Development And Performance Test Of Ohmic Heating Coagulation Device For Protein Gel Food

With improvement of people’s living standard,the gelatinous protein gel food which solidified by heating the soybean,egg,milk and other slurry material is loved by people because of its high nutritional value and diverse flavor.While the heating rate,holding temperature and holding timedirectly affect food gel formation rate,solidification degree and texture of protein gel food duringheating and solidification phaseand there is no independent device which can produce a variety of protein gel food currently.Therefore,in order to reduce the difficulty of protein gel food production,improve the production efficiency and quality and to fill the gaps in the market of household protein gel food production and processing equipment,a heating and solidifying device for protein gel food based on ohmic heating is designed which can realize various kinds of protein gel food making and heat sterilization of slurry material conveniently by controlling the heating rate,holding temperature,holding time in this paper.(1)Determination of the overall design scheme of ohmic heating solidification device: According to the function demand of the equipment,the overall design scheme of the protein gel food heating and solidificating device based on ohmic heating was determined by accessing to relevant literature,which is mainly composed of a shell,a heating liner,a control panel,a control board,a switch and a power socket.Then,The structure of ohmic heating solidification device was designed,and the prototype was manufactured.The heating linerwas made of food grade glass fiber reinforced PP board material,and the shell of the device was made of ABS material,which was formed by 3D printing.(2)The hardware circuit design of the control system of ohmic heating solidification device: The hardware circuit of the control system was designed.PWM AC zero voltage module comprises a PWM control circuit,driving circuit;The signal acquisition module comprises a voltage acquisition circuit,current sampling circuit,temperature acquisition circuit;Auxiliary function module is make up of serial communication circuit,function key circuit,LCD display circuit,LED status indication circuit,buzzer alarm sound circuit;DC5V switching power supply module consists of a EMI filter circuit,rectifier circuit,short-circuit protection,overload protection,over-voltage TL431 three terminal voltage reference control circuit.Finally,each module of hardware system was integrated and the main control board was printed.(3)The software program design of the control system of the ohmic heating solidification device: the modular C language program of control system was designed to realize the function of each module on the basis of the hardware circuit.The main program achieves the overall control system by coordination of each sub module program;PWM control subroutine respectively uses feedforward and feedback control of heating rate control algorithm and PID insulation control algorithm to control heating rate and holding temperature by changing AC voltage and regulate the heating power base on changing the duty cycle of PWM control signal;Serial send subroutine sends real-time datato the host computer through the microcontroller serial port;LCD1602 display subroutine displays related data and information in real-time to user during the running process;Function key subroutine achieves the system start,end,display interface conversion and parameter settings;Buzzer subroutine drives the buzzer to sound with start,button operation,error and the end of the work of the prompt tone;Information acquisition subroutine respectively reads voltage,current value and temperature value of food materialthrough AD conversion subroutine and temperature acquisition subroutine.(4)Control performance test of ohmic heating solidification device: The heating rate and temperature control experiments was conducted after the whole assembly and debugging of ohmic heating solidification device.The results show that when the heating rate is set at 6℃/min,8℃/min,10℃/min,12℃/min,14℃/min,16℃/min,18℃/min,20℃/min,it is a highly significant linear correlation between milktemperatureand time with 0.998~0.999 of R2 correlation coefficient of linear regression equation and 2.56%-1.38% of the relative error;when the holding temperature is set at 60℃,70℃,80℃,90℃,the milk temperature fluctuation is small and the maximum relative difference is less than or equal to 1℃.Therefore,it demonstrates that the device control system has good control effect on ohmic heating rate and holding temperature and effectively reduce the overshoot as well.On top of that,the heating efficiency is up to 96.8% at 20℃/min of heating rate.(5)Improve a key function of ohmic heating solidification device: a variety of protein gel food(Lactone tofu,egg milk pudding,soybean milk,yogurt)making experiments was completedthrough designing different orthogonal tests and the experimental results was analysed so that the optimum production parameters of different protein gel foodwas determined respectively: lactone tofu(0.35%GDL content,95℃temperature,6℃/min heating rate,15 min holding time);egg milk(85℃ temperature,8℃/min heating rate,15 min holding time);Soybean Milk(95℃ temperature,6℃/min heating rate,10 min holding time);yogurt(6% cane sugar,1% actic acid bacteria inoculation,40℃temperature,4.5h holding time).Finally,one key parameter setting program was compile to realize one button operation function of the device.