FR2792329A1 - Auto-oxidation of unsaturated fatty acids and derivatives by direct oxidation with gaseous oxygenated mixture in absence of visible or UV light - Google Patents

Abstract

Auto-oxidation of unsaturated fatty acids and derivatives comprises heating fatty acids to 50-110 deg C in the absence of visible or UV light and introducing finely divided oxygenated gas at a flow rate greater than 100 l/hour (h)/l of fatty acid, to obtain a hydroperoxide index or optimum peroxide, as a function of treated fatty acid, of greater than 300. Auto-oxidation of unsaturated fatty acids and derivatives comprises heating fatty acids to 50-110 deg C in the absence of visible or UV light and introducing finely divided oxygenated gas at a flow rate greater than 100 l/h/l of fatty acid, to obtain a hydroperoxide index or optimum peroxide, as a function of treated fatty acid, of greater than 300. The hydroperoxide or peroxide index is the number of millimoles of oxygen fixed per 2 kg of fatty acid.

Description

The present invention relates to a self-oxidation process for fatty acids

in

  saturated and their derivatives (methyl esters, triglycerides, etc ...) allowing to obtain

  hold a product of defined composition, substantially free of degreasing products

  low molecular weight polar donations, thereby improving cosmetic formulations

  ques or pharmaceuticals in which it is incorporated. There are many processes for the peroxidation of fatty substances, and the use

  pharmaceutical or cosmetic oxygenated oils has been known for centuries.

  The principle of chemical oxidation reactions of fatty substances is now well known. These reactions can be of 3 types: enzymatic, auto-oxidation and photo-oxygenation (Gunstone, F.D., 1996, Fatty acid and lipid chemistry, Chapman and hall, London). They result in the formation of primary oxidation products

  (hydroperoxides, endoperoxides) which transform into secondary oxidation products

  daire (hydroxyls, epoxides, aldehydes, ketones, acids, polymers, etc.).

  Several low molecular weight secondary oxidation products are re-

  known to be cytotoxic and / or smelly (malondialdehyde, aldehydes res-

responsible for the smell of rancid ....).

  Apart from enzymatic processes making it possible to obtain well-defined products, but in very small quantities, such as prostaglandins or leukotrienes with

  starting from arachidonic acid, the methods described so far for use

  pharmaceutical or cosmetological sation of the products obtained, all result in a mixture of unknown composition. The molecule (s) responsible for the activity of

  these products remain unknown until now.

  The peroxidation processes described are either continuous or discontinuous. They

  characterized by a limited oxygen supply and an energy supply in the form of

  their, most often in combination with ultraviolet or visible radiation.

  The use of radical initiators such as metal ions has also been described,

  same as the use of ionizing radiation (X, beta or gamma).

  The products obtained are characterized by their general peroxide index-

  between 50 and 150, the highest mentioned being 300, obtained in advance

sence of ultraviolet radiation.

  Most of the processes described use chemical reactions of photo-

  oxygenation, through the use of visible or ultraviolet radiation or

  ionizing ions (X, beta or gamma).

  Thus, patent FR 2 461 744 describes a peroxidation process using ultraviolet radiation, at a temperature above 50 ° C. and with an air flow rate of 5 to 100 liters per hour per liter of fat treated, the final peroxide number

ranging from 60 to 90.

  Patent EP 293 535 claims the use of a peroxidized oil by exposure

  intensive ultraviolet radiation so as to present a peroxide index of 50 to 120. The patents FR 2 591 112, EP 225 831, EP 250 832, EP 225 833 and EP 226 506

  claim the use of a hyperoxygenated oil by intensive exposure to ultra-

  purple so as to have a peroxide index of 30 to 300.

  Patent GB 227,212 describes a process in which the fat is ato-

  bet in an oxidizing atmosphere in the presence of ultraviolet rays.

  Patent FR 2,539,142 describes a discontinuous process carried out in the presence of

natural or electric light.

  The patents FR 2 880 M and GB 1 077 378 mention processes which, although

  that the use of radiation is not described, clearly specify that the reaction

  tion is carried out so as to exclude the formation of auto-oxidation products.

  Now, photo-oxygenation reactions of fatty substances lead to the formation

  many additional products compared to those formed by autooxidation.

  Among these, cyclic peroxides are more particularly unstable and degrade.

  tooth, among others, epoxides and malondialdehyde recognized cytotoxic.

