Developments And Applications Of Food Safety Instruments For Fast Analysis

In the rapid process of economic globalization, food safety has become a great problem in the world. In China, the number of food safety accidents rised amazedly in recent years. The best ways to solve the problem of food safety are finding and settling it as early as possible, so the techniques, procedures and instruments for the fast in situ determinations of harmful components in foods are absolutely necessary.In this thesis, some important items of the food safety analysis were researched, 2 instruments and the relevant procedures were developed. This work is of considerable significance and practical value.A novel fast food safety analyzer was developed, which can be applied to the in situ determinations of the harmful components in foods. The analyzer was made up of several high-brightness LEDs, a heat-resistant single monolithic light-to-frequency converter, several columniform absorption cells, a thermostatic system, a MCU, a LCD module, a mini-printer, a GSM module (optional) and several keys. The analyzer has a small, lightweight and portable body with no removable parts.In the course of development, the follow problems were solved: (1) The design of the optical dispersive system. The UV-VIS spectrophotometer with traditional optical dispersive system is very complex and brittle;the execrable environment such as shaking, dampness and high temperature will reduce thestability of light source, the precision of the monochromator and the life time of the spectrophotometer itself, so it can be applied in laboratory only. A cluster light source/monochromator was developed, in which the high-brightness LEDs were placed in a honeycomb style (7 LEDs at most) as light sources and monochromators;these LEDs can be lighten sequently in the course of analysis. A solid-state optical dispersive system made up of the cluster light source/monochromator and a light-to-frequency converter of TSL series is fitted for the portable in situ instruments, for it have a very simple design and many features such as inexpensive price, long life time, aseismatic and anti-cauterization performance. (2) Ensuring the stabilities and reducing the watts of the LEDs. A current stabilizer was used to ensure the stabilities of the LEDs. The current which drive the LEDs was supplied in the course of analysis only and the time intervals between the beginning of current supplying and light detecting were same. (3) Avoiding the decrements of the precision caused by the difference of position and material of the columniform absorption cell. The auto lock technique was applied to the analyzer to ensure the absorption cell was placed in the same unique position in every course of analysis.The fast food safety analyzer was applied to the fast determination of formaldehyde and nitrite in hundreds kinds of foods. The methods of sample preparation and the conditions of chromogenic reactions were investigated and optimized;the analysis of each sample can be completed in 30 minutes. The results were in good agreement with the results obtained by the nationalstandard method of the People's Republic of China and the standard method of the Ministry of Agriculture. The lower limit of formaldehyde is 1.0 mg/kg, the calibration curve (correlation coefficient: 0.997) is linear within the range of 1.0~100.0 mg/kg;the lower limit of nitrite is 2.0 mg/kg, the calibration curve (correlation coefficient: 0.998) is linear within the range of 2.0-200.0 mg/kg.An information management system for food safety was developed, which can be applied in the department of public health and business administration with the fast food safety analyzer. The system is based on the platforms of Linux, Apache, PostgreSQL, PHP and OpenSSH, so it has low software costs, high stabilities and securities.A novel spectral detector module made up of a fixed holographic grating, a linear CCD detector was developed, which can be applied to UV-VIS, AES, AAS and SPR instruments. By selecting of the circuit components, designing of the circuits and developing of the softwares, the following requirements were met: (1) The module should have the ability of processing the mass spectral data by itself. A 32-bit bus, high-speed ARM7TDMI MCU was applied to the module, which can process the mass spectral data read from the CCD detector quickly. (2) The minimum integration time of CCD was 2 ms. A high-speed A/D convertor (10 MSPS) was used to convert the signals of CCD to spectral data in the module. The high-speed MCU and A/D convertor made the integration time of CCD adjustable within the range of 2-65535 ms. (3) The module should have the ability of transmitting the spectral data to PCreal-timely. In practice, the module transmits spectral data with a full speed USB interface;the speed of data transfer is 1 MB/s above.A miniature simultaneous spectrophotometer was developed based on the spectral detector module. The light source of the spectrophotometer is an iodine tungsten lamp, the range of spectral wavelength is 350-750 run, the resolution of the wavelength QJAX) at 450.0 nm is 1900 above.The miniature simultaneous spectrophotometer was applied to the fast determination of hydrogen peroxide in calcium tablets and beverages. The methods of sample preparation and the conditions of chromogenic reactions were investigated and optimized;the analysis of each sample can be completed in 30 minutes. The lower limit of hydrogen peroxide in extraction solutions of calcium tablets is 0.50 mg/1, the calibration curve (correlation coefficient: 0.9995) is linear within the range of 0.50-40.00 mg/1;the lower limit of hydrogen peroxide in extraction solutions of beverages is 2.0 mg/1, the calibration curve (correlation coefficient: 0.9998) is linear within the range of 2.0-180.0 mg/1, the the recovery factor is 97.5%-104.1%.