Method for preparing grape skin extract vegetable dye

Abstract

The invention discloses a method for preparing a grape skin extract vegetable dye, which comprises the following main steps: (1) extracting grape skin by using water as a solvent to form a grape skin extracting solution; (2) filtering the obtained grape skin extracting solution, and respectively collecting filtrate and filter residues; (3) centrifugally separating the filtrate obtained in the step (2), and collecting supernate; (4) the filter residues obtained in the step (2) are repeatedly operated according to the steps (1)-(3), clear liquid is combined, and a total extracting solution is obtained; (5) performing vacuum concentration on the total extracting solution to obtain a concentrated solution; (6) freezing the obtained concentrated solution at 0 to-5 DEG C in advance, and then freezing at-20 to-40 DEG C; and (7) after complete freeze-drying, crushing to obtain the grape skin extract vegetable dye. According to the method disclosed by the invention, the vegetable dye can be prepared at a relatively high yield under the condition of not using a chemical reagent.

Description

Technical Field

[0001] The invention belongs to the technical field of natural plant dyes, and in particular relates to a method for preparing a grape skin extract plant dye. Background Art

[0003] Studies have shown that grape skin pomace is a rich source of various nutrients, including protein, essential amino acids, polyunsaturated fatty acids, dietary fiber, polyphenol compounds, etc., and also contains natural pigments from grape skin. Due to its rich nutrients, grape skin has a wide range of physiological activities, including antioxidant, free radical elimination, inhibition of foodborne pathogenic microorganisms, fatigue relief, spot removal and whitening effects. Therefore, grape skin has a high development value. For example, the formaldehyde extract of grape skin pomace plays an important role in protecting and restoring the liver structure and normal physiological function. For another example, taking grape skin pomace as a dietary supplement at a dose of 250 mg kg per day -1 Continuously adding it to the normal diet for 5 weeks can give the human body certain antioxidant and anti-inflammatory effects.

[0004] Grape anthocyanins, flavonoids and other substances are the effective ingredients of grapes. The higher their content, the better the effect. Existing studies have shown that grape skins are discarded quickly, resulting in the use of many nutrients in them. The content of polyphenols in fresh grape skins is about 101.55-104.84 mg·g -1 As the main pigment of grape skin, proanthocyanidins account for 75% to 85% of the total phenolic content.

[0005] The extraction process of natural pigment dyes in grape skins has been reported to include methanol / ethanol extraction, ultrasonic extraction, enzyme method, microwave-assisted combined extraction, etc. The determined processes are as follows: ① Methanol solution immersion extraction, pH value 8.0, solid-liquid ratio of 1:40, ultrasonic assisted power of 650W, extraction time of 2.5h, extraction temperature of 60°C. ② Ethanol concentration of 70%, solid-liquid ratio of 1:30, extraction temperature of 60°C, extraction time of 1h. ③ Ethanol concentration of 95%, solid-liquid ratio of 1:20, extraction time of 4h, temperature of 50°C. The natural pigments extracted from grape skins by these methods have high purity, but low yield, and the process is complicated and requires the use of chemical solvents such as alcohols. And although no alcohol solvent is added in CN103665927A and only water is used as the extractant, the yield of the pigment dye obtained by this method is low. Summary of the invention

[0006] [Technical issues]

[0007] No chemical reagents are used in the process of extracting and preparing the pigment dye, and a good preparation yield is still achieved.

[0008] [Technical solution]

[0009] To solve the above problems, the present invention uses water as solvent to extract various active substances such as natural pigments in grape skin, and uses freeze-drying method to prepare grape skin plant dye. No chemical reagents are used in the whole preparation process to prepare natural grape skin dye.

