Method for reducing the content of cyanogenic compounds in plant seeds
Patent Information
- Application Number
- EP2023711720
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-03-14
- Filing Date
- 2023-03-14
- Publication Date
- 2025-01-22
AI Technical Summary
Existing methods for depleting cyanogenic compounds in plant seeds, such as boiling or soaking, are harsh and destroy valuable flavors and proteins, making them unsuitable for food or animal feed unless processed, which results in a loss of sensory quality and integrity.
The use of electroporation, specifically Pulsed Electric Fields (PEF), to treat plant seeds, followed by drying under vacuum, which effectively reduces cyanogenic compounds without damaging the seeds, preserving their sensory qualities and ingredients.
This method produces edible plant seeds with significantly reduced cyanogenic compounds, maintaining their integrity and quality, making them suitable for human consumption while being gentle and scalable for large-scale use.
Smart Images
Figure 1.1
Abstract
Description
[0001] Process for the depletion of cyanogenic compounds in plant seeds
[0002] The field of the present invention is that of methods for depleting cyanogenic compounds in plant seeds.
[0003] Many plant seeds (especially flaxseeds and stone fruit kernels) contain cyanogenic compounds such as cyanogenic glycosides (e.g., amygdalin or linustatin). Since various enzymes convert these cyanogenic compounds into toxic hydrogen cyanide when the seeds are consumed, the seeds are toxic to consumers above a certain dose and therefore unsuitable for use as food or animal feed unless appropriately processed beforehand.
[0004] A common method for detoxification ("debittering") is to boil the plant seeds to deactivate the enzymes ultimately responsible for releasing hydrogen cyanide from the cyanogenic compounds. However, this destroys valuable flavors.
[0005] Another well-known approach—and often associated with boiling—is to soak the plant seeds in water for a longer period (usually about 24 hours) to promote the conversion of the cyanogenic compounds and the concomitant release of hydrogen cyanide. The hydrogen cyanide-containing water is then discarded. However, boiling or rinsing destroys or washes out flavors and proteins.
[0006] Sensorially, seeds that have been "debittered" using conventional methods, under which name they are often marketed, are of significantly poorer quality than before debittering.
[0007] The documents CN 110547391 A, CN 210988069 U and CN 210988068 U concern detoxification processes for linseed.
[0008] Yamashita et al. ("Development of a method to remove cyanogen glycosides from flaxseed meal." International Journal of food science & Technology 42.1 (2007) : 70-75.) concerns the detoxification of pressed flaxseed. In the disclosed process, defatted flaxseed is incubated for 18 hours in 0.1M sodium citrate buffer and then dried in a continuous steam oven at 120°C. However, this process has numerous disadvantages. These include the long incubation time, the high drying temperatures, and the use of the acidity regulator sodium citrate (E331). This process is also not well suited for large-scale use. Furthermore, the harsh processing conditions impair the flavor of the flaxseed and result in a loss of other valuable ingredients (particularly proteins).
[0009] Tuncel et al. have published two papers on debittering apricot kernels. The first describes cell disruption by grinding, cooking, and soaking bitter apricot kernels (Tuncel, G., M.J.R. Nout, and L. Brimer. "The effects of grinding, soaking, and cooking on the degradation of amygdalin of bitter apricot seeds." Food Chemistry 53.4 (1995): 447-451). A second study investigates the effect of heat exposure on the endogenous enzyme and the addition of exogenous enzymes, in addition to particle size (Tuncel, G., M.J.R. Nout, and L. Brimer. "Degradation of cyanogenic glycosides of bitter apricot seeds (Prunus armeniaca) by endogenous and added enzymes as affected by heat treatments and particle size." Food Chemistry 63.1).
[0010] (1998): 65-69). GN 105341629 A also discloses a process for debittering apricot kernels. In El-Adawy et al. ("Biochemical studies of some non-conventional sources of proteins Part 7. Effect of detoxification treatments on the nutritional quality of apricot kernels." Food / Nahrung 38.1 (1994): 12-20.), the quality of apricot kernels is investigated after a debittering process.
