Microwave drying characteristics and kinetic model of bitter gourd

Abstract: The effects of slice thickness, microwave power and loading on the microwave drying characteristics of bitter gourd were studied by single factor test. The microwave drying kinetics model of bitter gourd was established. 

microwave drying equipment 

The results showed that the microwave power had the greatest influence on the drying of bitter gourd, followed by the loading, and finally the slice thickness. The microwave drying of bitter gourd accelerated the drying stage and slowed down the drying stage. The fitting of 7 commonly used thin layer drying dynamics mathematical models is obtained by comparing the correlation coefficient R2, the square of the residue and the RSS and the chi square χ2. The tian model is most suitable for describing the microwave thin layer drying process of bitter gourd slices. Above 0.99.

Key words: thin layer drying; microwave drying; drying characteristics; bitter gourd; kinetic model bitter gourd,

Cucurbitaceae Momordica, in addition to water, protein, fat, carbohydrates, crude fiber and various vitamins, bitter gourd also contains bitter gourd, protein-like active substances and a variety of amino acids and a variety of essential mineral elements, with heat Detoxification, nourishing blood and replenishing qi, replenishing the kidney and protecting the spleen, nourishing the liver and clearing the effect, is a therapeutic treatment for diseases such as fire, fever, dysentery and swollen sores in summer. Fresh bitter gourd has a water content of more than 90%, which is not easy to store at room temperature.

bitter gourd microwave drying 

Effect of Drying Methods on Total Organic Acid Content of Total Flavonoids from Fructus Corni

Abstract: The effects of four kinds of microwave drying equipment on total flavonoids, total organic acids, vitamin C and color of hawthorn were studied, and the suitable drying methods of hawthorn were studied. Using hyperoside as standard, the content of total flavonoids in four kinds of drying methods was determined by colorimetric method. The total organic acid content in four kinds of drying methods was determined by acid-base titration with phenolphthalein as indicator. The content of vitamin C in hawthorn was determined by 2,6-dichlorophenol titration method. The color data of four kinds of dry hawthorn powder were determined by colorimeter.

microwave drying equipment

The results showed that the contents of total organic acids, total flavonoids and vitamin C in the four drying methods were significant. The total organic acid and vitamin C content of the freeze-dried samples were the highest, respectively 133. 25 mg / g and 0. 322 4 mg / g; the lowest in natural drying, 94. 55 mg / g and 0. 163 1 mg / g. The content of total flavonoids in microwave drying samples was the highest, and the content of naturally dried samples was the lowest, respectively. 26 mg / g and 32. 25 mg / g. In terms of color, vacuum freeze-dried hawthorn has the best color. Vacuum freeze-drying, on the basis of maximally retaining vitamin C, reduced the loss of total flavonoids to a certain extent and exhibited the most desirable color.

hawthorn microwave drying 

Optimization of apple microwave drying scheme based on electronic nose odor detection

Abstract: In microwave drying, improper setting of process parameters will cause material structure damage and surface burnt, which is often accompanied by the emission of characteristic odor. This article takes apple as the object, adopts 60, 70, 80 °C constant temperature, fuzzy logic control and linear temperature control 5 kinds of drying schemes, through the odor map collected by electronic nose, studies the emission law of characteristic odor, and optimizes the drying scheme. According to the variation rule of apple flavor peak and coke paste peak in the odor map of the constant temperature scheme, the fuzzy logic control scheme determined can realize the on-line adjustment of the magnetron power, preserve the flavor and reduce the burntness. Optimize the measured material temperature curve in the fuzzy logic control scheme, determine the linear temperature control scheme, and eliminate the electronic nose detection link, which is more suitable for industrial applications.

microwave drying equipment

By comparing the product quality of different microwave drying equipment, the quality of the dried product under the linear temperature control scheme is high, time-consuming and strong, and the drying ability is a priority. This study provides a technical basis for the application of odor detection technology to apple drying.

