Iris root extract as well as preparation method and application thereof

Abstract

The preparation method comprises the following steps: crushing and sieving iris tectorum roots, carrying out an enzymatic hydrolysis reaction by using a compound enzyme, and sequentially carrying out multi-stage membrane separation treatments of microfiltration membrane impurity removal, ultrafiltration membrane enrichment and nanofiltration membrane concentration to finally obtain the high-purity iris tectorum root extract. Through the synergistic effect of enzymolysis and membrane separation technologies, the method effectively destroys the cell wall structure of iris tectorum roots, improves the dissolution rate of effective components, avoids the problems of organic solvent residue, effective component destruction at high temperature and the like in a traditional extraction method, has the advantages of high extraction efficiency, high product purity, greenness, environmental protection and the like, and is suitable for industrial production. The method is suitable for industrial production of the iris root extract.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tobacco flavor extraction, and in particular to an iris root extract and a preparation method and application thereof. BACKGROUND

[0002] Tobacco flavor is a core component of cigarette formula, which plays an important role in enriching cigarette aroma and improving smoking quality. Iris root is the rhizome of plants in the genus Iris of the family Iridaceae, which has a sweet and sweet scent similar to violet. The extract thereof can give cigarettes unique and natural aroma, and has the effects of softening smoke and improving taste.

[0003] In the prior art, solvent extraction is usually used to extract iris root extract, such as the preparation method of iris root extract disclosed in the patent document with the publication number CN112956733A, which comprises the steps of pressure heat treatment, extraction, filtration and alcohol precipitation. However, solvent extraction requires the use of a large amount of organic solvent, which is easy to cause solvent residue, and the subsequent separation and purification steps are complex, resulting in high production cost. Some documents also use fungal fermentation to treat iris root, but biological fermentation requires the separation and screening of stable strains, which is difficult to be applied in industrialization. SUMMARY Based on the above deficiencies of the prior art, the technical problem to be solved by the present application is to provide an iris root extract with good treatment effect and a preparation method and application thereof, which can effectively utilize waste gas containing chemical components and meet the standard of safe emission.

[0004] To solve the above technical problems, the present application first provides a preparation method of iris root extract, comprising the following steps: S1. After removing impurities, the iris root is dried and crushed, and then sieved through a 60-mesh sieve to obtain iris root powder for standby; S2. The iris root powder is mixed with water, and after adjusting the pH value, a composite enzyme is added, and after water bath enzymolysis, the enzyme reaction is inactivated at 100℃ for 3h to obtain an enzyme hydrolysate; S3. The enzyme hydrolysate is transferred to a 500ml centrifuge tube, and after centrifugation, the supernatant is taken and filtered by a microfiltration membrane to remove suspended particles, incompletely hydrolyzed residues and macromolecular impurities, and a microfiltration permeate is obtained; S4. The microfiltration permeate is introduced into an organic ultrafiltration membrane system to obtain an ultrafiltration retentate; S5. The ultrafiltration retentate is concentrated by a nanofiltration membrane to a solid content of 20%~30% to obtain an iris root extract.

[0005] In the step S1, 2-3 years old iris root is selected; the iris root is crushed and vacuum freeze-dried for 1-2 hours to control the water content at 8-10% (which can be 8%, 9%, or 10%). Preferably, the vacuum freeze-drying is performed for 2 hours to control the water content at 8%.

[0006] In the step S2, the iris root powder is mixed with water at a mass ratio of 1:8-1:20 (which can be 1:8, 1:10, 1:12, 1:15, or 1:20), and the pH value is adjusted by using a citric acid-sodium citrate buffer. Generally, the optimum pH value of pectinase is 2.5-6.0, the optimum pH value of cellulase is 4.5-6.5, and the optimum pH value of xylanase is 3.5-6.5. The pH value of the citric acid-sodium citrate buffer is adjusted to 4.5-6.0. Preferably, the ratio of the iris root powder to water is 1:15 or 1:20, and the initial pH value of the citric acid-sodium citrate buffer is 4.5.

