Extraction of tocotrienols from annatto seeds by a pseudo continuously operated SFE process integrated with low-pressure solvent extraction for bixin production

• A successful pseudo continuous operating SFE unit was validated.
• High productivities of tocotrienols-rich oils were reached by working in pseudo continuously.
• Process integration was shown to be useful in obtaining tocotrienols and bixin-rich extract.
• The initial removal of the oil layer via supercritical CO2 favors the extraction of bixin.
• High yield of bixin (30 ± 2 g/100 g of extract) was obtained using ethanol as solvent.

A process to obtain tocotrienols from annatto seeds was studied in a supercritical fluid extraction (SFE) system containing two 1 L extractor vessels with height (HB) to internal diameter (DB) ratios of 7.1 (E-1) and 2.7 (E-2). Pseudo continuous operation of the SFE system was validated by producing clove volatile oil at 40 °C and 15 MPa. To obtain tocotrienols, the system was operated in pseudo continuous mode at 40 °C, 20 MPa and CO2 flow rate of 20.7 g/min. The extraction time, from a technical perspective, was set to 60 min, according to kinetic parameters obtained from an overall extraction curve (OEC) with processing time of 360 min. OECs were initially measured in batch mode (BM) and the kinetic parameters for the constant extraction rate (CER) period were determined to be lengths of the CER period (tCER) equal to 43 ± 1 and 42 ± 2 min for E-1 and E-2, respectively; mass transfer rates (MCER) of 0.22 ± 0.01 g/min for both E-1 and E-2; and total yields (RCER) of 50 ± 1 and 49 ± 1 g of extract/100 g of extractable mass for E-1 and E-2, respectively. No differences were observed between each group of kinetic parameters (tCER; MCER; RCER) obtained in BM. Following the measurement of OECs, the SFE system was operated in pseudo continuous mode for four extraction stages of 60 min each with the extractors organized in parallel. This organization improved the productivity of the process. We also proposed the integration of SFE with low-pressure solvent extraction (LPSE) using water and ethanol as solvents to remove bixin from the defatted annatto seeds. LPSE conditions were: 60 °C and solvent mass to feed mass ratio (S/F) of 8 g solvent/g annatto for ethanol and 50 °C and S/F of 8 g solvent/g annatto for water. LPSE assays were performed in an agitated bed over a 95 min time period. Using partially defatted annatto seeds as the feedstock for LPSE resulted in increased bixin extraction. LPSE with ethanol was found to increase the bixin content in the extract. Thus, the proposed process integration appears to be useful, mainly due to three aspects: (1) the initial removal of the oil layer via supercritical CO2 favors bixin extraction, (2) LPSE is a low-cost methodology for extracting bixin and (3) the cost of raw material in the second step is null.

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