Milk Plate Count Agar

LAB 115

Description

A medium recommended by the British Standards Institute and the International Organisation for Standardisation for the enumeration of viable bacteria in milk and other dairy products.

Method for reconstitution

Weigh 19.5 grams of powder, disperse in 1 litre of deionised water. Allow to soak for 10 minutes, swirl to mix then bring to the boil to dissolve the agar. Allow to cool to 47˚C and dispense into suitable containers. Sterilise by autoclaving at 121˚C for 15 minutes.

Appearance: Pale cream, opalescent gel.

pH: 6.9 ± 0.2

Minimum Q.C. organisms: E. coli NCIMB 50034

S. aureus NCIMB 50080

Storage of Prepared Medium: Capped container - up to 3 months at 15-20˚C in the dark.

Inoculation: Pour plate technique.

Incubation: 30˚C aerobically for 72 hours.

Interpretation: Count all colonies. Calculate back to determine viable organisms per ml

References

British Standards Institute. (1984). BS 4285 Section 1.2. International Organisation for Standardisation Draft International Standard. (1982) ISO/DIS 6610. D.I.N. 10192.