Key words: apple microwave drying; temperature; odor detection; control scheme; apple

Introduction

Apple is widely loved by consumers since the early 1920s.
More than 300 volatile aromatic substances have been isolated from the odor of apples. Only a small part (about 20-40 kinds) of volatile components have been determined to have a decisive influence on sensory quality. In recent years, there has been a lot of research on the smell of apples, but many studies have focused on the classification and storage of apples. Only a part of the research is related to the drying process or parameter control. Three representative volatile components of apple during hot air drying and freeze drying were analyzed by gas chromatography-mass spectrometer (GC-MS).

apple microwave drying

Microwave drying kinetics and energy consumption analysis of cotton stalk

Abstract: In order to study the effect of loading on the drying time, drying rate, drying efficiency and unit energy consumption during microwave drying of cotton stalks, the experiment used microwave drying equipment with a microwave frequency of 2 450 MHz and an output of 1 kW. The amount of cotton stalks ranging from 34 to 200 g is dried.

 microwave drying equipment 

The results show that: the microwave drying equipment is in the deceleration phase after a short speed increase; the dry data is nonlinearly fitted by 7 common thin layer drying models, and the coefficient, root mean square error and dispersion are determined by comparison. Sum of squares, the Midilli model was found to be the optimal model for microwave drying of cotton stalks. The drying coefficient decreased with the increase of loading. When the loading increased from 34 g to 200 g, the drying time increased from 10 min. By 20 min; the effective diffusion coefficient of water in the cotton stalk decreases with the increase of the loading, and the average value is between 1.8078×10-8～4.1997×10-8 m2/s, and the average is obtained based on the Arrhenius equation. The activation energy is 4.82 W/g; when the loading is 34-200 g, the microwave drying efficiency can be improved by increasing the loading (7.52% to 19.78%), and the unit energy consumption of microwave drying (12.49-35.90 MJ/kg) is reduced
microwave drying of cotton stalks

Microwave test of germinated brown rice

1.1 materials and reagents

Rice (Wuyunjing) Nanjing Yuanwang Selenium-rich Agricultural Products Co., Ltd; GABA Standard, 4-Chloro-3,5-Dinitrotrifluorotoluene Sigma Company; Selenium Standard Solution National Center for Analysis and Testing of Nonferrous Metals and Electronic Materials; Sodium Selenite West Asia Reagent Company; XBridge C18 Reversed-phase Column Waters Company; Acetonitrile, Methanol Company (All of them are chromatographic purity), nitric acid, hydrochloric acid (all of them are high-grade purity), and other chemical reagent companies are analytical pure Guoyao Group.

 Microwave Drying Equipment.

1.2 instruments and equipment

JLGJ4.5 inspection ridge machine Taizhou Grain Instrument Factory; PQX multi-section programmable artificial climate box Ningbo Southeast Instrument Co., Ltd; 101-

Shanghai Sujin Instrument and Equipment Factory; MCR-3 Microwave Chemical Reactor Xi'an Yuhui Instrument Co., Ltd; FW100 High Speed Universal Pulverizer Tianjin Tester Instrument Co., Ltd; THZ-D Desktop Thermostat Oscillator Taicang Qiangle Experimental Equipment Co., Ltd; TDL-5-A Flying Pigeon Centrifuge Shanghai Antinko Instrument Co., Ltd. Learning instrument factory; Dionex Ultimate

Microwave drying of germinated brown rice

Enrichment of Selenium in Germinated Brown Rice and Optimization of Microwave Drying and Extruding Process

Abstract: The effects of selenium-enriched germinated brown rice   and  microwave drying equipment  extrusion on the nutritional quality of selenium-enriched germinated brown rice were investigated by using common japonica rice as raw material.

 microwave drying equipment 

It was found that when the mass concentration of selenium was 10 mg/L, a higher quality selenium-enriched germinated brown rice could be obtained. Under this condition, the germination rate of brown rice was 97.9%, and the organic selenium content was 977.6 μg/kg (mass fraction 98.5%). The content of γ-aminobutyric acid is 445.9 mg/kg; the microwave drying at 40 °C is beneficial to maintain the content of selenium and γ-aminobutyric acid in germinated brown rice; the content of organic selenium and γ-aminobutyric acid in extruded products Compared with brown rice, it increased to 29 times and 5 times respectively.

Studies have shown that sodium selenite can be used as a selenium-enriched reagent to achieve effective selenium-enriched germinated brown rice, and selenium-enriched germinated brown rice can be used to develop related nutrient-expanded foods.

germinated brown rice microwave drying

Study on Microwave Drying Process of Lotus Seeds

Take lotus seed 300 g, fixed wind speed 1.5 m / s, set the wind temperature 40,
50, 60, 70, 80 °C, hot air drying, study the effects of different air temperature on the drying process and product rehydration, determine the appropriate microwave drying equipment conditions.

microwave drying equipment

1.3.2 lotus seed microwave drying equipment the study

Take 300 g of lotus seeds, set the microwave power of 1, 2 kW under vacuum condition of 0.1 MPa, vacuum microwave drying, study the influence of different microwave power on the drying process and product rehydration, and determine the appropriate vacuum microwave drying process. condition.

