Plate Count Agar w/ BCP

Composition**

Ingredients

Final pH (at 25°C): 6.8±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 24.64 grams in 1000 ml. distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Mix well and pour into sterile Petri plates.

Principle And Interpretation

Plate Count Agar with BCP is a slight modification of the medium recommended by APHA (1) for enumeration of Lactobacilli in cultured milk, yoghurt and sour creams. Lactobacilli grow on this medium and form colonies with yellowish peripheries in the depth and on the surface of the medium. Addition of polysorbate 80 and L- cysteine enhanced the growth of lactobacilli on this medium. Lactobacillus bulgaricus invariably forms yellowish colonies its detection and determination is easy.

Peptic digest of animal tissue supply nitrogenous and carbonaceous compounds. Yeast extract provides vitamin B complex and dextrose is the fermentable carbohydrate and energy source. Bromocresol purple is a pH indicator. Plate Count Agar can be incubated at 30°C for upto 72 hours for detection of mesophillic organisms. Polysorbate 80 supplies fatty acids required for the metabolism of lactobacilli.

Quality Control

Appearance

Light yellow to light green homogeneous free flowing powder

Gelling

Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium

Purple coloured clear to slightly opalescent gel forms in Petri plates

Reaction

Reaction of 2.46% w/v aqueous solution at 25°C. 6.8±0.2 pH: 6.8±0.2

pH

6.60-7.00

Cultural Response

M1351: Cultural characteristics observed after an incubation at 35-37°C for 18-48 hours.

Storage and Shelf Life

Store below 30°C in tightly closed container and prepared media at 2 8°C. Use before expiry date on label.

Reference

1. Downes F. P. and Ito K., (Eds.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th Ed., APHA, Washington, D.C.