Method for improving extraction rate of polyphenol in pomegranate rind by using steam explosion technology

Abstract

The invention relates to a method for increasing the extraction rate of polyphenol in pomegranate rind by using a steam explosion technology, which comprises the following steps: (1) steam explosion treatment of pomegranate rind: treating the pomegranate rind by using steam explosion equipment to obtain a pretreated raw material; (2) extraction of polyphenol substances: crushing the pretreated raw materials obtained in the step (1) in a crusher, sieving with a 60-mesh sieve, and extracting with an organic solvent; and (3) preparing a polyphenol substance crude product: carrying out vacuum rotary evaporation on the extracting solution obtained in the step (2), and carrying out vacuum drying to obtain the polyphenol substance. According to the method, the polyphenol extraction rate is increased by utilizing a steam explosion technology, acid and alkali are not used, wastewater discharge is reduced, environmental protection is facilitated, energy consumption and production cost can be reduced, and industrial production is facilitated.

Description

Technical Field

[0001] The invention relates to a method for extracting polyphenols from pomegranate peel, in particular to a method for improving the extraction rate of polyphenols from pomegranate peel by utilizing steam explosion technology. Background Art

[0002] Pomegranate peel is rich in polyphenols, including organic acids, flavonoids, aromatic alcohols, aromatic acids, aromatic ethers, etc., which have multiple functions, including antioxidant, anti-inflammatory, antibacterial, antiviral, anticancer, etc. They can also promote blood circulation, enhance immunity, lower blood lipids, lower blood pressure, inhibit platelet aggregation, prevent cardiovascular diseases, anti-aging, anti-cancer, etc., and are widely used in cosmetics, food, medicine and other fields.

[0003] Steam explosion technology (abbreviated as steam explosion technology) was first proposed by American scholar WH Mason. Its working principle is to fill the gaps in the materials with water vapor, and then treat them with high temperature and high pressure to vaporize the liquid between the materials, and then release the pressure instantly; at this time, the volume of water vapor between the materials expands instantly to achieve an "explosion" effect, causing the cells to tear, thereby releasing many substances that are difficult to extract from the cells.

[0004] At present, the traditional methods for extracting polyphenols from pomegranate peel mainly include solvent extraction, ultrasonic extraction, and distillation, which are often unable to effectively extract polyphenols from pomegranate peel, resulting in a low extraction rate of polyphenols. These methods have the disadvantages of high energy consumption, high cost, use of strong alkali, high wastewater treatment cost, and unfriendly to the environment, making it difficult to adapt to the needs of modern industrial production. Therefore, it is necessary to develop a new technology to improve the extraction rate of polyphenols from pomegranate peel. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, which does not use acid or alkali and reduces wastewater discharge, is beneficial to environmental protection, can reduce energy consumption and production costs, and is convenient for industrial production.

[0006] In order to solve the above technical problems, the present invention provides the following technical solution: a method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, comprising the following steps:

[0007] (1) Steam explosion treatment of pomegranate peel:

[0008] Treating pomegranate peels with steam explosion equipment to obtain pretreated raw materials;

[0009] (2) Extraction of polyphenols:

[0010] The pretreated raw material obtained in step (1) is crushed and passed through a 60-mesh sieve, and then extracted with an organic solvent;

[0011] (3) Preparation of crude polyphenols:

[0012] The extract obtained in step (2) is vacuum-rotated and vacuum-dried to obtain polyphenols.

[0013] Preferably, in step (1), the steam explosion treatment pressure is controlled at 0.5-2.0 MPa, and the treatment time is maintained at 60-180 s.

[0014] Preferably, the organic solvent in step (2) is an ethanol aqueous solution, the concentration of alcohol in the aqueous solution is 50% (V / V); the total amount of organic solvent is 25 times the weight of the raw material; the extraction temperature is 60° C.; and the extraction time is 1.5 h.

[0015] Preferably, the rotary evaporation temperature in step (3) is 50°C.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) the phenolic substance with the highest content in pomegranate peel is quercetin. If the traditional alkali and enzyme extraction method is used to prepare polyphenolic substances, a large amount of alkali is consumed, and the alkaline waste liquid generated will cause great environmental pollution. The use of enzyme method is costly and is not conducive to industrial production.

