Seasoning Microwave Extraction Jar

The principle and mechanism of microwave extraction

The principle of microwave extraction is that in the microwave field, the difference in microwave absorption ability causes certain regions of the matrix material or certain components in the extraction system to be selectively heated, thereby separating the extracted substance from the matrix or system and entering the extractant with relatively low dielectric constant and poor microwave absorption ability; Microwave extraction has the characteristics of simple equipment, wide applicability, high extraction efficiency, good reproducibility, time-saving, reagent saving, and low pollution. At present, in addition to being mainly used for environmental sample pretreatment, it is also used in fields such as biochemistry, food, industrial analysis, and natural product extraction.

The mechanism of microwave extraction can be explained as follows3Analyze from various aspects:

① The microwave radiation process is the process in which high-frequency electromagnetic waves penetrate the extraction medium and reach the microtubule bundles and glandular cell systems inside the material. Due to the absorption of microwave energy, the temperature inside the cell will rapidly rise, causing the pressure inside the cell to exceed the capacity of the cell wall to expand. As a result, the cell will rupture, and the active ingredients inside will freely flow out and dissolve in the extraction medium at a lower temperature. By further filtering and separation, the desired extract can be obtained.

② The electromagnetic field generated by microwaves can accelerate the diffusion rate of molecules of the extracted component from the interior of the solid to the solid-liquid interface. For example, when water is used as a solvent, under the action of a microwave field, water molecules transition from a high-speed rotating state to an excited state, which is a high-energy unstable state. At this point, water molecules either vaporize to enhance the driving force of the extracted components, or release their excess energy back to the ground state. The released energy will be transferred to molecules of other substances to accelerate their thermal motion, thereby shortening the time for the molecules of the extracted components to diffuse from the interior of the solid to the solid-liquid interface. As a result, the extraction rate is increased several times and the extraction temperature can be reduced, maximizing the quality of the extracted material.

③ Due to the correlation between the frequency of microwaves and the frequency of molecular rotation, microwave energy is a non ionizing radiation energy that causes molecular motion through ion migration and dipole rotation. When it acts on molecules, it can promote their rotational motion. If molecules have a certain polarity, they can produce instantaneous polarization under the action of microwave fields and24．5Billion times/sThe speed undergoes a polarity change motion, resulting in the formation of a keyVibration, tearing, and friction and collision between particles quickly generate a large amount of thermal energy, causing cell rupture and allowing cell fluid to overflow and diffuse into the solventIn microwave extraction, the difference in microwave absorption ability can selectively heat certain regions of the matrix material or certain components in the extraction system, thereby separating the extracted substance from the matrix or system and entering the extraction solvent with a smaller dielectric constant and relatively poor microwave absorption ability.

Characteristics and Related Applications of Microwave Extraction

Microwave refers to wavelengths between 1 and1000mmThe frequency is300～300000MHzElectromagnetic waves. It is between infrared and radio waves. The accumulation and permeation of energy in traditional extraction processes occur in an irregular manner,Poor selectivity in extraction. Limited selectivity can only be obtained by changing the properties of the solvent or extending the extraction time of the solvent,The former is limited by both solubility and diffusion coefficient,The selection surface is very narrow;The latter greatly reduces the extraction efficiency and speed.

Due to its particularity, microwave heating has the following characteristics and related applications:

