3. Extraction for food production

Among the methods used to obtain fast, accurate, and reliable results in food analyses, the first step is extraction process [8]. Extraction refers to the removal of another liquid phase by taking advantage of the different solubility characteristics of one or more compounds present in the solid or liquid phase [9]. The use of classical extraction methods such as Soxhlet, percolation, and steam distillation is very common in extraction stage [8]. Soxhlet extraction is the method that is frequently used in food extraction and analysis. However, the low efficiency in this method limits the use of the technique, which is low in the analysis and high in solvent consumption [10]. Taking all these conditions into account, the development of new extraction methods has been accelerated.

#### 3.1. Traditional extraction techniques

Separation of a substance from two or multicomponent mixtures or the removal of undesirable impurities by solvent aid is called extraction. "Liquid-liquid extraction" is that if the mixture to be separated consists of liquid components. If a substance or group is to be separated from a solid material, this process is called "solid-liquid extraction."

#### 3.1.1. Liquid-liquid extraction

Liquid-liquid extraction is called separation by contacting a substance dissolved in the liquid solution with another liquid, which does not mix with the solution. The first application of this process is the extraction of gold and silver from the liquid copper by the Romans using lead as solvent.

A simple extraction process consists of three basic components: solute, carrier, and solvent. The part rich in the feed liquid separated from the extractant is called raffinate (aqueous phase), and the part rich in solvent is called the extract (organic phase).

Extraction is generally preferred over distillation in the following cases. These are:


For example, water can be removed from acetic acid by distillation or liquid-liquid extraction using an organic solvent. Liquid-liquid extraction is used in the industrial separation of many mixtures. In the inorganic chemical industry, extraction is carried out at the removal of water from materials with high boiling points such as phosphoric acid, boric acid, and sodium hydroxide and organics containing hydrogen bonds such as formaldehyde.

#### 3.1.2. Solid-liquid extraction

The research shows that local products are sold in sustainable food systems and that products are produced by sustainable agricultural systems; thus, natural resources, especially local seeds, are protected. It is stated that the producers are actively involved, developing the producer and consumer interaction and increasing the solidarity. Provision of food safety and security in sustainable food systems, conservation and improvement of health, prevention of diseases, protection of nature, protection of agricultural biodiversity, strengthening of local and rural areas, and ensuring socioeconomic development are taken into consideration.

162 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

Among the methods used to obtain fast, accurate, and reliable results in food analyses, the first step is extraction process [8]. Extraction refers to the removal of another liquid phase by taking advantage of the different solubility characteristics of one or more compounds present in the solid or liquid phase [9]. The use of classical extraction methods such as Soxhlet, percolation, and steam distillation is very common in extraction stage [8]. Soxhlet extraction is the method that is frequently used in food extraction and analysis. However, the low efficiency in this method limits the use of the technique, which is low in the analysis and high in solvent consumption [10]. Taking all these conditions into account, the development of new extraction

Separation of a substance from two or multicomponent mixtures or the removal of undesirable impurities by solvent aid is called extraction. "Liquid-liquid extraction" is that if the mixture to be separated consists of liquid components. If a substance or group is to be separated from a

Liquid-liquid extraction is called separation by contacting a substance dissolved in the liquid solution with another liquid, which does not mix with the solution. The first application of this process is the extraction of gold and silver from the liquid copper by the Romans using lead as solvent.

A simple extraction process consists of three basic components: solute, carrier, and solvent. The part rich in the feed liquid separated from the extractant is called raffinate (aqueous phase),

Extraction is generally preferred over distillation in the following cases. These are: a. The presence of dissolved or complexed inorganic substances in the solution

c. Separation of components which are very close to boiling or melting points

3. Extraction for food production

methods has been accelerated.

3.1.1. Liquid-liquid extraction

3.1. Traditional extraction techniques

solid material, this process is called "solid-liquid extraction."

and the part rich in solvent is called the extract (organic phase).

b. The desire to separate a very low concentration component

d. Separation of azeotrope-forming mixtures

Solid-liquid extraction is called separation of one or more components contained in the solid with the aid of a bit solvent. The process can be considered in four stages:


Solid-liquid extraction is the process of separating sugar from sugar beet by means of hot water in a food industry; extracting oils from plants such as peanut, soybean, flaxseed, bean, and cottonseed through organic solvents such as hexane, acetone, and ether; and extracting oils of tea and fish from tea leaves to be used in different processes.

