ARTIFICIAL AGING METHOD FOR IRIS RHIZOMES INTENDED FOR THE ACCELERATED FORMATION OF IRONE ISOMERS

Abstract

The present invention relates to a process for accelerating the aging of iris rhizomes and for producing iris butter from the aged rhizomes. The process according to the invention comprises storing the iris rhizomes in an oxygen atmosphere having a partial pressure of oxygen of 0.5 bar or more at 25°C and a high temperature.

Description

Technical field

[0001] The present invention relates to a method for accelerating the aging of iris rhizomes and for producing iris butter from the aged rhizomes. State of the art

[0002] The rhizomes of the iris species Iris germanica, Iris pallida, and some of their hybrids, such as Iris barbata, contain terpenoid compounds called iridals, which can be converted into desirable fragrances known as irons through oxidative cleavage. The aging process is currently achieved by storing the dried rhizomes for at least three to four years [F.-J. Marner, Current Organic Chemistry, 1997, 1, 153-186]. The irons are concentrated in the essential oil, known as iris butter, by steam distillation of the aged rhizomes. This oil is used in the perfume, cosmetics, and food industries.

[0003] Several attempts have been made to accelerate the aging process. These include the development of wet-chemical oxidation methods using potassium permanganate or nitrite salts [F.-J. Marner, W. Krick, B. Gellrich, L. Jaenicke, W. Winter, J. Org. Chem., 1982, 47, 2531-2536; W. Krick, F.-J. Marner, L. Jaenicke, Z. Naturforsch., 1983, 38c, 179; FR-2 620 702, 24 / 3 / 89; US Pat. No. 6,224,874B1], and the testing of microbiological and enzymatic biotransformation processes [EP 0443 925; EP 0353 683; US Pat. No. 4,963,480; EP 0443 926; US Pat. No 5,100,790] or ionizing radiation used to treat fresh rhizomes [FR-2 653 637] to accelerate iron formation.

[0004] However, the aforementioned methods for accelerated iron formation are not implemented in practice because they are undesirable to consumers as a chemical pretreatment of natural products [B. Roger, X. Fernandez, V. Jeannot, J. Chahboun, Phytochem. Anal., 2010, 21, 483-488] or are not economically feasible.

[0005] WO 2009 / 004517 describes a method for maturing iris roots. The rhizomes are first briefly heated in water to kill pathogens, but without deactivating the enzymes required for subsequent fermentation. The roots are then crushed and fermented. The process is carried out with fresh rhizomes that are not dried. The report also describes an investigation of the fermentation process with externally added enzymes and under anaerobic conditions. It was found that iron formation is significantly impaired under anaerobic conditions. Task

[0006] The long storage time of iris rhizomes in the traditional production method, currently at least three years, is economically problematic because storage space must be provided, cash flow is interrupted, and significant losses due to pest infestation are possible. Furthermore, this reduces the motivation for farmers to establish new iris plantations. Known methods for accelerating the aging of iris rhizomes require considerable use of reagents such as oxidizing agents or enzymes, or the use of microorganisms, and there is a risk of low consumer acceptance due to the chemical pretreatment.

[0007] With regard to this problem, the present invention is based on the objective of providing a method for accelerating the aging of the rhizomes and for obtaining iris butter, which enables a significant reduction in storage time and is inexpensive to implement without requiring pretreatment with chemicals or enzymes.

[0008] To solve this problem according to the invention, iris rhizomes are stored under an oxygen-rich atmosphere, elevated pressure, and elevated temperature. Surprisingly, it was found that the iron content increases within a few days to a level higher than that found in rhizomes stored conventionally for three years. Summary of the invention

[0009] The present invention relates to a method for accelerating the aging of iris rhizomes, comprising storing iris rhizomes under an oxygen-containing atmosphere having an oxygen partial pressure of 1 bar or more at 25°C and at a temperature of 25°C or higher.

[0010] Furthermore, the invention relates to a method for obtaining iris butter from aged iris rhizomes, which, after storage, includes carrying out steam distillation or extraction. Advantageous effects of the invention

[0011] The advantages achieved through this process lie particularly in the fact that the storage time of dried iris rhizomes can be reduced from at least three years (and sometimes up to five years or more) to just a few days or weeks. This process does not involve oxidizing chemicals such as potassium permanganate or nitrite salts, nor does it require complex microbiological or enzymatic processes. Instead, it uses only oxygen-containing gas mixtures, such as technical oxygen, synthetic air, or compressed air under elevated pressure and temperature. This results in a residue-free product, which is important for customer acceptance in the cosmetics sector. Furthermore, it eliminates storage costs and the risk of losses or quality reduction due to pest infestation.Additionally, the duration of the process applied to dried iris rhizomes can influence and thus control the composition of the various iron isomers and, consequently, the scent of the resulting iris butter. A further advantage is the increased flexibility in production due to the reduced waiting time. Detailed description of the invention

[0012] The process according to the invention can be used in conjunction with all iris varieties suitable for iron production. In particular, these are irises of the following species: Iris germanica, Iris pallida, Iris pallida argentea variegata, Iris pallida aurea variegata, Iris pallida alba, Iris neglecta, Iris spectabilis, Iris macedonica, and / or other variations of the bearded iris ( Iris barbata ).

