Ginger (zingiber officiale roscoe) oleoresin extraction with supercritical CO2: effect of flow rate, co-solvent and microwave treatment

Abstract

Oleoresin from ginger (Zingiber officinale Roscoe) containing gingerols and shogaols is a good source of pungent compounds and antioxidants. Extraction of ginger oleoresin with supercritical CO2 was studied by evaluating effect of factors such as flow rate, co-solvent, microwave treatment on the extraction yield. In this study, dried gingers with 10.4% moisture content were used for extraction. The volatile oil, ash, and fiber content of the raw materials were 3.3, 5.5, 9.5%-w/w, respectively. The optimal process parameters for extraction were determined, such as CO2 flow rate at 15 g/min, co-solvent at 8% ethanol and microwave treatment at

35 seconds, while other parameters were kept constant (pressure 250 bar, temperature 45oC, duration time 2.5 hours and particle size 1.0 mm). At the same co-solvent inclusion (8%), extraction with methanol resulted in higher yield (6.39%) than with ethanol (5.84%). By using 1, 1-diphenyl-2-pircryl-hydrayl (DPPH) assay, at the same concentration (80 µg/mL), the free radical inhibition capacity of the oleoresin extracted with methanol and ethanol were 72.81% and 71.48%, respectively, quite closed to that of ascorbic acid as standard (76.6%). All

6 major pungent components in ginger, namely 6-, 8-, 10-gingerol and 6-, 8-, and

10-shogaol, were present in the SFE-CO2 extracted oleoresin making up 47.58% in the ethanol extract and 45.60% in the methanol extract, while the content of 6- gingerol was 22.11% and 20.25%, respectively.

Key words: ginger oleoresin, supercritical CO2 extraction, HPLC (high-performance liquid chromatography), DPPH, antioxidant properties.