METHOD FOR DEHYDRATING LIQUID, SEMI-LIQUID OR PASTELIKE PRODUCTS, INCLUDING A PRESSURE CRYOGENIC STEP AND A LYOPHILIZATION STEP

Abstract

The invention pertains to the field of products in dry powder form obtained by lyophilization. The invention relates more particularly to a lyophilization method including a prior step of cryogeny under pressure of a matrix containing dissolved gas. It also relates to the powder obtained by this method and to the uses thereof in food processing, cosmetics, pharmacy, and human and animal health.

Claims

1. Method for preparing a dehydrated product consisting in: a) providing a product in the form of a liquid, semi-liquid or paste-like matrix; b) dissolving a gas in said matrix by passing through an area dense in gas molecules, such a density being obtained (i) either by the gas flow generated by the evaporation of a cryogenic fluid, (ii) or by an increase in pressure, (iii) or by a combination of these two means; c) cryogenizing said gas-rich matrix obtained in step b) at a pressure allowing said dissolved gas to be maintained in order to obtain frozen granules, particles or beads; d) lyophilizing said granules, particles or beads; e) obtaining said dehydrated product in powder form.

2. Method according to claim 1, characterized in that the lyophilization step d) can be carried out either immediately following the cryogenic step c), or subsequently after storage of said frozen granules, particles or beads.

3. Method according to one of claim 1 or 2, wherein said gas is an inert gas.

4. Dehydrated powder capable of being obtained by the method as defined in one of claims 1 to 3.

5. Powder according to claim 3, characterized by the presence of spherical particles.

6. Powder according to one of claim 4 or 5, characterized in that the particle size is less than 30 microns measured by optical microscopy.

7. Powder according to one of claims 4 to 6, characterized in that it is in compacted form.

8. Powder according to one of claims 4 to 7, characterized in that it comprises spirulina, curcumin, ginger or truffle.

9. Use of a powder as defined in one of claims 4 to 8 in food processing or in cosmetics.

10. Powder according to one of claims 4 to 8 for use thereof in pharmacy or in human or animal health

11. Equipment for implementing the method as defined in one of claims 1 to 3, characterized in that it comprises: means for dispensing a liquid, semi-liquid or paste-like matrix; a receptacle containing a cryogenic fluid in which the matrix is received to be cryogenized therein and transformed into frozen granules, particles or beads; a matrix passage area located between the means for dispensing the matrix and the receptacle; means for generating an area dense in gas molecules in the passage area, said means being either (i) a gas flow generated by the evaporation of a cryogenic fluid, or (ii) a pressurization means, or (iii) or a combination of these two means; lyophilizing equipment for transforming the frozen granules, particles or beads in the form of dehydrated powders.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0080] FIG. 1: Represents the lyophilization kinetics observed for the 3 preparation conditions. Circle: Reference; Triangle: Cryo LP; Square: Cryo MP.

[0081] FIG. 2: Microscopic observations made on the three coffee powders according to the preparation conditions; A: lyophilized coffee particles obtained under cryo LP condition; B: lyophilized coffee particles obtained under Cryo MP condition; C: lyophilized coffee particles obtained under conventional conditions (reference freezer −20° C.).

[0082] FIG. 3: Correlation between powder density and rehydration time of coffee powders.

[0083] FIG. 4: Dissolution of “cryo MP” turmeric (on the left) and industrial turmeric (on the right), stirred for 1 minute, then left to stand for 10 minutes

[0084] FIG. 5: Chromatograms obtained following analysis by an electronic nose of the three powders obtained after lyophilization (Reference conditions, Cryo LP and Cryo MP). In graph 5B: the first peak marked with an arrow comes out at 34.73, corresponds to 2.5 dimethylpyrazine, IP=70.99; the second peak marked with an arrow comes out at 39.29, corresponds to trimethylpyrazine, IP=48.51; the third peak marked with an arrow comes out at 45.66, corresponds to (E, Z)-2.6-nonadienal, IP=35.36.

[0085] FIG. 6: PCA analysis on the olfactory profiles of the 3 coffees (Frozen reference; Cryo LP and Cryo MP)

[0086] FIG. 7: Correlation between densities and luminances of 3 lyophilized coffee powders.

[0087] FIG. 8: Thermal characterization of coffee powders by modulated DSC.

