Study On Sugar Permeability Technique By Microwave Of Low-sugar Blackberry Preserved Fruit Based On Dielectric Properties

Blackberry,also known as dewberry.Blackberry has abundant nutrition ingredients that are essential to the health of man,including vitamin C,vitamin E,vitamin B1,vitamin B2,organic acids,crude protein,etc.It is introduced into China from Nanjing Institute of Botany in 1986.Blackberry is the third generation of pure natural fruit products with high-nutrition and high oxidation resistance.Blackberry fruit is perishable and can be stored at room temperature for less than 24 hours after harvesting,therefore,it is essential to study the deep processing of blackberry.Blackberry was chosen as research object in this paper,to research the technology of sugar permeability with microwave in making low-sugar blackberry preserved fruit based on dielectric properties.Firstly,dielectric property of blackberry under the different conditions were investigated and the SAS software was used to establish the regression analysis model of blackberry moisture content and temperature dielectric property in a fixed frequency.Secondly,drying characteristics analysis,drying kinetics analysis and microwave drying process under different microwave power were studied.Finally,study on single factor experiments and orthogonal rotation tests to draw the best processing on sugar permeability with microwave,using the analytic hierarchy process(APH).The main work and conclusions were described as follows:(1)Dielectric properties of the blackberry was measured by a single factor method using a network analyzer.The frequency and temperature range were 5-3000 MHz and 20-100?,respectively.It was found from the experiments that dielectric properties of blackberry were decreased gradually with increasing frequency.The dielectric constant decreased with increasing temperature but increased with increasing moisture content,however,the loss factor increased with increasing temperature but decreased with increasing moisture content.The penetration depth decreased with increasing temperature and frequency but increased with increasing moisture content.Analyze the mathematical models under 915 MHz and 2450 MHz,it is feasible to predict the moisture content of blackberry based on dielectric properties.The moisture content decreased with increasing microwave power obviously in the same time by microwave drying.During the microwave drying process,the dielectric constant decreased while the loss factor increased then tend to be gentle.The microwave drying process of blackberry match the equation of Page.The experimental data was regression analyzed and the results showed that the obtained regression equations were very significant.The heat transfer analysis showed that the dielectric loss factor of the material was related to the temperature change during the microwave heating process.It shows that it is feasible to monitor the microwave process by measuring the dielectric properties of the blackberry.(2)Compared with the experimental data,the experimental data and the predicted equation are similar,which indicates that the microwave osmotic glucose experiments conform to the infiltration theory.The exponential equation suitable for microwave infiltration process is obtained by matlab fitting.Single-factor experiments were compared with the low-sugar blackberry preserved fruit of sugar permeability with microwave.The optimum single-factor results were as follows: the intensity of microwave was 180 W,the time by microwave was 10 min and the sugar concentration was 30%.The effect of hot air drying time on sensory evaluation was not significant,therefore,the drying condition was selected that the drying temperature was 60? and the drying time was 4 hours.(3)Orthogonal rotation tests were designed to calculate the composite score of low-sugar blackberry preserved fruit using the analytic hierarchy process(AHP).The composite grade points were listed in order to show that the optimum results were as follows: the intensity of microwave was 210 W,the time by microwave was 12 min and the sugar concentration was 35%.In addition,the different technology processing was compared by the microstructure of low-sugar blackberry preserved fruit.MWVD is more suitable for the blackberry preserved fruit processing production.