Heat Disinfection

Question 1

What are the optimal growth temps for Psychrophiles, mesophiles, thermophiles and hyperthermophiles?

Answer 1

Psychrophile: 15 *C or less

Mesophile: 25-40* C

Thermophiles: 45-80*C

Hyperthermophiles: 80*C or higher

Question 2

All human pathogens belong to what type of group of bacteria?

Answer 2

Mesophiles

Question 3

Human pathogens grow best at what temperature?

Answer 3

• near body temperature, 37*C

Question 4

What are psychrotrophs?

Answer 4

• mesophiles that are also able to grow at refrigerator temperatures
  
  • they grow best near human body temp (37C), but they still grow at a significant rate at temps near 4C

-Cause food Bourne illnesses

Question 5

At what temperature does typical bacterial pathogens start dieing?

Answer 5

-63*C

Question 6

At what temp does bacterial endospores start dying?

Answer 6

-85*C

Question 7

What are 3 examples of psychrotrophic pathogens

Answer 7

• listeria monocytogenes
• yersinia entercolitica
• some strains of clostridium botulinum

Question 8

How does heat disinfection destroy microorganisms?

Answer 8

-at high enough temps, proteins are denatured, which eventually kills off the microorganism

Question 9

What is the function of a fever in the body?

Answer 9

• high temp of the body may decrease the replication of any human viruses.

Question 10

What is pasteurization?

Answer 10

• heat disinfection technique
  
  • foods are exposed to high temps for a limited period of time: 63C for 30 min or 72C for 15 secs
• reduces load of microorganisms rather than destroying all
• kill foodborne pathogens
• kill spoilage organisms (longer lasting food)

Question 11

What makes a microorganism a thermoduric/thermotolerant?

Answer 11

• can survive pasteurization, but cannot reproduce at pasteurization temperatures
  
  • Example: endospores

Question 12

Does boiling water kill bacterial endospores?

Answer 12

-can kill most vegetative bacterial cells, but cannot reliably destroy bacterial endospores

Question 13

What are 2 reliable ways to kill bacterial endospores?

Answer 13

• autoclave: pressurized steam

- high temp for longer period of time ( 170*C for 1 hour)

Question 14

What is D-value?

Answer 14

• decimal reduction time

- amount of time for a specific treatment til kill 90% of a specific microbe

Question 15

How is DRT reflected on the slope of a line?

Answer 15

• the steeper the line, the smaller the DRT (faster the microbes die)
• the longer the line, the DRT is larger (microbes dies slower)

Question 16

What are the factors to consider when measuring at the effectiveness of disinfection

Answer 16

• number of microbes to start
• acceptable number of microbes to end
• length of disinfectant treatment
• factors that affect DRT

Question 17

What are the factors the affect the length of DRT?

Answer 17

• type of disinfectant treatment
• intensity of disinfection
• presence of organic matter (dirt)
• environment (temp, pH)
• characteristics of the microbe (vegetative vs spore, biofilm, Gram +/- vs enveloped etc)

Question 18

Is pasteurzied food sterile? Why?

Answer 18

-No; it will neutrally spoil due to the growth of thermoduric organisms

Question 19

What kind of radiation does UV light emit?

Answer 19

• nonionizing radiation

- damages DNA