[0011] The debittering processes described above, which are state-of-the-art, are all relatively harsh, resulting in the loss of valuable plant seed components and severely impairing their sensory properties. In many cases, the integrity (bite) of the plant seeds cannot be maintained, for example, because milling steps are required.
[0012] It is therefore an object of the present invention to provide a debittering process that overcomes at least one disadvantage of the prior art. In particular, it is desirable that this process be as gentle as possible (so that, for example, the flavor, as well as the overall sensory properties, and valuable ingredients of the plant seeds are preserved as much as possible, and the plant seeds remain as intact or firm as possible) and is well suited for large-scale use.
[0013] The present invention provides a method for depleting cyanogenic compounds in plant seeds, comprising the following steps: a) providing plant seeds, wherein the plant seeds contain cyanogenic compounds, b) treating the plant seeds with electroporation, in particular pulsed electric fields (PEF), and c) depleting cyanogenic compounds in the plant seeds treated (by electroporation). This method has been found to be particularly suitable for linseed and stone fruit kernels.
[0014] In one aspect, the present invention relates to treated plant seeds obtainable by this process.
[0015] In a further aspect, the invention provides treated plant seeds, preferably linseed or stone fruit kernels. The content of cyanogenic compounds in the treated plant seeds is so low that, based on the total mass of the treated plant seeds, less than 1000 mg / kg, preferably less than 800 mg / kg, more preferably less than 600 mg / kg, even more preferably less than 400 mg / kg or even less than 300 mg / kg, in particular less than 200 mg / kg or even less than 150 mg / kg of hydrocyanic acid can be released. In particular in the case of stone fruit kernels such as apricot kernels, the content of cyanogenic compounds in the treated plant seeds is preferably so low that, based on the total mass of the treated plant seeds, less than 50 mg / kg, preferably less than 25 mg / kg, even more preferably less than 20 mg / kg or even less than 15 mg / kg can be released.At least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 40% or even at least 50%, in particular at least 60% or even at least 70% of the cells of these treated plant seeds have pores in the cell membrane.
[0016] The process according to the invention is particularly gentle and well-suited for large-scale application. Treatment with electroporation (especially PEF) considerably simplifies the subsequent depletion step without being too harsh. The process according to the invention produces safely edible plant seeds that meet the highest quality standards. In other words, the treated plant seeds are suitable for human consumption.
[0017] In particular, the method according to the invention is suitable for plant seeds which are whole or intact ("whole seeds") and have a higher content of cyanogenic compounds, in particular linseed or stone fruit kernels which have a higher content of cyanogenic compounds. According to a preferred embodiment, the content of cyanogenic compounds (in particular of cyanogenic glycosides) in the plant seeds (in particular in the linseed or stone fruit kernels) is determined before depletion or in step a) of the process (in other words in the plant seeds provided) in such a way that more than 200 mg / kg, preferably more than 400 mg / kg, more preferably more than 600 mg / kg, even more preferably more than 800 mg / kg or even more than 1000 mg / kg, in particular more than 1200 mg / kg or even more than 1400 mg / kg (or even more than 2000 mg / kg) of hydrogen cyanide can be released (preferably based on the dry mass of the plant seeds).Electroporation is traditionally used in the food industry for preservation, especially for liquid foods; see, for example, Toepfl, S., V. Heinz, and D. Knorr. "High intensity pulsed electric fields applied for food preservation." Chemical engineering and processing: Process intensification 46.6 (2007): 537-546. Barba et al. (Barba, Francisco J., et al. "Current applications and new opportunities for the use of pulsed electric fields in food science and industry." Food research international 77 (2015): 773-798.) provides an overview of the use of pulsed electric fields in food technology. In Boussetta et al. In turn, the effect of pulsed electric fields on polyphenol extraction from flaxseed hulls - but not flaxseed - is investigated (Boussetta, Nadia, et al. "Valorization of oilseed residues: Extraction of polyphenols from flaxseed hulls by pulsed electric fields." Industrial Crops and Products 52 (2014) : 347-353. ).
[0018] However, in the course of the present invention, it has surprisingly been found that electroporation is suitable for treating plant seeds in order to increase the effectiveness of the subsequent depletion of cyanogenic compounds.
