8/24/2016 Sample Preparation Liquid sample To create a homogeneous sample,solid food I ml removed is mixed with sterile diluent,such as 0.1% and added to peptone water uffer diluent 1.Sample(25g)added to a sterile stomacher bag Sample spread in duplicate on plates using 2.Diluent (225 ml)added to the bag a sterile spreader ”lates 3.Processed in the stomacher incubated 4.Creates the first 1/10 dilution 中( 25250 ith Bacteria should not be allowed to multiply colonies are counted and work quickly and use appropriate expressed as buffers CFU mle A The Analysis Pour Plate Spread Plate Method Method Disadvantage of surface plating -two or more colonies grow together growth of spreaders Plate surfaces must be dry 9 8/24/2016 4 Sample Preparation To create a homogeneous sample, solid food is mixed with sterile diluent, such as 0.1% peptone water 1. Sample (25g) added to a sterile stomacher bag 2. Diluent (225 ml) added to the bag 3. Processed in the stomacher 4. Creates the first 1/10 dilution Bacteria should not be allowed to multiply • work quickly and use appropriate buffers 13 Sample spread in duplicate on plates using a sterile spreader Liquid sample 1 ml removed and added to buffer diluent Plates incubated Plates with 25-250 colonies are counted and expressed as CFU / ml14 Analysis Disadvantage of surface plating - two or more colonies grow together - growth of spreaders Plate surfaces must be dry 15 Pour Plate Method Spread Plate Method 16