#### 3.1.3. Solvent selection in extraction process

The most important key parameter in an effective extraction process is the choice of an appropriate solvent. "Similar solver" principle is used. In general, the following considerations are applied when choosing solvents:


#### 3.2. New green techniques for sustainable food production and processing

The efficient use of resources in different branches of the food industry and the maintenance of sustainability is a matter that has been on the move in recent times. At the same time as the use of renewable energy resources, the sector may be economically more advantageous in terms of product cost. Green technology can be applied in many important areas such as logistics, packaging, and waste disposal in food sector. The application of the green extraction technology, which has been particularly popular in recent years, to the food sector has been one of the important outputs of these researches. Extraction processes have also become commercially available in the fields of polymer technology, pharmaceutical industry, certain chemicals, and specialty oils. Products which cannot be obtained by conventional methods or which are difficult to obtain can be produced with high performance by this application. Such applications for environmentally friendly fluids offer significant potential for both technical and economic success. At present, there are many factors that are not paying attention to nutrition inevitably, and it is necessary to present an alternative by increasing the frequency of sharing meetings and by using new technological opportunities for consumers and using new technologies for healthy nutrition. Just as it is in green technology, it is a common view of the food industry that it is an important opportunity to emphasize that these studies have been successfully applied to agricultural products as a healthy alternative to food and that it is an opportunity to share new application fields as research models.

form of a container and fill it. It is not a liquid, but has near-liquid density and solubility values (Figure 1). Tc and Pc values are different for each supercritical fluid. Tc and Pc values for carbon dioxide, one of the most common supercritical fluids, are 31.1C and 7.38 MPa and 646.8C and 22.06 MPa for water, another fluid. Controlled increase in temperature and pressure values brings these two parameters together at a common point called the "critical point." The said Tc and Pc values are the temperature and pressure values possessed at the critical point. When this point is reached, the solvent is described as SCF. The properties in the SCF region are a combination of the good solvency of the fluids and the good diffusivity of

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Different thermodynamic properties that SCFs exhibit at the critical point and near these points can be predicted with the aid of phase diagrams. From these approaches, different

modeling and system optimization studies can be done on the way of engineering.

Property Gas SCF Liquid Density (g/mL) (0.6–2) <sup>10</sup><sup>3</sup> 0.2–1.0 0.6–1.6

) (1–3) <sup>10</sup><sup>3</sup> (1–9) <sup>10</sup><sup>3</sup> (0.2–3) <sup>10</sup><sup>2</sup>

) 0.1–0.4 (2–7) <sup>10</sup><sup>4</sup> (0.2–2) <sup>10</sup><sup>5</sup>

) 0 0 30–60

the gases (Table 1).

Figure 1. SCF temperature-pressure diagram.

1

Table 1. Properties of some fluids at critical conditions.

1

Surface tension (dynes cm<sup>1</sup>

Viscosity (g cm<sup>1</sup> s

Diffusivity (cm2 s

#### 3.2.1. Supercritical extraction

Many food items are produced using different methods and are used after a number of separations [11]. It is also possible to use alterative techniques in conditions more suitable to the particular techniques utilized in production. The primary goal of the production and decomposition processes is to have a process that contributes to the people in production, to the manufacturing enterprises, to the sector, and even to the environment. For this reason, supercritical fluids (SCFs), which have become increasingly popular in the last 40 years, have become the focus of many different food production processes [12–14]. As a result, legal regulations on solvent residue limits in food products and environmental regulations on sector wastes have become widespread, increasing the use of SCFs.

SCFs have several advantages over the conditions provided in conventional methods. The most important advantage is that it allows for less solvent consumption and shorter processing times, as well as achieving dimensions that will not harm the environment in waste regimes. Another important feature of SCFs is that the dissolution power can be controlled by changing the density because the physicochemical properties are located between the gas and liquid phases. A small change in the pressure and/or temperature parameters can make a significant difference in the fluid density used and can increase the solving power by about 80–100 times. Materials with different polarities on this count can be processed by using only one type of SCF. This is due to the fact that the molecular diffusion rate of SCFs is as high as that of gases and the solubility density is as effective as liquids [15]. In parallel with the technological developments used in recent years, new materials and methods have been started to be used in the food processes that are progressing to start with raw material supply [16]. Supercritical extraction (SFE), microwave extraction (MWE), and ultrasonic extraction applications are the most well-known examples.

