Detection System Design For Detecting Bacterial Numbers In Raw Milk By Conductance Method

The total number of bacteria is an important indicator, which is regularly used inraw milk quality detection and classification; It has got more and more attention.Now, the most reliable method traditional plate colony counting, it is not onlytime-consuming and laborious but also contaminated greatly. In this paper, Based onthe careful comparison of different bacteria quantitative methods used in the dairyindustry around the world, combined with the development trend of bacteria numberdetection method, we propose a new method to detect the bacteria numbers thatbased on electrical conductivity characteristic. The mechanization of this method is:During the process of raw milk bacterial culture, In culture media, the metabolicactivity of bacteria leading electro active molecules and ions replaced the electricinert molecules. cause the conductivity enhance and electrical conductivity increases.The purpose of this research is using electrical methods to detect the change ofconductivity in the solution. Through many experiments to find the mathematicalrelationship between the conductivity change and the total number of bacteria, themain content of subject as follows:First, analysis of impedance characteristics of the culture medium and simplifyits structure, select the appropriate operating frequency, depthly studied anddiscussed the mechanism of conductivity changes that caused by bacterial growth,the program of the conductivity detection of bacteria is conducted a detailed analysisand demonstration. Then, based on analyzing the characteristics of mediumconductivity, Shows the program of test system design and implementation, Includehardware circuit and software module, Introduce the detector’s work principle,tester’s configuration and test parameter’s enactment, Focused on analysis the designof hardware circuit and how signal conditioning circuit works. Last, combinelinearity regress theory and method, build linearity regress mathematical model andstandard curve of aerobic bacterial count and detect time. The tester focuses on STC89C52, and achieves the aim of testing well and truly by the SCM that has theability of estimate and account. We achieved detection system software design andbuilt specific design diagram and program flowchart, process control system makemeasuring results intuitive display on LCD module, the system can achieve thepurpose of rapid detection of bacteria.Make contrast experiment with impedance detector and the method of agarcounting to detect aerobic bacterial count in raw milk, make compare analysis to thetwo results. The experiments show that the detection time can be shorted to10h, thedetection errors are less than40%. It is shows that two results almost same, however,if we want to achieve more accurate detection, more valid sample data are needed forbuild a more standard credibility model．...