Analysis total plate count in non dairy creamer

1. Principle
- Method used bacterial culture plates of dry medium and cold H2O – soluble gel. Diluted test suspension are added to plates at a rate of 1.0 mL per plate. Pressure, when applied to plastic spreader placed on overlay film, spreads test portion over ca 20 sq.cm growtn area. Gelling agent is allowed to solidify and plates are incubate and then counted.

2. Scope
- Analysis Total Plate Count in Non Dairy Creamer by Petrifilm Aerobic Count Plate method.

3. Reference
- AOAC Official method 989.10 – Bacterial and Coliform Counts in Dariy Products – Dry rehyratable Film Methods

4. Appartus and Reagent
- Petrifilm Aerobic Count Plates
- Plastic spreader – designed to spread test portion evenly over plate growth area.
- Balance  có độ phân giải 0.01g
- Pipets – Calibrated for bacteriological use to deliver 1.0 mL.
- Dilution pepton (water) - aseptically

5. Preparation of test suspensions
- Aseptically prepare 1:10 dilution (11 g/ 99 mL dilution pepton). Mix well and plate. Prepare additional dilutions as required. Ordinarily, 1:10 and 1:100 dilutions are sufficient.

6. Analysis
- Use dry-film aerobic count plates. Place plate on flat surface. Lift top film and inoculate 1 mL test suspension onto ceter of film base.
- Carefully roll top film down onto inoculum. Distribute test suspension over prescibed growth area with downward pressure on center of plastic spreader device.
- Leave plate undisturbed 1 min to permit gel to solidify.
- Incubate plate 48 h ± 3 h at 320C ± 10C.
- In incubator, place plate in horizontal postion, clear side up, in stacks not exceeding 20 units.

7. Result
- Magnifier – illumination may also be used to facilitate counting.
- Colonies stain in various shades of red. Count all colonies in countable range.
- To compute bacterial count, multiply total number of colonies per plate (or average number of colonies per plate if counting duplicate plates of same dilution) by reciprocal of dilution used.