Research On Integrated Processing Technology And Equipment For Steam Blanching And Combined Drying Of Fruits And Vegetables

China is the largest country in the world in the production and processing of fruits and vegetables.The drying is an important means of processing fruits and vegetables.The traditional air-drying and hot air-drying of fruits and vegetables have some problems,such as low processing efficiency,poor quality and hygienic conditions of dried products.As the main pretreatment methods,hot water and steam blanching have some shortcomings,such as easy loss of soluble substances,low heat transfer efficiency and need to be re-distributed after blanching.In this project,combined drying technology and steam blanching technology are combined.Apples and carrots were used as raw materials to research the integrated processing technology of vacuum pulsating steam blanching and hot air vacuum combined drying of fruits and vegetables.Based on the experimental parameters,an integrated processing equipment for steam blanching and combined drying of fruits and vegetables was designed.The research provides ideas for the development of integrated processing technology and equipment for fruits and vegetables.The single factor and orthogonal experiments of vacuum pulsating steam blanching and hot air vacuum combined drying of apple raw materials were carried out.The experiment results were analyzed by range,variance and multiple comparisons by using SPSS,MATLAB and other statistical software.The effects of steam blanching parameters on the color,VC content of apple slices and combined drying parameters on drying time,shrinkage and rehydration were studied.The optimum processing parameters of steam blanching and combined drying for apple slices were obtained.The better parameters are blanching vacuum 0.08 MPa,blanching temperature 120℃,blanching time 2min and cycle number 2 times,hot air temperature 60℃,moisture content at conversion point 45%,vacuum temperature 50℃,vacuumdegree 0.07 MPa.Under this condition,the retention rate of VC in dried apple slices was 67.4%.The comprehensive quality of color,shrinkage and rehydration was the best.The single factor experiment and regression orthogonal experiment of vacuum pulsating steam blanching and hot air vacuum combined drying of carrot were carried out.Based on the results,the mathematical models of steam blanching and combined drying of carrot slices were established.The ideal integrated process of steam blanching and combined drying of carrot slices was obtained by optimizing the parameters.The retention rate of VC in dried carrot slices was 83.8%.The quality and shape of dried carrot slices were the best after rehydration when the blanching vacuum is 0.08 MPa,the temperature is 100℃,the time is 1 min and the cycle number is 3 times,the hot air temperature is 50℃,the moisture content at conversion point is 55%,the vacuum temperature is 50℃and the vacuum degree is 0.07 MPa.At the same time,the experiment results provide a theoretical basis for the design of integrated processing equipment for steam blanching and combined drying of fruits and vegetables.According to the experimental parameters,an integrated processing equipment of vacuum pulsating steam blanching and hot air vacuum combined drying for fruits and vegetables was designed.The overall structure of the equipment includes integrated processing box,pressure generating system,steam blanching system,hot air drying system,vacuum drying system and automatic control system.The integrated operation of steam blanching and combined drying of fruits and vegetables can be realized in this equipment.The equipment has advantages in integration degree,equipment cost,product quality and so on.The research on this project provides an integrated processing method and equipment for steam blanching and combined drying of fruits and vegetables.The research provides a new idea for the development of integrated processing technology and equipment for combined drying and blanching pretreatment of fruits and vegetables.It also has promoted the related research and technology popularization application.