#### 3.2.1.1. Definition and basic properties of supercritical fluids (SCFs)

SCF is defined as the fluid whose temperature and pressure values are above the critical temperature (Tc) and critical pressure (Pc) values. In other words, an element or a component can be defined as a mixture of Tc and Pc. Like a gas, it is a compressible flow that can take the form of a container and fill it. It is not a liquid, but has near-liquid density and solubility values (Figure 1). Tc and Pc values are different for each supercritical fluid. Tc and Pc values for carbon dioxide, one of the most common supercritical fluids, are 31.1C and 7.38 MPa and 646.8C and 22.06 MPa for water, another fluid. Controlled increase in temperature and pressure values brings these two parameters together at a common point called the "critical point." The said Tc and Pc values are the temperature and pressure values possessed at the critical point. When this point is reached, the solvent is described as SCF. The properties in the SCF region are a combination of the good solvency of the fluids and the good diffusivity of the gases (Table 1).

Different thermodynamic properties that SCFs exhibit at the critical point and near these points can be predicted with the aid of phase diagrams. From these approaches, different modeling and system optimization studies can be done on the way of engineering.

Figure 1. SCF temperature-pressure diagram.

important outputs of these researches. Extraction processes have also become commercially available in the fields of polymer technology, pharmaceutical industry, certain chemicals, and specialty oils. Products which cannot be obtained by conventional methods or which are difficult to obtain can be produced with high performance by this application. Such applications for environmentally friendly fluids offer significant potential for both technical and economic success. At present, there are many factors that are not paying attention to nutrition inevitably, and it is necessary to present an alternative by increasing the frequency of sharing meetings and by using new technological opportunities for consumers and using new technologies for healthy nutrition. Just as it is in green technology, it is a common view of the food industry that it is an important opportunity to emphasize that these studies have been successfully applied to agricultural products as a healthy alternative to food and that it is an

Many food items are produced using different methods and are used after a number of separations [11]. It is also possible to use alterative techniques in conditions more suitable to the particular techniques utilized in production. The primary goal of the production and decomposition processes is to have a process that contributes to the people in production, to the manufacturing enterprises, to the sector, and even to the environment. For this reason, supercritical fluids (SCFs), which have become increasingly popular in the last 40 years, have become the focus of many different food production processes [12–14]. As a result, legal regulations on solvent residue limits in food products and environmental regulations on sector

SCFs have several advantages over the conditions provided in conventional methods. The most important advantage is that it allows for less solvent consumption and shorter processing times, as well as achieving dimensions that will not harm the environment in waste regimes. Another important feature of SCFs is that the dissolution power can be controlled by changing the density because the physicochemical properties are located between the gas and liquid phases. A small change in the pressure and/or temperature parameters can make a significant difference in the fluid density used and can increase the solving power by about 80–100 times. Materials with different polarities on this count can be processed by using only one type of SCF. This is due to the fact that the molecular diffusion rate of SCFs is as high as that of gases and the solubility density is as effective as liquids [15]. In parallel with the technological developments used in recent years, new materials and methods have been started to be used in the food processes that are progressing to start with raw material supply [16]. Supercritical extraction (SFE), microwave extraction (MWE), and ultrasonic extraction applications are the

SCF is defined as the fluid whose temperature and pressure values are above the critical temperature (Tc) and critical pressure (Pc) values. In other words, an element or a component can be defined as a mixture of Tc and Pc. Like a gas, it is a compressible flow that can take the

opportunity to share new application fields as research models.

164 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

wastes have become widespread, increasing the use of SCFs.

3.2.1.1. Definition and basic properties of supercritical fluids (SCFs)

3.2.1. Supercritical extraction

most well-known examples.


Table 1. Properties of some fluids at critical conditions.

