Question

The permeability of packaging films to water vapour is usually expressed as:

• A. Oxygen Gas Transmission Rate
• B. Water Vapour Transmission Rate
• C. Permeability coefficient
• D. Volumetric flux

Hint:

Packaging: Oxygen → OTR, Water vapour → WVTR. Always match gas with its transmission rate term.

Answer 1

The Correct Option is B

Concept: In food packaging, permeability refers to the ability of gases or vapours to pass through a packaging material. For water vapour, the most commonly used practical measure is Water Vapour Transmission Rate (WVTR), which indicates how much water vapour passes through a material over a given time.

Step 1: Understanding permeability.
Permeability depends on:
• Nature of packaging material
• Thickness of film
• Temperature and humidity conditions

Step 2: Defining WVTR.
Water Vapour Transmission Rate (WVTR) is defined as:
• The amount of water vapour passing through a unit area of film per unit time It is usually expressed in units like g/m$^2$/day.

Step 3: Importance in food packaging.
WVTR helps in:
• Determining shelf life
• Preventing moisture loss or gain
• Selecting appropriate packaging materials

Step 4: Evaluating options.
• Oxygen Gas Transmission Rate — Measures oxygen permeability, not water vapour.
• Water Vapour Transmission Rate — Correct measure for water vapour permeability.
• Permeability coefficient — Theoretical parameter, not commonly used in practical packaging specifications.
• Volumetric flux — General term, not specific to packaging standards. Final Conclusion:
The permeability of packaging films to water vapour is expressed as Water Vapour Transmission Rate (WVTR). Hence, the correct answer is option (2).