CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of International patent application No. PCT/FR2014/099923, filed Jan. 31, 2014, which claims the priority of French application No. 1350853, filed Jan. 31, 2013, the subject matter of PCT/FR2014/099923 being incorporated in its entirety by reference herein.

The present invention relates to an original method for fractionating pea soluble fractions, comprising a microfiltration or centrifugation step, followed by an ultrafiltration step, and an optional reverse osmosis step. A reduction in the leakage of proteins to the soluble fractions, an improvement in the yield of the unitary step of concentration by evaporation of the soluble fractions and the selective isolation of proteins of interest are thus achieved. It is also a method that is easy to implement, the devices used at each unitary step being conventional and well known to those skilled in the art.

Since the 1970's, the pea has been the leguminous seed plant which has been most widely developed in Europe and mainly in France, in particular as a protein source for animal feed, but also for food for human consumption. The pea contains approximately 27% by weight of protein matter. The term “pea” is herein considered in its broadest acceptance and includes in particular all the wild-type varieties of “smooth pea” and all the mutant varieties of “smooth pea” and of “wrinkled pea”, regardless of the uses for which said varieties are generally intended (food for human consumption, animal feed and/or other uses).

Among the constituents of the pea, those which are currently most exploited are the starch, the fibers and the proteins, also referred to as noble constituents. The corresponding method of exploitation consists in initially preparing a starch milk, by mixing pea flour and water in a kneading machine. After having extracted the starch and the fibers from this milk, a protein-rich product is obtained. A flocculation operation is then carried out on the milk, in particular by thermocoagulation, the objective of which is to make the protein(s) of interest insoluble. At this stage of the method, it is necessary to carry out a separation, in particular by centrifugal decanting, so as to isolate a highly protein-rich composition also called “floc”. The supernatant constitutes what those skilled in the art generally refer to as “soluble fractions”.

It should first of all be specified that the term “soluble fractions” constitutes a misuse of language in the sense that said fraction contains a certain number of insoluble particles, such as various and varied colloids, but also and especially proteins. These soluble fractions must first of all be concentrated by evaporation, in such a way that the insoluble substances (and in particular the proteins) that they contain can be recovered. At the current time, the soluble fractions are exploited very little; they are used virtually exclusively as nitrogen source in fermentation and as nutritive feed for livestock once said fractions have been enriched with fibers.

The applicant has recently protected, through French patent applications No. 09 51962 and No. 12 57680, a method for extracting P-amylases from a soluble fraction from a starch plant, including the pea, said method comprising a step of clarification by microfiltration and a step of concentration/purification by ultrafiltration.

As it happens, it must be noted that the overall yield of the method leading from the initial pea to the protein-rich composition (the floc) is far from reaching 100%. It is considered that, at an industrial level, between 5% and 25%, but more generally around 20%, by weight of the proteins initially contained in the starting pea are found in the soluble fractions. This massive leakage of proteins, via the soluble fractions, raises a certain number of drawbacks.

The first of them is a dead loss of proteins of interest, which are currently only exploited through the protein floc resulting from the decanting step. If an overall isolation of the portion of proteins contained in the soluble fractions was achieved, said portion could advantageously be incorporated or redirected into the protein floc, with a view to enriching it.

The second problem raised by the method as it currently exists is a very mediocre yield at the level of the unitary step of concentration by evaporation of the soluble fractions: the rich protein content therein is such that the evaporator fouling phenomenon is very significant and requires frequent interruptions for cleaning. Indeed, by virtue of their heat sensitivity, proteins coagulate and have a predisposition to fouling the evaporation devices.

Finally and according to a third perspective, recent studies have shown that a portion of the proteins derived from the soluble fraction (the fraction termed PAlb) can be advantageously used in the production of an insecticide: this results from the teaching of document FR 2 778 407 A1. There is therefore also a technical advantage in selectively isolating one or more protein fractions actually within the soluble fractions.

To the applicant's knowledge, this problem has never been addressed as a whole, i.e. with a view to finding solutions aimed at solving the triple technical problem as stated above. The document “Pilot scale recovery of proteins from a pea whey discharge by ultrafiltration” (Lei (Leigh) Gao, Khai D. Nguyen and Alphonsus C. Utioh, Lebensm.-Wiss. u.-Technol., vol. 34, pp. 149-158, 2001) focuses on the recovery of the pea proteins by centrifugation followed by ultrafiltration. Patent application WO 2006/052003, for its part, relates to a method for preparing soluble polypeptides derived from a liquid effluent from pea conversion, by membrane filtration and then drying.

Working to find an overall solution for optimizing the yield of the method for extracting proteins from pea, the applicant has succeeded in developing a method which solves the triple technical problem:

of reducing the leakage of proteins to the soluble fractions,

of improving the yield of the unitary step of concentration by evaporation of the soluble fractions,

of selectively isolating the proteins of interest within the soluble fractions.

This method is based on the succession of various steps of separating said soluble fractions, a) by means of centrifugation or of microfiltration, b) then ultrafiltration, c) and, finally, optionally reverse osmosis.

Entirely advantageously, the implementation of these steps in a sequenced manner makes it possible, at the level of each filtration unit, to isolate a protein fraction of interest. Typically, the globulins and phytic acid are recovered in the microfiltration retentate or the centrifugation pellet (or sediment). The microfiltration permeate or the centrifugation supernatant then undergoes an ultrafiltration step: albumins then constitute most of the solids of the ultrafiltration retentate, the permeate being intended to undergo the optional reverse osmosis step. The latter makes it possible to isolate, on the one hand, a fraction rich in o-galactoside-type carbohydrates in the retentate, and, on the other hand, the amino acids, carbohydrates and other salts present in the permeate. Reference may be made to the diagram of the principle process illustrated inFIG. 1of the present application, as well asFIGS. 2-5.