[0007] The complex enzyme is composed of cellulase, pectinase, and xylanase at a certain mass ratio (cellulase:pectinase:xylanase=2:1:1). The cellulase can decompose cellulose in the cell wall, the pectinase can decompose pectin, and the xylanase can decompose hemicellulose. The synergistic effect of the three can effectively destroy the cell wall structure of the iris root, promote the dissolution of the effective components, and avoid the degradation of the effective components under the mild reaction conditions. The amount of the enzyme and the enzyme hydrolysis time also need to be limited. Too much enzyme and too long enzyme hydrolysis time will lead to excessive enzyme hydrolysis, and too little enzyme and too short enzyme hydrolysis time will lead to insufficient enzyme hydrolysis. Considering the enzyme hydrolysis activity and efficiency, the amount of the complex enzyme added in the present application is 0.5-1.5% (which can be 0.5%, 0.8%, 1.0%, 1.2%, or 1.5%) of the mass of the iris root powder, the enzyme hydrolysis temperature is 40-55°C (which can be 40°C, 45°C, 50°C, or 55°C), and the enzyme hydrolysis time is 2-4 hours (which can be 2 hours, 3 hours, or 4 hours). Preferably, the amount of the complex enzyme added is 1.5% (cellulase:pectinase:xylanase=2:1:1), the enzyme hydrolysis temperature is 40°C or 45°C, and the enzyme hydrolysis time is 3 hours.

[0008] In step S3, the enzymatic hydrolysate is centrifuged at 3000-5000 rpm (which can be 3000, 3500, 4000, 4500, or 5000 rpm) for 10-45 min (which can be 10, 15, 20, 25, 30, 35, 40, or 45 min). The supernatant is then filtered through a microfiltration membrane at an operating pressure of 0.1-0.3 MPa (which can be 0.1, 0.15, 0.2, 0.25, or 0.3 MPa) and a temperature of 20-40℃ (which can be 20, 25, 30, 35, or 40℃). Because the enzymatic hydrolysate contains residual undigested solid impurities and relatively large molecular weight colloids, polysaccharides, and starches, centrifugation and microfiltration can further remove these solid impurities. Microfiltration membranes are classified into three types: aqueous microfiltration membranes, organic microfiltration membranes, and mixed microfiltration membranes. For example, it can be polyvinylidene fluoride (PVDF), polyethersulfone (PES), polytetrafluoroethylene (PTFE), polypropylene (PP), mixed cellulose (MCE), polyacrylonitrile (PAN), aqueous cellulose acetate (CA), and polyamide (PA) microfiltration membranes, etc. Based on the microfiltration membrane flux, the preferred microfiltration membrane is determined to be a polyamide (PA) microfiltration membrane.

[0009] Since the viscosity of a liquid changes with temperature, the flux of a microfiltration membrane is generally positively correlated with temperature. However, high temperatures may accelerate membrane material aging. Simultaneously, within a certain pressure range, membrane flux increases with increasing pressure; however, excessive pressure can lead to membrane fouling and damage. The preferred conditions in this invention are centrifugation at 3000-4000 rpm for 25-35 minutes, filtration through a 0.2 μm microfiltration membrane, an operating pressure of 0.1-0.2 MPa, and a temperature of 30°C or 35°C.

