Process for purifying maritime pine bark, and extracts obtained from this purified bark.

Abstract

The invention relates to a process for purifying maritime pine bark by selective sieving and grinding, as well as the extracts obtained from this purified bark. The purified bark of the invention is obtained by a three-step process consisting of pre-sieving the raw bark, followed by selective grinding of the pre-sieved bark with a non-shearing grinder, followed by sieving of the selectively ground raw bark. The maritime pine bark extracts obtained from this purified bark can be obtained by extraction with water or with a mixture of water and ethanol. Extracts obtained by water extraction have a procyanidin content of between 65% and 75%, while extracts obtained with a mixture of water and ethanol have a procyanidin content greater than or equal to 70%.Extracts of maritime pine bark obtained from the purified bark of the invention can be used as ingredients for the formulation of food supplements, functional foods or cosmetic products.

Description

Title of the invention: Process for purifying maritime pine bark, and extracts obtained from this purified bark. Technical field of the invention

[0001] The present invention relates to a process for purifying maritime pine bark by a series of sieving and grinding operations, for use in extracting active ingredients for use in food supplements, functional foods, and cosmetic formulations. Technological background

[0002] Maritime pine (Pinus pinaster Aiton) is a conifer of the Pinaceae family, Reaching maturity around 40 years of age and up to 40 meters in height, it is found primarily around the Mediterranean and along the Atlantic coast of southwestern Europe, mainly in Portugal and in the Landes de Gascogne region of France. Maritime pine trunks are used for the production of timber (flooring, cladding, paneling), industrial wood (particleboard, pallets, raw material for paper pulp), and wood for energy (pellets, logs). The trunk's structure, from the inside out, consists of the heartwood (or duramen), the sapwood (the conductive layer of sap from the roots to the crown), the cambium (the tree's growth tissue), the phloem (the inner bark that conducts sap), and the rhytidome (the outermost layer of bark).Pure bark, or purified bark, refers to the rhytidome (outer part of the bark), and raw bark refers to the mixture of different constituents resulting from the debarking of maritime pines (wood, sapwood, cambium, phloem and rhytidome). Heartwood represents the largest proportion of the trunk, and it is this part that is used in various industrial applications. Before use, the wood must be stripped of its outer layers. Therefore, virtually all industries using maritime pine initially perform a debarking operation, which consists of removing the bark using various mechanical processes (primarily roller debarkers or ring debarkers). These processes, used by all industries employing maritime pine, such as sawmills, paper mills, and plants manufacturing panels or wood for energy, allow for the recovery of the heartwood and generate raw bark as a by-product. This raw bark consists of a mixture of rhytidome, sapwood, cambium, phloem, and wood fibers. The composition of this raw bark varies considerably depending on the debarking process used and the age of the pine trees that were debarked.Indeed, the older the pine trees, . and the higher the proportion of rhytidome (outer bark). These raw barks are the raw material used for the extraction of active ingredients. Maritime pine bark has been used for many years to produce maritime pine bark extracts containing the active ingredients procyanidins. Procyanidins, also