#### 3.2.1.2. Application areas of supercritical fluid extraction (SFE) in food industry

SFE is an important alternative to traditional extraction methods. The SFE process can be carried out as a continuous and continuous process depending on the production capacity. In the extraction process, the food substance to be extracted is placed in the extraction cell located in the heating chamber. SCF fed to the system with the aid of a pump is brought to the desired pressure value according to the polarity and solubility characteristics of the target food material and reaches the appropriate temperature level corresponding to the pressure value with the help of the heating reservoir. At this time, the solvent is transported to subcritical or supercritical conditions, and the sample migrates to the extracellular medium contained in the food. Throughout the extraction period, the pressure value of the solvent leaving the extraction cell begins to decrease by interfering with the food and extracting the target material with the polarity appropriate to it. This liquid which is loaded with the target substance and which is in the properties of SCF passes through the liquid fascia by lowering the pressure and, preferably, depending on the desired temperature value. It is separated from the target substance extracted from the difference of boiling point and density due to the physicochemical property. It is then fed back to the system for reuse with the pump again (Figure 2).

SFE has been used commercially in the food industry for the first time to remove caffeine from coffee. In addition, spices are used to obtain important components from many foodstuffs such

Ultrasonic sound waves are the sound waves on the level that the human ear can handle. Ultrasonic wave application is divided into two groups as low-energy and high-energy application in food industry. The amount of energy produced in this classification is the most

mine the physicochemical properties (rigidity, maturity, composition, particle size, acidity, etc.) of foods. High-energy ultrasonic application is used for microbial and enzymatic inactivation in food. High-energy ultrasonic application affects food physically, chemically, and mechani-

Ultrasound technique has been successfully used in food industry to determine chocolate content and eggshell thickness; to determine fat content; to determine lean tissue in meat; to determine contaminants such as metal, glass, or wood in food; and to determine food composition and particle size. In addition to these, it has been reported that it can be used as an alternative to traditional extraction methods in many studies such as extraction of phenolic compounds from the consortia, extraction of red and yellow pigments, extraction of fat and proteins from soybean, and oil extraction from oil seeds. Ultrasonic application increases the surface area between solid and liquid parts by decreasing particle diameter. The mechanical activity of the ultrasound accelerates the distribution of solvent toward the tissues. Because mechanically the cell wall is destroyed, the passage of the component to solvent, which is the solvent, will be facilitated. Ultrasonication also increases the extraction kinetics and the quality

In recent years it has been reported that the combination of ultrasound and supercritical carbon dioxide application significantly increases the extraction efficiency. There are many

Ohmic heating is a process applied by the passage of electric current through the food. It is also known as joule heating, electric-heating and electrical resistance heating. Ohmic heating is achieved by the conversion of electrical energy into heat energy, depending on the electrical resistance of the glass. In other words, when food shows resistance against flow, heat formation is seen. The higher the electrical resistance of a food, the more homogeneous heating is achieved. Therefore, since the conductivity of solid materials is higher, if the process conditions are applied correctly, it will heat up faster than liquid materials. One of the advantages of ohmic heating is that it homogenizes food very quickly. It is very suitable for materials sensitive to heat since the hot zone does not occur on the surface during heating. Other important advantages of the system are its high product quality, silent operation, and its ability to be used in particulate matter. The success of ohmic heating depends primarily on the rate of

more studies in which ultrasound techniques are used for extraction purposes.

). Low-energy ultrasonic application is most commonly used to deter-

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as aromatics, essential oils, medicinal plants, fruits and vegetables, and animal oils.

important criterion and is defined by sound power (W), sound density (W/m<sup>2</sup>

3.2.2. Ultrasound-assisted extraction

cally, while low-energy ultrasonic application does not.

energy density (W/m<sup>3</sup>

of the extract.

3.2.3. Ohmic heating-assisted extraction

The viscosity of the SCF is lower than the liquids, and the flow properties are good. Due to its low surface tension, it penetrates into food raw materials and increases extraction yield. The resolution values can be changed by adjusting the temperature-pressure values. Costs are low, solvents are used, and extraction does not leave waste as a result. Due to all these positive features, SFE operated using SCF has a wide use as a good example of green technology.

Figure 2. SFE system.

SFE has been used commercially in the food industry for the first time to remove caffeine from coffee. In addition, spices are used to obtain important components from many foodstuffs such as aromatics, essential oils, medicinal plants, fruits and vegetables, and animal oils.

#### 3.2.2. Ultrasound-assisted extraction

3.2.1.2. Application areas of supercritical fluid extraction (SFE) in food industry

166 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

It is then fed back to the system for reuse with the pump again (Figure 2).

Figure 2. SFE system.

