Research On A Rapid Colorimetric Detection For Coliforms In Food

As food-borne pathogen increasingly involved in food-poisoning outbreaks,there is a lotof attention to the study on the fast detection method of food microbes,in order to improvethe deficiency of traditional methods and meet the needs of rapid and accurate detection offood quality. Coliform group is the most popular food inspection indexes. In37℃,coliformsrefers to a group of need oxygen or facultative anaerobic of negative bacterium withoutbacillus who can fermentation of lactose and produce acid and gas. It is generally used fortesting method of coliform group by the fermentation multiple-tubefermentation,MTF,although traditional fermentation of coliforms detection has such advantages as accurate,reliable,it already can’t meet the actual monitoring needs because testing time longer andmore difficult even in the single sample on the food and water quality monitoringprocess.Therefore,this dissertation researched on the common cultivation of coliformgroup,study on the rapid detection of fast counting method based on the Color characteristicsidentification.This dissertation in this paper,the main reseach results obtained are as follows:1. Design the formula of culture medium about colorimetric method, the lauryl sulfonatetryptone agar (LST) as the basis, by adding nutrients, acid-base indicator, bacteriostatic agent,surface active agent and other components were optimized, to determine screening ofchromogenic medium the optimal formula was: LST4.56g, bromocresol purple0.03g,1.5%lactose solution0.1mL (40min after culture join), Tween0.2%,100mL sterile water. At thesame time the design of semisolid agar, by comparing different agar content on the drum ofinterception, determined the agar content0.8%observed biomass gas production the bestresults, ensure the judgment of coliforms accuracy.2. On coliform medium color number and study the relationship between, by measuringthe coliform group after fermentation acid culture medium color information, using a linear ornonlinear fitting method to establish the coliform numbers and medium color information between the model, ultimately determine the BP neural network model can get idealprediction results, and the establishment of the coliform group number and colorcorresponding to standard colorimetric board, applicable to the food safety supervisioninspection.3. Research about the rapid detection of coliform total number which from solidfoods,drinking water.Finally,provided the detection technology and ruslts are as follows:(1) Detection Technology: In a sterile condition accurately weighing25g solid samples,with50mL of sterile saline solution into the conical flask, a rocking bed for160r/minoscillator2min, mixing samples, with moderate quantitative filter paper filter sample liquidabsorbed, then the50mL of sterile saline flushing filter residue, a filtrate collection. Asepticoperation draw6mL fermentation liquid by membrane concentration, so that the cell in thefilter is evenly distributed, then the micropipet close to the membrane to draw20u L bacterialiquid. Measure the4.56g lauryl sulfonate peptone culture based on100mL distilled water,heating to dissolve, join0.03g bromocresol purple indicator and2%Twain reagent,oscillatory strain to cotton plug sealing, put in the sterilizing pot in121degrees Celsiustemperature sterilization20min. Body aseptic working platform, after the solution is cooled to37℃for adjusting pH value6.99. Using sterile micropipettor draw1mL medium into the1.5mL centrifugal tube, the liquid to be detected after adding concentration of20L,37DEGthermostat culture of120min. After40min of culture took placed on the worktable, adding1.5%of the lactose solution100u L, tightly centrifugal pipe cover, is arranged in the constanttemperature box to continue training. After120min of culture, removed by centrifugal pipe,observation of fermentation liquor color, controlled coliform count-color standardcolorimetric plate reads the coliform number estimation.(2) Detection Results:the method can be reached results at120min,and the results for theratio between rapid detection method and GB method is1.21,when refer to detect totalbacteria of solid food,This explains no significant difference between the two methods,butthe rapid detection method is more sensitivity and authenticity the GB method,and it has acertain warning capacity abort food quality early.This dissertation is based on the common organism culture, of coliforms,and improvedthe coliform medium, establish a model corresponding to coliform numbers and color, shortedthe detection time greatly, achieve rapid, accurate, real-time reporting of test results. Thecontrol of food safety not only play a very important role in promoting efficiency for food production,but also will bring certain economic benefits.