As can be seen in Table 2, microwave-drying treatment prior to
pressing greatly enhanced the EE. In this study, the EE could rise up
to 25% by using microwave-drying to reduce the moisture in the
fresh aril instead of air-drying. This is because the moisture inside
the material is heated up due to the effect of microwave, resulting
in evaporation and generating high pressure inside the cell wall. As
a result, the cell membrane is ruptured (Tatke and Jaiswal, 2011);
the oil from the ruptured cells is easily subsequently released and
extracted by the hydraulic press. In contrast, the rupturing of cell
membranes is not taking place in the air-drying process to the
same extent due to the evaporation occurring on the surface of
the material.