SFE is an important alternative to traditional extraction methods. The SFE process can be carried out as a continuous and continuous process depending on the production capacity. In the extraction process, the food substance to be extracted is placed in the extraction cell located in the heating chamber. SCF fed to the system with the aid of a pump is brought to the desired pressure value according to the polarity and solubility characteristics of the target food material and reaches the appropriate temperature level corresponding to the pressure value with the help of the heating reservoir. At this time, the solvent is transported to subcritical or supercritical conditions, and the sample migrates to the extracellular medium contained in the food. Throughout the extraction period, the pressure value of the solvent leaving the extraction cell begins to decrease by interfering with the food and extracting the target material with the polarity appropriate to it. This liquid which is loaded with the target substance and which is in the properties of SCF passes through the liquid fascia by lowering the pressure and, preferably, depending on the desired temperature value. It is separated from the target substance extracted from the difference of boiling point and density due to the physicochemical property.

The viscosity of the SCF is lower than the liquids, and the flow properties are good. Due to its low surface tension, it penetrates into food raw materials and increases extraction yield. The resolution values can be changed by adjusting the temperature-pressure values. Costs are low, solvents are used, and extraction does not leave waste as a result. Due to all these positive features, SFE operated using SCF has a wide use as a good example of green technology.

Ultrasonic sound waves are the sound waves on the level that the human ear can handle. Ultrasonic wave application is divided into two groups as low-energy and high-energy application in food industry. The amount of energy produced in this classification is the most important criterion and is defined by sound power (W), sound density (W/m<sup>2</sup> ), or sound energy density (W/m<sup>3</sup> ). Low-energy ultrasonic application is most commonly used to determine the physicochemical properties (rigidity, maturity, composition, particle size, acidity, etc.) of foods. High-energy ultrasonic application is used for microbial and enzymatic inactivation in food. High-energy ultrasonic application affects food physically, chemically, and mechanically, while low-energy ultrasonic application does not.

Ultrasound technique has been successfully used in food industry to determine chocolate content and eggshell thickness; to determine fat content; to determine lean tissue in meat; to determine contaminants such as metal, glass, or wood in food; and to determine food composition and particle size. In addition to these, it has been reported that it can be used as an alternative to traditional extraction methods in many studies such as extraction of phenolic compounds from the consortia, extraction of red and yellow pigments, extraction of fat and proteins from soybean, and oil extraction from oil seeds. Ultrasonic application increases the surface area between solid and liquid parts by decreasing particle diameter. The mechanical activity of the ultrasound accelerates the distribution of solvent toward the tissues. Because mechanically the cell wall is destroyed, the passage of the component to solvent, which is the solvent, will be facilitated. Ultrasonication also increases the extraction kinetics and the quality of the extract.

In recent years it has been reported that the combination of ultrasound and supercritical carbon dioxide application significantly increases the extraction efficiency. There are many more studies in which ultrasound techniques are used for extraction purposes.

#### 3.2.3. Ohmic heating-assisted extraction

Ohmic heating is a process applied by the passage of electric current through the food. It is also known as joule heating, electric-heating and electrical resistance heating. Ohmic heating is achieved by the conversion of electrical energy into heat energy, depending on the electrical resistance of the glass. In other words, when food shows resistance against flow, heat formation is seen. The higher the electrical resistance of a food, the more homogeneous heating is achieved. Therefore, since the conductivity of solid materials is higher, if the process conditions are applied correctly, it will heat up faster than liquid materials. One of the advantages of ohmic heating is that it homogenizes food very quickly. It is very suitable for materials sensitive to heat since the hot zone does not occur on the surface during heating. Other important advantages of the system are its high product quality, silent operation, and its ability to be used in particulate matter. The success of ohmic heating depends primarily on the rate of heat production, the electrical conductivity of the food, the composition of the food, the intensity of the electric field, and the duration of the waiting period.

rotation in the presence of electrical changes. The dipoles are arranged at 2450 MHz and distributed randomly at 4.9109 times in the second. As a result of this motion, heat is generated by the vibration. In the ionic conduction mechanism, the magnetic field is generated by the movement of ions at the end of the application. The solvent heats up by friction resulting from the resistance of the solvent to the ion flux. In most applications, two mecha-