[0010] In step S4, the microfiltration permeate is passed into an organic ultrafiltration membrane system and filtered using an ultrafiltration membrane with a pore size of 10-10 nm. The operating pressure is 0.1-2.0 MPa, and the temperature is 20-40℃. During ultrafiltration, small molecule impurities (such as monosaccharides and inorganic salts) pass through the ultrafiltration membrane, while the effective components in iris root (such as flavonoids and triterpenoids) are retained due to their larger molecular weight, thus achieving enrichment of the effective components and obtaining the ultrafiltration retentate. Both organic and inorganic ultrafiltration membranes can be used. However, most organic membranes have poor thermal stability, low mechanical strength, are prone to permanent fouling, have short service life, and extremely high process costs, lacking industrial applicability. The inorganic ceramic ultrafiltration membrane preferred in this study has high mechanical strength and good chemical stability. Flushing with chemical cleaning agents can effectively solve the membrane fouling problem, making it suitable for industrial production. The preferred conditions are ultrafiltration using a 50 nm inorganic ceramic membrane at a pressure of 0.1~0.5 MPa and a feed temperature of 30 °C.

[0011] In step S5, the nanofiltration membrane's surface separation layer is composed of polyelectrolytes, exhibiting a certain retention rate for inorganic salts. Membrane separation is simple to operate, requires no heating, and does not damage biological activity, making it widely applicable in various separation, purification, or concentration processes of bioactive substances from plants and animals. The molecular weight cutoff of nanofiltration membranes is typically 200–1000 Da, while the molecular weight of flavonoids in iris roots is mostly between 200 and 500 Da, allowing for effective retention. The ultrafiltration retentate is passed into the nanofiltration membrane system and concentrated using a membrane with a molecular weight cutoff of 200–1000 Da, at an operating pressure of 0.1–2.0 MPa and a temperature of 20–40 °C.

[0012] Nanofiltration membranes can retain active ingredients, while water molecules and some small molecule impurities permeate through the membrane, thus concentrating the ultrafiltration retentate. During concentration, the solids content of the concentrate is monitored. Concentration is stopped when the solids content reaches 20%–30%, yielding iris root extract. Preferred conditions include using a nanofiltration membrane with a molecular weight cutoff of 300 Da, operating at a pressure of 0.5–1.0 MPa, a temperature of 30°C, and stopping concentration when the solids content reaches 20%–30%, yielding iris root extract.

[0013] Iris root extract is prepared by any of the methods described above. The iris root extract is used as a flavoring agent for cigarettes to enrich the aroma of cigarettes and improve the smoking quality. When used, the iris root extract accounts for 0.01% to 0.1% of the dry weight of cigarette tobacco. Following the conventional flavoring and additive process, it is dissolved in pure water and sprayed evenly onto blank tobacco. The tobacco is dried at 60°C to a moisture content of 14% and then equilibrated at room temperature for 24 hours to produce cigarettes.

[0014] Enzymatic hydrolysis is a technology that utilizes the biocatalytic action of enzymes to break down large molecules (such as cellulose, proteins, and polysaccharides) in raw materials into smaller molecules under mild conditions. Its core lies in achieving targeted transformation of substances through the specific reactions of enzymes, and it is widely used in traditional Chinese medicine extraction, food processing, and biopharmaceuticals. Membrane separation technology, on the other hand, utilizes the selective permeability of membranes to separate and purify substances of different molecular weights, featuring high separation efficiency, low energy consumption, and no secondary pollution. Combining enzymatic hydrolysis and membrane separation technologies can fully leverage their synergistic effects, effectively addressing the shortcomings of traditional extraction processes and improving the extraction rate and purity of the active ingredients in iris root.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: This invention provides an iris root extract and its preparation method. The iris root is pulverized and sieved, then subjected to enzymatic hydrolysis using a compound enzyme. Following this, it undergoes a multi-stage membrane separation process involving microfiltration for impurity removal, ultrafiltration for enrichment, and nanofiltration for concentration, ultimately yielding a high-purity iris root extract. This invention effectively disrupts the cell wall structure of iris roots through the synergistic effect of enzymatic hydrolysis and membrane separation technologies, improving the dissolution rate of active ingredients. Simultaneously, it avoids problems such as residual organic solvents and high-temperature damage to active ingredients found in traditional extraction methods. This method offers advantages such as high extraction efficiency, high product purity, and environmental friendliness, making it suitable for the industrial production of iris root extract.

