This set of Fruits Processing Multiple Choice Questions & Answers (MCQs) focuses on “Non-Thermal Pasteurization of Fruit Juice Using High Voltage Pulsed Electric Fields”.
1. What is pulsed electric field?
a) Non-thermal food preservation method
b) Thermal food preservation method
c) Type of irradiation method
d) Combination of thermal and irradiation
View Answer
Explanation: Pulsed electric field (PEF) technique is a non-thermal method which preserves the food. For microbial inactivation, it uses small electricity pulses. It also executes negligible detrimental effect on food quality.
2. Which microbes are more resistant to the effect of pulsed electric field?
a) Gram positive bacteria
b) Gram negative bacteria
c) Mold
d) Mesophilic bacteria
View Answer
Explanation: Different bacteria have different sensitivities to electric field treatment. In general, Gram-positive bacteria and yeasts are more resistant to electric fields than Gram-negative bacteria. Therefore, it is used with combination of other preservation techniques.
3. How pulsed electric field destroys microorganisms?
a) Formation of large pores in the bacterial membrane
b) Formation of large pores in the bacterial chromosomes
c) Formation of large pores in the bacterial nucleus
d) Formation of large pores in the bacterial mitochondria
View Answer
Explanation: Pulsed electrical fields (PEFs) have been used for decades to preserve food by destroying bacteria. It is by causing the formation of large pores in the bacterial membrane. Recently PEF’s have been used to treat solid tumors.
4. What is electroporation method?
a) Technique to increase cell membrane permeability
b) Technique to decrease cell membrane permeability
c) Technique to increase DNA permeability
d) Technique to decrease DNA permeability
View Answer
Explanation: Electroporation is used in high voltage pulsed electric fields. It is defined as a technique to increase cell membrane permeability to hydrophilic molecules under an applied electric field. It is a physical transfection method that uses an electrical pulse to create temporary pores in cell membranes
5. How is electropermeabilization achieved?
a) Use of long high-voltage pulses
b) Use of short high-voltage pulses
c) Use of short low-voltage pulses
d) Use of short low-voltage pulses
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Explanation: Electropermeabilization uses the short high-voltage pulses to overcome the barrier of the cell membrane. A position-dependent reversible local membrane permeabilization is induced leading to an exchange of hydrophilic molecules across the membrane. It can be used to load cells with therapeutic molecules.
6. Which of the following products can use pulsed electric field as a preservation method?
a) Apple juice
b) Chocolate
c) Cereals
d) Nuts
View Answer
Explanation: The pulsed electric field (PEF) technology is a mild food processing technology. It is suitable for preserving liquid and semi-liquid food products. This processing method uses short electric pulses to achieve microbial inactivation in food products while preserving the fresh characteristics.
7. Which of the following is not an important factor in pulsed electric field?
a) Frequency of the pulse
b) Shape of the pulse
c) Amplitude of the pulse
d) Pressure of the pulse
View Answer
Explanation: The main step in the pulsed electric field (PEF) process is the application of pulses of an electrical field of a part of a liquid stream. The frequency, shape and amplitude of the pulses result in the intensity of the treatment. Together with the shape of the treatment chamber the efficiency is determined.
8. The application of pulsed electric field allows the preservation of heat sensitive products like juices.
a) True
b) False
View Answer
Explanation: The application of pulsed electric field allows the preservation of heat sensitive products such as juices. There are only minor detrimental effects on the quality. It allows an easy implementation into existing production lines.
9. Pulsed electric field enhances the extraction rate of pectin from fruit pomace.
a) True
b) False
View Answer
Explanation: Pectin is a very useful component found in many fruits that is traditionally being extracted through enzymatic reaction. But this reaction has less yield of pectin due to poor efficiency. Alternatively, Pulsed electric field is employed as short pulses to avoid excessive heat and undesirable electrolytic reactions. It enhances the extraction rate of pectin from fruit pomace.
10. What intensity of pulsed electric field is used for food preservation?
a) 1-8 kV/cm
b) 10-80 kV/cm
c) 100-800 kV/cm
d) 1000-8000 kV/cm
View Answer
Explanation: Pulsed electric field is also called High Electric Field Pulses (HELP). It is the application of very high field strength for a very short time to foods placed between electrodes. It uses short electric field pulses to preserve food. It works in intensity of 10-80 kV/cm with duration of micro to milliseconds.
11. What is the principle behind pulsed electric field?
a) Electroporation
b) Electrofocusing
c) Electrophoresis
d) Electric suction
View Answer
Explanation: Pulsed electric field (PEF) is based on the principle of electroporation. The use of an external electric field for a few micro seconds induces local structural changes. There will be a rapid breakdown of the cell membrane which is important component on cell. Cells that undergo PEF can respond to pulses reversibly or irreversibly.
Sanfoundry Global Education & Learning Series – Fruits Processing.
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