[0019] Typically, the plant seeds are soaked in an aqueous solution (e.g., tap water) before electroporation (with mixing if necessary). This increases the efficiency of electroporation. The aqueous solution can then be removed from the plant seeds, for example, by filtration.
[0020] The depletion of cyanogenic compounds can then be achieved, for example, simply by drying the plant seeds, because the converted hydrogen cyanide escapes during this process. Particularly in the case of linseed, sufficiently low concentrations of cyanogenic compounds can be achieved in this way. According to a preferred embodiment, the plant seeds are dried after electroporation, or step c) comprises drying the plant seeds. Preferably, drying is carried out to a residual moisture content of less than 20 wt.%, preferably less than 15 wt.%, even more preferably less than 10 wt.%, or even less than 7.5 wt.%, in particular less than 5 wt.%.
[0021] However, to accelerate or increase the depletion efficiency, the depletion step is carried out at least partially under vacuum in a preferred embodiment. It is evident to those skilled in the art that "under vacuum" in this (industrial-scale) context does not mean that an absolute vacuum is achieved, but merely that a significant degree of negative pressure is generated. Preferably, "under vacuum" should be understood to mean that a pressure of 600 mbar, preferably 500 mbar, more preferably 400 mbar, even more preferably 350 mbar, or even 300 mbar is temporarily undershot (e.g., for at least 15 minutes, preferably at least 30 minutes, more preferably at least 60 minutes, in particular at least 120 minutes or even at least 360 minutes).
[0022] The use of two vacuum stages has proven particularly advantageous (see also Fig. 2). Therefore, step c) preferably comprises the depletion of cyanogenic compounds in a first vacuum stage and a second vacuum stage, wherein the pressure of the first vacuum stage is higher than the pressure of the second vacuum stage. The pressure of the first vacuum stage is preferably between 300 and 500 mbar. The pressure of the second vacuum stage is preferably below 200 mbar, more preferably below 150 mbar, in particular below 100 mbar.
[0023] Additionally or alternatively, heating has proven useful for accelerating the depletion process. Consequently, in a further preferred embodiment, step c) is carried out at least partially with heating (preferably so that a temperature between 30°C and 80°C is achieved). If multiple vacuum stages are used, the temperature during the first vacuum stage (preferably 30°C to 40°C) is expediently lower than during the second vacuum stage (preferably 40°C to 80°C). According to a further preferred embodiment, step c) is carried out at least partially at more than 25°C, preferably more than 30°C, more preferably more than 35°C, even more preferably more than 40°C, in particular more than 45°C or even more than 50°C (at atmospheric pressure or under vacuum).
[0024] Furthermore, for a uniform and controlled process, it is advantageous if step c) is carried out at least partially with mixing.
[0025] In a particularly preferred embodiment of the process according to the invention, the plant seeds (or the treated plant seeds) remain substantially intact (in particular, firm to the bite). In other words, they remain whole and are not crushed (ground).
[0026] Usually, the plant seeds treated according to the invention are no longer capable of germination (due to electroporation).
[0027] It is particularly preferred if the content of cyanogenic compounds (in particular of cyanogenic glycosides) in the plant seeds treated according to the invention is so low that less than 1000 mg / kg, preferably less than 800 mg / kg, more preferably less than 600 mg / kg, even more preferably less than 400 mg / kg or even less than 300 mg / kg, in particular less than 200 mg / kg or even less than 150 mg / kg of hydrocyanic acid can be released (preferably based on the dry mass of the plant seeds).
[0028] Sometimes the treated plant seeds have a residual content of cyanogenic compounds such that, in relation to the total mass of the treated plant seeds, more than 1 mg / kg or even more than 2 mg / kg, preferably more than 5 mg / kg or even more than 10 mg / kg, more preferably more than 20 mg / kg, even more preferably more than 50 mg / kg or even more than 75 mg / kg, in particular more than 100 mg / kg or even more than 125 mg / kg, of hydrogen cyanide can be released (preferably based on the dry mass of the plant seeds). For example, the residual content in linseed can be more than 50 mg / kg or more than 100 mg / kg. In stone fruit kernels (in particular apricot kernels), the residual content can be, for example, more than 5 mg / kg or more than 10 mg / kg.
