Process for coating seed, and coated seed

Abstract

The invention relates to a method for coating seed, comprising the steps of: - providing an aqueous coating solution comprising a gelatine having a Bloom value of approximately 150 g or less and a viscosity of approximately 2.5 mPa∙s or less, the viscosity in a 6.67% gelatine solution being measured at 60°C; and - applying the coating solution to the surface of the seed and letting the coating solution dry in order to obtain a gelatine-based coating on the seed.

Description

[0001]A 501001 p Applicant: GELITA AG April 30, 2024 Uferstrasse 7 p-295 69412 Eberbach Method for coating seeds and coated seeds The present invention relates to a method for coating seeds. The invention further relates to seeds coated according to this method. It is known to coat seeds before sowing. Such a coating can, on the one hand, serve to protect the seeds during storage and transport. However, the coating can primarily be used to promote growth by adding plant nutrients and / or plant protection agents, which are released from the coating after sowing. Known coating materials for seeds often contain synthetic polymers such asPolyvinyl acetate, polyvinyl alcohol, polyvinylpyrrolidone, or polyacrylates, which are not or only very poorly biodegradable and therefore lead to environmental pollution of the soil and groundwater, particularly in the form of microplastics. The invention is based on the object of proposing a method for coating seeds which leads to a biodegradable coating. This object is achieved according to the invention by a method for coating seeds, comprising the steps: - providing an aqueous coating solution comprising a gelatin with a bloom value of approximately 150 g or less and a viscosity of approximately 2.5 mPa∙s or less, wherein the viscosity is measured on a 6.67% gelatin solution at 60°C; and A 501001 p 30.April 2024 p-295 - 2 - - Applying the coating solution to the surface of the seed and allowing the coating solution to dry to obtain a gelatin-based coating on the seed. In the process according to the invention, the seed is provided with a gelatin-based coating. The use of gelatin has long been known in various technical fields, in particular in the food and pharmaceutical industries. As an extraction product from the collagen of animal connective tissue, gelatin is completely biodegradable and harmless to health and the environment. The physical and rheological properties of gelatin are characterized in particular by the bloom value, i.e., the gel strength, and the viscosity. The standard methods for determining these two parameters are described in the GME monograph "Standardized Methods for the Testing of Edible Gelatin."All bloom values ​​and viscosities mentioned in the context of this invention are to be determined according to these standard methods. In order to coat seeds with gelatin, the gelatin must, on the one hand, exhibit sufficient gelation and film formation in order to form an effective protective layer on the seeds. On the other hand, the aqueous coating solution should be easy to process with the available coating devices, and in particular, it should have good sprayability. These two requirements for the properties of the gelatin used are contradictory. However, within the scope of the present invention, it has surprisingly been found that a gelatin with a bloom value of approximately 150 g or less and a viscosity of approximately 2.5 mPa·s or less is excellently suited for coating seeds.The coating process can be carried out using known devices, resulting in an abrasion-resistant coating on the seeds. Furthermore, the dried coating is non-sticky, and the seeds are thus free-flowing. In the process according to the invention, the application of the coating solution to the surface of the seeds and the drying of the coating solution take place essentially simultaneously within the framework of a continuous process. Advantageously, the coating solution is sprayed onto the surface of the seeds, and various known coating devices can be used for this purpose, in particular a drum coater, a rotary coater, a coating pan, or a fluidized-bed dryer. The spray rate of the aqueous coating solution is typically in the range of 200 to 500 g / h. The coating solution is preferably at a temperature of approx.50°C or more, more preferably of approximately 55°C or more, applied, in particular sprayed, to the surface of the seed. At this temperature, the coating solution has a sufficiently low viscosity to be easily processed. Higher temperatures above 60°C are