[0010] To achieve the purpose of the present invention, the following main process steps are adopted: grape skin → extraction → filtration → centrifugation → re-extraction, filtration → concentration → freezing → freeze drying → uniform crushing → plant dye. Grape skin is obtained by using certain extraction conditions in water with a certain solid-liquid ratio, and the active substance is concentrated after filtering and centrifugation to obtain a pre-product. Subsequently, the freeze-dried method is adopted to freeze the substance containing a large amount of water into a solid by cooling in advance, and water vapor is directly sublimated from the solid under vacuum conditions, while the substance itself is left in the frozen rack, so that the freeze-dried product maintains its original state. After freeze-drying, the grape skin extract obtained after drying is loose and porous, which is conducive to crushing it easily. By evenly crushing it under a universal grinder, the grape skin plant dye can be obtained.

[0011] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0012] A method for preparing a grape skin extract plant dye comprises the following steps:

[0013] (1) extracting grape skins using water as a solvent to form a grape skin extract, wherein the mass of the water is 5-50 times the mass of the grape skins;

[0014] (2) filtering the obtained grape skin extract, and collecting the filtrate and the filter residue respectively;

[0015] (3) centrifuging the filtrate obtained in step (2) and collecting the supernatant;

[0016] (4) Repeating steps (1) to (3) with the residue obtained in step (2), combining the clear liquids, and obtaining a total extract;

[0017] (5) concentrating the total extract under reduced pressure to obtain a concentrated solution;

[0018] (6) freezing the obtained concentrated solution at 0 to -5°C in advance and then freezing it at -20 to -40°C;

[0019] (7) After being completely freeze-dried, the mixture is crushed to obtain a grape skin extract plant dye.

[0020] In one embodiment of the present invention, in step (1), grapes of different diameters are selected using a volume selection tool, and the selected grape skins are respectively from local ripe fresh grapes, and the diameters are respectively one or more of 0.5 cm, 0.8 cm, 1.0 cm, 1.2 cm, 1.5 cm, 1.8 cm, 2.0 cm, 2.2 cm, and 2.5 cm.

[0021] In one embodiment of the present invention, in step (1), water is used as a solvent to extract grape skin, and the solid-liquid ratio, i.e., the mass ratio of grape skin to water, is one of 1:5, 1:10, 1:15, 1:25, 1:30, 1:35, 1:40, 1:45, and 1:50.

[0022] In one embodiment of the present invention, in step (1), the extraction temperature is 50-95°C; specifically, one of 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 85°C, 90°C, and 95°C can be selected.

[0023] In one embodiment of the present invention, in step (1), the extraction time is 50-90 min; specifically, one of 50 min, 60 min, 70 min, 80 min, and 90 min can be selected.

[0024] In one embodiment of the present invention, in step (2), the grape skin extract is filtered using a metal screen with a mesh size of 200-500. The mesh size of the metal screen is selected to be one of 200 mesh, 300 mesh, 400 mesh and 500 mesh.

[0025] In one embodiment of the present invention, in step (3), centrifugal separation is performed at room temperature using a centrifuge to obtain a relatively transparent grape skin extract with a certain color, and the centrifugation method adopted is centrifugation at 3000-5000 rpm for 10-30 min. The specific centrifugation conditions can be selected from: centrifugation at a speed of 3000 rpm for 10 min, centrifugation at a speed of 3000 rpm for 20 min, centrifugation at a speed of 3000 rpm for 30 min, centrifugation at a speed of 4000 rpm for 10 min, centrifugation at a speed of 4000 rpm for 20 min, centrifugation at a speed of 4000 rpm for 30 min, centrifugation at a speed of 5000 rpm for 10 min, centrifugation at a speed of 5000 rpm for 20 min, and centrifugation at a speed of 5000 rpm for 30 min.

[0026] In one embodiment of the present invention, in step (4), the grape skin residue is extracted repeatedly using the above steps (1) to (3), and the grape skin extract is filtered using the above filtration process, and the number of repetitions is 0-6 times. Specifically, the number of repetitions is one of 0 times, 1 times, 2 times, 3 times, 4 times, 5 times and 6 times.

