3.1.1. Effects of extraction time and temperature
Lipid extractions were conducted for 80 min at 60 and 80 C.
The pressure was constant at 30 MPa and 20 g of dried microalgal
powder was used in each experiment. Table 1 (under ‘Experimental
lipid yield’) shows that lipid was extracted most rapidly in the
beginning of the extraction (before 20 min) and that the rate of lipid
extraction decreased with experimental time. The asymptotic
profile obtained was characteristic of most SCCO2 extraction reported
in other microalgal studies (Cheung, 1999). The model correlated
well with the experimental data for lipid evolution
(compare ‘Theoretical lipid yield’ with ‘Experimental lipid yield’,
r2
60C ¼ 0:93, r2
80C ¼ 0:92) and was consistent with the expected diffusion-
driven nature of the SCCO2 process, where the extraction
rate was directly proportional to the amount of unextracted intracellular
lipids (Ozkal et al., 2005).