Microwave extraction Comparison with other extraction methods
1 , the microwave extraction mechanism
Microwave extraction mechanism can be considered in two ways , one is high-frequency electromagnetic microwave radiation penetrates during the extraction medium to reach the material 's internal vascular and glandular cell systems . Due to the absorption of microwave energy , the cell internal temperature rose rapidly , so that the internal cell pressure exceeds the capacity of the cell wall expansion , cell rupture . Flow freely intracellular active ingredient , at a lower temperature conditions to capture the extraction medium and dissolved. By further filtration and separation , will be awarded for extraction materials. On the other hand , the microwave electromagnetic field generated by the acceleration component extracted by the solvent extraction of the interface portion of the diffusion rate of water as solvent , in the microwave field , the water molecules become excited state of high-speed rotation , which is a high-energy unstable state, or vaporization of the water molecules , to enhance the driving force of the extracted components ; or the water molecule itself release the energy to the ground state , the release of energy to other molecules of matter , their thermal motion speed , shorten the extracted components from the raw material molecules diffuses into the extraction solvent interface of the time , so that the extraction rate increased several times , while also reducing the extraction temperature , extraction to ensure maximum quality .
There is described in the literature : the frequency of the microwave frequency of rotation associated molecule , the microwave energy is a dipole by an ion migration and molecular motion caused by the rotation of the non- ionized radiation . When it acts on the molecule , to promote the rotational motion of molecules , molecules with a certain polarity if the case , then under the action of microwave electromagnetic field in a transient polarization , and 245 million times / second polarity inversion doing exercise , thereby generating the vibration key , tear and friction between the particles , collisions, to promote molecular activity portion ( polar part ) to better contact and reaction while quickly generate a lot of heat , to promote cell lysis , the cell liquid spill to and spread into the solvent.
2 , the advantages of microwave extraction
Heat extraction is based on the traditional heat conduction , heat radiation from outside to inside , etc. carried out , while the microwave extraction is done by dipole rotation and ionic conduction in two ways inside and outside while heating . Conventional thermal extraction and conventional thermal extraction , microwave extraction has the following characteristics :
1 ) high quality, can effectively protect the food , pharmaceuticals and other chemical materials in the functional component ;
2 ) large output ;
3) extracts with high selectivity ;
4 ) save time , you can save 50 % to 90 % of the time ;
5 ) less solvent consumption ( compared with the conventional method may be at least 50 % to 90% ) ;
6 ) low energy consumption .
Extraction of microwave radiation technology in the food industry and the chemical industry on applied research , though started only a few years time, but the existing research results and application of the results is sufficient to show its following advantages :
1 ) fast reaction or extraction ;
2 ) high yield, good quality products ;
3 ) to facilitate post-processing ;
4 ) Safety ;
5 ) non-polluting, is the green engineering ;
6 ) production line composed of simple , saving investment ;
Microwave extraction technology in food and herbal active ingredients extracted from a new technology. Microwave extraction reportedly started late compared with supercritical fluid extraction , microwave extraction technology for organic compounds first papers published in 1986 , R.NGEDYE et al sample is placed in a common household microwave power by selecting the file , the role of time and solvent type in just a few minutes to extract conventional heating requires several hours or even ten hours of target substances. 1987 G ANGLER was extracted from cottonseed real cotton candy , extracted from beans beans bases.
Early nineties, by the Canadian Ministry of Environmental Protection and the Canadian (CWT-TRA N companies work together to develop a microwave extraction system Microwave Assisted Process referred MAP) has been widely applied to spices, seasonings, natural pigments , herbs, cosmetics and soil analysis , etc. fields, and in 1992 began to get the United States, Mexico, Japan , Western Europe , South Korea's patent licensing . With large-scale production line in mint, seaweed extract active substances are to be successful.
Microwave extraction efficiency , high purity , low energy consumption , generate less waste , less operating costs , in line with environmental requirements . It can be widely used in Chinese herbal medicine , spices, health food , food, cosmetics , tea drinks , seasonings , pectin , high viscosity chitosan and other industries, has been present in China for a number of microwave extraction invasion of Chinese herbal medicine production line being taken , such as arrowroot, tea, ginkgo . Microwave extraction has been listed as China's twenty-first century modernization of food processing and Chinese pharmaceutical promotion techniques.
A traditional Chinese medicine research institute researchers have used hundreds of microwave extraction approach to medicine . Whether extraction rate, extraction efficiency or extraction process quality are excellent to take much more than the conventional results.
3 , microwave extraction Comparison with other extraction methods
Microwave extraction technology and compared to other existing extraction technology has obvious advantages. Chemical solvent extraction energy consumption, supplies and more time-consuming, inefficient extraction , industrial pollution volume. Supercritical fluid extraction in the extraction efficiency is greatly improved, but the method requires sophisticated equipment , solvent selection range is narrow , high pressure vessels and pressure required to pump , so the higher investment costs , the establishment of large-scale extraction production line works are difficult.
Relevant foreign researchers studied samples from plants microwave-assisted extraction of pesticides applicability. Microwave irradiation at 10min , 50% of the maximum power under optimal conditions , microwave extraction with conventional supercritical extraction (SFE) of pesticides recoveries without much difference , but obviously saves time and solvent , and multiple samples can be processed simultaneously . Same study showed that the optimum recovery of microwave extraction temperature and extraction plant sample matrix is closely related to the type and pesticides , for the different samples , different insecticides , with the corresponding extraction temperature and time to obtain than the supercritical extraction of high recovery is entirely feasible .
Traditional methods and microwave assisted extraction recoveries and time comparison:
Compound Recovery ( % ) Time
Microwave extraction traditional methods of microwave extraction traditional methods
Natural fats ( food ) 98 100 < 15 minutes > 3h
Pesticides (soil ) 100 90 < 10 minutes <1.5h
Autinutritives 100 40 <15分钟≥ 3h
Microwave extraction rough process:
Choice of materials - Cleaning - smash - Microwave Extraction - Separation - enrichment - drying - powder - Products

 

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