[0027] In one embodiment of the present invention, in step (5), the extract is concentrated under reduced pressure using a rotary evaporator for a concentration time of 20-80 min. The specific concentration time can be selected from 20 min, 40 min, 60 min, and 80 min.

[0028] In one embodiment of the present invention, in step (6), the concentrated liquid is pre-frozen at 0 to -5°C, and then placed in a freeze dryer for freezing, and the freezing process is characterized by: the cold trap temperature is -20 to -40°C, and the freezing time is 20-50 hours. Specifically, the cold trap temperature is one of -40°C, -35°C, -30°C, -25°C, and -20°C, and the freezing time is generally one of 50 hours, 40 hours, 30 hours, and 20 hours.

[0029] In one embodiment of the present invention, in step (7), the completely freeze-dried concentrated grape skin extract is placed in a high-speed universal grinder for grinding, the universal grinder has a rotation speed of 16000-24000 rpm, and the grinding time is 30-60s. Specifically, the universal grinder has a rotation speed of 16000 rpm, 18000 rpm, 20000 rpm, 22000 rpm, and 24000 rpm, and the grinding time is 30s, 40s, 50s, and 60s.

[0030] The present invention provides a grape skin extract plant dye based on the method.

[0031] The invention also provides application of the grape skin extract plant dye in the field of dyeing.

[0032] The beneficial effects of the present invention are:

[0033] The invention provides a method for preparing a grape skin extract plant dye. No other chemicals are involved in the preparation process of the grape skin extract plant dye. Only water is used to extract various active substances in the grape skin, and a good yield can be achieved.

[0034] At the same time, various physical methods are used to retain the active substances in the grape skin. A large amount of polyphenols in the grape skin and its own natural pigments are retained in the active substances. This grape anthocyanin can be prepared as a natural dye. The grape skin plant dye prepared by freezing and lyophilizing the concentrate can release natural pigments and has the potential to be used in dyeing textiles. At the same time, this natural grape skin extract plant dye is non-toxic and harmless to the human body and has various beneficial effects. DETAILED DESCRIPTION

[0035] The present invention is further described below through specific examples, but the embodiments of the present invention are not limited thereto.

[0036] In the following embodiments, grapes with a diameter greater than 1.8 cm are selected and their grape skins are used as raw materials for preparing grape skin extract plant dye.

[0037] Embodiment 1:

[0038] A method for preparing a grape skin extract plant dye comprises the following steps:

[0039] S1: Extraction

[0040] After selecting the raw materials, grape skin is used as solvent to extract the grape skin to obtain grape skin extract. The extraction process conditions are: the mass of water is 20 times the mass of grape skin, that is, the material-liquid ratio is 1:20, the extraction temperature is 70°C, and the extraction time is 60 minutes.

[0041] S2: Filter

[0042] The grape skin extract was filtered using a metal sieve with a mesh size of 400, and the obtained filtrate and filter residue were separated.

[0043] S3: Centrifugation

[0044] The collected filtrate is centrifuged at 4000 rpm using a centrifuge at room temperature to obtain a relatively transparent supernatant with a certain color.

[0045] S4: Extraction and filtration again

[0046] The above-mentioned S1-S3 was repeated twice to extract the grape skin residue, and the supernatants were combined to obtain a total extract.

[0047] S5: Decompression and concentration

[0048] The total extract was concentrated under reduced pressure using a rotary evaporator, and the concentration time was set to 40 min to obtain a grape skin concentrate with a pigment mass percentage content of 5%.

[0049] S6: Frozen Grape Skin Concentrate

[0050] The grape skin concentrate was pre-frozen at -5°C and then placed in a vacuum freeze dryer for freezing at a freezing temperature of -40°C for 48 hours.

[0051] S7: Smash

[0052] The completely freeze-dried concentrated grape skin extract is put into a high-speed universal grinder for grinding, the speed of the universal grinder is set to 20000 rpm, and the grinding time is set to 40s to obtain the grape skin extract plant dye.

[0053] The yield of the obtained grape skin extract plant dye is 4.13%.