  Patent FR 2 747 127 describes a process which can be carried out sheltered from

  ultraviolet light. This process is characterized by a lower reaction temperature

  less than 50 C and an air flow limited to 25 liters per hour per liter of treated oil. Linen-

  dice of peroxide of the final product is between 50 and 160.

  The use of ozone has also been mentioned, but this is another type of chemical reaction (ozonolysis) which results, among other things, in the formation of very complex compounds.

  unstable and of different chemical nature.

  The use of hydrogen peroxide has also been described, but also leads to the formation of very unstable products due to the presence of free radical species

water during the reaction.

  Apart from the enzymatic reactions, there is no process for obtaining

  hold a standardized product of defined composition and substantially free of

  cytotoxic polar degradation products.

  The subject of the present invention is a process for the oxygenation of fatty acids and their derivatives using exclusively auto-oxidation chemical reactions, making it possible to limit the formation of cytotoxic secondary degradation products and to obtain a product of defined composition . This process is characterized, among other things,

  by reaction conditions making it possible to obtain an oxygenated fatty substance present

  as a hydroperoxide (or peroxide) index greater than 300, and more particularly-

  greater than 600 in the case of triglycerides.

  The auto-oxidation process according to the invention consists in heating the fatty substance in an enclosure completely sealed against ultraviolet radiation or visible to a

  temperature between 50 ° C. and 110 ° C., by introducing into the fatty body li-

  that a very finely divided oxygenated gas mixture with a flow rate greater than 100

  liters of air per hour and per liter of fat. The reaction is continued until the

  tion of an optimum hydroperoxide index, variable according to the composition of the fatty substance

  treated, but which will always be greater than 300. More particularly, this hydro-

  peroxide will be greater than or equal to 800. At the end of the reaction, the introduction of the gaseous mixture can be continued for several hours until complete cooling

  of the fatty substance thus peroxide exclusively by auto-oxidation.

  The hydroperoxide (or peroxide) index corresponds to the number of millimoles of molecular oxygen fixed for 2 kg of fatty substance. It also represents the number

  millimoles of hydroperoxide functions per 2 Kg of fatty substances created by the reaction

oxidation.

  The fatty acids treated are chosen from the group of unsaturated fatty acids.

  Monounsaturated fatty acids such as oleic acid are not very reactive, and fatty acids comprising more than two double bonds such as linolenic acid are most often odorous and give rise to numerous, more unstable products, and

therefore difficult to standardize.

  Thus, preferentially, the fatty acids will be chosen to be predominantly

  in the group of di-unsaturated such as linoleic acid.

  These fatty acids can be in all forms such as esters

  (ethyl, methyl, etc.), glycerides, salts, etc. The average iodine index of aci-

  unsaturated fats must be greater than 150. In the case of triglycerides, these will therefore preferably be chosen from the group of oils having a level of linoleic acid greater than 50% of total fatty acids and a low level of linolenic acid (less than 2%) such as corn oil, sunflower oil, grapeseed oil, etc., without

  this list is exhaustive. Under these preferential conditions of the invention, the composition

  tion of the product obtained is defined as more than 99%, at least 95% of fatty acids

  being oxygenated by 9-hydroperoxyoctadecadienoic acids and 13-

hydroperoxyoctadecadienoic.

  The process described is carried out at atmospheric pressure. But, according to a va-

  laughing at the invention, this process can be carried out at a pressure above atmospheric pressure, from 1 to 8 bars, preferably 4 bars, in order to reduce the reaction time. Likewise, the addition to a non-treated fatty substance, of a part of fatty substance thus peroxide and playing the role of initiator, or of any initiator of the reaction

  auto-oxidation, also reduces the reaction time.

  The oxygenated gas used can consist of all or part of mixed oxygen

  managed in any proportion with one or more inert gases. Preferably, this oxy-

  generated consists of purified air.

  The amount of oxygen supplied during the auto-oxidation reaction is primarily

  dial, this can be a limiting factor of the reaction.

  According to the invention, the oxygen supply must always be in excess relative to

to the needs of the reaction.

  Thus, the flow rate of finely divided oxygenated gas within the fatty substance is always greater than 100 liters per hour and per liter of fatty substance, but preferably is greater than 200 liters per hour and per liter of fatty substance. Too much gas flow does not disturb the reaction, but causes significant heat loss. Thus, economically, this flow rate can be limited to 600 liters per hour per liter of

fat body.