[0017] The invention utilizes steam explosion to process pomegranate peel, which is beneficial to the release of polyphenols in the pomegranate peel, and the steam explosion treatment can also destroy the structure of the pomegranate peel, which is beneficial to the subsequent extraction of polyphenols. Compared with the traditional alkali and enzyme extraction process, the invention obtains the same product as the alkali and enzyme extraction, but avoids the pollution problem of alkali and wastewater in the traditional process, and has low cost, simple process, energy saving and environmental protection.

[0018] (2) Pomegranate peel is a byproduct of the food processing industry, and most of it is discarded, resulting in serious waste of resources. Using pomegranate peel as a raw material for producing polyphenols can also expand the scope of use of pomegranate peel, and the organic solvents used in the extraction and purification steps can be effectively recovered, saving production costs. Therefore, the present invention has broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The scanning electron microscope images of pomegranate peels with different steam explosion degrees (powder passed through a 60-mesh sieve);

[0020] Figure 2 FTIR images of pomegranate peels with different steam explosion degrees;

[0021] Figure 3 The content and extraction rate of phenolic compounds in pomegranate peel extracts with different steam explosion degrees;

[0022] Figure 4Antioxidant activity (DPPH radical scavenging activity, ABTS, and total reducing power) of pomegranate peels subjected to different steam explosion degrees. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] Example 1

[0025] A method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 0.5 MPa for 60 seconds, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2 g of the above raw material is weighed, added with 5 ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1 hour, and then the operation is repeated for 0.5 hours, and the two extracts are combined, fixed to 10 ml, diluted by a corresponding multiple, and the polyphenol content is determined by the Folin phenol method.

[0026] Example 2

[0027] A method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 0.5 MPa for 120 seconds, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2 g of the above raw material is weighed, added with 5 ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1 hour, and then the extraction operation is repeated for 0.5 hours, the two extracts are combined, the volume is fixed to 10 ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0028] Example 3

[0029] A method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 0.5 MPa for 180 seconds, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2 g of the above raw material is weighed, added with 5 ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1 hour, and the extraction operation is repeated for 0.5 hours, the two extracts are combined, the volume is fixed to 10 ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0030] Example 4

[0031] A method for improving the polyphenol extraction rate in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 1.5 MPa for 60 seconds, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2 g of the above raw material is weighed, added with 5 ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1 hour, and then the extraction operation is repeated for 0.5 hours, the two extracts are combined, the volume is fixed to 10 ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0032] Example 5

[0033] A method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 1.5 MPa for 120 seconds, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2 g of the above raw material is weighed, added with 5 ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1 hour, and then the extraction operation is repeated for 0.5 hours, the two extracts are combined, the volume is fixed to 10 ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0034] Example 6

[0035] A method for improving the polyphenol extraction rate in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 1.5 MPa for 180 seconds, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2 g of the above raw material is weighed, added with 5 ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1 hour, and then the extraction operation is repeated for 0.5 hours, the two extracts are combined, the volume is fixed to 10 ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0036] Example 7

[0037] A method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 2MPa for 60s, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2g of the above raw material is weighed, added with 5ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1h, and then the extraction operation is repeated for 0.5h, the two extracts are combined, the volume is fixed to 10ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0038] Example 8

[0039] A method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 2MPa for 120s, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2g of the above raw material is weighed, added with 5ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1h, and then the extraction operation is repeated for 0.5h, the two extracts are combined, the volume is fixed to 10ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0040] Example 9

[0041] A method for improving the extraction rate of polyphenols in pomegranate peel by using steam explosion technology, wherein the pomegranate peel is placed in a steam explosion device, maintained at a pressure of 2MPa for 180s, and then instantly exploded to obtain the pomegranate peel in an exploded state, and then crushed through a 60-mesh sieve to obtain a processed raw material. 0.2g of the above raw material is weighed, added with 5ml of 50% ethanol, and extracted on a 60°C constant temperature shaker for 1h, and then the extraction operation is repeated for 0.5h, the two extracts are combined, the volume is fixed to 10ml, and the corresponding multiples are diluted, and the polyphenol content is determined by the Folin phenol method.