generally unfavorable, as they can lead to thermal degradation of the gelatin. The coating solution is advantageously applied and allowed to dry at a temperature of approximately 30 to approximately 60°C. The evaporation of the water from the coating solution at these temperatures results in the gelatin-based coating on the seed. The amount of coating solution applied to the seed can vary over a relatively wide range depending on the type of seed and the precise purpose of the coating. Typically, the coating solution is applied in an amount of approximately 50 to approximately 1.000 g per kilogram of seed onto its surface. The gelatin used in the coating solution according to the invention has a viscosity of approximately 2.5 mPa∙s or less. More preferably, the viscosity of the gelatin is approximately 2.3 mPa∙s or less, in particular approximately 2.1 A 501001 p April 30, 2024 p-295 - 4 - mPa∙s or less, in each case measured on a 6.67% gelatin solution at 60°C. The gelatin can be produced from a collagen-containing starting material from the skin or bones of mammals. The collagen-containing starting material is, in particular, pork rind. It has been shown that pork rind gelatin can be used particularly advantageously within the scope of the invention. The gelatin can be a type A or type B gelatin, or a mixture thereof. Very suitable within the scope of the invention is, for example,an acid-digested pork rind gelatin of type A with a Bloom value in the range of approximately 100 g and a viscosity in the range of approximately 2 mPa∙s. However, type B gelatins, such as bovine bone gelatin, with corresponding viscosity and Bloom values ​​can also be used. Various gelatins can also be characterized based on their molecular weight or molecular weight distribution, with the molecular weight correlating to a certain extent with the Bloom value. The gelatin for the process according to the invention preferably has a weight-average molecular weight of approximately 20 to approximately 100 kDa, more preferably of approximately 39 to approximately 84 kDa. The weight-average molecular weight of gelatin is determined in particular by means of gel permeation chromatography.To further optimize the rheological properties of the coating solution, depending on the type of gelatin used, it may be advantageous for the coating solution to further comprise one or more protein hydrolysates. These are preferably selected from collagen hydrolysate, hydrolysates of plant proteins, and mixtures thereof. Preferred plant proteins for producing corresponding hydrolysates are, in particular, soy proteins, wheat proteins, and whey proteins. A 501001 p April 30, 2024 p-295 - 5 - Collagen hydrolysate is produced from gelatin or directly from a collagen-containing starting material by chemical or enzymatic hydrolysis. Due to its low molecular weight, collagen hydrolysate has no gelling ability. The collagen hydrolysate used in the process according to the invention preferably has a weight-average molecular weight of approximately 0.5 to approximately 18 kDa, more preferably approximately 2 to approximately5 kDa, in particular from approximately 2.5 to approximately 3.5 kDa. By replacing part of the gelatin with collagen hydrolysate – or with another protein hydrolysate – the molecular weight distribution of the peptides contained in the coating solution as a whole can be specifically influenced. From this point of view, it is generally preferred if the coating solution comprises a proportion of at least approximately 10 wt.% gelatin and optionally protein hydrolysate with a molecular weight of up to 18 kDa, based on the total amount of gelatin and protein hydrolysate. Furthermore, it is preferred if the coating solution comprises a proportion of at least approximately 40 wt.% gelatin and optionally protein hydrolysate with a molecular weight of up to 39 kDa, based on the total amount of gelatin and protein hydrolysate. In a preferred embodiment of the invention, the coating solution comprises a total of approximately 5 to approximately 30 wt.% gelatin and optionally protein hydrolysate, preferably approximately 8 to approximately 20 wt.