Freshwater Fish Freshness Micro-computer Unit Testing System Based On Bio-impedance

Fish and its products are easy to corruption. Hence, it cannot be preserved for a long time. Freshness is important quality parameter of fish, which has a huge influence on the quality of final products. Currently, Freshness was usually tested by chemical methods, sensory organ and sensor et al. However, these methods all embrace some problems such as inadaptability, complicated procedures and sample destruction need to be solved in the future. Bio-impedance is an electrical character was able to reflect the tissue, organ and cell status. Impedance character will change dramatically during the pathological changes. Therefore, tissue status can be tested quickly, correctly and nondestructively through bio-impedance measurement.Freshness of freshwater fish testing is the main purpose of this project. Existing problems of current freshness testing methods were point out according to analysis result. A new fish freshness testing method based on bio-impedance was proposed. In this study, Chub was taken as research object, the relationship between its impedance and freshness was studied on the self-made virtual instrument fish impedance-testing platform. The influences of drive frequency, testing position, direction and environment temperature were affirmed through experiments. Chub freshness indexes based on impedance were set up. According to these indexes, a freshness testing system comprised by S51 and some relevant components was build up and validated through experiments. The conclusions were draw as follow:1. Chub were storaged under 25℃. There was a difference between impedance tested on different positions at the same postmortem hours, and the impedance amplitude tested on different positions decreased with the increase of storage hours. The relationship between storage hours and impedance, which tested on the part of cheek parallel direction, has a significant regulation. Hence, cheek is the best testing position. When storage hours was more than 9 hours, the 5.7KHz frequency impedance was less than 65Ω, phase angle was below 3.5°, the content of TVBN was more than 20mg/100g, it indicated that the fish spoiled already2. Chub impedance decreased with the increase of drive frequency. When frequencies were above 50 KHz, the impedance just had a small difference between different storage hours. Approximate 5 KHz was perfect frequency to research the impedance character.3. The impedances of chub body had a significant difference between tested under 5±2℃and 30±2℃during the process of spoilage. Environment temperature had influence on impedance amplitude. When the fish body spoiled completely, the difference was insignificant. However, variance analysis result of the 5.7 kHz and 48.9 kHz frequency impedance ratio Z_5.7kHz/Z_48.9kHz indicated that the environment temperature influence on impedance was insignificant.4. Both 5.7 kHz and 48.9 kHz frequency phase angles also have small difference between tested under 5℃and 30℃temperatures. But the difference were less than 1°after 6 hours when storage under 25℃environmental temperature.variance analysis shows the differences of phase angle were insignificant during the whole process of spoilage between tested under 5±2℃and 30±2℃.so testing result was also valid5. When impedance of fish body was below 65Ωor ratio of impedance amplitude Z_5.7kHz/Z_48.9kHz less than 1.16 that mean fish body spoiled. When impedance offish body was more than 85Ωor ratio of impedance amplitude Z_5.7kHz/Z_48.9kHz was above 1.27, it means fish was fresh. The 5.7 kHz frequency impedance and impedances ratio Z_5.7kHz/Z_48.9kHz were able to be taken as freshness indexes.6. A fish freshness testing system based on S51 MCU was build up. Experiments results demonstrated that fish freshness can be tested correctly and nondestructively by this system. The accuracy was 90 percent. In addition, the testing procedure was swift and low cost. Softwares were programmed by C and LabVIEW. They were characterized by simple and understandable, can be modified and called easily and conveniently. Furthermore, this device provided a RS232 data transportation port. It offers a reliable solution for data exhibition and preservation. All the works lay a foundation for further study...