Pressing is a procedure that one performs on:
– Fresh plants, seeds and fruit to press and squeeze the material and obtain the juice or oil that’s contained within the material.
– Exhausted plants, that is, when the process of extraction (maceration, percolations, etc.) is concluded, to recuperate the solvent that remains inside the plant material.
The material placed in extraction always keeps a certain quantity of extractive solution. This gets recuperated because:
1. It’s rich in active ingredients and, if added to the extraction previously obtained, it will go and increase the yield.
2. The recuperated solvent can be utilized for other uses.
3. The residual plant becomes liberated from the withheld solvent and can be reused for ulterior extractions. The leftover plant becomes free from the excess solvent and can be used for successive extractions.
The plant material that is to be pressed is first cleaned from foreign material (topsoil, weeds, insects, parts not suitable for pressing, etc.) and then cut. The dimensions depend on the type of product being utilized. The compression of the material happens because of the action of a piston that is manually activated by a screw, or automatically through a hydraulic piston.
In order to get all the liquid out, more successive operations are necessary.
The pressing ends only when, also after the descent of the piston, there isn’t a significant discharge of the liquid.
It can occur in performing a pressing, principally on pieces of fruit, the strong pressure exercised on the material can make it squirt: so, in order to avoid the loss of the product and to dirty the work environment, one is recommended to use Plexiglas protection that is placed around the pressing bin.
If seeds are used for a pressing, they are put inside linen bags for their containment and then get pressed.