.

1.3.3 Research on Vacuum Freeze-drying Process of Lotus Seeds

300 g of lotus seeds were taken and pre-frozen at -40 °C for 2 h in a vacuum freeze dryer. Under the conditions of vacuum of 60, 90 and 120 Pa, the freeze-drying conditions were set to the first stage -20 °C/12 h. The second stage was -10 °C / 12 h, and the post-drying stage was 30 °C for 10 h. The effects of different vacuum degrees on the freeze-drying process and product rehydration were studied, and the suitable vacuum freeze-drying process conditions were determined.

1.3.4 Research on the hot air-vacuum microwave drying process of lotus seeds

Take 300 g of lotus seeds, dry the lotus seeds with suitable hot air drying conditions to a moisture content of 20%, 30%, 40%, and wet at 6 °C for 6 h, then under a vacuum of 0.1 MPa. Vacuum microwave drying was carried out under the condition of microwave power of 1 kW. The effects of different pre-drying moisture content on the drying process and product rehydration were studied, and the suitable hot air-vacuum microwave drying process conditions were determined.

 lotus seed microwave drying equipment 

Effect of Different Drying Methods on the Quality of Lotus Seeds

Abstract: Five different drying methods of hot air drying, vacuum microwave drying, vacuum freeze drying, hot air-vacuum microwave drying and hot air-air puffing drying of lotus seeds and their effects on physical properties, main nutrients and microstructure of lotus seed dry products were studied. .

 microwave drying equipment

The results show that the order of total color difference is vacuum freeze-drying>hot air-air puffing drying>hot air drying>vacuum microwave drying>hot air-vacuum microwave drying; hardness order is hot air drying>vacuum microwave drying>hot air-vacuum microwave drying> Hot air-air puffing and drying>vacuum freeze-drying, and the order of brittleness is vacuum freeze-drying hot air- Airflow puffing and drying>hot air-vacuum microwave drying>vacuum microwave drying>hot air drying; rehydration order is vacuum freeze drying>hot air-air puffing drying>hot air-vacuum microwave drying>vacuum microwave drying>hot air drying

The content of protein and crude fiber in the five products was not much different; the microstructure of vacuum freeze-drying, hot air-vacuum microwave drying and hot air-air-expansion drying products was observed, and the hot air drying product was still dense. Only a small amount of voids appear in the microwave drying equipment. In general, hot air-air puffing and drying can be used as a suitable processing method for developing lotus seed snack food.

lotus seed microwave drying

Establishment of Microwave Drying Characteristics and Kinetic Model of Instant Mushrooms

Abstract: In order to improve the microwave drying equipment in the production process of instant mushrooms, the effects of microwave power and loading on the microwave drying of ready-to-eat mushrooms were studied. The microwave drying characteristics of ready-to-eat mushrooms were obtained. The effect of water content on the sensory quality of ready-to-eat mushrooms was discussed. The optimum moisture content of ready-to-eat mushrooms was obtained. The kinetic model of ready-to-eat mushrooms microwave drying was studied. The fitting data was fitted by DPS software, and the fitting equation which accorded with the microwave drying law of ready-to-eat mushrooms was obtained. The effect is good; it provides a theoretical basis for the production of ready-to-eat mushrooms.

 microwave drying equipment

Key words: ready-to-eat mushrooms microwave drying; sensory quality; kinetic model

Lentinus edodes is a fungus of the fungus medicinal fungus. It is a fungus of the genus Lactuca, which is also known as the mushroom, the mushroom, the citron, commonly known as the Chinese mushroom. In 2010, the output of shiitake mushrooms in China has reached 4.01 million tons. At present, in addition to fresh food, shiitake mushrooms are processed into snack foods, seasonings and functional foods and medicines.