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The frequency, microwave power and heating speed, temperature, mass of food, water content, density, physical geometry, thermal properties, electrical conductivity, and dielectric properties of food are affected by microwave heating. Microwave, which has been used for various applications in food for many years, is also a preferred method for increasing extraction efficiency (Table 2). Contrary to classical heating, in the case of microwave heating, for example, all are heated uniformly and quickly at the same time. The cells are heated by microwave radiation by the moisture in them and apply pressure to the cell wall as a result of evaporation. The cell wall is disrupted by this high pressure, and the passage of the components to the solvent is ensured. One of the most important parameters in extraction process is solvent choice. Solvents with a larger dipole moment will heat up faster. According to the solvent dipole moments, acetonitrile, methanol, acetone, ethyl acetate, water, ethyl alcohol and hexane are the most commonly used solvents for phenolic substance extraction from plant source. The nonpolar solvent hexane (dipole moment <0.1) will not heat up in the microwave. Microwave extraction is performed with two different systems (Figure 3). The most common system is the closed system extrusion made in a closed container that can control temperature and pressure. The other method is carried out in an open container under atmospheric pressure. The advantage of this method is that the amount of extraction and the amount of solvent used are small at large. The principle of heating using microwave energy is based on the direct effect of the microwave on the molecule through ion conduction and dipole rotation (rotation). In most applications, these two mechanisms come into play simultaneously. Ionic conduction is the electrophoretic migration of ions when a magnetic field is applied. The solution results in

Application Purpose Product

Table 2. Microwave applications in the food industry.

Tempering Temperature rise below freezing point Meat, fish, butter

Vacuum drying Moisture content reduction Seeds, cereals, citrus juices Freeze drying Moisture content reduction Meat, vegetables, fruits Drying Moisture content reduction Pasta, rice, snacks Cooking Aroma and texturing Ham, meatballs, potatoes Bleaching Inactivation of impaired enzymes Fruit, corn, potato Baking Heating and activation of bleaching agents Bread, pasta, donut Roasting To develop heating and heating reactions Coffee, cocoa, berries

Pasteurization Inactivation of vegetative microorganism Dairy products, ready-to-eat foods Sterilization Inactivation of microbial spores Pastries, cheeses, milk, fruit juices

nisms occur simultaneously.

Preliminary treatment of rice brass raw materials and extraction of oils by solvent extraction are examples of studies in which ohmic heating systems are used as pretreatment in extraction processes. For food samples pretreated using ohmic heating method, the yield varied between 49 and 92%, while for non-pretreated samples, the yield was 53%.

### 3.2.4. Pulsed electric field extraction

Pulsed electric field (PEF) technology is a food preservation process that is based on the use of the electric field to eliminate food-borne pathogenic microorganisms and to control microorganisms that destroy food, is nonthermal, and does not adversely affect food quality. A typical PEF unit consists of a high-voltage boost generator, application chamber, flow control system, control, and monitor device. The most important one of these is the application chamber, and it must be treated with care during design.

The successful results of PEF technology in liquid foods (especially fruit juice, milk, etc.) are noteworthy and lead to the production of high-capacity systems. In the near future, it is known that in developed countries, high-quality products will be obtained by processing liquid and semiliquid foods with PEF technology. In this context, it will be inevitable that many countries will follow these developments as the result of the conjunctural changes that will take place in the competition of international food trade. For this purpose, attention should be paid to other disciplines (such as machinery, industry, electrical-electronics, materials, and food engineering) to produce PEF technology in our country. Initiation of studies on PEF technology, transmission, and dissemination of this technology in the industry will enable the technology to be produced by the domestic industry.

#### 3.2.5. Microwave-assisted extraction

The use of microwave technology, which has been in use since the Second World War, in the analytical laboratory was at the end of the 1970s. Microwaves are electromagnetic radiation that varies in the range of 0.3–300 GHz and are usually extracted at 2.5–75 GHz in natural products. The efficiency of microwave energy depends largely on the content of the solvent, the plant material, and the applied microwave power. The advantage of microwave heating is the decomposition of oxidized weak hydrogen bonds at the poles of the molecules. Extraction with microwave is realized with two different systems. The most common system is the closed system extrusion made in a closed container that can control temperature and pressure. The other method is carried out in an open container under atmospheric pressure. The advantage of this method is that the amount of extraction and the amount of solvent used are largely small.
