Meat and Milk Assay Setup

Meat and Milk Assay Setup

02_dilution_blank_P1010001

The following stations should be set up in a logical arrangement 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 10^2 0.1 mL
2: milk 10^2 1.0 mL
Meat:

2 meat suspension dry
3 dilution: meat 101 9.0 3: meat 10^1 1.0 mL
4 dilution: meat 102 9.0 4: meat 10^2 1.0 mL
5 dilution: meat 103 9.0 5: meat 10^3 1.0 mL

STATIONS FOR MEAT AND MILK ASSAY

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

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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

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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):

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2 mL pipets
1 mL pipets
pipet bulbs
vortex
pipet recepticle

V.  Two agar pouring Stations: Pouring agar into the prepared plates:

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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

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