The mushroom snack food is delicious and convenient to eat, and is favored by consumers. At present, it has been processed into mushroom candied fruit, mushroom puffed food and mushroom fluffy with the mushroom or mushroom foot, but the mushroom snack food accounts for a small proportion of the processed mushroom products. It is far from meeting the needs of consumers and has a broad market prospect. Instant mushroom is a ready-to-eat food of dried mushrooms, which is produced by rehydration, halogenation, drying, cooling, vacuum packaging, sterilization, etc. The drying process is an important part in the production process of instant mushrooms, which affects the taste quality of the products. And storage stability.
ready-to-eat mushrooms microwave drying

Effect of microwave drying and blast drying on rice quality

The experiment was conducted to study the changes of bursting waist rate, germination rate, moisture content and RVA linguistic characteristics of different varieties of rice under the conditions of hot air and microwave drying equipment. The results show that microwave drying is more likely to cause Valley, especially indica rice burst and reduce germination rate.


microwave drying equipment


The RVA spectrum characteristic value was closely related to the apparent amylose and popping waist rate, and the decrease value of hot air and microwave drying was positively correlated with the apparent amylose and popping waist rate, and the correlation coefficients were 0.889","0.906"and 0.789", "and 0.846" respectively. There was also a significant positive correlation between the apparent straight chain detergent and the increase of bursting waist rate during hot air drying and microwave drying, and the correlation coefficient was 0.848 "" and 0.971 ". Drying affected the taste of Japonica Rice and glutinous rice, and the hardness of rice increased slightly. Rice has high amylose content, and microwave drying has great influence on its quality, which is not conducive to later storage and consumption.

Key words: rice microwave drying, hot air drying, burst waist, RVA characteristics

The moisture content of newly harvested rice is very high. If not treated in time, the materials and methods will change every time, which will affect the processing quality and edible quality of rice. On the other hand, the bursting waist rate was related to the basic index of rice. Some studies showed that the basal tamping index of different rice varieties was related to their appearance, and the cracking was most serious in the varieties with wide shape. It has been found that rice varieties with more amylose are more susceptible to cracking than rice varieties with more amylose when they are heated and dried.
 rice microwave drying

Effect of microwave drying on the content of sulforaphane in different parts of broccoli

ABSTRACT: Broccoli was used as raw material to determine sulfur content of radish in three different parts of broccoli flower, stem and leaf by high performance liquid chromatography (HPHC). Radish in the samples dehydrated by microwave drying equipment (wave power 900W, time 10min) and electric blast drying equipment (1000 drying temperature is 90 C, time is 2h) were compared and analyzed. The effects of microwave drying on the content of sulforaphane in broccoli were studied.

microwave drying equipment 

The results showed that the content of sulfur radish in different parts of broccoli dried by microwave was (152.50 t 0.27), (82.75 (1.28) and (23.720.18 mg kg, respectively. The content of sulfur radish in broccoli stems was about twice and seven times of that in broccoli leaves dried by electrothermal blast, and the content of sulfur radish in different parts of broccoli was the same. It is the highest in stems, 56.321.37mgkg, and (85.04 + 1.13) mgkg and (53.262.78) mgkg respectively in flowers and leaves.

Microwave drying and electric blast drying, broccoli leaf sulfur content surging greater, the stem and flower is not affected much, the leaves should be used electric blast drying stems and flowers can be used either wave thousand drying, or can also be used electric blast thousand drying keywords: wave thousand drying; broccoli; different parts; sulfur content of radish, contrast points The difference of sulforaphane content in broccoli samples obtained by microwave thousand drying (wave power 900W, time 10min) and electrothermal blast thousand drying (thousand drying temperature 90, time 2h) was analyzed. The effect of microwave thousand drying on sulforaphane content in broccoli was studied.

broccoli dried by microwave 

Experiment on microwave drying lotus root

1 materials and methods

1.1 materials and reagents

"Beauty Red Lotus Root: In May 2012 by the Jiangsu Province Yangzhou Baoying County Tianhe Food Co., Ltd. Lotus root is tender and tender, with pure white color and no obvious mechanical injury. After washing and peeling lotus root, the lotus root was sliced into 5-6 mm thick slices with stainless steel knife, and immediately soaked in 0.2% citric acid and 0.2% citric acid.

Microwave Drying Equipment 

1% sodium chloride color protector, half an hour later take out, blanching in boiling water for 3 minutes, flow water cooled to room temperature, put in 2% maltodextrin solution soaked for 1 hour, take out and drain, put in the refrigerator about - 18, freeze and reserve. The initial moisture content of lotus root slices before microwave drying is about

84%.

Citric acid, sodium chloride, maltodextrin are food grade; ascorbic acid, 2,6-dichloroindophenol, Folin reagent, acetone, sodium bicarbonate, oxalic acid, gallic acid, sodium carbonate are analytical pure.

