master jose luis

Extraction of compounds from blackberry (Rubus sp.) bagasse using supercritical CO2 assisted by ultrasound

Author: José Luis Pasquel Reátegui (2014)

Blackberry (Rubus sp.) has attracted the attention of producers and consumers in recent years, since it is a good source of bioactive compounds that offers health benefits. Agro-industrial wastes resulting from blackberry processing have demonstrated to be a good source of flavonoids, which are phenolic compounds widely known for their antioxidant activity. The objective of this work was to produce extracts from blackberry bagasse using supercritical fluid extraction assisted by ultrasound. For the supercritical fluid extraction a Box-Behnken design was performed with extraction pressure (15, 20 and 25 MPa), temperature (40, 50 and 60 °C) and ultrasound output power (0, 200 and 400 W) as independent variables. The CO2 flow rate (2.77 x 10-4 kg/s) was maintained constant for all experiments done with pure CO2. The highest yield was found at 50 °C and 25 MPa with an ultrasound output power of 400 W. After selecting the best process condition, a study was done to determine the kinetic parameters of the supercritical extraction process. The composition of the extracts was estimated by spectrophotometry, and the highest quantities of phenolics compounds were observed at 60 °C and 20 MPa without ultrasound. Furthermore, an increase of the antioxidant activity was observed at 60 °C, 15 MPa and 200 W of ultrasound power in comparison to other results obtained by supercritical extraction. With the objective to compare the yield and the composition of the extracts a cosolvent was added in the supercritical extraction process, at the extraction conditions of 60°C, 15 MPa and 200 W; these process conditions were selected based on the antioxidant activity present in the extracts obtained with pure CO2. An enhancement in the overall yield was observed when ethanol (10% v/v) was applied as cosolvent. On the other hand, the use of water (10 % v/v) as cosolvent was more appropriate for the recovery of phenolic compounds, anthocyanins and antioxidant activity from dried milled blackberry bagasse. It was also observed that the raw material without any pretreatment showed higher content of anthocyanins in the extracts obtained by supercritical extraction with water (5% v/v) as cosolvent. From the UPLC-QTOF-MS analyses, it was possible to identify four anthocyanins, two major anthocyanins (cyanidin-3-O-glucoside and cyanidin-3-O-rutinoside) and two minor anthocyanins (cyanidin-3-malil-glucoside and cyanidin-3-O-rutinoside), present in the blackberry bagasse. Finally, when the morphology of the raw material was analyzed before and after the extraction by scanning electron microscopy (SEM), it was observed that the use of ultrasound produced physical changes in the cell walls.