[0088] FIG. 9: Schematic diagram of the method used showing the effects of pressure and gas dissolution/release in the product, a. preparation of the product at atmospheric pressure; b. gas dissolution in the product, partial pressure Pp of the dissolved gas being the sum of the pressure of the enclosure Pe1 and the local pressure linked to a gas flow Pf1; c. cryogenics of the product containing the dissolved gas, operating at a pressure Pc greater than or equal to partial pressure Pp of the gas contained in the product, the pressure Pc itself being able to result from the combination of a chamber pressure Pe2 and the local pressure linked to a gas flow Pf2; d. possible storage of the product in the form of solid beads at atmospheric pressure and at a temperature below the melting point of the product; e. lyophilization under partial vacuum, resulting in the sublimation of the water contained in the product and the release of the gas trapped therein, causing the creation of a microporous structure in the solid product beads; f. storage of the powder obtained at the end of lyophilization, after any crushing of the dry microporous beads.

[0089] The arrows represent the gas that is applied to the surface of the product in step b., which remains in equilibrium in step c. and which escapes in step e.

[0090] FIG. 10: variation of the quantity of phycocyanin-C during storage of lyophilized spirulina powder.

EXAMPLES

Example 1: Implementation of the Method According to the Invention

[0091] 1.1. General Description of the Method

[0092] The method according to the invention consists in dissolving a large quantity of a gas in a matrix, in cryogenizing said matrix in the form of granules or beads and then in lyophilizing said matrix.

[0093] The gas dissolution and cryogenics steps can be carried out in two distinct ways: [0094] either by incorporating gas at a pressure greater than atmospheric pressure, then by carrying out rapid freezing using cryogenic fluid, as described in application WO2008/043909; [0095] or by incorporating gas by immersion in a cryogenic fluid; in this embodiment, the step of gasifying the matrix consists in dissolving a large quantity of the gas generated by the evaporation of a cryogenic fluid in a matrix so that the product is at least saturated with said gas, the dissolution being carried out by increasing the number of gas molecules in an area of high gas density, called a “high molecular density area,” located above the surface of the cryogenic fluid and on the path of the matrix drops before their immersion in the fluid, said high molecular density area being created by carrying out the gasification and cryonics of the gasified matrix within a closed chamber provided with a vent arranged to allow evacuation of the gas generated by the evaporation of the cryogenic fluid by natural convection and to keep the interior of the enclosure at a pressure greater than or equal to atmospheric pressure; [0096] or by incorporating gas by immersion in a cryogenic fluid while applying a pressure greater than atmospheric pressure.

[0097] The matrices rich in gas and in the form of frozen granules, particles or beads are then subjected to lyophilization according to conventional conditions. On leaving the lyophilizing equipment, dehydrated beads a few millimeters in diameter are obtained. These very easily turn into powder, simple friction causing the very porous structure of the obtained beads to crumble.

[0098] 1.2. Special Experimental Conditions

[0099] The experimental conditions implemented to cool the samples analyzed in the examples that follow are as follows: [0100] Conventional freezing in a cold room, grinding and then spreading the pieces on the trays of the lyophilizing equipment; this condition is called “Reference”; [0101] Cryogenics under low pressure (corresponds to a relative pressure equivalent to approximately 0.5 bars obtained by bringing into contact with a cryogenic fluid), to dissolve a small quantity of gas but still benefit from the shape and temperature advantages of the cryogenics method “under pressure,” then directly spreading the obtained beads on the trays of the lyophilizing equipment. This condition is called “Cryo LP” for Low Pressure. [0102] Cryogenics under 5 bars of pressure, then spreading of the obtained beads directly on the trays of the lyophilizing equipment; this condition is called “Cryo MP,” for Medium Pressure.

[0103] 1.3. Matrix Preparation

[0104] a/Coffee

[0105] For the tests carried out on coffee, the matrix was prepared from a preparation of 3 L of filtered coffee, separated into 3 batches of 1 L each and then subjected to cooling as described above.

[0106] b/Turmeric

[0107] For the tests on turmeric, the matrix was prepared from a turmeric juice obtained by entraining and grinding the roots of said plant between two endless screws enclosed in an eight-shaped tube. For 1 kg of roots, approximately 750 g of juice is obtained. The latter was then subjected to the method that is the subject of the invention without further intermediate treatment.