[0029] Furthermore, it is particularly preferred if at least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 40% or even at least 50%, in particular at least 60% or even at least 70% of the cells of the treated plant seeds have pores in the cell membrane. This has, among other advantages, that these plant seeds are better suited for further treatment steps (e.g. enrichment with vitamins by temporarily soaking in vitamin solutions or leaching sugar from the seeds or treatment steps for which increased swelling capacity is useful). The porous cells can usually be stained with propidium iodide (in other words, successful electroporation can be detected). Propidium iodide is a DNA-intercalating dye that does not penetrate the membrane of healthy cells.The number of stained cells can then be determined using a fluorescence microscope, for example, while the total number can be determined by counting in a light microscope. The use of propidium iodide to detect electroporation is shown, for example, in Steuer, Anna. Effects of nanosecond pulsed electric fields on cells in a monolayer. Dissertation, University of Rostock, 2016 (especially section 2.5 "Detection of Electroporation" on p. 24).
[0030] The treated plant seeds are typically in dry form. It is preferred that the treated plant seeds have a residual moisture content of less than 20 wt%, preferably less than 15 wt%, even more preferably less than 10 wt% or even less than 7.5 wt%, in particular less than 5 wt%. The invention is explained in more detail below with reference to preferred, non-limiting examples and drawings. Fig. 1 schematically shows an embodiment of the method according to the invention.
[0031] Fig. 2 shows schematically an embodiment of the depletion of cyanogenic compounds (ie step c).
[0032] Example 1 - Electroporation and depletion of cyanogenic compounds in cherry stone seeds
[0033] Cherry stone seeds with an initial cyanide content of 1500 mg / kg are mixed with water in a ratio of 1:4 (w / w) (e.g. 300 g seeds and 1200 g water) and soaked at room temperature for 1 h.
[0034] Dry matter raw material before soaking: 94.32%, dry matter after soaking: 45%.
[0035] The swollen seeds are treated in a PEF treatment cell with the following parameters:
[0036] Treatment cell: Batch - 9 cm electrode spacing (parallel) Pulse shape: Rectangular pulse
[0037] Number of pulses: 4000 pulses (2 cycles of 2000 pulses each - stirred between cycles)
[0038] Field strength: 10 kV / cm
[0039] Pulse width: 5 ps
[0040] Frequency: 30 Hz
[0041] Total amount: 1.8 kg
[0042] Conductivity water: 360 pS
[0043] The treated seeds are then incubated for 2 hours at room temperature and then dried either for 2 hours at 50°C hot air in a drum dryer or for 19 hours at 50°C hot air in a drying cabinet (tray drying). This depletes cyanogenic compounds. (Alternatively or additionally, the depletion process shown schematically in Fig. 2 can also be used.)
[0044] Dry matter content after 2 hours of drum drying: 95.68% and after 19 hours of oven drying: 96.7%. Cyanide concentration after drying, calculated on dry matter, is < 1000 mg / kg.
[0045] A simplified, schematic representation of the process is shown in Fig. 1.
[0046] Example 2 - Depletion of cyanogenic compounds in electroporated flaxseed
[0047] Electroporated linseed is mixed with water in a vacuum tank at a vacuum of 300-500 mbar and a temperature of 45°C (vacuum stage 1). At this temperature-pressure combination, the cyanide can evaporate, but the water cannot. The process is continued until the desired amount of cyanide has been extracted (or the specified cyanide concentration limit, e.g., 150 mg / kg, has been reached). The vacuum and temperature are then increased to evaporate the water (vacuum stage 2). This is then collected in a condenser. By separating the two phases, it can be ensured that the cyanide does not migrate into the evaporated water, but can be separated. During the evaporation process, the reactor is continuously purged with a non-reactive gas such as nitrogen to ensure better removal of HCN gas. When the desired degree of dryness (e.g.,Once the residual moisture content (7% by weight) has been reached, the process is terminated. The duration of vacuum stage 1, for example, is 2 hours, and that of vacuum stage 2, for example, is also 2 hours.