[0013] Iris rhizomes are typically peeled, chopped, and then dried before storage. For chopping, the rhizomes can be cut into pieces 1-3 cm in size. Grinding them to further increase the surface area and accelerate iron formation is also possible.

[0014] Alternatively, the rhizomes can also be used in untreated form or simply dried, which is preferred by some perfume manufacturers. However, in the storage method according to the invention, the reduced surface area would then lead to a decrease in the rate of reaction with oxygen, so that it might be necessary to increase the oxygen concentration, the temperature and / or the storage time accordingly.

[0015] Drying can be achieved by simple storage at room temperature, or at elevated temperatures of, for example, 30–40°C or higher, particularly around 45–60°C. To further improve drying efficiency, the pressure can be reduced or drying can be carried out under vacuum. However, under such conditions, iron formation might be reduced due to the volatility of the terpenes, which are the starting material for the irons. Therefore, mild drying conditions are preferred.

[0016] The drying time is not specifically limited. Generally, drying is stopped when a constant weight is reached. With vacuum drying or hot air drying, this can occur within a few hours, for example, within 5 to 48 hours, particularly 10 to 24 hours. With simple drying by storage, several days to weeks may be required. The smaller the rhizomes are cut, the faster the drying process.

[0017] Storage then takes place in a pressure-resistant, heated container such as an autoclave in an oxygen-containing atmosphere such as air, oxygen / inert gas mixtures or pure oxygen.

[0018] The crucial factor is the oxygen concentration, which can be calculated using the equation pO2V = nO2RT from the temperature and the oxygen partial pressure pO2. At a fixed temperature, the concentration cO2 = nO2 / V is proportional to the partial pressure, i.e., pO2V = (nO2 / V) * RT.

[0019] According to the invention, the concentration is selected such that the partial pressure of oxygen at 25°C (298 K) is 0.5 bar or more. Preferably, the partial pressure of oxygen is 2 bar or more, more preferably 5 bar or more, and even more preferably 20 bar or more. A pure oxygen atmosphere can be used; in this case, the partial pressure values ​​given above correspond to the total pressure at 25°C. When using pure oxygen, the partial pressure of oxygen can be easily determined by filling the reaction vessel at 25°C and measuring the pressure. If filling takes place at a different temperature, the measured pressure would need to be converted to the value at 25°C using the equation above.

[0020] Alternatively, an oxygen-inert gas mixture or even air can be used, in which case the total pressure must be increased accordingly, depending on the oxygen content of the mixture, so that the oxygen partial pressure falls within the range mentioned above. The oxygen partial pressure is also determined by measuring the pressure of the gas being introduced, but in this case, it must be multiplied by the oxygen content of the gas. For example, if air with an oxygen content of approximately 21% is used, then a total pressure of approximately 2.5 bar would be necessary to obtain the required oxygen partial pressure of at least 0.5 bar.

[0021] There is no specific upper limit for the partial pressure of oxygen. However, the maximum pressure may be limited by the type of container used. It should also be noted that the pressure may increase further due to heating.

[0022] Storage takes place at a temperature of at least 25°C, preferably in the range of 30-80°C, particularly 40-60°C. Elevated temperatures accelerate iron formation; however, at very high temperatures there is a risk that the formation of undesirable byproducts may be promoted or decomposition reactions may occur, which could reduce the amount of iron formed.

[0023] There is no specific limit to the storage duration. Typically, the iron content initially increases significantly with storage time, reaching a maximum, and can decrease again during very long storage periods due to decomposition reactions. The exact time course can depend on the oxygen concentration, pressure, and temperature.

[0024] A suitable storage period can be determined by measuring the time course of the iron content and may, for example, be two days or more, preferably one week or more. Conversely, with regard to the economic viability of the process and the risk of iron decomposition, the storage period is typically no longer than 12 weeks. Thus, a typical storage period is 1–12 weeks, preferably 1–8 weeks, and particularly preferably 1–4 weeks.

[0025] Iron-containing iris butter is extracted from aged rhizomes using conventional methods, such as steam distillation or extraction with solvents like supercritical carbon dioxide. Examples Example 1:

[0026] Rhizomes of Iris germanica of Moroccan origin are used. The fresh rhizomes are peeled and cut into pieces approximately 2 cm long. These are then subjected to different drying methods. Some are dried in an adsorption dryer in an air stream at 45°C, while others are dried in a heated vacuum oven at 50°C until a constant weight (approximately 30-40%) is achieved. The pieces are then placed in stainless steel pressure bombs, which are filled with oxygen (20-30 bar at 25°C) and sealed gas-tight before being placed in an oil bath at 50°C. Rhizome pieces from the same batch stored in ambient air serve as a negative control.

