Abstract
Solvents have a bad reputation in the cosmetics world, at least as regards the production of specialty vegetable oils used in this market. In order to do without these solvents, the cosmetics industry tends to use only mechanically produced oils. However, there is a range of seeds for which mechanical extraction is not satisfactory. This is the case with rare, expensive, and oil-poor seeds for which pressing does not give good yields, and results in high production costs. These are also hard seeds that cannot be pressed without causing the presses to become intensely hot, and this affects the quality of the oils. In recent years, our laboratory has worked on the development of extraction techniques with ethanol and the EcoXtract® solvent (2-methyloxolane) in order to provide professionals with production methods compatible with the COSMOS standard. Ethanol is not a good solvent for oils, especially in the presence of water and at low temperature. This drawback can be turned into an advantage to recover the oil (without distillation of the solvent) by cold decantation. The extraction is carried out on the hot components, and the oil is recovered by cooling the saturated miscella for the precipitation of the lipid phase. This process makes it possible to limit the energy consumption necessary for the recovery of the oil and the regeneration of the solvent. The great advantage for oils intended for the cosmetic market is that ethanol has a better solvent power for polar lipids compared to hexane and mechanical extraction. It is possible to split the lipid extract into neutral lipids and polar lipids by adjusting the precipitation temperature or by partial distillation. At the refining step, it is also possible to deacidify and remove contaminants from crude oil by liquid-liquid extraction with ethanol. We have recently obtained interesting results by reducing the phthalate concentration of walnut oils by 90%. The use of ethanol for oil neutralization is a process which generates less loss of neutral oil than the alkaline neutralization of a mixture with high acidity, and this is less harmful than physical refining during the production of 3-MCPD esters, esters of glycidol, and trans fatty acids. EcoXtract® is a solvent derived from the chemistry of pentoses in biomass. This solvent has very good oil solvation capacities and less biological toxicity than hexane. Its production has an acceptable carbon footprint and good sustainability characteristics. It is recognised by Ecocert as suitable for producing COSMOS ingredients. Compared to ethanol, its use requires fewer preparation steps (ethanol requires rigorous drying before extraction) and it requires less circulating solvent per kilo of oil extracted. The solvent removal from the meal requires less energy and allows the use of direct steam to aid in the removal of the solvent since the miscibility of water in this solvent is limited to 4.5 g/100g.
Highlights
In the world of cosmetics, solvents have a public acceptability problem because they are associated with carcinogenic chlorinated solvents or with petroleum cuts of ill-defined composition which may contain toxic molecules
– The solvent must come from renewable materials, – Its manufacture must comply with the green chemistry charter, – No product derived from GMOs must have been used to ensure its production – The solvent must not be toxic, – No residue should be found in the oil, – It must not harm the health of the workers who use it
With a given walnut oil containing 5.8% free fatty acids, different concentrations of ethanol and water were tested at a temperature of 27 °C and several washes with a solvent oil ratio of 1:2 (m/m) were carried out, thereafter allowing the mixture to settle at 7 °C overnight
Summary
In the world of cosmetics, solvents have a public acceptability problem because they are associated with carcinogenic chlorinated solvents or with petroleum cuts of ill-defined composition which may contain toxic molecules. The dogmatic rejection of solvents is not part of the COSMOS standard (COSMOS, 2020) which provides guiding rules for the preparation of cosmetics ingredients based on “organic” material. This allows their use with certain precautions when the physical methods are insufficient to achieve the desired quality. – The solvent must come from renewable materials, – Its manufacture must comply with the green chemistry charter, – No product derived from GMOs must have been used to ensure its production – The solvent must not be toxic, – No residue should be found in the oil, – It must not harm the health of the workers who use it
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