2. Water vapour transmission rate of a packaging film is 4g/m2 /day. A food product is packed in a rectangular
pouch measuring 0.12m x 0.16m. The maximum amount of moisture lost in 90 days is
1. 0.15 g
2. 13.82 g
3. 0.04 g
4. 18.34 g

How to Calculate Moisture Loss Through Packaging Using Water Vapour Transmission Rate (WVTR)

In food packaging, controlling moisture loss is critical to maintaining shelf life and product quality. One key factor in this is the Water Vapour Transmission Rate (WVTR), which measures how much water vapor passes through a packaging material over time.

Let’s solve the following problem:

Question:

A food product is packed in a rectangular pouch measuring 0.12 m × 0.16 m. The WVTR of the packaging film is 4 g/m²/day. What is the maximum amount of moisture lost in 90 days?

Options:

1. 0.15 g

2. 13.82 g

3. 0.04 g

4. 18.34 g

Step-by-Step Solution:

1. Calculate the Surface Area of the Pouch

The pouch has two sides (front and back), each of:

Area=0.12 m×0.16 m=0.0192 m2\text{Area} = 0.12\ m \times 0.16\ m = 0.0192\ m^2Area=0.12 m×0.16 m=0.0192 m2

Since both front and back surfaces allow moisture transmission:

Total surface area=2×0.0192=0.0384 m2\text{Total surface area} = 2 \times 0.0192 = 0.0384\ m^2Total surface area=2×0.0192=0.0384 m2

2. Use the Water Vapour Transmission Rate (WVTR)

WVTR = 4 g/m²/day
Time = 90 days

Moisture loss per day=4 g/m2/day×0.0384 m2=0.1536 g/day\text{Moisture loss per day} = 4\ g/m^2/day \times 0.0384\ m^2 = 0.1536\ g/dayMoisture loss per day=4 g/m2/day×0.0384 m2=0.1536 g/day $$\text{Total moisture loss in 90 days}=0.1536g/day\times 90days=13.824g$$

✅ Correct Answer: (2) 13.82 g

Why Moisture Control in Packaging Matters

Understanding and controlling moisture loss is essential in the food industry to:

• Prevent spoilage or staling

• Maintain texture and flavor

• Extend shelf life

• Meet regulatory requirements for packaging materials

Using WVTR values, manufacturers can choose appropriate packaging films for different types of food products, especially those sensitive to humidity.

Summary

To calculate moisture loss using WVTR:

1. Find the surface area through which vapor passes

2. Multiply the surface area by WVTR to get daily moisture loss

3. Multiply daily loss by the number of days

Final Result: The maximum moisture lost in 90 days is approximately 13.82 g.