FOOD MICROBIOLOGY
MICROORGANISMS IN FOOD
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
plating aliquots of dilutedsamples on nutrient agar/suitable media&counting
|
|
|
centrifuging aliquotsofdilutedsamples onnutrient agar/suitable media&count
|
|
|
freezing aliquots of dilutedsamples on nutrient agar/other suitable media
|
|
|
heating aliquots of dilutedsamples on nutrient agar/other suitable media
|
Detailed explanation-1: -Calculate the number of bacteria (CFU) per milliliter or gram of sample by dividing the number of colonies by the dilution factor multiplied by the amount of specimen added to liquefied agar.
Detailed explanation-2: -The dilution formula is calculated by using the volume sample divided by the total volume of the sample and the diluted blank: 1/(1+9) with a dilution factor (1+9)/1 = 10. The final dilution is calculated by multiplying the dilution of the previous tube to the subsequent tube 1/10 x 1/10.
Detailed explanation-3: -A plate having 30-300 colonies is chosen because this range is considered statistically significant. If there are less than 30 colonies on the plate, small errors in dilution technique or the presence of a few contaminants will have a drastic effect on the final count.