11. Controlling Microbial Growth

How does irradiation control microbial growth?

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?

How does high pressure processing (HPP) control microbial populations?

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.

Which of the following cannot be used to sterilize a heat-labile solution stored in a plastic container?

a. gamma radiation

b. ethylene oxide

c. supercritical fluids

d. autoclaving

e. short-wavelength radiation

Which of the following is most likely to be bactericidal?

a. membrane filtration

b. ionizing radiation

c. lyophilization (freeze-drying)

d. deep-freezing

e. all of the above

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.

Which type of radiation is used to preserve foods?

a. ionizing

b. nonionizing

c. radiowaves

d. microwaves

e. all of the above

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

Foods packed in plastic for microwaving are

a. dehydrated.

b. freeze-dried.

c. packaged aseptically.

d. commercially sterilized.

e. autoclaved.

Which of the following pathogens would hyperbaric oxygen therapy, a treatment that increases the level of dissolved oxygen in tissues, most likely ward off? Select all that apply.

a. Anaerobic thermophile

b. Anaerobic mesophile

c. Facultative anaerobic thermophile

d. Facultative anaerobic mesophile

e. Microaerophilic mesophile

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?

Lyophilization can be described as ________.

a. Freeze-drying

b. Deep-freezing

c. Refrigeration

d. Pickling

A sample of E. coli has been subjected to heat for a specified time, and 90% of the cells have been destroyed. Which of the following terms best describes this event?

a. Thermal death point

b. Thermal death time

c. Decimal reduction time

d. None of the above