[0108] c/Spirulina

[0109] For the spirulina tests, 200 g of a spirulina paste (fresh seaweed collected, drained and pressed) was diluted in 800 g of water containing 2 g/L of salt. The preparation was then subjected to the method that is the subject of the invention without further intermediate treatment.

Example 2: Reduction in Method Execution Time

[0110] The method according to the invention allows dehydrated products to be prepared in a shorter time than the deep-freezing-lyophilization method of the state of the art.

[0111] First of all, the sample preparation time is reduced, since pressurized cryogenics is an instantaneous method, unlike freezing and cryogenics methods without applied pressure. The product can then be lyophilized directly, without a prior cooling step, since the temperature of the products is about −60° C. when entering the lyophilizing equipment.

[0112] The time required to obtain a lyophilized product was studied. The result is shown in FIG. 1.

[0113] These are three coffee samples prepared by applying the particular experimental conditions described in paragraph 1.2.

[0114] First of all, it is observed that the time required to extract all the available water is halved when cryogenics Cryo under 5 bars (MP) is used, compared to the use of conventional freezing (Reference). This time savings is considerable. It is also observed that cryogenics Cryo under low pressure (LP) also induces an interesting benefit, although less significant.

Example 3: Physicochemical Properties of the Powders

[0115] The properties of the powders obtained by the method according to the invention were then compared with those of powders obtained by a conventional method (Reference).

[0116] 3.1. General Observations

[0117] It is observed that regardless of the pressure applied, the cryogenized beads containing dissolved gas (Cryo LP and cryo MP) make it possible to obtain a fine powder, which can be handled simply because it can be measured and is not sticky. The resulting powder does not pick up moisture easily when left under ambient conditions.

[0118] Conversely, the Reference lyophilization only makes it possible to obtain product agglomerates, which must generally be reprocessed (by grinding, for example) to facilitate or even allow their use.

[0119] 3.2. Powder Density

[0120] Very surprisingly, the lyophilized powders obtained from cryogenized products containing dissolved gas (Cryo LP and Cryo MP) are much less dense than those obtained from conventionally frozen products.

[0121] Table 1 above shows the density measurements carried out on the coffee powders obtained under the three different conditions.

TABLE-US-00001 TABLE 1 Apparent density of coffee powders without settling Method Powder density Reference 1.15 Cryo LP 0.78 Cryo MP 0.40

[0122] It is observed that the Cryo MP powder is almost 3 times less dense than the Reference powder, which is considerable.

[0123] 3.3. Observations of the Particles in Optical Microscopy

[0124] These measurements could also be correlated with microscopic observations made on the three coffee powders, obtained under the three experimental conditions. Reproductions of these microscopic observations are shown in FIG. 2.

[0125] Surprisingly, although the frozen beads are non-porous (the incorporated gas is dissolved and allows the product to retain its “full,” non-porous structure), a release of nitrogen takes place during lyophilization, which allows the formation of small, very porous particles. The more the quantity of dissolved gas increases, the greater the porosity. The method under pressure thus produces a powder of very low apparent density (see Table 1) that does not require grinding (the dehydrated beads are reduced to powder by simple crumbling or crushing).

[0126] The powder can still be easily compacted if necessary (e.g. pharmaceutical applications).

[0127] 3.4. Dissolution Rate

[0128] Observations of particle sizes can be correlated with differences in the rate of dissolution of the obtained powders in water. The hot rehydration being very fast (a few seconds), dissolution kinetics were carried out at 22° C. to be more discriminating.

[0129] 3.4.1. Dissolution of a Coffee Powder

[0130] The rehydration times of preparations at 1% of coffee are shown in Table 2 below. For each preparation condition, 1 g of lyophilized coffee is poured into 99 g of demineralized water stirred using a magnetic stirrer (IKA Lab Disk model set at 160 rpm). The measured rehydration time is that necessary so that no more solid grains are visible in the solution.

TABLE-US-00002 TABLE 2 Rehydration in distilled water at 22° C. of 1 g of coffee in 99 g of water Sample Rehydration time Reference Coffee 1′53″ Cryo LP Coffee 1′23″ Cryo MP Coffee  .sup. 58″

[0131] These results show that the rehydration is almost 2 times faster for the Cryo MP samples compared to that of the Reference samples. This is explained by a lower density of the lyophilized powder, which leads to greater porosity and therefore an accentuated capillary effect allowing faster hydration.

[0132] This correlation is shown in FIG. 3.