1.2 instruments and equipment

DHG-9073B5-III Electric Heating Constant Temperature Blasting Drying Box (Shanghai Xinmiao Medical Device Manufacturing Co., Ltd.); MVD-1 Microwave Drying Equipment (Nanjing Xiaoma Mechanical and Electrical Equipment Factory); QDPH-5 Electric Heating Air Expansion Equipment (Tianjin Qinde New Material Technology Co., Ltd.);QTS texture analyzer (CNS Farnell, UK); FW100 high-speed universal crusher (Tianjin Tester Instrument Co., Ltd.); FA2104 cushion analysis balance (Beijing Saidoris Scientific Instrument Co., Ltd.); WSC-S color difference analyzer (Shanghai Precision Scientific Instrument Co., Ltd.); JSM-

5610LV scanning electron microscope (Japan Electronics);

JFC01600 gold plating instrument (Japan Jeol company).

microwave drying lotus root

Effects of different drying methods on the quality of lotus root chips

ABSTRACT: In order to determine the best drying method for leisure lotus root crisp slices, six different drying methods were adopted, including hot air drying,microwave drying equipment, hot air-vacuum microwave drying, hot air-air puffing drying, vacuum Microwave-Air puffing drying, hot air-vacuum Microwave-Air puffing drying. After drying, the quality indexes such as color, shrinkage, hardness, brittleness, VC retention, polyphenol retention and microstructure were analyzed.
microwave drying equipment

The results showed that hot air drying had little effect on the color of lotus root crisp slices, but the hardness was too low, brittleness was poor, VC and polyphenol loss was the most serious; vacuum microwave drying lotus root crisp slices VC and polyphenol retention rate was high, brittleness was good, but the hardness was too high, 

product shrinkage was serious, color difference and browning were high; The quality of lotus root crisp slices was better than that of single drying. The shrinkage and browning degree of lotus root slices dried by hot air-vacuum Microwave-Air puffing were significantly lower than that dried by vacuum microwave drying, while the retention rate of VC and polyphenols was significantly higher than that dried by hot air drying. The hardness, brittleness were moderate and the porosity was good. To sum up, hot air-vacuum Microwave-Air puffing drying is the most suitable method for processing lotus root leisure crisp slices.
 lotus root microwave drying

Study on variable temperature control method of Apple microwave drying

 Abstract: Microwave drying equipment can effectively shorten the drying time and improve the quality of apple dehydration. Six constant temperature microwave drying schemes and three variable temperature microwave drying schemes were used to study the drying characteristics and quality of apples under different schemes.

Microwave drying equipment 

The experimental results show that the drying rate of "constant temperature" drying scheme decreases slowly in the middle drying stage, which will result in lower quality of products. In the "drying rate control" scheme, the drying rate is controlled at a constant speed in the middle of drying, but there are some defects in the initial drying control; in the "linear temperature control" scheme, the drying rate is basically maintained at a constant speed in the middle of drying, and the drying time and energy consumption are reasonable, sensory quality and color quality are superior to the constant temperature drying; In the three-stage temperature control scheme, the complexity of the equipment used in the linear temperature control scheme is simplified. Although the product quality index is slightly decreased, the equipment is simplified, which is more conducive to industrial application. This study provides a technical basis for the application of microwave drying technology to Apple drying theory.

Key words: microwave drying, drying rate, temperature change, apple

Microwave drying technology is widely used in food industry because of its high efficiency and low energy consumption. In the process of Apple microwave drying, the electromagnetic wave emitted by magnetron directly acts on the ions and dipole molecule of the material, causing its vibration and mutual friction to produce heat, thus rapidly increasing the temperature of the object. If the magnetron stops working, the action of ions and dipole molecules in the object will stop immediately, and the temperature will drop faster than other ways of heating and drying from outside to inside. Therefore, by automatically adjusting the microwave power can quickly and effectively control the temperature of the object in the microwave drying process.

