Study On The Microwave Vacuum Drying Characteristics Of Lonicera Japonica And Optimization Of The Drying Technology

Honeysuckle, named as Lonicera japonica, is the half caprifoliaceae perennial evergreen woody plants. It is known as the heat-clearing and detoxicating medicine since ancient times. Modern research has shown that honeysuckle contains chlorogenic acid, mignonette glycosides and other pharmacological active ingredients, and has antimicrobial, anti-inflammatory and antipyretic effects. Traditional honeysuckle drying technologies are mostly focused on natural air drying and hot air drying, which may cause serious loss of effective components, long drying time and bad appearance of the product. The microwave vacuum drying technology was introduced in this thesis and was applied for honeysuckle drying process. This thesis investigated the effects of the steaming pre-treatment processes on the comprehensive quality of honeysuckle, and the characteristics of microwave vacuum drying of honeysuckle and its drying kinetics model, the effect of drying parameters on the honeysuckle effective components. Then the honeysuckle microwave vacuum drying technology was optimized, and chlorogenic acid dissolution kinetics model was established finally. The main contents are summarized as follows:1. Investigate the effects of the steaming pre-treatment process on the activity of polyphenol oxidase and peroxidase, the contents of chlorogenic acid, flavonoid and polysaccharide and amino acids. The steaming process was as follows:the honeysuckle was flat on steamer with the lid, treated with boiling water steam for 1 min. Based on the results obtained, the activity of polyphenol oxidase and peroxidase of honeysuckle were greatly inhibited, while the chlorogenic acid content, the flavonoid content and the polysaccharide content increased by 77.49%,144.08% and 116.52%, respectively.2. Research on the honeysuckle microwave vacuum drying characteristics. The experimental results showed that the honeysuckle microwave vacuum drying process can be divided into three stages, including the acceleration, constant speed and deceleration based on the water loss rate.The higher power of microwave and vacuum degree, the faster of the honeysuckle water loss rate was obtained. The higher loading capacity, the slower of the honeysuckle water loss rate was observed. To enhance the power of microwave and vacuum degree can effectively shorten the drying time.3. According to the water loss rate during the honeysuckle microwave vacuum drying process, the drying kinetics model of water loss rate and drying time was established. The model equation is MR=e-rlN,r=e-2.038-0.007x1+0.018x2-0.0004x3 N=0.699+0.001x1-0.003x2+0.0001x3. X1 is load/g, X2 is vacuum/kPa, and X3 is microwave power/W. Through the fitting test, the R value of the Page model is 0.9804. It was proved that the model data and the experimental data were nearly accordant, and the model could be used for describing the moisture change in honeysuckle during microwave vacuum drying.4. The effects of microwave vacuum drying on the quality of honeysuckle were studied. Experimental results showed that, the chlorogenic acid and flavonoids content reached the maximum value of 50.816 mg/g and 105.576 mg/g when the power is 2 kW. When the power is 3 kW, the polysaccharides and free amino acid content reached the maximum value of 40.120 mg/g and 37.879 mg/g. When the vacuum is-75kPa, chlorogenic acid, flavonoid and free amino acid content reached the maximum with 51.494 mg/g,109.576 mg/g and 36.712 mg/g. At vacuum-85 kPa, the polysaccharide content is the highest,46.539 mg/g. When the loading capacity was 75 g, chlorogenic acid and flavonoids content reached the maximum of 50.867 mg/g and 108.110 mg/g; when the loading capacity was 50 g, polysaccharides and free amino acid content reached the maximum of 42.013 mg/g and 36.095 mg/g.5. The microwave vacuum drying technology of honeysuckle was optimized. Using the response surface method, the optimized process conditions were determined with 80.64 kPa of vacuum degree,1.71 kW of microwave power and 69.54 g of loading capacity. The maximum response value of chlorogenic acid content was 48.621 mg/g and flavonoids content was 107.386 mg/g using model prediction.6. The dynamic model of dissolution of chlorogenic acid in honeysuckle by microwave vacuum drying was established. Based on Fick law, the chlorogenic acid dissolution kinetics model was deduced, R2=0.9388. The model could be used to describe the dissolubility changes of chlorogenic acid in honeysuckle over the time under different temperatures and solid-liquid ratios.