[0054] Among them, yield = quality of plant dye product / quality of raw grape skin.

[0055] Example 2

[0056] S1: Extraction

[0057] After selecting the raw materials, the grape skin is extracted with water as solvent to obtain the grape skin extract. The extraction process conditions are: the mass of water is 15 times the mass of grape skin, that is, the material-liquid ratio is 1:15, the extraction temperature is 60°C, and the extraction time is 60 minutes.

[0058] S2: Filter

[0059] The grape skin extract was filtered using a metal sieve with a mesh size of 400, and the obtained filtrate and filter residue were separated.

[0060] S3: Centrifugation

[0061] The collected filtrate is centrifuged at 4000 rpm using a centrifuge at room temperature to obtain a relatively transparent supernatant with a certain color.

[0062] S4: Extraction and filtration again

[0063] The above-mentioned S1-S3 was repeated once to extract the grape skin residue, and the supernatants were combined to obtain a total extract.

[0064] S5: Decompression and concentration

[0065] The total extract was concentrated under reduced pressure using a rotary evaporator, and the concentration time was set to 40 min to obtain a grape skin concentrate with a pigment mass percentage content of 5%.

[0066] S6: Frozen Grape Skin Concentrate

[0067] The grape skin concentrate was pre-frozen at -5°C and then placed in a vacuum freeze dryer for freezing at a freezing temperature of -40°C for 48 hours.

[0068] S7: Smash

[0069] The completely freeze-dried concentrated grape skin extract is put into a high-speed universal grinder for grinding, the speed of the universal grinder is set to 20000 rpm, and the grinding time is set to 40s to obtain the grape skin extract plant dye.

[0070] The yield of the obtained grape skin extract plant dye is 3.03%.

[0071] Example 3

[0072] S1: Extraction

[0073] After selecting the raw materials, the grape skin is extracted with water as solvent to obtain the grape skin extract. The extraction process conditions are: the mass of water is 15 times the mass of grape skin, that is, the material-liquid ratio is 1:15, the extraction temperature is 80°C, and the extraction time is 40 minutes.

[0074] S2: Filter

[0075] The grape skin extract was filtered using a metal sieve with a mesh size of 400, and the obtained filtrate and filter residue were separated.

[0076] S3: Centrifugation

[0077] The grape skin extract is centrifuged at 4000 rpm at room temperature to obtain a relatively transparent supernatant with a certain color.

[0078] S4: Extraction and filtration again

[0079] The above-mentioned S1-S3 was repeated once to extract the grape skin residue, and the supernatants were combined to obtain a total extract.

[0080] S5: Decompression and concentration

[0081] The total extract was concentrated under reduced pressure using a rotary evaporator, and the concentration time was set to 40 min to obtain a grape skin concentrate with a pigment mass percentage content of 5%.

[0082] S6: Frozen Grape Skin Concentrate

[0083] The grape skin concentrate was pre-frozen at -5°C and then placed in a vacuum freeze dryer for freezing at a freezing temperature of -40°C for 48 hours.

[0084] S7: Smash

[0085] The completely freeze-dried concentrated grape skin extract is put into a high-speed universal grinder for grinding, the speed of the universal grinder is set to 20000 rpm, and the grinding time is set to 40s to obtain the grape skin extract plant dye.

[0086] The yield of the obtained grape skin extract plant dye is 3.34%.

[0087] Example 4

[0088] Referring to Example 1, the number of extractions in the fifth step was adjusted, and the other steps remained unchanged. The results are shown below:

[0089] Number of extractions 1 time 2 times 3 times 4 times 5 times 6 times Extraction rate 3.45 0.68 0.14 0.09 0.04 -

[0090] It can be seen that the extraction of grape skin pigment is mainly in the first two times. From the perspective of cost saving and extraction rate, the number of extractions should be selected as 2 times.

