Relative merits of liquid and supercritical CO2 as extraction solvents for hops

4 Relative merits of liquid and supercritical CO2 as extraction solvents for hops 

While sharing an advantage over organic chemical solvents of consumer acceptability and genrally less hazardous properties, liquid and supercritical carbon dioxide differ in some important respects. 

Selectivity [19] A significant proportion of the hop extract produced is further processed to isomerised extracts used post-fermentation and some are fractionated to yield an essential oil for aroma and flavour purposes. Both 

While low molecular weight, non-polar agrochemicals may be expected to dissolve in both liquid and supercritical CO2, most will be substantially rejected, particularly by liquid CO2. 

Temperature By definition, extraction with supercritical CO2 takes place at temperatures above 31°C and usually at not less than 40°C. The temperature is normally 50°-60°C and may be as high as 80°C if a total extract is being produced. The milder conditions of liquid CO2 extraction and CO2 removal are especially favourable for retaining the essential oil. Liquid CO2 is thus the chosen solvent for oil and aroma products. 

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