%. The coating solution may further comprise one or more crosslinking agents for gelatin, preferably selected from tannins, polyphenols, and aldehydes such as glyoxal, glutaraldehyde, and formaldehyde. Crosslinking the gelatin can influence the solubility and water absorption capacity of the coating, while the crosslinked gelatin also remains biodegradable, albeit possibly over a longer period. Natural crosslinking agents such as tannins or tannin-containing plant extracts are preferred. A 501001 p 30.April 2024 p-295 - 6 - Furthermore, it can be advantageous if the coating solution further comprises one or more plasticizers, which are preferably selected from sugar alcohols and sugars, in particular from glycerol, sorbitol, sorbitan, mannitol, maltitol, xylitol, glucose and sucrose, or from propylene glycol, polypropylene glycol and polyethylene glycol. Such plasticizers can increase the flexibility of the coating and reduce brittleness, as is known, for example, from the field of soft gelatin capsules. It is particularly advantageous if the coating solution further comprises one or more active ingredients, which are preferably selected from plant nutrients, growth-promoting substances and plant protection agents such as insecticides and fungicides. Such active ingredients in the coating, which are released into the soil after sowing, can specifically promote seed germination and plant growth.Aside from such active ingredients, the gelatin-based coating also has a growth-promoting effect due to its water absorption capacity: After sowing, the gelatin can absorb several times its own weight in water from the soil and form a hydrogel that optimizes the water supply to the seeds. In addition to gelatin, water, and the aforementioned ingredients, the coating solution can contain other components to specifically adapt the properties and / or functionality of the coating. In particular, the coating solution can comprise one or more additives and / or fillers selected from pigments such as titanium dioxide and iron oxides, minerals such as bentonites and kaolin, biodegradable fibers such as cellulose and keratin, polysaccharides such as starch and chitosan, or mixtures thereof.The method according to the invention is suitable for coating any type of seed. The seed is preferably selected from cereal seeds such as wheat, rye, barley, oats, corn, rice, and millet; from seeds of legumes such as beans, peas, lentils, soybeans, chickpeas, sweet peas, and lupins; from pseudocereal seeds such as buckwheat, quinoa, and amaranth; or from oilseeds such as rapeseed, linseed, and sunflowers. The method according to the invention can also be used for the seeds of other types of crops or ornamental plants. The present invention further relates to the use of an aqueous coating solution for coating seeds, wherein the coating solution comprises a gelatin having a bloom value of approximately 150 g or less and a viscosity of approximately 2.5 mPa·s or less, wherein the viscosity is measured on a 6.67% gelatin solution at 60°C.Particular advantages and preferred embodiments of the use according to the invention have already been explained in connection with the process according to the invention. Furthermore, the invention relates to seed with a gelatin-based coating, wherein the seed is produced according to the process according to the invention. Particular advantages and preferred embodiments of the seed according to the invention have likewise already been explained in connection with the process according to the invention. These and further advantages of the invention are explained in more detail with reference to the following exemplary embodiments, which, however, do not limit the subject matter of the invention in any way. Examples Gelatin types used and collagen hydrolysate A 501001 p April 30, 2024 p-295 - 8 - The commercially available gelatin types listed in Table 1 were used in the following exemplary embodiments to carry out the process according to the invention.These are Type A gelatins from porcine skin or bovine hide. Table 1. For gelatin type PS100, the molecular weight distribution determined by gel permeation chromatography is shown in Table 2: Table 2 A 501001 p April 30, 2024 p-295 - 9 - From this distribution, it is clear that the preferred gelatin types comprise a high proportion of relatively low-molecular-weight peptides with a molecular weight of up to 18 kDa, in the case of PS100, more than approximately 28 wt.