  The reaction temperature is between 50 ° C. and 110 ° C. Preferential-

  ment, it is between 70 C and 95 C. A temperature above 10 C

  drags a rapid increase in the formation of secondary degradation products.

  Under preferential conditions of the invention, the products thus obtained ex-

  clusively by auto-oxidation can then be deodorized by any process

  naked by a person skilled in the art. This can be achieved by any process which does not use temperatures above 110 C or reducing substances. Treatment with activated carbon or with bentonite can for example be carried out. Of

  even, treatment with supercritical CO2 gives good results.

  Under other preferential conditions of the invention, the products obtained, with or without deodorization, are advantageously stabilized by treatment with a chelating agent in solution, followed by washing and drying. The chelator used is chosen from EDTA (ethylenediaminetetraacetic acid) and its salts, DTPA (diethylenetriaminepentacetic acid) and its salts, citric acid and its salts, etc., without

this list is exhaustive.

  The products obtained can also be stabilized by the addition, at the end of the

  cess, one or more non-reducing antioxidants soluble in the product and

  molar concentrations up to once that of the hydroperoxides present. These anti

  oxidants are chosen from tocopherols, BHA (butyltertiary hydroxyanisol), BHT (dibutyl-tertiary paracresol), NDGA (nordihydroguaiaretic acid), citric esters of mono and diglycerides, etc., without this list being exhaustive. The following examples illustrate the present invention without limiting its possibilities and

the implementation variants.

Example 1

  In a 100 liter stainless steel tank that can be pressurized

  With a heating device and an air diffuser, 65 liters of corn oil are introduced. The temperature is brought to 80 ° C. and the flow rate of the filtered air is adjusted to

  230 liters per hour per liter of oil, or 15m3 per hour. In this example, the reaction

  tion is carried out at atmospheric pressure, the tank being completely sealed against any light radiation. After 60 hours, the hydroperoxide (or peroxide) index is

  800. The heating is stopped and the air flow is maintained until it has completely cooled down.

of the product.

Example 2

  By keeping the same parameters as in Example 1, but by operating

  under a pressure of 4 bars, the duration of the reaction to obtain a hydrope index-

  800 oxide is 50 hours. After treatment with supercritical CO2, the product does not

  has no particular odor. It is substantially free of detergents

  low molecular weight polar gradations. At least 95% of the fatty acids oxy-

  genes correspond to 9- hydroperoxyoctadecadienoic and 13hydrope-

  roxyoctadecadienoic. The total composition of the product is defined at more than 99%.

Claims (10)

  1. Process for the oxidation of unsaturated fatty acids and their derivatives, characterized in that it is carried out exclusively by self-oxidation, by heating the fatty substance to a temperature between 50 ° C. and 110 ° C. in the total absence of any visible or ultraviolet radiation, and by introducing a finely divided oxygenated gas with a flow rate greater than 100 liters per hour and per liter of fatty substance, until the optimum hydroperoxide or peroxide index is obtained as a function of the treated fatty substance and which will always greater than 300.   2. Method according to claim 1, characterized in that the flow rate of the oxy-   over 200 liters per hour per liter of fat.   3. Method according to one of claims 1 or 2, characterized in that the tem-   temperature is between 70 C and 95 C.   4. Method according to one of claims 1 to 3, characterized in that the reaction   tion is carried out under overpressure relative to atmospheric pressure.   5. Method according to one of claims 1 to 4, characterized in that the body   fat, before treatment, is added with an initiator of auto-oxidation reaction.   6. Method according to one of claims 1 to 5, characterized in that the aci-   fats or their derivatives are chosen to be predominantly in the group of di-   unsaturated such as linoleic acid.   7. Method according to claim 6, characterized in that the triglycerides are   preferably chosen from the group of oils with a level of linoleic acid   more than 50% and a low level of linolenic acid (less than 2%) such as   corn, sunflower, grapeseed oil, hydroperoxide or pe-   oxide at the end of the reaction being greater than or equal to 800.   8. Method according to one of claims 1 to 7, characterized in that the product obtained is then deodorized.   9. Method according to one of claims 1 to 8, characterized in that the product   obtained is treated with a chelating agent in solution followed by washing and drying.   10. Method according to one of claims 1 to 9, characterized in that the pro-   duit is stabilized by the addition of one or more non-reducing antioxidants.