[0016] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, the following detailed description is provided in conjunction with preferred embodiments. Detailed Implementation

[0017] The following detailed description of specific embodiments of the present invention is part of this specification. The principles of the present invention are illustrated through examples, and other aspects, features and advantages of the present invention will become apparent from this detailed description.

[0018] A method for preparing an iris root extract includes the following steps: S1. After removing impurities, the iris root is dried, pulverized, and passed through a 60-mesh sieve to obtain iris root powder for later use. S2. Mix the iris root powder with water, adjust the pH value, add a compound enzyme, hydrolyze in a water bath, and then inactivate the enzyme at 100°C for 3 hours to obtain the enzymatic hydrolysate. S3. Transfer the enzymatic hydrolysate to a 500ml centrifuge tube, centrifuge, take the supernatant, filter it using a microfiltration membrane to remove suspended particles, incompletely enzymatically hydrolyzed residues and macromolecular impurities, and obtain the microfiltration permeate. S4. Pass the microfiltration permeate into an organic ultrafiltration membrane system to obtain the ultrafiltration retentate; S5. The ultrafiltration retentate is concentrated using a nanofiltration membrane until the solid content is 20%~30% to obtain iris root extract.

[0019] Example 1 (1) Raw material pretreatment: Select 2-3 year old iris roots, remove impurities, clean them and cut them into 2mm thin slices, crush them and pass them through a 60-mesh sieve to obtain iris root powder; freeze dry the powder under vacuum for 2 hours and control the moisture content to 8%.

[0020] (2) Enzymatic hydrolysis: Iris root powder and deionized water were mixed at a mass ratio of 1:20. The pH value was adjusted to 4.5 with citrate-sodium citrate buffer. A compound enzyme (cellulase: pectinase: xylanase = 2:1:1) was added at a mass of 1.5% of the Iris root powder. The mixture was enzymatically hydrolyzed at 45℃ for 3 hours and then the enzyme was inactivated at 100℃ for 3 hours to obtain the enzymatic hydrolysate. (3) Microfiltration membrane impurity removal: Centrifuge the enzyme hydrolysate at 3000 rpm for 30 min and take the supernatant; use a ceramic microfiltration membrane with a pore size of 0.2 μm to filter at 0.2 MPa and 35℃ to obtain the microfiltration permeate.

[0021] (4) Ultrafiltration membrane enrichment: A 50 nm inorganic ceramic membrane was used to filter the microfiltration permeate at 0.16 MPa and 30 °C to obtain the ultrafiltration retentate.

[0022] (5) Nanofiltration membrane concentration: The ultrafiltration retentate was concentrated at 0.8 MPa and 30 °C using a nanofiltration membrane with a molecular weight cutoff of 300 Da until the solid content was 20%, thus obtaining iris root extract.

[0023] Example 2 (1) Raw material pretreatment: Select 2-3 year old iris roots, remove impurities, clean them and cut them into 2mm thin slices, crush them and pass them through a 60-mesh sieve to obtain iris root powder; freeze dry the powder under vacuum for 2 hours and control the moisture content to 8%.

[0024] (2) Enzymatic hydrolysis: Iris root powder and deionized water were mixed at a mass ratio of 1:15, and the pH was adjusted to 4.5 with citrate-sodium citrate buffer. A compound enzyme (cellulase: pectinase: xylanase = 2:1:1) was added at a mass of 1.0% of the Iris root powder. The mixture was enzymatically hydrolyzed at 45℃ for 3 hours and then the enzyme was inactivated at 100℃ for 3 hours to obtain the enzymatic hydrolysate. (3) Microfiltration membrane impurity removal: Centrifuge the enzyme hydrolysate at 3000 rpm for 35 min and take the supernatant; use a ceramic microfiltration membrane with a pore size of 0.2 μm to filter at 0.1 MPa and 30℃ to obtain the microfiltration permeate.