known as proanthocyanidins, procyanidols, or proanthocyanidols, are oligomers or polymers of catechin and epicatechin, which may be partially esterified by phenolic acids or partially etherified by sugars. Extracts of maritime pine bark are used as ingredients in the formulation of food supplements, functional foods, and cosmetic products, particularly for their antioxidant properties. A food supplement is defined as a foodstuff intended to supplement a normal diet and which constitutes a concentrated source of nutrients or other substances with a nutritional or physiological effect; food supplements are intended for oral administration and are packaged in doses in the form of tablets, capsules, lozenges, ampoules, or any other dosage form.A functional food is defined as a food that has effects on one or more target bodily functions, beyond its nutritional benefits, improving the well-being or health of individuals, or reducing the risk of disease; it may be a natural food containing certain active molecules or a food artificially enriched with various ingredients that have beneficial effects on health. A cosmetic product is defined as any substance or mixture intended to be placed in contact with the external parts of the human body or with the teeth and the mucous membranes of the mouth, with a view exclusively or primarily to cleaning them, perfuming them, changing their appearance, protecting them, keeping them in good condition, or correcting body odors. Procyanidins are present mainly in the outer part of the bark (rhytidome), and to a lesser extent in the phloem, where they are mixed with other extractables. The raw bark from the debarking of maritime pine trunks in sawmills, paper mills, and wood-for-energy plants constitutes the raw material for procyanidin extraction. In addition to the rhytidome, it contains a quantity of wood fibers, bast, sapwood, and cambium that can represent 30% to 70% of the mixture with the rhytidome. Since procyanidins are present in significant quantities only in the outer bark (rhytidome), the proportion of the other constituents will influence the purity of the procyanidins extracted from the raw bark. This fluctuation in the composition of raw bark, and therefore of the extracts derived from it, has led to the development of rather complex and costly processes for treating this raw material in order to obtain standardized procyanidin extracts. For example, patent FR2722498 describes a process for obtaining procyanidins from maritime pine bark in four main steps: hot water extraction, salt addition, ethyl acetate extraction, and washing with a chlorinated solvent. Patents FR2092743, FR2372823, and FR2643073 describe similar processes with variations in the solvents used for procyanidin extraction and purification.Patent CN110538204A describes a process for extracting procyanidins from pine bark using enzymes, patents CN103755676A and US2009124818A1 describe a process for purifying procyanidins from pine bark using macroporous resins or membranes, and patent KR100908931B1 describes the use of an alkaline solution for the procyanidin extraction step. These processes, necessary to obtain high and standardized procyanidin concentrations in the extract, are complex to implement, costly, have low yields, and use one or more toxic solvents. Furthermore, patents CN211250481U, CN217473705U and CN215197365U describe processes for grinding pine bark, but these processes are not selective with respect to the different constituents of the raw bark, and therefore do not represent a solution to the problem of the composition of the raw bark used in subsequent procyanidin extraction operations. Description of the invention

