11. Controlling Microbial Growth

How can campers effectively treat stream water to remove pathogenic protozoa, bacteria, and viruses?

Pasteurization is what type of microbial control method?

During chemical treatment of drinking water and wastewater, which of the following microbes is least likely to be inactivated or killed?

a. Algae

b. Viruses

c. Fungal spores

d. Bacteria

A heat-sensitive liquid in a laboratory has been contaminated with E. coli bacteria. Which form(s) of microbial growth control could you use to remove this E. coli population from the liquid?

Describe five physical methods of microbial control.

The term 12D treatment refers to

a. Heat treatment sufficient to kill 12 bacteria.

b. The use of 12 different treatments to preserve food.

c. A 10¹² reduction in C. botulinum endospores.

d. Any process that destroys thermophilic bacteria.

Why is a can of blackberries preserved by commercial sterilization typically heated to 100°C instead of at least 116°C?

Hyperthermophilic prokaryotes may remain viable in canned goods after commercial sterilization. Why is this situation not dangerous to consumers?

What is the difference between thermal death point and thermal death time?

How do salts and sugars preserve foods? Why are these considered physical rather than chemical methods of microbial control? Name one food that is preserved with sugar and one preserved with salt. How do you account for the occasional growth of Penicillium mold in jelly, which is 50% sucrose?

Which of the following does not kill endospores?

a. Autoclaving

b. Incineration

c. Hot-air sterilization

d. Pasteurization

e. All of the above kill endospores

While hiking, Huda wants to ensure that the river water is clean enough to drink and will not cause any intestinal infections. How could she treat water from a stream so that it is safe to drink?