[0025] (4) Ultrafiltration membrane enrichment: A 50 nm inorganic ceramic membrane was used to filter the microfiltration permeate at 0.16 MPa and 30 °C to obtain the ultrafiltration retentate.

[0026] (5) Nanofiltration membrane concentration: The ultrafiltration retentate was concentrated using a nanofiltration membrane with a molecular weight cutoff of 300 Da at 0.5 MPa and 30 °C until the solid content was 20%, thus obtaining the iris root extract. Example 3 (1) Raw material pretreatment: Select 2-3 year old iris roots, remove impurities, clean them and cut them into 2mm thin slices, crush them and pass them through a 60-mesh sieve to obtain iris root powder; freeze dry the powder under vacuum for 2 hours and control the moisture content to 8%.

[0027] (2) Enzymatic hydrolysis: Iris root powder and deionized water were mixed at a mass ratio of 1:20. The pH value was adjusted to 4.5 with citrate-sodium citrate buffer. A compound enzyme (cellulase: pectinase: xylanase = 2:1:1) was added at a mass of 1.5% of the Iris root powder. Enzymatic hydrolysis was carried out at 40℃ for 3 hours, and the enzyme was inactivated at 100℃ for 3 hours to obtain the enzymatic hydrolysate. (3) Microfiltration membrane impurity removal: Centrifuge the enzyme hydrolysate at 3500 rpm for 25 min and take the supernatant; use a ceramic microfiltration membrane with a pore size of 0.2 μm to filter at 0.2 MPa and 30 °C to obtain the microfiltration permeate.

[0028] (4) Ultrafiltration membrane enrichment: A 50 nm inorganic ceramic membrane was used to filter the microfiltration permeate at 0.2 MPa and 30 °C to obtain the ultrafiltration retentate.

[0029] (5) Nanofiltration membrane concentration: The ultrafiltration retentate was concentrated at 0.8 MPa and 30 °C using a nanofiltration membrane with a molecular weight cutoff of 300 Da until the solid content was 20%, thus obtaining iris root extract.

[0030] Comparative Example 1 The process is largely the same as in Example 3, except that fresh iris root is used as the raw material, and "2-3 year old iris root" is replaced with "fresh iris root". The other steps are the same to obtain iris root extract.

[0031] Comparative Example 2 The results were largely the same as in Example 3, except that nanofiltration membranes were not used for concentration to obtain iris root extract.

[0032] Another objective of this invention is to provide an application of iris root extract in cigarettes. Adding this extract to cigarette tobacco can enhance the sweet and woody aroma of tobacco, improve the taste, mask off-flavors, and improve the quality of flue-cured cigarettes.

[0033] As a preferred embodiment of the present invention, the mass ratio of iris root extract to cigarette tobacco is 0.01% to 0.1%, for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%, preferably 0.05%.

[0034] Iris root extracts obtained in Examples 1-3 and Comparative Examples 1 and 2 were added at a rate of 0.05% of the dry weight of tobacco shreds. Following conventional flavoring and additive processing procedures, the extracts were dissolved in purified water and evenly sprayed onto blank tobacco shreds. The tobacco shreds were dried to a moisture content of 14% at 60°C and equilibrated at room temperature for 24 hours to produce cigarettes. Sensory evaluation results were obtained according to the standard "YCT 497~2014 Sensory Evaluation Method for Chinese-style Cigarettes," as shown in Table 1.

[0035] Table 1 Sensory Evaluation Table

[0036] The above results indicate that adding the iris extract prepared by the method described in this invention to tobacco can enrich the tobacco aroma, increase the sweet and woody aroma, and make the smoke smooth, delicate, and harmonious, without obvious spiciness, irritation, or discomfort such as residue on the oral cavity and tongue.

[0037] All the raw materials listed in this invention, as well as the upper and lower limits and ranges of the raw materials, and the upper and lower limits and ranges of the process parameters (such as temperature, time, etc.), can realize this invention. Examples are not listed one by one here.

