History of Food Poisoning Exploration

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What is the relationship between pH and cell energy according to the text?

pH has no effect on cell energy levels.

The lower the pH, the more energy the cell has to spend on maintaining its intracellular pH near neutrality and the less energy it has for other processes. (correct)

pH affects the growth rate of the cell, but not its energy expenditure.

The higher the pH, the more energy the cell has to spend on maintaining its intracellular pH near neutrality and the less energy it has for other processes.

What is the upper pH limit for growth of most foodborne pathogens?

pH 8 to 9 (correct)

pH 6.5

pH 7.0

pH 4.4

Which of the following food items has a pH value in the range of 6.5 - 5.3?

Egg albumen

Raw beef (correct)

Cottage cheese

Tomatoes

What is the purpose of 'hurdle technology' according to the text?

To inhibit microbial growth through the use of antimicrobial agents, ozone, irradiation, and shifts in pH and aw. Signup and view all the answers

What is the typical pH range for foods considered 'low-acid'?

pH >7.0 Signup and view all the answers

What is the relationship between pH and processing requirements for food according to the text?

Foods with lower pH values require milder processing than foods with higher pH values. Signup and view all the answers

What was a major cause of deaths during the Middle Ages?

Ergot poisoning Signup and view all the answers

What is the relationship between pH and acidity in food?

A food with a pH of 5 is 100 times more acidic than one with a pH of 7. Signup and view all the answers

What are the two main types of factors that influence microbial growth in food?

Intrinsic and extrinsic factors Signup and view all the answers

Which of the following is an example of an intrinsic factor that influences microbial growth in food?

pH Signup and view all the answers

Which of the following is an example of an extrinsic factor that influences microbial growth in food?

Temperature Signup and view all the answers

What volume of a sample dilution is typically dispensed onto the surface of an agar plate?

1 ml Signup and view all the answers

What is the purpose of using selective or differential media?

To inhibit the growth of all bacteria except the targeted organism Signup and view all the answers

What is the purpose of making a series of dilutions (e.g., 10^-1 to 10^-7) before plating?

To create a range of dilutions that will yield countable colonies Signup and view all the answers

What is the purpose of using a "hockey stick" to spread the sample on the agar surface?

To ensure even distribution of the sample across the entire agar surface Signup and view all the answers

What is a colony-forming unit (CFU)?

A cluster or chain of bacteria that forms a single visible colony Signup and view all the answers

How is the total number of bacteria in a sample calculated?

By multiplying the colony count by the dilution factor Signup and view all the answers

What pH values cause a marked decrease in resistance?

pH values below 5 or above 9 Signup and view all the answers

What is the effect of higher temperatures on the heat resistance of C.botulinum spores?

Higher temperatures result in spores with greater heat resistance, possibly through the formation of heat shock proteins. Signup and view all the answers

How do C.botulinum spores of groups I and II compare to most vegetative cells in terms of resistance to irradiation?

C.botulinum spores are more resistant to irradiation compared with most vegetative cells. Signup and view all the answers

Which of the following is not an effective way to inactivate C.botulinum spores?

Irradiation Signup and view all the answers

What is the purpose of the heat treatment given to thermally processed low-acid foods?

To kill spores of C.botulinum but not more heat-resistant spores. Signup and view all the answers

What is the effect of heating on filamentous fungi and yeasts in acidic foods?

Heating for a few minutes at 60-75°C kills most filamentous fungi and yeasts. Signup and view all the answers

What is the primary processing goal for low-acid canned foods?

Inactivate C. botulinum spores Signup and view all the answers

What is the typical time and temperature requirement for achieving a 12D treatment in low-acid canned foods?

3 to 6 minutes at 121°C Signup and view all the answers

What is the definition of the D value?

The time required for a 1-log reduction in viability at a given temperature Signup and view all the answers

What is the definition of the z value?

The temperature change required to alter the D value by a factor of 10 Signup and view all the answers

What is the key difference between conventional and aseptic processing of food?

Conventional processing involves hermetically sealing the product in the container, while aseptic processing sterilizes the product outside the container Signup and view all the answers

Which genus of Gram-positive, spore-forming bacteria is known to cause spoilage in juices due to its ability to survive hot-fill processes?

Alicyclobacillus Signup and view all the answers