Food Process Engineering & Operations

Pulsed Electric Field (PEF) is a non-thermal pasteurization technology that destroys vegetative microbial cells by electroporating cell membranes. However, food quality-deteriorating enzymes (such as polyphenol oxidase, pectin methylesterase, and peroxidase) possess globular tertiary structures that are highly resistant to electric pulses alone. Thus, PEF does NOT adequately inactivate endogenous enzymes unless combined with thermal heat; statement 4 is false (making it the correct answer).

Option analysis:

• It inactivates vegetative bacteria: True, electroporation achieves multi-log pathogen reductions.
• It is not effective against spores: True, bacterial endospores are resistant to electric field strengths.
• The products treated with PEF needs distribution in the refrigerated condition: True, chill chain is mandatory because spores and enzymes survive.
• It inactivates enzymes and products are stable for enzymatic spoilage: Not true (false statement), enzymes survive PEF treatment.

Ionizing radiation consists of subatomic particles or electromagnetic waves with photon energy sufficient to ionize atoms or molecules by detaching electrons. In food processing and preservation, gamma rays (emitted by Cobalt-60 or Cesium-137), high-energy electron beams, and X-rays are legally and scientifically classified as ionizing radiation. Microwaves, radio waves, and UV are non-ionizing.

Option analysis:

• Gamma rays: Correct, high-frequency, high-energy electromagnetic waves standardly defined as ionizing radiation.
• UV rays: Non-ionizing optical radiation (causes excitation, not cellular ionization).
• Radio waves: Extremely low frequency, non-ionizing electromagnetic radiation.
• Microwaves: Non-ionizing radiation causing dipole molecular rotation.

A bactericidal agent or treatment directly causes the lethal destruction and killing of bacteria. Ionizing radiation (gamma rays from Cobalt-$60$, electron beams, or X-rays) directly damages microbial DNA and generates lethal free radicals (radiolysis of water), destroying bacterial cells lethally (bactericidal). Membrane filtration physically removes cells (not killing), while freeze-drying and deep freezing are bacteriostatic (inhibiting metabolic activity without necessarily killing cells).

Option analysis:

• Membrane filtration: Physical separation/removal process, not bactericidal.
• Freeze-drying: Preservation technique that preserves bacterial viability (used to store culture stocks).
• Ionizing radiation: Correct, causes irreversible DNA strand breaks leading to bacterial cell death.
• Deep freezing: Bacteriostatic preservation method; bacterial cells can survive frozen storage.

Matching advanced food processing technologies with their technological descriptions:

• High Pressure Processing (HPP): Utilizes isostatic pressures of $400$ to $600\text{ MPa}$ for pasteurization of ready-to-eat (RTE) meat, juices, and guacamole -> (A) matches (III).
• Ohmic Heating (Joule heating): An electrical current is passed directly through food material to generate heat internally by electrical resistance -> (B) matches (I).
• Pulsed Electric Field (PEF): Involves application of short high-voltage electrical pulses ($20$ to $80\text{ kV/cm}$) across foods for electroporation of microbial cell membranes -> (C) matches (IV).
• Microencapsulation: Spray drying is the most prevalent industrial technique for encapsulating bioactive core ingredients and flavors into protective carrier matrices -> (D) matches (II).