that terpenes may dissolve in these alternative solvents
according to the principle ‘‘like extracts like’’. The relative
energy difference (RED) numbers have been used to
characterize and quantify solute–solvent interactions.
Table 3 represents the RED modelling optimization of
solvents for the extraction of target terpene. All solvents
(0 < RED < 1) that were close to the centre (RED = 0) could
be considered as good solvents for each terpene. The
solubility of alternative solvents used in the extraction of
target solutes has been respectively characterized using
the 2D graph for an easy understanding of the solubility of
various solvents in solid–liquid extraction. (circles materialize
the prediction data). The alternative solvents showed
various theoretical solubilities for each terpene, with a
significant difference that would be validated by experiments.
This result could be explained by the difference in
the solvents’ polarities. Hexane and a-pinene included
clusters of monoterpenes and sesquiterpenes. Indeed,
a-pinene solvent showed solubility parameters with
aroma compounds similar to those of hexane. MeTHF
and ethyl acetate are more polar than hexane, and thus
included clusters of oxygenated monoterpenes