Methods Used for Extraction of Maize (zea Mays, L.) Germ Oil-a Review

Maize oil is high in polyunsaturated fat, which is a heart-healthy fat, and low in saturated fat. Extraction of oils from oilseeds is a key step for their commercialization. The extraction process has a direct effect on the quality and quantity of protein and oils obtained. Various methods like cold pressing, solvent, super-critical fluid and aqueous extractions are in practice for oilseed extraction. The use of solvents for oil recovery has shown several drawbacks such as high safety hazard, high energy input, low quality oil, environmental risk, toxicological effects and low quality meal. Conventionally, hexane has been used for decades to extract oil from oilseeds with massive construction and operational costs. Because of the safety, environmental issues and potential health risks, the edible oil industry is in urgent need of replacing hexane-extraction with some suitable and environment friendly techniques. Like others, bio-renewable solvents (alcohols, supercritical fluids), the use of water as the most economical extracting agent is gaining interest, especially with the aim of replacing toxic solvents. Aqueous oil extraction has emerged as a promising technique for extraction of oil from certain oil-bearing materials e.g. peanut, coconut, maize etc. Recently, enzymatic pre-treatment has emerged as a novel and an effective means to improve the oil yield in cold pressing and aqueous extraction techniques. There are two general approaches for enzymatic oil extraction: enzyme assisted aqueous extraction (EAAE) which may offer a number of advantages as compared to conventional extraction. In enzyme-assisted aqueous process, the enzymatic action is reported to improve the oil recovery by degrading the seed cell wall, and rupturing the polysaccharide-protein colloid which may cause emulsion formation, resulting in low yield. Aqueous enzymatic oil extraction is one such alternative eco-friendly process based on simultaneous isolation of oil and protein from oilseed by dispersing finely ground seed in water and separating the dispersion by centrifugation into oil, solid, and aqueous phases. The presence of certain enzymes during extraction enhances oil recovery by breaking cell walls and oil bodies.