 Apple microwave drying

Study on the characteristics and quality of drying with hot air and microwaves of the germinated brown rice

The effect of the hot air drying equipment and the  microwave drying equipment on the drying characteristics, main nutrients, enzymatic power. The hardness and color of the sprouted brown rice were established. The mathematical model provides a basis for the prediction of microwave drying quality and the control of drying conditions.

 microwave drying equipment

The dry model and the Page equation based on the Fick diffusion law can be well adjusted to the hot air curves and microwave drying of the sprouted brown rice. With the increase of the temperature of the hot air or the increase of the specific power of the microwave, the speed of constant drying and the effective diffusion The energy of activation of the drying of hot air of the germinated brown rice was of 55.76 kJ / mol. The drying conditions have a significant effect on the main nutrient content, the enzymatic hydrolysis and the hardness of the sprouted brown rice. The sprouted brown rice undergoes a browning reaction during the drying process, and the color is probably yellow. The reddening of the germinated brown rice is obtained by drying with microwaves. It is greater than that of hot air drying.

Keywords: germinated brown rice; drying with hot air; drying with microwaves; mathematical model; γ-aminobutyric acid

It was germinated to obtain germinated brown rice under suitable environmental conditions such as temperature and humidity. During the germination process, the endogenous enzyme is activated, the outer layer of the crude fiber is softened enzymatically, the protein is degraded into polypeptides and amino acids. And the starch becomes sugar. Phytase degrades phytic acid in inositol and phosphoric acid, and also produces γ-aminobutyl. Physiologically active ingredients such as acid, ferulic acid and hexa-inositol phosphate improve the nutritional composition and taste of brown rice. .

Among them, GABA is a widely existing inhibitory neurotransmitter, which has the effects of preventing Alzheimer's disease, hypertension, anxiety and the search for lipid metabolism.

Fresh sprouted brown rice has a high water content, rich nutrition and mold, and drying is the key technology to improve the shelf life of sprouted brown rice. Currently, the research on the drying of the sprouted brown rice focuses mainly on the effect of the drying process on the speed of drying, the composition of nutrients, the processing properties and the color of the sprouted brown rice.

microwave drying of sprouted brown rice 

Vacuum microwave drying characteristics and kinetic model of Pleurotus abalone

Abstract: In order to understand the change of moisture content in Abalone Mushroom in vacuum microwave drying equipment, vacuum microwave drying experiments were carried out, and the effects of different vacuum (- 50, - 70, - 85 kPa), microwave power (250, 750, 1250 W) and loading amount (50, 100 and 150 g) on the vacuum microwave drying characteristics of abalone mushroom were obtained. The results showed that the vacuum microwave drying process of abalone mushroom conformed to Page equation (P This study provides a theoretical basis for the optimization and control of Pleurotus abalone in vacuum microwave drying process.

 microwave drying equipment

Keywords: Pleurotus abalone; vacuum microwave; drying characteristics; kinetic model.

Pleurotus is not only of high nutritional value and high pharmacological value, but also has broad prospects for deep processing. However, abalone mushroom has high moisture content, browning occurs on the surface of the mushroom after several days of storage at room temperature, autolysis of the fungus cover film occurs, and white flocculent mold grows and begins to rot, eventually losing edible value. This post-harvest ripening restricts the transportation and fresh sale of abalone mushroom. Therefore, we need to dry the Pleurotus mushroom to prolong its storage life. At present, the traditional drying methods of mushrooms are hot air drying and sun drying, but the drying time is long, resulting in dark color and nutritional loss of mushrooms. After rehydration, the mushroom body can not maintain the color and shape of the original mushroom body, affecting the edible sense organs. Therefore, the application of modern high-tech food drying technology to the dry production of Pleurotus eryngii is of great significance to improve the level of dry processing of Pleurotus eryngii and promote the production of Pleurotus eryngii.

Microwave drying technology of Pleurotus eryngii is a combination of vacuum drying and microwave drying technology, which has the advantages of high speed and efficiency. The change of material moisture content is significant for drying process and directly affects product quality. Limited to the modern drying technology, it is still a difficult problem to realize the on-line detection of moisture content in the drying process. Therefore, the study of moisture variation during the drying process will provide more theoretical basis for actual production.

Microwave drying technology of Pleurotus 

Effect of vacuum microwave drying on main carotenoids in pumpkin slices

Abstract: The main carotenoids in pumpkin slices were determined qualitatively and quantitatively by C30 column and high performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization tandem mass spectrometry. The results showed that the total carotenoid content of pumpkin slices dried by vacuum microwave was significantly higher than that dried by hot air (P < 0.05). Microwave intensity had the greatest influence on carotenoids in pumpkin slices, followed by vacuum and slice thickness.

microwave drying equipment

With the increase of microwave intensity, the content of total carotenoids in pumpkin slices decreased significantly (P Meanwhile, the contents of main carotenoids alpha-, beta-carotene and lutein in pumpkin slices decreased with the increase of microwave intensity, and increased with the increase of vacuum and slice thickness, while the cis-isomers of beta-carotene decreased with the increase of vacuum, but the content of cis-isomers did not change significantly with the increase of slice thickness. It can be seen that increasing the vacuum and the thickness of the slices is beneficial to increase the carotenoid retention rate, while high microwave intensity makes the carotenoid content decrease.

