Question 1

Which of the following statements about the human Rotavirus is correct?

Accepted Answer

Its genome is composed of double-stranded RNA.

Question 2

Which chemical disinfectant is most effective against Rotavirus on food contact surfaces?

Accepted Answer

Sodium hypochlorite (bleach) at 1000 ppm

Question 3

A food sample is tested for Salmonella spp. using serial dilution and spread plating. If 0.1 mL of a $$10^{-4}$$ dilution yields 25 colonies, what is the concentration of Salmonella spp. in the original sample (CFU/mL)?

Accepted Answer

$$2.5 	imes 10$$^{5}$$ CFU/mL

Question 4

Which of the following best explains why Gram staining of food does not always yield a safe color when bacteria are present?

Accepted Answer

Some bacteria may be present in numbers below the detection limit.

Question 5

Which of the following is a characteristic of Bacillus spp. endospores that makes them highly resistant to heat?

Accepted Answer

Presence of dipicolinic acid and calcium ions

Question 6

Saccharomyces cerevisiae metabolizes pyruvate under anaerobic conditions primarily by which pathway?

Accepted Answer

Alcoholic fermentation

Question 7

Which of the following is a correct description of the hurdle technology principle in food microbiology?

Accepted Answer

Combining multiple preservation factors at lower intensities to inhibit microbial growth

Question 8

A batch of cheese is inoculated with $$10^5$$ cells/g of Listeria monocytogenes. After pasteurization at $$72^{\circ}C$ for 15 seconds, the D-value is 2$ minutes. What is the expected number of survivors?

Accepted Answer

$$10^2$$ cells/g

Question 9

Which of the following is a physical, non-thermal food preservation method?

Accepted Answer

High-pressure processing

Question 10

Which antimicrobial agent is commonly present in raw milk and inhibits the growth of Gram-positive bacteria?

Accepted Answer

Lysozyme

Question 11

During alcoholic fermentation by Saccharomyces cerevisiae, which product is generated from pyruvate?

Accepted Answer

Ethanol

Question 12

Which of the following best describes the function of resazurin in media used for the cultivation of anaerobes?

Accepted Answer

It serves as an oxygen indicator.

Question 13

A food sample is treated with a bacteriostatic compound. What is the expected impact on the total and viable count of microorganisms?

Accepted Answer

Total count remains unchanged, viable count remains unchanged.

Question 14

Which of the following spices contains a compound that can exhibit minimal antimicrobial activity?

Accepted Answer

Black pepper (piperine)

Question 15

Which of the following is a bacteriostatic compound found in spices?

Accepted Answer

Eugenol from cloves

Question 16

Which of the following best explains why lactic acid bacteria are important in cheese production?

Accepted Answer

They lower the pH by producing lactic acid, inhibiting spoilage organisms.

Question 17

Which of the following is a correct statement about the DEFT (Direct Epifluorescent Filter Technique) method?

Accepted Answer

It quantifies both viable and non-viable cells in a liquid sample.

Question 18

Which of the following is a reason why Bacillus cereus can survive in cooked rice?

Accepted Answer

It forms endospores that are resistant to cooking temperatures.

Question 19

Which of the following is a correct application of the hurdle technology in food preservation?

Accepted Answer

Using high salt concentration and refrigeration together to inhibit microbial growth.

Question 20

Which of the following is a correct statement about the function of Saccharomyces cerevisiae in bread making?

Accepted Answer

It ferments sugars to produce carbon dioxide, causing the dough to rise.

Microbiology Study Notes: Foodborne Pathogens, Microbial Growth, and Food Safety

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