[0003] The present invention, by purifying the raw bark before the procyanidin extraction step, makes it possible to obtain purified bark containing a mass proportion of 90% to 100% rhytidome, which surprisingly leads to extracts with a high and reproducible procyanidin content using only water, or a mixture of water and ethanol, in the extraction step. Furthermore, the yields are higher and the extraction costs are lower than with traditional processes, without the use of toxic solvents. The principle of bark purification according to the present invention is based on the selective sieving and grinding of the bark (grinding and classification), taking advantage of the differences in hardness and friability of the various constituents of the raw bark. Sieving, screening, or classification refers to a unit operation that separates a population of material fragments according to their size into two (or more) parts. This is achieved using a perforated surface (sieve) that allows fragments smaller than the perforation size (mesh size of the sieve) to pass through while retaining larger fragments. The portion of the sample that is not processed will be called the residue. passed through the mesh of the sieve, and sieved the part of the sample that passed through the mesh of the sieve. The outer bark (rhytidome) is a hard, brittle material, unlike the other components of raw bark, such as the sapwood, phloem, cambium, and wood fibers, which are more elastic. Using a grinder that crushes the mixture without shearing it allows for the selective grinding of the outer bark, leaving the other components of the raw bark virtually intact after grinding. Sieving then allows the ground outer bark powder to be recovered, removing the other components. The purified ground bark can then be extracted directly or further ground to a finer consistency before extraction to obtain procyanidins. The process for obtaining purified maritime pine bark from raw bark of the present invention comprises the following three successive steps: - A pre-screening of the raw bark, with removal of the screenings and recovery of the rejects. - Grinding of the residue from the previous step with a non-shearing grinder. - Sieving of the raw, ground bark from the previous step, with removal of the residue and recovery of the sieved material. These three successive steps are detailed as follows: The first step involves pre-sieving the raw bark to remove the screenings, which consist of small particles (sand, soil, small pieces of bark, or wood dust). During this process, the smallest constituents (smaller than the sieve mesh) are removed, and the oversize (constituents larger than the sieve mesh) is collected for the next step. Any type of sieve can be used for this stage; industrial rotary (possibly centrifugal) or vibrating sieves are perfectly suited and allow for continuous operation. The mesh size of the sieves used in this stage ranges from 5 millimeters (5 mm) to 50 millimeters (50 mm). A mesh size smaller than 5 mm does not sufficiently remove small impurities, while a mesh size larger than 50 mm leads to excessive loss of raw material.Between these minimum and maximum values, the mesh size of the sieve used for pre-screening will be adapted according to the nature of the raw bark to be processed: raw bark from industries using older pine trees (over 25 years old), primarily sawmills, is characterized by a higher proportion and larger size of outer bark, allowing the use of sieves with the largest mesh sizes (30 to 50 mm) with minimal loss of raw material. Bark from various industries using younger pine trees, on the other hand, is characterized by a... Since the initial average size of the raw bark is smaller, it is advisable in this case to use sieving with finer mesh (5 to 30mm) to limit the loss of raw material. The second step in the process involves grinding the residue from the previous pre-screening stage using a non-shearing mill, such as a jaw crusher, roller mill, press, grinding wheel, or ball mill. Industrial mills are used to reduce the particle size of a material. Depending on their type and design, they operate through impact between particles or percussion between particles and the mill wall, crushing between the mill walls, attrition, abrasion, or shearing. The different types of industrial mills include hammer mills, knife mills, roller mills, crushers (jaw, cone, gyratory, grinding wheel, or impact), and air jet mills.Crushers with rapidly rotating parts, such as hammer mills, knife mills, or cone and gyratory crushers, all have a shearing action that makes them suitable for processing any raw material, but they are not very selective with respect to the material fed to them and are therefore not suitable for the process of the invention. Roller mills (also called cylinder mills, roller crushers, or roller presses) also have rapidly rotating parts (counter-rotating cylinders), but if the two rollers that make up the grinding system rotate at the same speed, the shearing action during grinding is very low, making this type of mill perfectly suited to the invention. Similarly, crushers whose operating principle is based on crushing the material by the walls of the mill, such as jaw crushers or impact crushers, are perfectly suited to the process of the invention.Ball mills, or grinding mills, are slow-rotating drums filled with a grinding material (in this case, balls or pellets). The diameter of the balls ranges from one to several centimeters, depending on the desired final particle size. The slow rotation of the drum lifts the balls, which then grind the material as they fall back down. This type of crusher, perfectly suited to the process of the invention, can operate industrially continuously, with the crushed product being discharged through slots