Disruption of glandular trichomes with compressed CO2: alternative matrix pre-treatment for CO2 extraction of essential oils

The disruption of essential oils glandular trichomes by contact with compressed carbon dioxide followed by rapid decompression was studied at isothermal condition (310 K). The pre- and post-expansion pressures, the exposure time to the pre-expansion pressure and the rate of decompression were all found to have a significant effect on the efficiency of the disruption process. The efficiency of the disruption process (percentage of glands disrupted during the fast decompression) was deduced from the results of subsequent extraction tests using compressed CO2 under standard conditions. The damage to the glands was observed by SEM microscopy. The efficiency of the disruption process seems to be closely related to the amount of gas dissolved within the glands, the rate of decompression of the bed and the permeability of the glands. The experimental results revealed that for an exposure time of 60 min and a rate of decompression of 2 kg m−3 s−1, the decompression from 70 barg to atmosphere led to a maximum efficiency of the disruption process. At these conditions, the improvement in the extractability of essential oils by compressed CO2 was similar to that obtained by cryogenic comminution of the matrix and better than that obtained by ambient comminution. One advantage of the fast decompression treatment method is that it virtually eliminates the losses of essential oils observed in mechanical treatments. A further advantage is that it selectively liberates the essential oils with respect to higher molecular weight material. This results in a final extract with a higher content of essential oils.