Key words: Pumpkin slices; microwave drying equipment; carotenoids Pumpkin (Cucurbita moschata) is widely planted in China. It contains not only amino acids, vitamins, carbohydrates, pectin and trace elements, but also rich in carotenoids, especially alpha-carotene and beta-carotene. It has anti-oxidation, anti-cancer, prevention and treatment of cardiovascular diseases and immune system. Obstacles and other effects. Pumpkin is mainly used for fresh food, and its processing capacity is small. It often decomposes because it can not be sold or processed in time.

microwave drying of pumpkin

Research progress of microwave drying technology and equipment for agricultural products

Abstract: Taking the microwave drying technology as the research object, the research status of microwave drying equipment in agricultural products processing was expounded, and some technical problems such as uneven drying and partial burning in microwave drying were put forward. Then, the research progress of hot air microwave fluidized drying, vacuum microwave drying, freeze microwave drying and other combined technologies and equipment were introduced. Finally, by analyzing the advantages and disadvantages of different processing technology, it is pointed out that microwave combined drying technology is the development trend of  microwave drying industry for agricultural products. 

microwave drying equipment

Key words: agricultural products; microwave drying; equipment; research progress 0 Introduction

Drying is an important means to ensure the quality of agricultural products. It is also a common food processing technology. China's agricultural products are relatively scattered, and the processing level is backward, resulting in a large number of losses in the transportation, storage and marketing links after harvest. Timely and effective post-harvest drying is of great significance to reduce the production costs and economic losses of grain, fruits and vegetables, edible fungi and other agricultural products.

In recent years, the demand for dehydrated fruits and vegetables has been increasing rapidly both in China and in the international market. The dried products after dehydration are not only convenient for transportation, storage and sale, but also improve the added value of agricultural products, and have great market potential and development space. It is particularly important to improve the drying technology level of agricultural products.

microwave drying industry for agricultural 

Combined drying test of hot air and microwave

Microwave drying equipment has a significant advantage in drying efficiency, and there is a certain difference in drying quality between microwave drying equipment and hot air drying equipment. Lu Weiqiao et al. analyzed the quality of ginger slices dried by microwave and hot air through scanning electron microscope. The results showed that the structure of ginger slices dried by microwave changed, the cell wall became confused under microwave, and mixed with starch granules. The change of structure would affect the rehydration ability and rehydration ability of the products. After the physical properties.

Microwave drying equipment

Microwave drying is the whole volume heating. If the water is not dispersed in time, the material will deteriorate due to overheating. Microwave drying speed is too fast, the final moisture content will be difficult to control, these technical defects to a single microwave drying challenges. Hot air drying at the beginning and the final stage can save energy and control the final state of the product. In the process of atmospheric pressure, hot air can effectively remove the free water from the surface of the material, and the dehydration process is mild and slow, which can ensure that the cytoskeleton of the material is not destroyed. The microwave drying process can accelerate the migration of moisture in the material. The combination of microwave and hot air in the middle stage can improve the working efficiency and drying quality

2.1 hot air atmospheric pressure microwave drying

Hot-air microwave drying under atmospheric pressure is to optimize the drying process combination by synergistic dehydration of internal and external materials with microwave and hot air. The drying time of carrot by microwave was shortened by 25%-90% compared with that without microwave, and the better drying quality was obtained at low power. The microwave combination drying of Agaricus bisporus can not only shorten the processing time, but also improve the product quality and rehydration ability

Microwave drying of garlic 

Thermophysical properties and porous properties of Soybean under microwave drying mechanical equipment

Abstract: The temperature and quality changes of Soybean samples during microwave drying were measured in real time by using

microwave drying machine

test system. The variations of physical properties such as density, thermal conductivity, specific heat and thermal diffusivity of samples with different moisture content during drying were analyzed. 

