ANSWER
According to European Food Safety Authority (2008), the content of reference antioxidant compounds carnosic acid and carnosol in the rosemary extracts were extracted using supercritical CO2 or acetone show comparability of the solvent extracts. The dried rosemary leaves are extracted by means of a supercritical carbon dioxide.
During the extraction, carbon dioxide-soluble substances are dissolved in the carbon dioxide. The carbon dioxide fraction obtained is precipitated. In a second process-step the raw extract is deodorised by supercritical CO2 to define the content of essential oil as well as to ensure a defined concentration of the antioxidative compounds, carnosol and carnosic acid. Finally the deodorised extract is homogenised and mixed with appropriate food-grade carriers to convert the extract into a powder or liquid-oil form.
A carnosic acid-rich plant extract can be produced by extracting a dried and comminute plant material containing carnosic acid with supercritical CO2 at a pressure of at least 200 bar and at a temperature of at most 100° C ( U.S. Patent No. US8,513,456 B2, 2013).
Figure 1.0: Solubilities of carnosic acid from rosemary extract in CO2 (points are experimental values and lines are calculated values)
References
European Food Safety Authority. (2008). Use of rosemary extracts as a food additive – Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Materials in Contact with Food. EFSA Journal, 6(6), 721.
Wiesmueller, J., Michlbauer, F. & Kahleyss, R. (2013). Method for producing a carnosic acid-rich plant extract. U.S. Patent No. US8,513,456 B2.
