C – 2 kg h^-1 spray drying condition. The spray drying process reduced the concentration and changed the profile of the phenolic compounds. The lower effect was observed at the lower temperatures (160 °C) and higher feed flows (3 kg h^-1).