[0048] The treated flaxseeds obtained after the depletion process are ideally suited for further use in the food and feed industries.
Claims
Patent claims 1. A method for removing cyanogenic compounds from plant seeds, comprising the following steps: a) providing plant seeds containing cyanogenic compounds, b) treating the plant seeds with electroporation, in particular pulsed electric fields (PEE), and c) removing cyanogenic compounds from the treated plant seeds.
2. Method according to claim 1, wherein the plant seeds are selected from flax seeds and stone fruit kernels.
3. Method according to claim 1 or 2, wherein step c) is carried out at least partially under vacuum.
4. Method according to claim 3, wherein step c) comprises the removal of cyanogenic compounds during a first vacuum stage and a second vacuum stage, wherein the pressure of the first vacuum stage is higher than the pressure of the second vacuum stage.
5. Method according to any one of claims 1 to 4, wherein step c) is carried out at least partially with heating, preferably wherein the temperature during the first vacuum stage is lower than during the second vacuum stage.
6. Method according to any one of claims 1 to 5, wherein step c) is carried out at least partially under mixing.
1. A method according to any one of claims 1 to 6, wherein the The plant seeds remain essentially intact.
8. Method according to any one of claims 1 to 7, wherein in step a) the content of cyanogenic compounds in the plant seeds is such that, with respect to the total mass of the plant seeds, more than 200 mg / kg, preferably more than 400 mg / kg, more preferably more than 600 mg / kg, even more preferably more than 800 mg / kg or even more than 1000 mg / kg, in particular more than 1200 mg / kg or even more than 1400 mg / kg hydrogen cyanide can be released.
9. Method according to any one of claims 1 to 8, wherein the plant seeds are dried, preferably to a residual moisture content of less than 20 wt%, preferably less than 15 wt%, even more preferably less than 10 wt% or even less than 7.5 wt%, in particular less than 5 wt%.
10. Method according to any one of claims 1 to 9, wherein step c) is carried out at least partially at more than 25°C, preferably more than 30°C, more preferably more than 35°C, even more preferably more than 40°C, in particular more than 45°C or even more than 50°C.
11. Treated plant seeds, preferably flax seeds or stone fruit kernels, obtainable according to the method of any one of claims 1 to 10, preferably wherein the content of cyanogenic compounds in the treated plant seeds is so low that, with respect to the total mass of the treated plant seeds, it is less than 1000 mg / kg, preferably less than 800 mg / kg, more preferably less than 600 mg / kg, even more preferably less than 400 mg / kg or even less than 300 mg / kg, in particular less Hydrogen cyanide can be released in amounts as low as 200 mg / kg or even less than 150 mg / kg.
12. Treated plant seeds according to claim 11, wherein at least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 40% or at least 50%, in particular at least 60% or at least 70% of the cells of the treated plant seeds have pores in the cell membrane, preferably wherein these porous cells are stainable with propidium iodide.
13. Treated plant seeds, preferably flax seeds or stone fruit kernels, wherein the content of cyanogenic compounds in the treated plant seeds is so low that, with respect to the total mass of the treated plant seeds, less than 1000 mg / kg, preferably less than 800 mg / kg, more preferably less than 600 mg / kg, even more preferably less than 400 mg / kg or even less than 300 mg / kg, in particular less than 200 mg / kg or even less than 150 mg / kg of hydrogen cyanide is releaseable, and wherein at least 10%, preferably at least 20%, more preferably at least 30%, even more preferably at least 40% or even at least 50%, in particular at least 60% or even at least 70% of the cells of the treated plant seeds have pores in the cell membrane, preferably wherein these porous cells are stainable with propidium iodide.
14. Treated plant seeds according to one of claims 11 to 13, wherein the treated plant seeds have a residual moisture content of less than 20 wt%, preferably less than 15 wt%, more preferably less than 10 wt% or even less than 7.5 wt%, in particular less than 5 wt%.
15. Treated plant seeds according to any one of claims 11 to 14, wherein the treated plant seeds have a residual content of cyanogenic compounds such that, in relation to the total mass of the treated plant seeds, more than 1 mg / kg, in particular more than 5 mg / kg, hydrogen cyanide can be released.