【作者】 胡波；

【导师】 李小昱；

【作者基本信息】 华中农业大学 ， 农业机械化工程， 2008， 硕士

【摘要】 鱼类及其制品不耐保藏，容易发生腐败和变质。新鲜度是评价鱼肉质量的一个重要指标，对最终产品的质量有极大的影响。现阶段采用的如化学法、感观法、传感器法等检测方法存在着适应性不足、检测过程繁琐及具有破坏性等诸多问题，需要开展进一步的研究。生物阻抗是反映生物组织、器官、细胞电学性质的物理量，随着生物组织病变的发生，其电阻抗特性会发生显著变化。因此，通过对生物基体电阻抗特性测量，能快速、准确、无损地检测其组织发生的变化情况。该项研究以淡水鱼新鲜度检测为主要研究内容，分析了目前各种淡水鱼新鲜度检测方法存在的问题，提出了基于生物阻抗原理的淡水鱼新鲜度检测的新方法；建立了基于虚拟仪器的淡水鱼电阻抗测量平台；并以鲢鱼为研究对象，研究了鲢鱼电阻抗特性与其新鲜度之间的关系；确定了激励频率、测量部位、测量方向及环境温度对鲢鱼电阻抗特性的影响；建立了基于电阻抗特性的鲢鱼新鲜度评价指标；并以此为理论基础，设计了基于生物阻抗的淡水鱼新鲜度单片机检测系统，并对建立的单片机检测系统进行试验验证，得出的主要结论有：1．贮藏于25℃的鲢鱼，鱼体各部位所测得的电阻抗特性值（阻抗幅值和相位）存在差异，但其值都随贮藏时间的增加而减少；鱼体鳃部平行于侧线方向测得的阻抗与贮藏时间之间的变化规律性最强，为最佳测量部位；当死亡时间超过9h，激励频率为5．7kHz时的鳃部阻抗幅值小于65Ω，相位差小于3．5°，鱼体内的挥发性盐基氮（TVBN）含量>20mg／100g，表明鱼体腐败。2．鲢鱼阻抗随着激励频率的增大而减小，在频率大于50kHz时，不同贮藏时间内的鱼体阻抗差异较小，因此，5kHz左右是研究鱼体阻抗随贮藏时间变化较为理想的频率范围。3．贮藏于25℃的鲢鱼，在5kHz和50kHz激励频率下，环境温度对鱼体阻抗测量值有影响，分别在5℃和30℃环境温度中所测得的阻抗幅值存在差异，但这种差异随着鱼体腐败的进行而逐渐减小，当鱼体完全腐败时，差异皆小于2Ω，环境温度对鱼体阻抗幅值影响不显著；而对5．7kHz和48．9kHz激励频率下的阻抗幅值比Z_5.7kHz／Z_48．9kHz进行方差分析表明，环境温度对其影响不显著。4．贮藏于25℃的鲢鱼，在5．7kHz和48．9kHz频率下，分别在5℃和30℃坏境温度中所测得的相位差值有差异，但这种差异在贮藏时间超过6h后皆小于1°。在从新鲜到完全腐败过程中，测量环境温度对相位差的影响不显著，因此，环境温度不会影响判别结果。5．当激励频率为5．7kHz时的鱼体阻抗值Z_5.7kHz<65Ω或激励频率为5．7kHz和48．9Hz时阻抗幅值比Z_5．7kHz／Z_48．9kHz<1．16时时可以判定该鲢鱼腐败；当Z_5.7kHz>85Ω或Z_5．7kHz／Z_48．9kHz>1．27判定该鲢鱼新鲜。激励频率为5．7kHz时的阻抗幅值以及阻抗幅值比Z_5.7Hz／Z_48．9kHz作为新鲜度评价指标。6．利用S51单片机为主芯片建立淡水鱼新鲜度检测系统，试验结果表明该系统能够无损、准确检测鲢鱼的新鲜度，正确率为90％，且检测速度快，检测成本低廉。软件部分采用了C语言和LabVIEW来进行模块化设计，具有简单、直观明了的特点，可以方便地进行修改和调用。同时，该装置提供了RS232数据传输接口，为后续研究提供可靠的数据显示和保存方式，为进一步研究开发打下基础。更多还原

【Abstract】 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更多还原