2.3. Sample-extraction procedure
The consistency of the samples (purees, wines and vinegars)
made it necessary to establish an extraction system prior to analysis.
The method employed was based on the extraction procedures
designed and optimised previously by Ubeda, Hidalgo, et al. (2011).
Twenty grams of sample were mixed in a beaker with 40 ml of
extract for 10 min while shaking at 800 rpm.
The sample was then subjected to ultrasonication followed by a centrifugation at
4000 rpm for 15 min.
The supernatant was recovered, and the pellet was re-extracted with 40 ml of solvent following the same procedure.
Both extracts were subsequently mixed, and the organic solvent was removed under vacuum.
Finally, the extract was filtered, and MilliQ water was added to a final volume of 15 ml.
Every extraction was performed in duplicate. We tested different
condition to get the maximum values of AA, TPI and TA as well as
economy of solvent used and time.
Thus, the parameters studied to select the best extraction conditions were: type of solvent (acetone,
methanol or ethanol), percentage of solvent (80% or 100%) and
ultrasonic extraction time (15, 25, 35 or 50 min).