[0038] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing an iris root extract, characterized in that, It includes the following steps: S1. After removing impurities, the iris root is dried, pulverized, and sieved to obtain iris root powder for later use. S2. Mix the iris root powder obtained in step S1 with water, adjust the pH value, add a compound enzyme, hydrolyze in a water bath, and then inactivate the enzyme to obtain the enzymatic hydrolysate. S3. After centrifuging the enzymatic hydrolysate obtained in step S2, take the supernatant and filter it through microfiltration to obtain the microfiltration permeate. S4. Pass the microfiltration permeate obtained in step S3 into an organic ultrafiltration membrane system to obtain the ultrafiltration retentate; S5. The ultrafiltration retentate obtained in step S4 is concentrated using a nanofiltration membrane until the solid content is 20%~30%, which is the iris root extract.

2. The method for preparing the iris root extract as described in claim 1, characterized in that: In step S1, a 60-mesh sieve is selected for sieving, and the iris root is selected from 2-3 year old iris roots. After the iris root is crushed, it is vacuum freeze-dried for 1-2 hours to control the moisture content at 8%-10%.

3. The method for preparing the iris root extract as described in claim 1, characterized in that: In step S2, iris root powder and water are mixed at a mass ratio of 1:8 to 1:20; the pH value is adjusted to 4.5 to 6.0 using a citric acid-sodium citrate buffer solution.

4. The method for preparing the iris root extract as described in claim 1, characterized in that: In step S2, the complex enzyme is composed of cellulase, pectinase and xylanase in a mass ratio of 2:1:

1. The amount of complex enzyme added is 0.5% to 1.5% of the mass of iris root powder. The enzymatic hydrolysis temperature is 40 to 55°C and the enzymatic hydrolysis time is 2 to 4 hours.

5. The method for preparing the iris root extract as described in claim 1, characterized in that: In step S3, the enzymatic hydrolysate is centrifuged at 3000-5000 rpm for 10-45 min, and the supernatant is filtered through a microfiltration membrane. The operating pressure is 0.1-0.3 MPa and the temperature is 20-40℃.

6. The method for preparing the iris root extract as described in claim 1, characterized in that: In step S3, the microfiltration membrane is one of the following: aqueous microfiltration membrane, organic microfiltration membrane, and mixed microfiltration membrane; the microfiltration conditions are centrifugation at 3000 rpm for 30 min, filtration through a 0.2 μm microfiltration membrane, operating pressure of 0.2 MPa, and temperature of 35 °C.

7. The method for preparing iris root extract as described in claim 6, characterized in that: The microfiltration membrane is a polyamide (PA) microfiltration membrane.

8. The method for preparing the iris root extract as described in claim 1, characterized in that: In step S4, the microfiltration permeate is passed into an organic ultrafiltration membrane system, and ultrafiltration is performed using an ultrafiltration membrane with a pore size of 10~10nm. The operating pressure is 0.1~2.0MPa and the temperature is 20~40℃.

9. The method for preparing the iris root extract as described in claim 1, characterized in that: In step S5, the ultrafiltration retentate is passed into a nanofiltration membrane system and concentrated using a membrane with a molecular weight cutoff of 200~1000 Da. The operating pressure is 0.1~2.0 MPa and the temperature is 20~40℃.

10. An application of an iris root extract, characterized in that: The iris root extract is prepared by the method described in any one of claims 1 to 9. The iris root extract is used as a tobacco flavoring to enrich the aroma of cigarettes and improve the smoking quality. When used, the iris root extract accounts for 0.01% to 0.1% of the dry weight of cigarette tobacco. Following the conventional flavoring and additive process, it is dissolved in pure water and sprayed evenly onto blank tobacco. The tobacco is dried at 60°C to a moisture content of 14% and then equilibrated at room temperature for 24 hours to produce cigarettes.

Images