Method for continuously enriching an oil produced by microalgae with ethyl esters of DHA
The invention concerns a method of preparing an oil enriched with ethyl esters of DHA produced by fermenting microorganisms, characterized in that it comprises a step of purification by so-called “short path” molecular distillation.
1. A process for preparing an oily composition enriched with ethyl esters of docosahexaenoic acid (DHA) from a fermentation broth produced by microalgae belonging to the family Thraustochytriales , the process comprising the steps of:
1) preparing a crude oil containing a mixture of DHA-rich triglycerides and unsaponifiable compounds composed essentially of squalene, from a fermentation broth of microalgae of the Thraustochytriales family,
2) optionally refining the resulting crude oil by a series of degumming, deacidifying, discoloring and deodorizing steps,
3) extracting the squalene from the crude oil by “short path” molecular distillation so as to obtain a raffinate devoid of squalene,
4) transesterifying the resulting raffinate by alcoholic transesterification in the presence of a basic or enzymatic catalyst,
5) fractionating the mixture of fatty acid esters in step 4) by “short path” molecular distillation, so as to obtain an extract rich in short-chain fatty acid esters and a raffinate rich in long-chain fatty acid esters,
6) purifying the mixture of long-chain fatty acid esters obtained during step 5) by “short path” molecular distillation, so as to obtain an extract enriched in long-chain esters, devoid of impurities,
7) optionally, refining this extract enriched in long-chain esters by a series of discoloring and deodorizing steps, and
8) recovering the resulting oily composition enriched with ethyl esters of DHA.
2. The process of claim 1 , wherein the molecular distillation steps are carried out under a high vacuum, at a value of less than 0.1 mbar.
3. The process of claim 1 , wherein the “short path” refers to a contacting time of less than 1 minute.
4. An oily composition enriched with ethyl esters of docosahexaenoic acid obtainable by the process as defined in claim 1 .
5. The oily composition of claim 4 , said composition being suitable for use in food sectors.
6. The process of claim 1 , wherein the microalgae belonging to the family Thraustochytriales is of the species Schizochytrium sp., Aurantiochytrium sp. or Thraustochytrium sp.
7. The process of claim 1 , wherein the temperature of the evaporator in step 3) is from 200° C. to 240° C.
8. The process of claim 1 , wherein the temperature of the evaporator in step 5) is from 100° C. to 150° C.
9. The process of claim 1 , wherein the temperature of the evaporator in step 6) is from 180° C. to 220° C.