Analysis yeast and mold in non dairy creamer
- 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.
- Analysis Yeast and Mold Count in Non Dairy Creamer by Petrifilm Yeast and Mold Count Plate method.
- AOAC Official method 997.02 – Yeast and Mold counts in Foods – Dry rehyratable Film Methods
4. Appartus and Reagent
- Yeast and mold count plates
- Plastic spreader – designed to spread test portion evenly over plate growth area.
- Pipets – Calibrated for bacteriological use to deliver 1.0 mL.
- Dilution pepton (water) – aseptically. Autoclave 15 min at 1210C.
5. Preparation of test suspensions
- Aseptically prepare 1:10 dilution (10 g/ 90 mL dilution pepton). Mix well and plate. Prepare additional dilutions as required. Ordinarily, 1:10 and 1:100 dilutions are sufficient.
- 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. Do not slide spearder across film.
- Leave plate undisturbed 1 min to permit gel to solidify.
- Incubate plates 5 days at 20 – 250C.
- In incubator, place plate in horizontal postion, clear side up, in stacks not exceeding 20 units.
- Yeast apprear as blue - green or off - white in color and form small defined colonies.
- Mold colonies are usually blue but may also assume their natural pigmentation (e.g., black, yellow, green). They tend to be larger and more diffuse than yeast colonies.
- Colonies stain in various shades of red. Count all colonies in countable range.
- To calculate yeast and mold 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.