biotech Technology

Subcritical Water Extraction (SCWE)

Characteristic image

Unique selling points

  • Green Technology
  • No use of organic solvents
  • No residual organic solvents in the extract
  • Faster Extraction Time

Description of the technology

Subcritical Water Extraction (SCWE) is a method that benefits from the solvent properties of subcritical water. i.e. water at temperatures above the boiling point i.e., elevated pressures in order to keep it in liquid state, as seen in the phase diagram below Figure 1, with a working range between 100-250°C and 100-200 bar.

The subcritical water extraction can also be applied directly on undried matrices.

Figure 1 Phase diagram of water





Figure 2 Scheme of a Subcritical Water Extraction System: 1. Water tank 2. Pump 3. Mass flow meter 4. Valve 5. Back-pressure regulator 6. Pressure gauge 7. Pre-heater 8. Temperature gauge 9. Heated extractor 10. Temperature gauge 11. Valve 12. Condenser 13. Valve 14. Separator 15. Valve 16. Valve 17. Collector

Subcritical water extraction follows the same principles of the liquid extraction but the pressurized conditions diversify the properties of the water as a solvent (Castro-Puyana et al., 2013).

Figure 4  Picture of the Subcritical Water Extractor

Flow scheme of the technology

In the framework of the ULTIMATE project, in the Work Package 1, Subcritical Water Extraction is applied to extract antioxidants (polyphenols) from fruit processing water by-product. The industrial by-product flows through a macroreticular, non-fuctionalised adsorbent resin where the polyphenols are adsorbed. These polyphenols are recovered by subcritical water extraction.

Figure 3 Flow diagram of the process

Synergetic effects and motivation for the implementation of the technology

  • Green Technology

Subcritical Water Extraction reduces or even eliminates the use of organic solvents thus it be categorized as a green environmentally friendly method.

  • Quality of the extract

A major advantage of the elimination of organic solvents is that the final product/extract is free of organic residues thus it is of higher quality and safer for consumption.

Links to related topics and similar reference projects



Antioxidants from winery waste

(Aliakbarian et al., 2012)

Extraction of polyphenols from lotus seed pop

(Yan et al., 2020)

Olive polyphenols extraction

(Xynos et al., 2012)