Mechanical Extraction of Wheat Germ Oil

Wheat germ oil (WGO) is one of the richest natural sources of vitamin E and contains a number of other health-beneficial bioactive compounds, including polyunsaturated fatty acids, policosanol, and phytosterols. The conventional WGO extraction technique uses hexane, which may cause environmental and human health risks. The objective of this study was to optimize a solventless WGO extraction process that produces good-quality oil. To achieve this goal, a mechanical extraction process was examined. WGO was expressed using a heavy-duty screw press. The screw press shaft speed, cage temperature, backpressure at the meal discharge end, shaft arrangement, and germ pretreatment conditions were optimized for maximum oil yield. The free fatty acids, peroxide value, and p-anisidine value of oil obtained by mechanical pressing were lower than those for commercially hexane-extracted oil, but the mechanically pressed WGO was rich in essential fatty acids and tocopherols. Mechanical pressing is an environmentally benign alternative to hexane extraction, specifically for specialty oils such as WGO. Solvent-free oil and cake from mechanical extraction can be used in functional foods and nutraceutical formulations and can add value to the wheat milling byproduct wheat germ.