[0091] Comparative Example 1

[0092] S1: Extraction

[0093] After selecting the raw materials, the grape skin is extracted with water as solvent to obtain the grape skin extract. The extraction process conditions are: the mass of water is 15 times the mass of grape skin, that is, the material-liquid ratio is 1:15, the extraction temperature is 50°C, and the extraction time is 45 minutes.

[0094] S2: Filter

[0095] The grape skin extract was filtered using a metal sieve with a mesh size of 400, and the obtained filtrate and filter residue were separated.

[0096] S3: Centrifugation

[0097] The collected filtrate is centrifuged at 4000 rpm using a centrifuge at room temperature to obtain a relatively transparent supernatant with a certain color.

[0098] S4: Extraction and filtration again

[0099] The above S1-S3 was repeated twice to extract the grape pomace, and the supernatants were combined to obtain a total extract.

[0100] S5: Add dyeing auxiliaries

[0101] 3% by mass of glyceryl monostearate was added to the total extract, and the mixture was placed under an ultrasonic power of 35 W for 10 minutes to be evenly mixed to obtain a dye.

[0102] The extraction rate of the obtained grape skin extract plant dye is 2.82%.

[0103] Comparative Example 2

[0104] A method for extracting grape skin pigment comprises the following steps:

[0105] a. Grape pretreatment: Mix grape skins and water in a mass ratio of 1:10, let stand overnight, and drain for later use;

[0106] b. Pulping: Mix grape skins and water in a mass ratio of 1:3, and then pulverize with liquid nitrogen;

[0107] c. Extraction of pigment: adjust pH to 2.0 with citric acid, shake in a 40℃ water bath for 10h, filter out the residue and extract in a mixed water bath with a residue and water mass ratio of 1:3, repeat until the color of the grape skin turns light purple, and collect the filtrate each time;

[0108] d. Freeze drying: at -5°C to a moisture content of 8%;

[0109] e. Crushing: Crushing, passing through 120 mesh, the product is obtained.

[0110] The yield of the obtained grape skin extract plant dye is 2.11%.

[0111] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing a grape skin extract plant dye, characterized in that: The steps include: (1) extracting grape skins using water as a solvent to form a grape skin extract, wherein the mass of the water is 5-50 times the mass of the grape skins; (2) filtering the obtained grape skin extract, and collecting the filtrate and the filter residue respectively; (3) centrifuging the filtrate obtained in step (2) and collecting the supernatant; (4) Repeating steps (1) to (3) with the residue obtained in step (2), combining the clear liquids, and obtaining a total extract; (5) concentrating the total extract under reduced pressure to obtain a concentrated solution; (6) freezing the obtained concentrated solution at 0 to -5°C in advance and then freezing it at -20 to -40°C; (7) After being completely freeze-dried, the mixture is crushed to obtain a grape skin extract plant dye.

2. The method according to claim 1, characterized in that In step (1), the extraction temperature is 50-95°C.

3. The method according to claim 1, characterized in that In step (1), the extraction time is 50-90 minutes.

4. The method according to claim 1, characterized in that: In step (2), the grape skin extract is filtered using a metal sieve with a mesh size of 200-500.

5. The method according to claim 1, characterized in that In step (3), the centrifugation condition is 3000-5000 rpm for 10-30 min.

6. The method according to claim 1, characterized in that In step (4), the grape skin residue is extracted repeatedly using the above steps (1)-(3), and the grape skin extract is filtered using the above filtration process, and the number of repetitions is 0-6 times.

7. The method according to claim 1, characterized in that In step (5), the extract is concentrated under reduced pressure using a rotary evaporator, and the concentration time is 20-80 minutes.

8. The method according to any one of claims 1 to 7, characterized in that: In step (7), the completely freeze-dried concentrated grape skin extract is placed in a high-speed universal grinder for grinding, the universal grinder has a rotation speed of 16000-24000 rpm, and the grinding time is 30-60 seconds.

9. A grape skin extract plant dye prepared by the method according to any one of claims 1 to 8.

10. Use of the grape skin extract plant dye according to claim 9 in the field of dyeing.