[0027] Samples from the negative control were taken after 1, 2, and 4 weeks, and samples from the pressure bombs were taken after 1, 2, 4, 6, 10, and 12 weeks and analyzed for their iron content. While the iron content of the negative control remained low at values ​​between 10 and 30 mg / kg over 4 weeks, it increased sharply in the samples from the pressure bombs (see Figures 1 and 2). In rhizomes dried in the adsorption dryer, a maximum total iron content of 496 mg / kg was reached after 2 weeks ( Figure 1 ). In rhizomes dried in a vacuum drying oven, the maximum was 358 mg / kg and was reached after 4 weeks ( Figure 2 It can also be observed that the ratio of the isomers cis-α-iron to γ-iron changes in favor of γ-iron if the rhizomes remain in the pressure bombs for a longer period of time.

[0028] For iron analysis, 0.5 g of the rhizomes are finely ground for each sample and mixed with 100 µl of a methanolic ionone solution with a concentration of 10 mg / ml as an internal standard, corresponding to an addition of 1 mg of ionone per sample. The samples are then mixed with 5 ml of diethyl ether and extracted in an ultrasonic bath for 15 min. The supernatant is removed, and the extraction is repeated with 3 ml of diethyl ether and 5 min in an ultrasonic bath. The supernatants of each sample are combined, concentrated in a nitrogen stream, and, after filtration through syringe filters, serve as the analytical solution. The samples are measured in a gas chromatograph with a flame ionization detector. Quantification is performed by comparing the peak areas of the internal standard ionone with those of the iron isomers. To determine a correction factor, the peak areas of equal amounts of ionone and an authentic mixture of the iron isomers are compared. Example 2:

[0029] Rhizomes of Iris germanica of Moroccan origin are used. The fresh rhizomes are peeled and cut into pieces approximately 2 cm in size and dried in a drying oven at 45 °C. The dried rhizomes are then ground into a powder (particle size approximately 1 mm). Further processing is carried out as described in Example 1.

[0030] For comparison, a three-year-old iris sample (naturally aged) was extracted using the same procedure as described in Example 1 and measured. The results are in Figure 3 As shown, analogous to Example 1, the iron content increases sharply after 1, 2, 3, 4, and 5 weeks using the artificial aging method according to the invention, while the iron content of the rhizomes stored openly in ambient air (control) remains low. After just 1 week of artificial aging, the iron content of these rhizomes exceeds that of the rhizomes stored for 3 years ( Figure 3 ). Description of the illustrations

[0031] Figure 1 Iron content of differently treated, freshly dried (adsorption drying) iris rhizomes (Iris germanica). The iron isomer content of the three control groups (Contr.) was significantly lower after 1, 2, and 4 weeks of storage in ambient air than in rhizomes stored for 1, 2, 4, 6, 10, and 12 weeks under an oxygen atmosphere (20–30 bar at 25°C) and elevated temperature (50°C) (O₂). The total iron content is given in mg / kg. Figure 2Iron content of differently treated, freshly dried (vacuum drying oven) iris rhizomes (Iris germanica). The iron isomer content of the three control groups (Contr.) was significantly lower after 1, 2, and 4 weeks of storage in ambient air than in rhizomes stored for 1, 2, 4, 6, 10, and 12 weeks under an oxygen atmosphere (20–30 bar at 25°C) and elevated temperature (50°C) (O₂). However, in this experiment, the maximum iron content was reached after 4 weeks. The total iron content is given in mg / kg. Figure 3Iron content of differently treated, freshly dried (drying oven, forced air) iris rhizomes (Iris germanica). The iris rhizomes were pulverized after drying. The iron isomer content of the five control groups (Contr.) was significantly lower after 1, 2, 3, 4, and 5 weeks of storage in ambient air than in rhizomes stored for 1, 2, 3, 4, and 5 weeks under an oxygen atmosphere (20–30 bar at 25°C) and elevated temperature (50°C) (O₂). The total iron content is given in mg / kg.

Claims

1. Method for accelerating the ageing of iris rhizomes which comprises the storage of iris rhizomes under oxygen-containing atmosphere which at 25°C has an oxygen partial pressure of 0.5 bar or more and a temperature of 25°C or more.

2. Method according to claim 1, wherein irises of the species Iris germanica, Iris pallida, Iris pallida argentea variegata, Iris pallida aurea variegata, Iris pallida alba, Iris neglecta, Iris spectabilis, Iris macedonica, and / or other varieties of the bart iris (Iris barbata) are used.

3. Method according to claim 1 or 2, wherein peeled and / or unpeeled cut and / or pulverised and / or whole rhizomes are used.

4. Method according to at least one of claims 1 to 3, which comprises drying of the rhizomes before storage.

5. Method according to at least one of claims 1 to 4, wherein the atmosphere at a temperature of 25°C has an oxygen partial pressure of 2 bar or more, preferably 5 bar or more.

6. Method according to at least one of claims 1 to 5, wherein a pure oxygen atmosphere is used.

7. Method according to at least one of claims 1 to 6, wherein the temperature during storage is 25-80°C.

8. Method according to at least one of claims 1 to 7, wherein the storage period is at least two days, preferably at least one week.

9. Method according to at least one of claims 1 to 8, wherein storage is carried out in an autoclave.

10. Method for recovering iris butter from iris rhizomes which comprises carrying out the method according to one of claims 1 to 9 and after storage carrying out extraction or steam distillation or that is to say hydrodistillation.