Although it is possible to avoid organic solvent contamination when using pressure expulsion techniques, however it recovers only half of oil present in the germ. The solvent extraction method is more effective as 99% of oil can be recovered. The solvents used for wheat germ oil extraction are hexane, 1, 2-dichloroethane, and ethanol. The catabolism of nutritionally important components of wheat germ oil can be minimized by avoiding higher extraction temperatures and by using techniques such as cold pressing and supercritical carbon dioxide assisted extraction. These techniques either avoid or reduce the use of extraction temperature that might be detrimental of heat sensitive nutrients (Panfili et al., 2003). The oil yield is 5.2–15% using petroleum hydrocarbon solvents or diethyl ether during extraction whereas it may increase slightly (7.2–15.5%) with use of more polar solvents. The differences between these values results from oil loss during milling and limitations of some solvent extraction methods. Mechanical pressing, aqueous, and enzymatic techniques have also been used for wheat germ oil recovery. Mechanical procedures may yield solvent-free oil however yield may be lower than that from hexane extraction(Al-Obaidi et al., 2013).
Seed moisture and other operating conditions in respective extraction methods can significantly affect oil yield. Seeds with too low moisture cannot be freed from oil whereas high moisture can result in the material in the press. The optimum moisture for seeds varies depending on the type of seed and the method used for extraction such that a maximum oil yield (37%) can be obtained at 1.5% moisture content of germ by using a germ oil press.
The wheat germ oil yield can be 92% during extraction with solvents when innovating approaches such as supercritical carbon dioxide extraction is applied which may also reduce the use of toxic solvent. Hence, taking into account, the effects of various extraction methods and the respective extraction variables is crucial for wheat germ oil quality and its industrialization(ÖZCAN et al., 2013).