The seeds, nuts, or plant tissue containing the oil must be properly stored and prepared for extraction to maintain the high quality of the final product. If the oil bearing material is dry, it must be stored so that it remains dry for optimal extraction and quality of the oil. If the oil bearing material is wet- plant tissue, it should be processed for oil extraction immediately after harvest so that the storage time is kept to a minimum. Oils in the presence of water deteriorate rapidly, forming free fatty acids and rancid off-flavors.
After the oil bearing material has been taken out from storage, the first step in preparing them for oil extraction is to clean them. Cleaning is done so that the oil is not contaminated with foreign materials and that the extraction process can proceed as efficiently as possible. During the process inspection of the seeds is carefully done to remove stones, sand, dirt and spoilt seeds. Dry screening technique is often used to remove all material that is over or under sized. Sometimes washing is also resorted to but it must be avoided as the plant tissue will have to be dried at a later stage.
It is the final step for preparing the raw material for oil extraction. Heating leads to increased oil yield. Heating helps in killing those enzymes present in the plant tissue which have a deteriorating effect on oil quality. Moreover, if oilseed cake is to be used for feed or feed, heating is useful as it increases protein availability.
Sometimes oil bearing material is pressed without being heated . Oil extracted in this way is called cold press oil.
The mustard seeds are emptied from the sacks into the silo for storage of seeds , this seeds are transferred to the chalna for seeds cleaning from where the clean seeds are fed into the automatic feeding system for Ghani.
This is a batch type process where the seeds are crushed for an hour and oil yield is 23%to 26%.then the residual cake is manually extracted from the ghani and fed into the conveyor elevator system, which carries into the 1st expeller .the crushing of the cake take place in to the high pressure chamber and recovery in the first expeller press is about 5% to 7%.
Next process the cake again fed into the 2nd expeller for 2nd crushing from where its transferred to the next expeller with the help of elevator where the third crushing takes place, the 4th and 5th crushing takes place in the following expeller the total oil yield is between 33% to 37% depending in the quality of the seed.
The unfiltered oil is stored in unfiltered tank from where the plunger pump feeds in into the filter press for filtration to give filtered mustard oil ready for packing and dispatch.
The final cake having residual oil content of about 7 to 7.5% is the by-product and ready to sent in solvent plant.