1. High selectivity: Microwaves only selectively heat polar molecules, and the entire extraction process is carried out by microwave radiation penetrating the medium and reaching the interior of the material, causing the temperature inside the matrix to rapidly rise and increasing the solubility of the extracted components in the medium. Then, the electromagnetic field generated by microwaves accelerates the diffusion of the target substance into the solvent. Therefore, it has strong selective dissolution of active ingredients in natural products, and the stronger the polarity of the active ingredient molecules, the higher the selectivity.The core of microwave extraction process is a series control process of desorption and diffusionThe speed of desorption and diffusion determines the rate of extraction process. Many people attribute the microwave-assisted enhanced extraction process to cell rupture caused by microwaves, but in fact, cell rupture mainly enhances the diffusion of active ingredients. When other quantities remain constant, as the extraction time and microwave power increase, the extraction concentration increases, that is, the desorption amount increases. At the beginning, the desorption amount rapidly increases with time, and then tends to remain constant with time; The desorption amount increases with the increase of microwave power. In addition, in a microwave field, if the displacement polarization is the same or the relative shift polarization is ignored, polar molecular substances gain more energy than non-polar molecular substances, and microwave extraction of polar molecular substances is more effective. Jiao Shuqing mentioned that compared with the traditional solvent extraction method, microwave technology extracts pigments from safflower sheephoof beetle flowers. It has the characteristics of time-saving, convenient operation, and high pigment extraction rate; The method of combining microwave cell lysis with solvent extraction is used to extract salidroside from the callus tissue of Rhodiola rosea. After 1 minute of microwave treatment, the medicinal material is extracted from water at room temperature10Separation can fully extract salidroside, which has the advantages of short time, no need for heating, and less impurities in the extraction solution compared to traditional extraction methods; Microwave extraction was applied to extract total flavonoids and puerarin from Pueraria lobata, and the results showed that the extraction efficiency was significantly improved, the extraction time was significantly shortened, and the yield of effective ingredients was significantly increased; The microwave extraction technology was used to extract hawthorn polysaccharides, and the results showed that the extraction rate could be improved by traditional extraction methods10．05%Raise to16．07%The extraction time is determined by3hShorten to20minThe microwave extraction technology was used to extract polysaccharides from Plantago asiatica, and compared with the water extraction method. The results showed that the extraction times were65s, and30minThe extraction rates are, respectively1．867%The1．764%It can be seen that the microwave extraction method has the shortest extraction time and the highest selectivity for the target substance, i.e. the extraction rate. Ethanol was used as a solvent to extract total flavonoids from Poria cocos. The effects of extraction time, microwave power, ethanol concentration, solid-liquid ratio, and extraction temperature on the extraction rate of total flavonoids from Poria cocos were studied. The results showed that the microwave-assisted extraction rate of total flavonoids from Poria cocos was93．2%, higher than traditional heating extraction method17．4%.

2. Efficiency: In the extraction of the same object, traditional methods require several hours to tens of hours, while microwave extraction only takes a few seconds to minutes to complete, and the target component extraction rate is higher. It can be seen that the microwave extraction rate has increased by tens to hundreds of times, even thousands of times, greatly shortening the extraction time. The comparative experimental results show that compared with the solvent extraction method, the extraction time of pigments from safflower sheephoof flowers by microwave method is longer20 hreduce to30 sThe pigment content is similar, and the extraction rate has been improved; It is mentioned that this method has great advantages compared to traditional extraction methods, mainly manifested in saving extraction time and improving the chlorophyll extraction rate of the product compared to traditional extraction methods20％左右。

3. The superiority of material saving, energy saving, and environmental protection. Microwave extraction, due to its small microwave power and short radiation time, consumes tens or even hundreds or even thousands of times less energy than traditional methods. This is because microwave leaching can significantly enhance the solid-liquid leaching process, and its leaching efficiency is much higher than that of traditional methods. On the other hand, due to the limited affinity of the solvent, there are more solvents to choose from, which can reduce the amount of non-toxic or low toxic solvents used. It can be seen that this technology not only saves material and energy consumption, but also achieves green environmental protection. The extraction of ursolic acid using microwave technology greatly shortens the extraction time, saves solvents, and achieves a high extraction yield. Conclusion: Microwave extraction and reflux extraction methods are effective in extracting fresh ginger6-The content of gingerol is similar, but the ginger extract obtained by microwave extraction method contains6-The purity of gingerol is very high, but the reflux extraction method takes a long time, has low efficiency, and is difficult to operate. The resulting ginger extract contains6-The purity of gingerol is very low and there are many impurities. Microwave extraction method is superior to reflux extraction method in terms of extraction efficiency and energy saving.

4. Uniform heating: Conventional heating requires an increase in heating temperature to improve heating speed, which can easily lead to the phenomenon of external coke generation. The various parts of an object heated by microwave can usually uniformly penetrate electromagnetic waves and generate heat, thus greatly improving uniformity.