[0133] This correlation was not expected, as very low-density powders generally experience difficulties with rehydration. They tend to float more easily on the surface of the liquid, water in our case, without dissolving there. In the case of the present invention, this correlation is most certainly explained by the aspects of crystal size, illustrated in FIG. 2, which in turn induce these variations in apparent densities.

[0134] 3.4.2. Dissolving a Turmeric Powder

[0135] Turmeric is used as a food ingredient in many preparations and recipes. Its solubility is a major problem for its addition in aqueous preparations.

[0136] The method according to the invention allows a turmeric powder to be obtained that is very easily dispersible in food. An experiment for dissolving a powdered commercial turmeric and turmeric prepared by the “cryo MP” method was carried out.

[0137] Stirring for one minute was carried out for the 2 products in distilled water at 22° C. After stirring, visually, the “pressurized Cryo” product is very well dispersed or even very significantly solubilized. The industrial product is only very slightly solubilized.

[0138] To demonstrate the differences in solubilization, the 2 products are left to stand for 10 minutes. The photo reproduced in FIG. 4 shows that the method described in this patent produces a very homogeneous solution (FIG. 4A), while the industrial product is not solubilized at all and the turmeric is deposited at the bottom of the beaker (FIG. 4B).

Example 4: Organoleptic Properties of the Powders

[0139] The organoleptic properties were then studied.

[0140] The olfactory profile of each coffee was determined by double ultra-rapid gas phase chromatography (Heracles II electronic nose, AlphaMos). To do this, 0.01 g of each sample was taken in a 20 ml vial and placed at 40° C. for 1 hour to allow the release of the aromas, which are then analyzed automatically. Each analysis is repeated 3 times.

[0141] 4.1. Electronic Nose Analysis

[0142] Three analyses (in triplicate) were performed on each sample and the average chromatograms are presented in FIG. 5.

[0143] We note that the profiles of the 3 preparations (frozen reference, cryogenized LP and MP) show the same aroma peaks. The LP cryogenic coffee even has 3 additional peaks at retention times of 35 s, 40 s and 46 s. Overall, we also notice that the intensity of the detected peaks is higher for the products cryogenized under pressure compared to the Reference. This results in a better olfactory intensity during the rehydration of the coffee (cf. sensory analysis).

[0144] Very surprisingly, the organoleptic properties of the products obtained from cryogenized products containing dissolved gas (cryo LP and cryo MP) under pressure are much less altered than those obtained under Reference conditions from conventionally frozen products (Cref). In particular, the tastes and aromas are much better preserved in the case where cryogenics under pressure (LP or MP) is used.

[0145] Two remarkable phenomena are observed. First, the peak intensity is lower for the Reference (FIG. 5A, lower curves), regardless of the peak. The highest intensity is most often obtained for Cryo LP conditions. In FIG. 5B, it is also observed that certain peaks are very pronounced for Cryo LP (peak highlighted by the arrows), while they are very slight or even absent in the other two cases. Analysis of the molecules responsible for these peaks indicates that they are most likely known aromatic molecules of freshly roasted coffee. These molecules are all available from purified flavor molecule suppliers to enhance the taste of coffee and other food preparations. It is therefore very interesting that these molecules are “naturally” more present in the preparations obtained by means of the method that is the subject of the present invention.

[0146] These results show the greatest aromatic potential of the lyophilized coffees obtained according to the method that is the subject of the invention.

[0147] 4.2. Principal Component Analysis

[0148] A Principal Component Analysis (PCA) is performed on the different coffee samples to assess their overall olfactory rendering by the electronic nose.

[0149] The results are shown in FIG. 6.

[0150] This overall analysis leads to obtaining a discrimination index between the samples of 62, which is significant. More than 75% of this discrimination index can be explained by the difference in area between the peaks (represented by the main component 1, denoted MC1).

[0151] The Euclidean distances between samples are shown in Table 3.

TABLE-US-00003 TABLE 3 Euclidean distance between samples Compared Samples Euclidean distance Significance (Cryo LP - Cryo MP) 4.8 p < 0.001 (Cryo LP - Reference) 8.84 p < 0.001 (Cryo MP - Reference) 12.72 p < 0.001

[0152] Euclidean distances are significant between pressurized cryogenic coffees and the frozen Reference. The products are very significantly different. Cryogenics under pressure produces coffees with aromatic profiles that are different from conventional deep freezing. The higher the pressure, the greater the distance. Overall, the increase in pressure increases the olfactory intensity of coffees.

