3.3. Comparison of supercritical technologies with screw
pressing
Maximum oil extraction yield obtained by SFE and
GAME are compared to yield obtained by screw pressing in
Fig. 6. For each process, the corresponding total polyphenol
content in oil is also indicated.
Among the three studied processes, the highest oil yield
is obtained by screw pressing (73 5%). This result can be
explained by the combination of shear and compression
forces applied on the seeds during screw pressing unlike for
GAME where expression is only performed by uniaxial
compression. For SFE, oil extraction is performed by a
continuous flux of CO2 through the seed bed. The amount of
oil extracted then is dependent on the solubility of CO2
towards oil. Interestingly, uniaxial expression without CO2 of
grape seeds does not allow oil extraction. Given the results
presented in Fig. 6, it can be concluded that expression
combined with the use of supercritical CO2 improves oil
extraction. This observation was partially explained by
Venter et al. [31] and Willems et al