Janelly's work (page 152, questions 1-6)

1. Compare the heat sensitivity of fungal spores to that of bacterial endospores.

• Fungal spores are more sensitive to heat than bacterial endospores. For example, fungal spores can be killed at 60 C. However, the endospores of bacillus can stand 100 C. It takes 121 C in the autoclave to sterilize things.  

2. Compare the effectiveness of autoclaving and dry heat.

• Sterilization in an autoclave is most effective when the organisms are either contacted by the steam directly or are contained in a small volume of aqueous (primarily water) liquid. Under these conditions, steam at a pressure about 15 psi; attaining temperature (121oC) will kill all organisms and their endospores in about 15 minutes.
• Dry heat sterilization can be an effective method of sterilization, using gravity or mechanical convection ovens. Dry heat can also sterilize items that can not be sterilized in steam or chemical sterilizers, such as powders and oils, or those that are prone to rust. In addition, Dry heat can be used for glassware, as it will not score or erode the surface as, steam might do, and dry heat will not corrode or rust instruments or needles.

3. Give an example of an application (use) of thermal death time.

• In order to make sure our food is sterile enough to eat, we must know the thermal death time of whatever type of microbes might be living in it. An example is, when food canning is taking place.

4. In the exercise, was the thermal death time or thermal death point determined?

5. Give an example of a nonlaboratory use of each of the following methods to control microbial growth:

• a. Incineration: cremation of the dead
• b. Pasteurization: milk
• c. Autoclaving: metals to be inserted into surgical tools and equipment

6. Define pasteurization. What is the purpose of pasteurization?

• Pasteurization is a process of heating food, which is usually a liquid, to a specific temperature for a predefined length of time and then immediately cooling it after it is removed from the heat
• Its purpose is to reduce the bacterial population of a liquid such as milk and to destroy organisms that may cause spoilage and human disease.