From the point of view of porous media, the variations of pore properties such as porosity, fractal dimension, pore diameter and specific surface area in different drying nodes (100%, 85%, 70%, 55%, 40%) were studied. Law. By changing the microwave heating power, the influence of microwave power on the heat and mass transfer of samples is analyzed. The results showed that during the microwave drying process, a dense membrane was formed in the cortex cells of soybean, which hindered the water migration. When the moisture content was reduced to 30%, the coke appeared inside the sample, and then the cells in the center collapsed completely. But the density of the whole drying process is not large, and the reduction is about 5 kg /m3

. Soybean microwave drying equipment

Temperature dependent properties of wood during microwave drying

It can be said that the microwave radiation power has a significant effect on the temperature variation characteristics of wood. The higher the power is, the faster the heating rate is, and the shorter the isothermal time is. The thicker the sample is, the slower the heating rate is, but the difference is not big. The temperature distribution inside the wood during the microwave drying process is abnormal. The temperature distribution inside the wood is uniform, and the temperature gradient from the center to the wood surface is not ten. The temperature of wood increased during the late stage of drying.

Distribution and variation of water content field in wood during

  microwave drying equipment

During microwave drying of wood, the moisture distribution in wood interior is very different from that in conventional drying. In conventional drying, the moisture movement speed of interior is usually less than that of evaporation on the surface of wood, and the surface layer reaches below the fiber saturation point rapidly, and the central part is larger. Water content gradient. In the process of microwave vacuum drying, the moisture content distribution in wood showed different laws.

microwave drying of wood 

Analysis of moisture migration mechanism of wood during microwave drying

The microwave drying equipment test showed that the temperature distribution in wood was uniform during the microwave vacuum drying process, and there was no fixed distribution pattern of overall internal high, external high and external low or external high and internal low. Uniform, there is no obvious integral moisture gradient in the direction of wood thickness; with the decrease of wood moisture content, the moisture distribution inside the wood is more uniform; in the early stage of wood drying, there is moisture accumulation on the surface of the wood.

microwave drying equipment

In the course of microwave drying, when the moisture content of wood is below the fiber saturation point, there is no obvious internal high and external low moisture content field and fixed internal high and external low temperature field.

Therefore, the effect of moisture gradient on moisture diffusion and heat diffusion can be neglected during microwave drying of wood. Moisture migration in wood is mainly driven by the total pressure gradient, which is removed by osmotic flow in the form of liquid water or steam. When the moisture content of wood is below the fiber saturation point, the absorbed water in the wood itself does not move, but moves toward the adjacent area.

microwave drying of wood 

Study on microwave drying of wood

Wuxi No.2 Furniture Factory developed a wood microwave dryer in May 1977. Through several years of production practice, the technical performance of the microwave drying equipment is basically stable, and the drying production is relatively normal. Sometimes it can maintain two shifts of production, and has accumulated certain production experience, which is beneficial to the research and popularization of wood microwave drying technology in China. Contribution.

wood microwave dryer 
In order to summarize the experience, make the drying standard and promote the drying production, Northeast Forestry College cooperated with Wuxi Furniture Factory II. During 1981-1982, the productive technology experiment of wood microwave drying was carried out under the production conditions of the factory.

The test equipment and methods The test equipment is a microwave dryer with a Novo cavity, which consists of a microwave source, a resonant cavity, an energy suppressor, a humidity exhaust device and a transmission system.

microwave drying equipment 

Study on microwave drying

Based on the test results and years of production experience, the microwave output power listed in the microwave drying reference list of some commonly used tree species and sawn timber specifications is proposed. For a channel

microwave dryer 

like Wuxi Furniture Factory II, which consists of four two resonant cavities in series, the first three (1-3) can be of medium power. Begin to gradually increase to the maximum upper limit, the last (fourth) take the minimum power (lower limit), to avoid serious mismatch, damage pipe 2.

The results showed that the quality index of wood microwave drying could be added with carbonization index on the basis of convective drying quality index (average final moisture content, drying uniformity, moisture content gradient, stress deviation, visible defects such as cracking, bending, etc.). There are 385 samples in this experiment, only 9 of them are carbonized, accounting for 2.3%. If the moisture content gradient on the thickness of the wood according to the above drying criteria, the result of this test is satisfactory.

It reflects the obvious law that the water content of surface layer is higher than that of core layer (see Table 1).This is the characteristic of microwave drying different from convection drying. The distribution of final moisture content of 01.2.6 Xin Lan song 48 was uniform along the length of test material.

wood microwave drying