Method for extracting phenolic compounds from olive fruit water and preparation of an extract titrated with olive and grape polyphenols
The present invention relates to a method for extracting phenolic compounds with low molecular weights from olive fruit water; the invention also relates to compositions enriched with phenolic compounds including at least 40% of dry matter, said dry matter consisting of at least 30% hydroxytyrosol; the invention also relates to a method for drying said compositions by spraying using grape polyphenol extracts as a drying medium as well as to powders titrated with phenolic compounds of olives and grapes obtained after drying.
1. A method for preparing a composition enriched with low-molecular-weight phenolic compounds from olive wastewaters, the method consisting of:
(a) acidification of olive wastewaters so as to reach a pH of less than or equal to 4.3 a step of clarification of said acidified olive wastewaters;
concentration of the acidified and clarified olive wastewaters by vacuum concentration for storage thereof; storage of the concentrated acidified olive wastewaters; and then dilution of the concentrated acidified olive wastewaters in a solvent at approximately 4% of the acidified, clarified, and concentrated olive wastewaters;
(b) a step of tangential ultrafiltration of the diluted wastewaters obtained in step (a) through a tubular ceramic membrane having a cutoff threshold of between 100 and 200 kDa to obtain a permeate, and of recovery of the permeate;
(c) a step of nanofiltration of said permeate obtained in step (b) through a spiral organic membrane having a cutoff threshold of between 150 and 400 Da at a pressure of between 1 and 3 MPa to obtain a permeate; said membrane is such that it comprises an active layer comprising at least 50% of polyamide and that it makes it possible to obtain a retentate comprising at least 80% of dry matter contained in said wastewaters, and at most 25% of hydroxytyrosol,
(d) a step of adsorption of the phenolic compounds contained in the permeate obtained in step (c) by passing the latter over a polymeric matrix, followed by elution of the phenolic compounds adsorbed on said matrix, with an organic polar solvent, and obtaining of an eluate;
(e) a step of concentration, by distillation under vacuum, of the eluate obtained in step (d) and obtaining a Composition A; and
(f) a step of drying said Composition A.
2. The method according to claim 1 , wherein said step of drying consists of the following steps:
(f1) mixing said Composition A with a grape extract to obtain a mixture comprising at least 60% of total polyphenols; said mixture comprises an amount of said Composition A such that the dry matter of said Composition A represents between 5 and 40% of the total dry matter of the mixture;
(f2) drying the mixture obtained in step (e1), by spray drying to obtain a powder.
3. The method according to claim 1 , wherein said steps (a), (b), (c), (d), and (e) are carried out successively.
4. A method for preparing a composition enriched with low-molecular-weight phenolic compounds from olive wastewaters, the method consisting of:
(a) a step of clarification of said wastewaters;
(b) a step of tangential ultrafiltration of the clarified wastewaters obtained in step (a) through a tubular ceramic membrane having a cutoff threshold of between 100 and 200 kDa to obtain a permeate, and of recovery of the permeate;
(c) a step of nanofiltration of said permeate obtained in step (b) through a spiral organic membrane having a cutoff threshold of between 150 and 400 Da at a pressure of between 1 and 3 MPa to obtain a permeate; said membrane is such that it comprises an active layer comprising at least 50% of polyamide and that it makes it possible to obtain a retentate comprising at least 80% of dry matter contained in said wastewaters, and at most 25% of hydroxytyrosol,
(d) a step of adsorption of phenolic compounds contained in the permeate obtained in step (c) by passing said permeate over a polymeric matrix, followed by elution of the phenolic compounds adsorbed on said matrix, with an organic polar solvent, and obtaining of an eluate;
(e) a step of concentration, by distillation under vacuum, of the eluate obtained in step (d) and obtaining a Composition A; and
a step of drying said Composition A.
5. A method of making a food product comprising the step of adding a powder obtained by the method according to claim 2 to a food product.