Question

Given below are two statements:
Statement I: Foods of low water activity stored in high RH environment leads to transfer of water from the environment to the food thereby increasing in water activity of food
Statement II: Foods with high water activity when stored in low RH environment loose moisture and become unfit for consumption due to loss of quality
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is correct but Statement II is false
• D. Statement I is incorrect but Statement II is true

Hint:

Water Activity & RH Equilibrium: $a_w = \text{ERH}/100$. High RH environment $\rightarrow$ Low $a_w$ food absorbs moisture. Low RH environment $\rightarrow$ High $a_w$ food loses moisture (desiccates).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Moisture sorption isotherms and Equilibrium Relative Humidity (ERH): thermodynamic water vapor gradients drive moisture flux between food and surrounding headspace air until equilibrium ($a_w = ext{ERH}/100$) is attained.
Key Formula or Approach:
\[ \text{Equilibrium Condition: } a_w = \frac{\text{ERH}}{100} \quad \implies \quad \begin{cases} \text{If } \text{RH} > 100 \cdot a_w \implies \text{Food adsorbs water (Moisture Gain)} \text{If } \text{RH} < 100 \cdot a_w \implies \text{Food desorbs water (Moisture Loss)} \end{cases} \]

Step 2: Detailed Explanation:
1. Statement I: Water Activity ($a_w$) and relative humidity follow thermodynamic moisture equilibrium ($a_w = \text{ERH}/100$). When a dry, low-$a_w$ food (e.g., dried fish, $a_w = 0.60$) is stored in an ambient high relative humidity atmosphere (e.g., $\text{RH} = 85\%$), water vapor transfers from the humid air into the food, raising its water activity and precipitating mold growth. Hence, Statement I is true.
2. Statement II: When high-$a_w$ fresh/moist foods ($a_w = 0.95$) are stored in a dry, low-RH environment ($\text{RH} = 50\%$), water rapidly evaporates from the food surface into the air, leading to surface desiccation, case hardening, weight shrinkage, freezer burn, and quality loss. Hence, Statement II is true.

Step 3: Final Answer:
Thus, Both Statement I and Statement II are true, corresponding to option (A).