Draw Dilution Blanks
SET UP FOR MEAT AND MILK ASSAY
©David B. Fankhauser, Ph.D.
Professor of Biology and Chemistry
University of Cincinnati Clermont College
Batavia OH 45103.
Preparing dilution blanks

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weighing out meat sample
,

The following stations should be set up in a logical arangement in the lab to expedite the class testing of bacterial counts in meat and milk.

Before the exercise, each student should collect the following dilution tubes and empty plates and label as indicated:

FIRST:         CONSTRUCT A TABLE in your lab book  listing:
                        the five  plates you will pour, the specimen,s the dilutions, the aliqouts, the CFUs/plate, and the final CFUs/g or mL.

SECOND:    COLLECT AND LABEL TUBES AND PLATES:
                       five 16 x 150 mm tubes in rack (see 'tube marking' column in table)
                       five empty sterile plates (see last three columns in table)

THIRD:        ALIQUOT OUT STERILE dH2O IN THE DILUENT IN TUBES:
 
specimen:
tube
 tube marking
diluent 
plate #, specimen
dilution
aliquot
  CFU/g or mL
Milk: 
1
dilution: milk 102
9.9 mL
  
1: milk 
102
0.1 mL
       
2: milk
102
1.0 mL
Meat:
2
meat suspension
dry 
     
 
3
dilution: meat 101
9.0
3: meat
101
1.0 mL
 
4
dilution: meat 102
9.0
4: meat
102
1.0 mL
 
5
dilution: meat 103
9.0
5: meat
103
1.0 mL

STATIONS FOR MEAT AND MILK ASSAY

I.  A single blank station:  Aliquot out Dilution Blanks:

flame
Repipet with sterile dH2O, set on 9.9 mL (one for dilution of milk)
Repipet with sterile dH2O, set on 9.0 mL (three for dilution of meat suspension)
II.  Two weighing stations: Meat Weighing (in pairs, side by side): One for each ground meat:
two balances
two 16 x 150 mm test tube ½ full of 95% EtOH
two sets of four microspatulas in the EtOH tubes
flame, shared
hot soapy water in nearest sink to wash off meat and fat from spatulas
III.  One suspension Station: Meat Suspension Station on a bench near the weighing stations
flame
Repipet with sterile dH2O, set on 3 mL
Repipet with sterile dH2O, set on 7 mL
vortex
IV.  Four sample dilution, aliquoting Stations: Dilution of Samples, Aliquoting to Plates.  (in pairs, side by side):
flame
2 mL pipets
1 mL pipets
pipet bulbs
vortex
pipet recepticle
V.  Two agar pouring Stations: Pouring agar into the prepared plates:
flame
deep hot block, 45 C, with liquid 45 C Plate Count Agar (covered with a folded towel to prevent solidification)
tub of warm water to receive emptied test tubes