%. By adding collagen hydrolysate, this proportion of low-molecular-weight peptides in the coating solution can be further increased, which also results in a reduction in the Bloom value and viscosity for the corresponding mixture of gelatin and collagen hydrolysate. In the following working examples, the mixtures of gelatin PS100 and a collagen hydrolysate with a weight-average molecular weight of 3.2 kDa (available under the name GELITA Peptiplus) listed in Table 3 were used: Table 3 Example 1: Coating of Seeds Using a Coating Pan Aqueous coating solutions with different gelatin types and, in some cases, varying gelatin concentrations were used to coat seeds using a coating pan, as shown in Table 4. The coating solutions also contain a pigment (titanium dioxide) to make the coating of the seeds visually recognizable. A 501001 p April 30, 2024 p-295 - 10 - Table 4 150 g of seed (chickpeas or green peas) were coated with these coating solutions in a coating pan. For this purpose, the solution is kept liquid above the setting temperature at approximately 60 °C and sprayed onto the seed, with a process temperature in the coating pan of 20 to 24 °C. The coating solution is sufficient to completely coat and color the seed. The result is a relatively thick coating that adheres very well to the seed and forms a stable film that dries very well, is abrasion-resistant, and non-sticky. Example 2: Coating of Seed Using a Drum Coater. For the coating of seeds using a drum coater with a spray head from Glatt, an aqueous coating solution consisting of 18 g of gelatin PS100, 3-5 g of pigment (FeOx), and 82 g of water was used.The temperature of the spray solution is 50-66 °C, the spray rate is 200 g / h, and the process temperature in the drum coater is 31-35 °C. In this case, just 5 to 10% of the total coating solution is sufficient to completely coat and color 100 g of seed (chickpeas or green peas). The entire coating solution results in a thick coating shell that adheres very well to the seed and forms a stable film that dries very easily. A 501001 p 30 April 2024 p-295 - 11 - Alternatively, it was also possible to completely coat and colour 100 g of seed using a 1:10 diluted gelatin solution (i.e. 1.8 g gelatin PS100, 98.2 g water and 3-5 g pigment) with the same process parameters, although the time required was significantly longer.Example 3: Coating with gelatin and collagen hydrolysate For the coating of seeds using a drum coater, the mixtures of gelatin PS100 and collagen hydrolysate according to Table 3 above were used in these examples. FeO was used as the pigment. x The specific compositions of the coating solutions and the process parameters are given in Table 5: Table 5 The coating was carried out in the drum coater as described in Example 2. The addition of collagen hydrolysate reduces the viscosity and gelling temperature of the coating solution, thus reducing the risk of clogging the lines if the spray solution temperature is too low. In all Examples 3.1 to 3.4, just 5 to 10% of the total coating solution is sufficient to completely coat and color 100 g of seed (chickpeas or green peas). A 501001 p April 30, 2024 p-295 - 12 - The entire coating solution results in a thick coating shell that adheres very well to the seed and forms a stable film that dries very easily.In these examples, it was also possible to completely coat and color 100 g of seed using a 1:10 diluted gelatin / collagen hydrolysate solution (but with the same pigment content) and the same process parameters, although the required time was significantly longer. Example 4: Coating of Seed with Additional Ingredients In these examples, a hydrophilic ingredient (ethanol) or a hydrophobic ingredient (medium-chain triglycerides, MCT) was added to the coating solution. These serve as model substances or as possible matrices / carriers for corresponding active ingredients that can be used in seed coating. The compositions are listed in Table 6: Table 6. The coating was carried out in the drum coater as described in Example 2. In these examples, too, 100 g of seed (chickpeas or green peas) could be completely coated and colored with 5 to 10% of the total coating solution, despite the addition of ethanol or MCT. The total coating solution results in a thick coating shell that adheres very well to the seed and forms a stable film that is very easy to dry. A 501001 p April 30, 2024 p-295 - 13 - In Example 4.2, it was also found that the addition of MCT reduced the stickiness of the coating, so this addition can also be used advantageously to reduce the risk of the individual coated seeds sticking together.Example 5: Addition of crosslinking agents. The coating solutions according to the above examples can additionally contain a crosslinking agent to extend the degradation time of the coating after sowing by crosslinking the gelatin. Crosslinking agents that can be used here include, for example, tannin powder (in an amount of 0.1 to 2 wt.%), olive leaf extract (0.1 to 15 wt.%), glyoxal (1,000 ppm), or glutaraldehyde (100 ppm), each based on the amount of the coating solution.

