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Extraction of phenolic compounds with bioactive potential from industrial orange pomace and fermented orange pomace using supercritical CO2

Author: Faber Ariel Espinosa Pardo (2016)

Abstract: The high consumption of fruits brings multiple benefits to human health, due to their high levels of antioxidants, which are characterized by the ability to scavenge free radicals. These compounds can be found both in the pulp of fruits such as in skin and seeds. Therefore, the aim of the present work was to investigate the Supercritical Fluid Extraction (SFE) of phenolic compounds with high nutraceutical value from the orange pomace from the industrial processing of juice. This by-product is widely available, without commercial cost and potentially rich in polyphenols. SFE was evaluated under three pressure conditions (15, 25 and 35 MPa), three temperatures (40, 50 and 60 °C) and the use of cosolvent (ethanolic mixtures) in terms of global extraction yield (Xo), total phenolic content and antioxidant capacity by free radical scavenging activity – DPPH and oxygen radical absorbance capacity – ORAC. Additionally, for best SFE condition it was evaluated the biotransformed orange pomace in order to evaluate the modification of the phenolic profile and the improvements in antioxidant capacity of the extracts obtained by SFE. For this purpose, the orange pomace was inoculated with Paecilomyces variotii and fermented for 72 hours. All results were analyzed using Tukey‟s test, by analysis of variance (ANOVA) and significance of 5%. The SFE results showed low affinity of supercritical CO2 for phenolic compounds when cosolvents were not used. The global extraction yield was favored by increasing the extraction pressure ranging between 2.01 and 2.62%, while the total phenolic content had small variation (from 18 to 21.8 mg galic acid equivalent (GAE/g extract) by modifying the extraction conditions. The antioxidant capacity of the extracts showed no correlation with the total phenolic content, with higher antioxidant capacity for extracts obtained at low to moderate pressures. The highest antioxidant capacity was obtained at 15 MPa – 60 °C, with values of 45.0 μmol Trolox/mg extract, and 434 μmol Trolox/g extract for DPPH and ORAC, respectively. When the orange pomace was biotransformed, the total phenolic content (47 mg GAE/g extract) increased more than twice in SFE CO2 + 6% ethanol (90%), when compared with the non-fermented pomace. The antioxidant capacity of the extracts evaluated by DPPH and ORAC also increased with changes in the phenolic profile that resulted from fermentation process. The biotransformation showed to be beneficial in obtaining higher yields of phenolic compounds and antioxidant capacity due to hydrolysis of polyphenols into simple compounds with greater degree of hydroxylation. The extraction kinetics showed that at the end of the falling extraction rate (FER), 92% of the available solute had been extracted.