Extracts from guarana integument incorporated by supercritical impregnation

Food waste is often underutilized in countries with a strong agro-industrial base, such as Brazil. In the processing of guarana (Paullinia cupana), the integuments are rarely explored, in contrast to seeds and peel, which are widely studied in extraction processes. However, the guarana integuments also present potential for obtaining bioactive compounds, which can be extracted by high-pressure technologies and applied in impregnation processes with supercritical fluids in polymeric matrices. This work recovered bioactive compounds from guarana integuments using pressurized liquid extraction (PLE) and promoted the impregnation of the extracts in corn starch aerogel by supercritical fluid impregnation (SFI) with CO₂. The antioxidant capacity of the extracts was evaluated by ORAC and FRAP and the total reducing capacity (TRC) was also determined. PLE was conducted using 100% ethanol as solvent at 100 °C for 5 min. SFI was performed under nine different conditions, with temperatures of 55, 65 and 75 °C and pressures of 225, 300 and 375 bar. The extract’s TRC was 300±3.39 mg gallic acid equivalent (GAE)/ g sample, and the ORAC and FRAP were 182.78±0.54 and 184.8±3.39 mg Trolox equivalent (TE)per g sample, respectively. The TRC of the impregnated extracts ranged from 3.94±0.08 (65 °C, 225 bar) to 19.66±0.33 (65 °C, 375 bar) mg GAE/g sample. The ORAC varied between 27.98±0.02 (75 °C, 225bar) and 178.11±0.10 (65 °C, 375 bar), and FRAP between 3.32±0.27 (75 °C, 225 bar) and 9.83±0.06 (65 °C, 300 bar) mg TE/g sample. In this way, it was possible, for the first time, to obtain a concentrate rich in bioactive compounds from guarana integuments, as well as successfully impregnating these extracts into a polymer matrix. It was found that both temperature and pressure significantly influenced the SFI process, which was expected since these are key variables that directly affect the efficiency of this type of technology.