Define Procedure for Detection of Number of Bacteria in Milk?

1. Place a clean, non-greasy slide over the graph paper.

2. Spread 0.01 ml of the milk over an area of 1 cm2 as a thin even film.

3. Dry the smear by gently passing through the flame.

4. Defat the smear by flooding with xylol for 1 minute.

5. Wash the slide with alcohol to remove xylene followed by washing with water to remove the alcohol.

6. Stain the smear with methylene blue for 15-30 second.

7. After washing with water, observe the dried preparation under oil immersion. Count the number of bacteria in about 25 microscopic field.

8. Determine the average number of bacteria per microscopic field and multiply with microscopic factor (500,000) to get bacterial counts per ml of the milk sample.