[0042] In the above-mentioned Examples 1-9, the steam explosion equipment adopts QBS-80 analytical steam explosion test bench for steam pretreatment, and the pomegranate peel is evenly sprayed with 100 grams of distilled water and placed in a sealed container covered with a plastic film for hydration, and the process is maintained at 15°C for 4-6 hours; then, the pomegranate peel is wetted and placed in a room, and exposed to saturated steam with steam pressures of 0.5 MPa, 1.5 MPa and 2.0 MPa for 60 seconds, 120 seconds and 180 seconds respectively.

[0043] The above embodiments are combined with Figure 3 It can be seen that the content of polyphenols in pomegranate peel after steam explosion treatment has increased significantly compared with that before treatment, indicating that steam explosion treatment is beneficial to the release of polyphenols in pomegranate peel.

[0044] Figure 1 The scanning electron microscope images of pomegranate peel powder (passed through a 60-mesh sieve) under different treatment conditions are listed respectively. It can be seen that the surface structure of the pomegranate peel powder SEM images (Figure A, Figure a) without steam explosion treatment is relatively complete. With the continuous increase of pressure and the extension of pressure maintenance time, the degree of rupture of the pomegranate peel powder becomes more serious, and its structure becomes loose and porous, which promotes the contact accessibility of the active ingredients in the raw materials with the solvent and is beneficial to the dissolution of phenolic substances.

[0045] Figure 2 The FTIR images of pomegranate peels with different steam explosion degrees are shown below. Common characteristic bonds of polyphenols include hydrogen bonds formed by hydroxyl groups and other groups, methoxy CH, aromatic hydrocarbon skeleton C=C and CO bonds, etc. The characteristic absorption peak of hydrogen bonds formed by hydroxyl groups in the molecule and other groups is 3500-3200cm-1 , it is inferred that the absorption peak of the hydroxyl group of phenolic substances in pomegranate peel is 3415cm -1 ( Figure 2 ).2924cm -1 It is the absorption peak of the stretching vibration of the methoxy group CH in the molecule. After comparing the spectral lines in the figure, it is found that the pomegranate peel after blasting has no new chemical structure and functional group. Compared with the untreated group, the pomegranate peel of the blasting group has a higher absorption peak at 3415cm -1 and 2924cm -1 The absorption at the point is weakened, which may be due to the fact that the blasting process breaks the molecular chains in the raw materials, resulting in a reduction in hydrogen bonds.

[0046] like Figure 3 , 4 As shown in the figure, steam explosion pressure and time have a significant effect on the extraction rate and antioxidant activity of polyphenols in the raw materials. After steam explosion treatment, the content of phenolic substances increased significantly, and with the increase of steam explosion intensity, the content of phenolic substances generally showed an upward trend. The antioxidant capacity of phenolic extracts in pomegranate peel after explosion was higher than that in the non-explosion group, and the changes in the antioxidant activity of the extracts in different treatment groups were basically consistent with the changes in the polyphenol content of the extracts, which showed that with the continuous increase of explosion pressure and time, the antioxidant capacity of polyphenols in pomegranate peel showed an overall upward trend.

Claims

1. A method for improving the extraction rate of polyphenols in pomegranate peel using steam explosion technology, characterized in that: The following steps are involved: (1) Steam explosion treatment of pomegranate peel: Treating pomegranate peels with steam explosion equipment to obtain pretreated raw materials; (2) Extraction of polyphenols: The pretreated raw material obtained in step (1) is crushed and passed through a 60-mesh sieve, and then extracted with an organic solvent; (3) Preparation of crude polyphenols: The extract obtained in step (2) is vacuum-rotated and vacuum-dried to obtain polyphenols.

2. The method according to claim 1, characterized in that: In step (1), the steam explosion treatment pressure is controlled at 0.5-2.0 MPa, and the treatment time is maintained at 60-180 s.

3. The method according to claim 1, characterized in that: In step (2), the organic solvent is an ethanol aqueous solution, the concentration of alcohol in the aqueous solution is 50% (V / V); the total amount of the organic solvent is 25 times the weight of the raw material; the extraction temperature is 60° C.; and the extraction time is 1.5 h.

4. The method according to claim 1, characterized in that: The rotary evaporation temperature in step (3) is 50°C.

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