Development And Application Of An Instrument For Detecting Palm Oil Adulterated In Edible Oils

In this thesis,a kind of instrument for detection palm oil adulterated in edible oil was developed,and the quantitative detection of adultant in edible oil was carried out by spectral analysis.In the present,the methods of evaluating the quality of edible oil in our country and the methods of detecting adulterants in edible vegetable oil reported in the literature all require complicated pretreatment of samples,and need professional examiners.The methods can only be completed in the laboratory.According to the demand of on-the-spot detection of edible oil adulterated with palm oil,a kind of on-the-spot detection instrument for edible oil adulterated with palm oil was developed in this thesis.In the sample pretreatment,ozone oxidation is used to eliminate the interfering substances in the sample.The sample pretreatment device of edible oil,which is suitable for the treatment of different kinds of edible oils,includes an ozone generator,a gas flow meter device,a reactor of sample,a exhaust gas processor,integrated circuit design and software system,display system and performance test system.The hardware structure system of edible oil adulterted with palm oil instrument,includes microprocessor module,light detection module,temperature control module and so on.The microprocessor module consisted of ARM7's LPC series control chip,which has the functions of data processing,timing counting,signal control and serial port transmission.The light source of the light detection module was super-bright light emitting diode,which has the advantages of low energy consumption and long service life.In the light detection module when the hight from the reflected light from the sample was measured the light source was irradiated on the sample.The photoelectric sensor S1133 is used to collect the optical signal,convert the optical signal into an electrical signal,then amplify the electrical signal by a secondary amplification circuit,then convert the voltage into frequency with a voltage-frequency converter,and finally store the signal in the microprocessor for data processing.The temperature control module can accurately control the fixed-point temperature and cooling rate of the instrument.The semiconductor cooling plate was used in refrigeration system,which has the advantages of fast refrigeration,safe and reliability.In the control circuit the work of the semiconductor cooler was controled with a field effect transistor(FET).The edible oil adulterated with palm oil instrument software system,includes frequency measurement,program temperature control unit.The frequency measurement is based on the periodic measurement method.The two timers T0 and T1 of the microprocessor are used to time andcount respectively,and the sampling frequency is calculated accurately.In the program cooling control system,the optimized PID algorithm is used to improve the basic PID algorithm,which shortens the time of reaching stability and improves the precision of control.To develop the instrument,the whole structure of the instrument,the optical-frequency conversion system,the temperature control system and the human-computer interaction interface were studied and selected.The core device of the instrumant is the sample measuring cell.The compatibility and rationality of the sample measuring cell can directly affect the reliability and practicability of the instrument.Key devices include reflective light detector,light source,microprocessor,printer,Bluetooth module,liquid crystal display and temperature sensor.The core control system of the instrument is optical-frequency conversion system and temperature control system.The man-machine interface is beautiful and easy to operate.In the aspect of the application of determig palm oil in edible oil with the instrument,the factors affecting the measurement results were examined one by one,and the optimal sample capacity,measurement method,sample pool temperature,sample temperature,measurement time and LED intensity were selected.The precision and r value of the calibration curve meet the expected standard of the instrument,and 19 kinds of soybean oils available in the market were analyzed.The resultsare in good agreement with thuse abtained with chromatographic instrument.