In previous studies, centrifuge temperature during sample
preparation was not considered critical during flavanone extraction.
In the current experiment, the importance of the centrifuge
temperature during centrifuge extraction was demonstrated.
When grapefruit juice was extracted with ACN in centrifuge, two
clear phase separations were observed at 0 and 10 ◦C but not at
20 ◦C. However, variations in the flavanone levels in the top and
bottom 1mL of centrifuge tubes were found to be significantly different
at three different centrifuge temperatures (Fig. 5). Though
MeOH extracts did not show phase separations at all the three
temperatures tested (data not shown), the flavanone levels were
different at 0 and 10 ◦C (Fig. 5). The MeOH extracts from 20 ◦C centrifuge
temperature did not show any difference in the flavanone
levels from the top and bottom 1mL. In case of DMSO extracts, flavanone
levels in the top and bottom 1mL of centrifuge tubes were
not significantly different in all the centrifuge temperatures tested.
The differential densities in the extraction mixture were observed
because the individual solvent components (ACN and water in the
juice) showed different response towards applied temperature and
centrifugal force.