Claims

A 501001 p April 30, 2024 p-295 - 14 - Patent claims 1. A method for coating seeds, comprising the steps of: - providing an aqueous coating solution comprising a gelatin having a bloom value of approximately 150 g or less and a viscosity of approximately 2.5 mPa·s or less, the viscosity being measured on a 6.67% gelatin solution at 60°C; and - applying the coating solution to the surface of the seeds and allowing the coating solution to dry in order to obtain a gelatin-based coating on the seeds.

2. The method according to claim 1, wherein the coating solution is sprayed onto the surface of the seeds, in particular in a drum coater, a rotary coater, a coating pan, or a fluidized bed dryer.

3. Method according to one of the preceding claims, wherein the coating solution is at a temperature of approximately 50°C or more, preferably approximately55°C or more, is applied to the surface of the seed.

4. The method according to any one of the preceding claims, wherein the application and drying of the coating solution takes place at a temperature of approximately 30 to approximately 60°C.

5. The method according to any one of the preceding claims, wherein the coating solution is applied to the surface of the seed in an amount of approximately 50 to approximately 1,000 g per kilogram.

6. The method according to any one of the preceding claims, wherein the gelatin has a bloom value of approximately 125 g or less, preferably approximately 100 g or less. A 501001 p April 30, 2024 p-295 - 15 - 7. Process according to one of the preceding claims, wherein the gelatin has a viscosity of approximately 2.3 mPa∙s or less, preferably of approximately 2.1 mPa∙s or less, measured on a 6.67% gelatin solution at 60°C.

8. Process according to one of the preceding claims, wherein the gelatin is produced from a collagen-containing starting material from the skin or bones of mammals, in particular from pig rind.

9. Process according to one of the preceding claims, wherein the gelatin is an acid-digested type A gelatin, an alkaline-digested type B gelatin, or a mixture thereof.

10. The method according to any one of the preceding claims, wherein the gelatin has a weight-average molecular weight of approximately 20 to approximately 100 kDa, preferably approximately 39 to approximately 84 kDa. 11.Method according to one of the preceding claims, wherein the coating solution further comprises one or more protein hydrolysates, which are preferably selected from collagen hydrolysate, hydrolysates of vegetable proteins and mixtures thereof.

12. Method according to claim 11, wherein the collagen hydrolysate has a weight-average molecular weight of approximately 0.5 to approximately 18 kDa, preferably approximately 2 to approximately 5 kDa, more preferably approximately 2.5 to approximately 3.5 kDa.

13. Method according to one of the preceding claims, wherein the coating solution contains a proportion of at least approximately 10 wt.% of gelatin and optionally protein hydrolysate with a molecular weight of up to. A 501001 p April 30, 2024 p-295 - 16 - to 18 kDa, based on the total amount of gelatin and protein hydrolysate.

14. The method according to any one of the preceding claims, wherein the coating solution comprises a proportion of at least approximately 40 wt.% of gelatin and optionally protein hydrolysate with a molecular weight of up to 39 kDa, based on the total amount of gelatin and protein hydrolysate.

15. The method according to any one of the preceding claims, wherein the coating solution comprises a total of approximately 5 to approximately 30 wt.% gelatin and optionally protein hydrolysate, preferably approximately 8 to approximately 20 wt.%.

16. The method according to any one of the preceding claims, wherein the coating solution further comprises one or more crosslinking agents for gelatin, preferably selected from tannins, polyphenols, and aldehydes such as glyoxal, glutaraldehyde, and formaldehyde. 17.Method according to one of the preceding claims, wherein the coating solution further comprises one or more plasticizers, which are preferably selected from sugar alcohols and sugars, in particular from glycerol, sorbitol, sorbitan, mannitol, maltitol, xylitol, glucose and sucrose, or from propylene glycol, polypropylene glycol and polyethylene glycol.

18. Method according to one of the preceding claims, wherein the coating solution further comprises one or more active ingredients, which are preferably selected from plant nutrients, growth-promoting substances and plant protection agents such as insecticides and fungicides.

19. Method according to one of the preceding claims, wherein the coating solution further comprises one or more additives and / or fillers. A 501001 p April 30, 2024 p-295 - 17 - which are selected from pigments such as titanium dioxide and iron oxides, from minerals such as bentonites and kaolin, from biodegradable fibers such as cellulose and keratin, from polysaccharides such as starch and chitosan, or from mixtures thereof.

20. The method according to any one of the preceding claims, wherein the seed is selected from cereal seeds such as wheat, rye, barley, oats, corn, rice and millet, from seeds of legumes such as beans, peas, lentils, soybeans, chickpeas, sweet peas and lupins, from pseudocereal seeds such as buckwheat, quinoa and amaranth, or from oilseeds such as rapeseed, linseed and sunflowers.

21. Use of an aqueous coating solution for coating seeds, wherein the coating solution comprises a gelatin having a bloom value of approximately 150 g or less and a viscosity of approximately2.5 mPa.s or less, wherein the viscosity is measured on a 6.67% gelatin solution at 60°C.

22. Seed with a gelatin-based coating, wherein the seed is produced according to the method of any one of claims 1 to 20. * * *.

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