[0153] This is a completely surprising result and validates the interest of using cryogenics under pressure.

[0154] 4.3. Sensory Analysis of Coffees

[0155] 45 people were asked to compare the 3 coffees (prepared according to the Reference, Cryo LP and Cryo MP conditions as previously described), to detect whether differences exist between the 3 coffees and, if differences exist, to classify them in order of preference.

[0156] The “reference” coffee was detected as being significantly different from the other 2 coffees by 93% of the tasters. This coffee was detected 76% of the time as “less aromatic” than the other two.

[0157] The two Cryo LP and Cryo MP coffees were detected as different by 61% of the tasters. This difference is therefore less appreciable than the difference between cryogenic coffees and the Reference. Among the tasters who judged the 2 cryogenic coffees to be different, 64% preferred the Cryo MP coffee because of a “more marked aromatic development.”

[0158] This analysis shows that the method described here produces a coffee that is different from a conventional freezing method (Reference) and that in the case of a coffee, increasing the pressure in the method improves the aromatic quality of the coffee.

Example 5: Powder Colors

[0159] The color of the coffee powders was analyzed as a function of the three preparation conditions described above.

[0160] The colorimetric analyses were carried out using a DataColor Konica-Minolta colorimeter according to the standardized measurement procedure in the L, a, b reference system.

[0161] The results are shown in Table 4.

TABLE-US-00004 TABLE 4 Colorimetric analyses of coffee powders according to the L, a, b standard. Method L a b Cryo MP 79.25 11.14 27.07 Cryo LP 73.75 11.55 23.65 Reference 64.42 8.23 11.83

[0162] The measurements show that the “luminance L” (also called “clarity”) increases with the quantity of dissolved gas and therefore when the density of the powder decreases. The coffee cryogenized under 5 bars of pressure and then lyophilized has a distinctly lighter shade (higher luminance) than the other samples.

[0163] This relationship between density and luminance is validated in FIG. 7, which shows the strong correlation (R.sup.2=0.98) that exists between the densities and luminances of the 3 lyophilized coffee powders.

[0164] For the color factors (a and b), it appears that the Cryo MP and Cryo LP″ methods lead to similar values, while the Reference freezing method provides a less red (parameter a) and less yellow (parameter b) powder than the other 2 cryogenic powders. The color difference ΔE* between the Reference and the Cryo MP powder is highly significant (ΔE*=21.46). This significant difference in color allows the identification of cryonically pressurized powders.

[0165] These results are an additional indicator of the difference in the quality of the coffee powder depending on the lyophilization methods implemented.

[0166] In conclusion, coffees prepared under pressure, according to the method of the invention, are clearer, more aromatic, and dissolve better than coffee prepared according to the Reference method. These properties are due to the method and, as shown by the results obtained with turmeric, are generally applicable to all types of products.

Example 6: Thermal Property of the Powders

[0167] The thermal characterization measurements of the 3 coffee powders were carried out by modulated DSC (Differential Scanning Colorimetry).

[0168] The results are shown in FIG. 8.

[0169] These results show a glass transition of the lyophilized coffees under the Reference conditions and under very similar Cryo LP conditions. Conversely, there is a very significant difference (around 10° C.) for the Cryo MP method. This reflects a change in structure modifying the transition area of the product to lower temperatures. Indeed, since the composition is the same and in the absence of water, this reduction can only be due to a different molecular organization with more interactions in the Reference and Cryo LP systems. The molecules are freer and more mobile (fewer interactions) in the Cryo MP method.

Example 7: Preservation of Active Principles Present in the Matrix

[0170] Powdered spirulina samples, treated according to the three protocols described in point 1.2, were stored over time, at room temperature, and measurements of the amount of phycocyanin C were carried out at regular intervals by spectrophotometry, after rehydration of the samples and lysis of the cells by sonication. The results are shown in FIG. 10.

[0171] It is observed that the quantity of phycocyanin C decreases during storage for all the samples. However, the amount remains greater in the samples treated according to the present invention (LP and MP) than in the samples treated conventionally (Reference). Interestingly, the results are comparable regardless of the pressure applied under the two conditions presented.

[0172] The method according to the invention therefore makes it possible to conserve and preserve active agents in dry and stable form over time, in a much more efficient manner than what can be obtained by conventional freezing, then lyophilization.