Answer:
To determine the total count per g of the original sample, we need to calculate the number of colony-forming units (CFUs) per gram of hummus.
First, we need to determine the number of CFUs per milliliter in the fourth decimal dilution. We know that 230 colonies developed in a plate containing 0.1 ml of the fourth decimal dilution. To determine the number of CFUs per milliliter, we divide the number of colonies by the volume of the sample:
230 colonies / 0.1 ml = 2300 CFUs/ml
Next, we need to determine the number of CFUs per milliliter in the fifth decimal dilution. We know that 19 colonies developed in a plate containing 0.1 ml of the fifth decimal dilution. To determine the number of CFUs per milliliter, we divide the number of colonies by the volume of the sample:
19 colonies / 0.1 ml = 190 CFUs/ml
Now that we have the number of CFUs per milliliter in both dilutions, we can calculate the total number of CFUs per milliliter in the original sample. We know that the sample was decimally diluted five times. Therefore, we multiply the number of CFUs per milliliter in the fourth decimal dilution by 10^5 (10 raised to the power of 5) and the number of CFUs per milliliter in the fifth decimal dilution by 10^4 (10 raised to the power of 4) to determine the number of CFUs per milliliter in the original sample:
2300 CFUs/ml x 10^5 = 2.3 x 10^7 CFUs/ml
190 CFUs/ml x 10^4 = 1.9 x 10^6 CFUs/ml
The total CFUs/ml in the original sample = 2.3 x 10^7 CFUs/ml + 1.9 x 10^6 CFUs/ml = 2.49 x 10^7 CFUs/ml
Finally, we need to determine the number of CFUs per gram of hummus. We know that 35 g of hummus was blended with 90 ml diluent. To determine the number of CFUs per gram of hummus, we divide the number of CFUs per milliliter in the original sample by the number of milliliters of diluent used:
2.49 x 10^7 CFUs/ml / 90 ml = 27722 CFUs/g
So, the total count per g of the original sample is 27722 CFUs/g.