Bacteria colony detecting board

1. Principle & application scope

Bacteria colony detecting board which is commonly used as testing index of microorganism test items can determine the total bacterial number in unit area through certain culture condition. Bacteria colony detecting board contains nutrient medium, soluble water absorbent gel, and dehydrogenase indicator (TCC), and colony shows red on count plate. This product is suitable to detect total bacterial number on the surface of food material, utensil and instrument. 

Executive standard: Food Safety National Standard, Food Microbiology Testing Bacteria Colony (GB 4789.2) 

2. Using method

2.1 Sample preparation: Prepare the 1:10 solution by placing 25g or 25mL sample into 225mL sterile saline, then, prepare 1:100 solution by sucking1mL solution (1:10) with sterile pipette into 9mL sterile saline, and so on to prepare solution of different dilution ratio. If necessary, use 1 mol/L NaOH or 1 mol/L HCL to adjust the PH to 6.6-7.2.

2.2 Inoculation: Select 2 or 3 dilution ratio sample solution for ordinary food, while for the liquid solution which has little bacteria directly suck raw liquid to do the test. Place the Bacteria colony detecting board on the sterile experiment table, uncover the film on the surface. Suck 1mL solution with sterile pipette, and then drop it slowly and evenly on the detecting board. Then cover the film quickly and shake the detecting board horizontally to let sample solution be absorbed by the filter paper on the detecting board. Stand it for about 10s until sample solution is absorbed completely. Inoculate two detecting boards for each dilution ratio. At the same time do a blank control.  

2.3 Culture: Superimpose the detecting boards together and place them upside down in the incubator. For ordinary food, the temperature of culture should be 36℃±1℃ and cultivation time should be 15-24h. While for aquatic food, the temperature of culture should be 30℃±1℃, and cultivation time should be 48hs. 

3. Results:

Colony shows red spot on bacteria colony detecting board. Count the quantity of colonies of which the quantity is between 30CFU and 300CFU, and then multiply it by dilution ratio as result data.