on the opposite side of the raw material feed. Grinding wheels can also be used for the invention, provided that their rotational speed does not induce shearing during grinding. Press mills operate on the same crushing principle as jaw mills and are therefore suitable for the process of the invention. Finally, air jet mills operate by impact between small particles and are used to obtain due to very fine particle sizes, this type of crusher is not suitable for the process of the invention. The crushers typically used industrially for plant-based raw materials are generally hammer or knife crushers, optionally equipped with a sieving screen to obtain the desired particle size for the crushed material. When raw maritime pine bark is crushed in this type of crusher, all the constituents are crushed with very little selectivity, thus preventing separation based on size. In contrast, using crushers with very low shear action allows the outer bark (rhytidome) to be crushed without damaging the other constituents. This non-shearing crushing significantly reduces the particle size of the outer bark, while detaching it from the phloem, without altering the particle size of the other constituents.The crushed outer bark, whose size will have been greatly reduced during this stage, can therefore be easily separated from the other constituents of the raw bark during the final sieving stage. The third step of the process consists of separating, by sieving, the outer bark crushed in the second step (selective crushing) from the other components of the raw bark (phloem, cambium, sapwood, and wood). During this step, the sieved material, consisting of smaller components (smaller than the sieve mesh), is collected, and the retained material, consisting of components larger than the sieve mesh, is discarded. Sieves similar to those used in the first pre-screening step can be used for this step, such as vibrating or rotary sieves. The sieve mesh size must be chosen to allow only the crushed bark to pass through while retaining the larger components. Therefore, the sieve mesh size used in this step must be smaller than or equal to that used in the pre-screening.For example, if a 40mm mesh was used during pre-sieving, the mesh size of the sieve used during sieving must be less than or equal to 40mm. The purified barks obtained at the end of the three stages of the process of the invention contain a mass proportion of 90% to 100% of rhytidome, depending on the combinations chosen between the mesh size of the pre-screening and final screening sieve, and the type of selective crusher used. The purified bark obtained through the process of the invention can then be used to manufacture maritime pine bark extracts, by any extraction process. In particular, maritime pine bark extracts from purified bark can be obtained by extraction with water (aqueous extract), or with a mixture of water and ethanol, in order to solubilize the active principles (procyanidins) in the chosen solvent. The solvent and bark mixture is then filtered to recover the aqueous or hydro-alcoholic phase. The solvent is then evaporated to recover the maritime pine bark extract in the form of a dry powder, standardized for procyanidins. The bark purification process described in the invention makes it possible to consistently obtain a high procyanidin content in the extract, regardless of the origin of the raw material (sawmill, paper mill, panel or wood-for-energy plant), the age of the debarked pines, and the initial proportion of rhytidome in the raw bark, using only water as the extraction solvent. The water used for extraction is food-grade or demineralized. The procyanidin content in the maritime pine bark extract obtained from aqueous extraction is always between 65% and 75%. However, the procyanidin extraction should be carried out with water at a minimum temperature of 60°C, and preferably between 90°C and 100°C, in order to obtain a sufficient extraction yield for industrial application.The extraction ratio between water and bark will be at least 2 parts water by mass to part bark, and preferably 8 to 10 parts water by mass to part bark for good procyanidin yield. The bark particle size will typically be 1 mm on average. The extraction time will depend on the bark particle size and will typically be between 10 and 120 minutes, depending on the extraction conditions chosen. The aqueous phase containing the procyanidins will be recovered by filtration after extraction, and the solvent will be evaporated to recover the maritime pine bark extract as a dry powder standardized for procyanidins. Extracts of maritime pine bark from the purified bark of the invention can also be obtained by extraction with a mixture of water and ethanol (also called a hydro-alcoholic mixture), resulting in maritime pine bark extracts containing at least 70% procyanidins, and potentially up to 90%, depending on the operating conditions. The extraction can be carried out with a hydro-alcoholic mixture containing 20% ​​to 80% ethanol by mass, at a temperature between 20°C and 80°C, preferably between 60°C and 70°C, with a minimum solvent mass ratio of 2:1 to the bark, for an extraction time of 10 to 120 minutes. The hydro-alcoholic phase containing the procyanidins will be recovered by filtration after extraction, and the solvent evaporated to recover the maritime pine bark extract in the form of a dry powder standardized in procyanidins. Extracts of maritime pine bark obtained from the purified bark of the invention, and in particular obtained by extraction with water or a mixture of water and ethanol under the conditions described above, are usable as ingredients for the formulation of food supplements, functional foods or cosmetic products, thanks to their high and repeatable procyanidin content. Examples

