Hexane-Free Green Solvent Extraction of Canola Oil From Microwave-Pretreated Seeds and of Antioxidant-Rich Byproducts

Abstract

The ethanol extraction from microwave-pretreated and untreated canola seeds is studied. Two process are used to obtain the oil: in a control process (P1), the solvent-free total extract (E) is washed with hexane, obtaining an oil fraction (OF). The second process (P2) consists of the partial evaporation of the solvent of the total extract (E), cooling, centrifugation, and separation by decantation of the generated phases: oil-rich phase (OF + Ethanol), solvent-rich phase (EthF + Ethanol), and solid phase (SF); and then evaporating the solvent to obtain OF and an extract of soluble in the phase rich in ethanol (EthF). No significant differences due to microwaves are detected in the yields. P2 gave mean yields of 32.8%db of OF, lower than obtained with P1 (42.1%db), 4.2%db of precipitated solids, and 7.7%db of EthF, which present a mean content of hexane-solubles of 5.1%db. However, the quality analysis shows a smaller oxidative damage and an increase in canolol content due to the microwaves. P2 also generates an antioxidant-rich byproduct, allowing to recover the canolol prior to a refining stage of the oil. Practical Applications: The use of organic solvents for the extraction of vegetable oils have some disadvantages, such as health and safety problems. At the same time, ethanol has begun to be studied as an alternative solvent due to its lower production costs than other alternative solvents, and to the fact that it is recognized as a “bio-renewable” solvent. Numerous studies have shown the extraction of oil and impurities obtained with ethanol. However, no method have been developed for obtaining an insoluble-free canola oil from the extract obtained with ethanol without using hexane. In addition, a favorable effect of the canolol content pretreated with microwaves in the canola oil is reported, nevertheless, the canolol is eliminated during the refining stage of the crude oil. The hexane-free development process allows to obtain canola oil and an antioxidant-rich byproduct, allowing to recover the canolol prior to a refining stage of the oil. Green solvent (ethanol) extraction from microwave-pretreated canola seeds and a hexane-free separation process is developed. The results show a high yield of canola oil and the production of an antioxidant-rich byproduct.