Due to their special solubility properties, lipids may be extracted from plant tissues with alcohol or ether. Such an extraction removes other classes of lipids like leaf alkanes and steroids. The actual method of isolation of lipids from natural sources is largely dependent on the nature of the lipid and its source.

Conventional vegetable oils are separated from the plant tissue by expression. In this, the seeds are crushed by rollers and pressed in hydraulic press or continuous expellers, when the oil separates leaving behind the “oil cake,” which was earlier used as fodder. Such oil is called virgin or cold-pressed oil. When heat assists expression, it is hot-pressed oil. Solvent extraction is used to extract the remaining oil from the pressed cake. The crude oil or fat is treated with a little alkali to neutralize free acid and also to coagulate any colloidal impurities present. It is then bleached by warming at 70–80°C with animal charcoal, fuller’s earth, or plaster of paris. After about half an hour, the decolorized oil is filtered through filter press and then deodorized by passing superheated steam through it. The oil is then quickly cooled and withdrawn, so that its odor may not be impaired. Seeds being rich sources of oils may be conveniently processed by expression.

For small-scale laboratory isolation of simple lipids, the fresh plant material may be coarsely injured and then subjected to hot continuous percolation with hexane or petroleum ether for complete extraction of all the fatty matter. The percolate may then be evaporated to yield the lipids present in it.

When plant tissue is being processed for the separation of lipids, the following general procedure may be used:

1. The freshly collected plant material is homogenized in 100 parts of isopropyl alcohol (to inhibit lipases that rapidly hydrolyze the plant lipids releasing free fatty acids). For tissues such as cereals in which the lipids are very tightly bound, extraction with chloroform: ethanol: water (200:95:5) is preferred.
2. It is filtered and the marc is re-extracted with 1:1 v/v chloroform, isopropanol by sufficient mixing.
3. It is filtered and the combined filtrates are vacuum evaporated. The residue is dissolved in minimum volume of 2:1 v/v chloroform, methanol.
4. This solution is then washed with 1/5^th volume of 0.9% sodium chloride solution. After gentle vortexing, the mixture is centrifuged at 2000 rpm to separate the two phases.
5. The upper phase containing the polar lipids is taken for appropriate analysis and the lower phase containing the neutral lipids is vacuum evaporated to yield the pure lipid.
6. Alternatively the residue in step 3 can be column chromatographed on silica gel in ethereal solution. The neutral lipids such as oils and fats will pass through, leaving the phospholipids and glycolipids adsorbed.
7. These can be recovered by eluting the column with chloroform–methanol mixture.

Plant lipids are being extracted using a number of techniques such as super critical fluid extraction, pressurized fluid extraction, ultrasound-assisted extraction, and even automated robotic extraction.