Analysis Of Germicidal Efficacy And Temperature Measurement Of Material Based On Skin Heating Sterilization

With the rapid development of economy and the improvement of people’s consumer safety awareness, the quality and safety of spice is more and more important, sterilization and packaging of spices is an important link to ensure its quality and safety. In this paper, we study on the sterilization technology of electric heating based on the skin effect by using spice as the object. The main research contents are as follows:In order to realize the conveying of solid powder, we designed a sealed type sterilizing cavity, the cavity is equipped with scraper helical blade, the helical blade heating by mains with high frequency and low voltage, materials in the cavity pushing and heating by the conveyor axial to achieve continuous feeding and sterilization. The excess water which generated by the auxiliary materials heating were removed through inleting a small amount of hot steam in the sterilizing cavity. After the sterilization, the qualified materials enter into the rapid cooling unit, then packaging the spice when the temperature of material is reduced to room temperature. The whole process of sterilization can be carried out in a sealed space, and the key points of controlling can be monitored.The temperature acquisition system which is based on Lab VIEW is compiled to realize the measurement and control of key temperatures. Using PT100 temperature sensor and FLEX4015 thermal resistance module to acquire and converse the resistance signal, in order to measure the point of controlling temperature inside the cavity. In this research, we use Lab SQL language and NI company’s additional DCT tookit for Lab VIEW to realize the remote access to Access Microsoft type database.The equipment can be adjusted under 48 V, the current-output below 3500 A, the current frequency is during 10 KHz to 20 KHz, the spiral blade inside the equipment will produce electromagnetic field which is mainly to magnetic field. In the research,we designed the PT100 thin film platinum resistance which is equipped with a non metal protective sleeve and combined with the Mn-Zn ferrite shield,in order to reduce and eliminate electromagnetic interference,the shielding effectiveness of ourself-designed metal shield can reach 40 d B. By the Butterworth low-pass filter,we can eliminate the interference of other parts which is caused by the instantaneous high temperature, Thus,we can measure the actual temperature of the material directly.In the research, we constructed heat transfer model in the porous media by the COMSOL. In order to analogue simulation of the temperature distribution and materials’ temperature rise in heat sterilization process of skin effect. For the spice,the average temperature reaches the sterilization temperature prescribed by sterilization process should be not less than 120 seconds. According to the measured temperature data, we applied the Z value model to calculate the integral of the temperature time by formula, and achieve the online fast operation by the complex trapezoidal integration method. We set up the equivalent time of the Z value model of sterilization time 10 min when the temperature is 121℃as the sterilization process.In the process of sterilization,we can contrast the integral calculation value and the setting of the process parameters, when spices close to the discharge port, if the integral is greater than the value of the process parameters and the time longer than120 seconds at the same time,we deem the sterilization process finished, otherwise,controlling the discharge port to ensure materials are discharged from the bypass.After the sterilization, the total number of spices’ bacteria colonies were studied, and the results achieved the standard of green spices sterilization.Before and after the sterilization,we used spice materials for solid phase micro extraction, and adopted the Gas Chromatograph Mass Spectrometer(GC-MS) for the determination of contents of volatile substances,we found that the contents declined slightly after sterilization,and the change of the relative content was little, in other words,the volatile chemical composition of spices changed little.