This study examines pressurized hot water extraction of anthraquinones from dried
roots of Morinda citrifolia (Noni). The effects of various operating conditions such as
water temperature (110, 170, and 220 °C), and water flow rate (2, 4, and 6 mL min-1)
on extraction yield and extraction rate were determined. At 220 °C, the extraction
yield was the highest and was approximately 43.6 mg g-1. Subcritical water extraction
at 4 mLmin-1 or higher was found to be able to recover all the antraquinones present
in the roots within 3 h of extraction, even at 170 °C. Pressure had no significant effect
on the results for the range of temperatures studied. The flow rate of 6 mL min-1
resulted in the highest extraction rate, but the extraction efficiency, as measured by
the amount of anthraquinones extracted per unit volume of water was lower than
that of 4 mL min-1. Anthraquinones solubility in pressurized hot water was
determined. The results indicate a presence of a mass transfer limitation in the
extraction process from solid matrix.