As shown in Fig 3, TPC of pomegranate peels with PWE was
about 3-fold higher than that of water extractions at atmospheric
pressure conditions. The difference between PWE and magnetic
stirrer extraction conditions is mainly high pressure applied at
PWE. Water at atmospheric conditions was as effective an extractant
as ethanol and acetone for polyphenols of pomegranate peels.
The increment of TPC of the extracts obtained by PWE in comparison
to magnetic stirrer water extraction could be attributable to
swelling of pomegranate peels with water at high pressure and
easier penetration of water molecules into pores of the peels. On
the other hand, PWE is performed in a closed system and water
is degassed to remove dissolved oxygen before the start of extraction
process that prevent the possible oxidation of polyphenols. Inert
sea sand mixed with the peel and added into extraction cell
might also affect the extraction results positively by increasing
the surface of the peel particles