[0004] The following examples illustrate, by way of pure illustration and not limitation, practical implementations of the invention:

[0005] [Tables 1] Test Bark Type Sieve Type Mesh (mm) Yield (%) 1 Class 1 Vibrating 5 92 2 Class 1 Vibrating 10 85 3 Class 1 Vibrating 20 78 4 Class 1 Vibrating 30 62 5 Class 1 Vibrating 40 44 6 Class 1 Vibrating 50 32 7 Class 2 Vibrating 5 94 8 Class 2 Vibrating 10 89 9 Class 2 Vibrating 20 86 10 Class 2 Vibrating 30 81 11 Class 2 Vibrating 40 67 12 Class 2 Vibrating 50 48 13 Class 3 Vibrating 5 97 14 Class 3 Vibrating 10 94 15 Class 3 Vibrating 20 93 16 Class 3 Vibrating 30 90 17 Class 3 Vibrating 40 86 18 Class 3 Vibrating 50 84 19 Class 1 Rotary 10 83 20 Class 2 Rotary 30 78 21 Class 3 Rotary 50 81

[0006] [Tables2] Pre-screened bark Crusher type Mesh size (mm) % Rhytidome % PC aq % PC ha Test 2 Jaws 10 90 65.7 70.8 Test 18 Jaws 30 100 74.3 88.4 Test 9 Jaws 20 92 68.3 75.6 Test 11 Jaws 20 97 72.2 82.3 Test 2 Rollers 10 90 65.2 70.1 Test 18 Rollers 30 100 72.4 86.8 Test 9 Rollers 20 92 67.5 73.3 Test 11 Rollers 30 95 70.9 80.1 Test 2 Balls 10 91 66.2 71.6 Test 18 Balls 40 100 74.8 89.7 Test 9 Balls 20 94 69.0 77.1 Test 11 Balls 20 96 73.0 84.1

[0007] Table 1 summarizes the results of pre-screening raw bark obtained from maritime pines of different ages, according to the type of screener and the screen mesh size used. The Bark Type column corresponds to the type of raw bark used. Class 1 bark comes from pines less than 15 years old; Class 2 bark comes from pines aged 15 to 25 years; Class 3 bark comes from pines older than 25 years. The Screen Mesh column corresponds to the mesh size in mm of the pre-screening screen. The Yield column corresponds to the mass yield of the material retained during the pre-screening stage. Table 2 summarizes the grinding results of the raw bark from the various trials listed in Table 1 and the extraction of procyanidins after final sieving, using different mesh sizes. The Mesh column corresponds to the mesh size of the sieve used for final sieving. The % Rhytidome column corresponds to the rhytidome content in the purified bark as a mass percentage. The %PC aq column corresponds to the procyanidin content in the aqueous extract. The %PC ha column corresponds to the procyanidin content in the hydro-alcoholic extract. Pre-screening procedure: Raw bark recovered from sawmills or paper mills is classified according to the age of the debarked pine trees (less than 15 years: Class 1, between 15 and 25 years: Class 2, more than 25 years: Class 3). The bark is pre-screened on a vibrating or rotary sieve with mesh sizes of 5 mm, 10 mm, 20 mm, 30 mm, 40 mm, or 50 mm. Vibrating sieve screening is performed with 200 g of raw bark per test on a machine equipped with a 200 mm diameter metal mesh sieve for a duration of 5 minutes. Rotary sieve screening is carried out in a steel cylinder equipped with perforations, the diameter corresponding to the sieving mesh, loaded with 200g of pre-sifted raw bark and rotated at 60 revolutions per minute for 20 minutes. Operating procedure for selective grinding: the pre-screened bark selected in the previous step is then ground with different types of grinders (roller, jaw or ball mills) Ball mill: a drum mill is used, loaded with 20mm diameter steel balls and raw bark, at a rotation speed of 10 revolutions per minute for 20 minutes. Roller mill: a mill is used with two smooth steel cylinders mounted in parallel and counter-rotating at the same speed, with an air gap of the same size as the mesh of the pre-screening sieve. Jaw crusher: a crusher with steel jaws and a slot width of value less than or equal to the mesh size of the pre-screening sieve is used. Final sieving procedure: a vibrating sieve is used under the same conditions as the pre-sifting, with metal mesh sieves of the dimensions mentioned in Table 2. Procedure for aqueous extraction: 50 g of purified bark and 400 g of demineralized water are placed in a 1-liter three-necked flask fitted with a stirrer, a condenser, and a thermometer. The mixture is heated to 95°C with stirring for 1 hour, then filtered through a 25 µm nylon bag followed by an 1 µm bag. The aqueous phase is then evaporated to dryness in a rotary evaporator. Procedure for the hydro-alcoholic extraction: 50 g of purified bark and 400 g of a mixture of 200 g of demineralized water and 200 g of ethanol are placed in a 1-liter three-necked flask fitted with a stir bar, a condenser, and a thermometer. The mixture is heated to 65 °C with stirring for 1 hour, then filtered through a 25 µm nylon bag followed by an 1 µm bag. The hydro-alcoholic phase is then evaporated to dryness in a rotary evaporator. The results in Table 1 indicate that pre-screening can be carried out on bark from older pine trees with 50 mm mesh while maintaining good yields. Mesh sizes larger than 30 mm should be avoided for pre-screening raw bark from pine trees aged 15 to 25 years, and mesh sizes larger than 20 mm for pine trees younger than 15 years, to maintain acceptable pre-screening yields. The results in Table 2 indicate that all aqueous extracts have procyanidin contents between 65% and 75%, with this content tending to increase with the percentage of rhytidome in the purified bark. All hydroalcoholic extracts have procyanidin contents greater than 70%, depending on the percentage of rhytidome in the purified bark.

