Q1.  Pathogenic bacteria cannot grow below a water activity of?

1. 0.45–0.56
2. 0.35–0.46
3. 0.65–0.76
4. 0.85–0.86

ANSWER: D. 0.85–0.86

• Explanation – Water is a necessary component of all diets. A microorganism or a group of microorganisms can no longer multiply if their water activity falls below a certain level. This is in the 0.6–0.7 water activity range for most meals. Pathogenic bacteria cannot grow below a water activity of 0.85–0.86, although yeast and molds can tolerate a lower water activity of 0.80, no growth occurs below 0.62.

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Q2. The danger zone for microbial growth is considered to be between _____.

1. 1°C-6°C
2. 2°C-4°C
3. 0.5°C-3°C
4. 5°C-60°C

ANSWER: D. 5°C-60°C

• Explanation – Inhibition methods include those that rely on environmental control (e.g., temperature control), those that come from specific processing methods (e.g., microstructural control), and those that rely on intrinsic features built into specific foods (e.g., regulation of water activity or pH value). Because the danger zone for microbial growth is regarded to be between 5°C and 60°C, chilling and keeping food below 5°C is one of the most popular food preservation strategies.

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Q3. _____ stimulation has been explored as a method of bacterial control in meat.

3. Microwave heating
4. Ohmic heating
5. Low electric field
6. All of the above

ANSWER – C. Low electric field

• Explanation: Bacterial control in meat has been investigated using low electric field stimulation. After being subjected to an electric field, cell plasma membranes become permeable to tiny molecules, causing swelling and eventual rupture of the cell membrane. The intensity of the electric field, the number of pulses, and the duration of the pulses all influence whether a cell wall membrane ruptures reversibly or irreversibly.

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Q4. ______ is a sterilization method in applications where light can access all the important volumes and surfaces.

1. UV radiation
2. Irradiation
3. Pulsed light
4. Ohmic heating

ANSWER: C. Pulsed light

• Explanation: Pulsed light is a sterilizing technology that can reach all of the critical volumes and surfaces in an application. Packaging materials, surfaces, transmissive materials (such as air, water, and many solutions), and a wide range of medications and medical products are examples. A high-power, high-voltage pulse is used to electrically ionize a xenon gas-filled lamp for a few hundred millionths of a second, producing a white light pulse. It would be difficult to tell the difference between inhibition and inactivation in many circumstances.

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Q5. _____ means the condition obtained in a food that has been processed by the application of heat, alone or in combination with other treatments, to render the food free from viable forms of microorganisms.

1. Pasteurization
2. Commercially sterile
3. Sterilization
4. Canning

ANSWER: B. Commercially sterile

• Explanation – Commercially sterile refers to the state in which food has been processed by applying heat alone or in combination with other treatments to render it free of viable forms of microorganisms, including spores, capable of growing in the food at the temperatures at which it is designed to be held during distribution and storage.” As a result, commercial sterilizing entails the elimination of germs that cause deterioration and disease. Small amounts of thermophilic bacterium spores may be present in commercially sterile foods; nevertheless, the spores cannot germinate and create actively developing cells at room temperature.

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