Claims

Demands

1. A process for obtaining purified maritime pine bark from raw bark, characterized in that it comprises the following three successive steps: a. Pre-screening of the raw bark, with removal of the over-screening material and recovery of the residue. b. Grinding of the residue from the previous step with a non-shearing grinder. c. Screening of the ground raw bark from the previous step, with removal of the residue and recovery of the over-screening material.

2. A process according to claim 1, characterized in that the raw bark used consists of a mixture of wood fibers, sapwood, cambium, phloem and rhytidome, and obtained from a debarking operation of maritime pine trunks in sawmills, paper mills, panel manufacturing plants or wood for energy.

3. A process according to claim 1, characterized in that the purified barks contain a mass proportion of 90% to 100% of rhytidome.

4. A method according to claim 1 characterized in that the first pre-sieving step is carried out with a sieve having a mesh size between 5 mm and 50 mm.

5. A method according to claim 4 characterized in that the pre-sieving is carried out with a rotary or vibrating sieve.

6. A method according to claim 1 characterized in that the second non-shearing grinding step is carried out with a roller mill, a jaw mill, a ball mill, a press or a grinding wheel.

7. A process according to claim 1 characterized in that the third sieving step of the crushed raw bark is carried out with a sieve whose mesh size is less than or equal to that used during the first pre-sifting step.

8. An extract of maritime pine bark, characterized in that it is obtained from purified bark according to any one of claims 1 to 7.

9. An extract of maritime pine bark according to claim 8, characterized in that it is obtained by extraction with water at a temperature between 60°C and 100°C, preferably between 90°C and 100°C.

10. An extract of maritime pine bark according to claim 9, characterized in that its procyanidin content is between 65% and 75%.

11. An extract of maritime pine bark according to claim 8, characterized in that it is obtained by extraction with a mixture of water and ethanol at a temperature between 20°C and 80°C, preferably between 60°C and 70°C.

12. An extract of maritime pine bark according to claim 11, characterized in that it is obtained by extraction with a mixture of water and ethanol having a mass proportion of ethanol between 20% and 80%.

13. An extract of maritime pine bark according to claim 11, characterized in that its procyanidin content is at least equal to 70%.

14. An extract of maritime pine bark according to any one of claims 8 to 13, characterized in that it is used as an ingredient for the manufacture of food supplements, functional foods or cosmetic products.