Question Bank • QB_DFE_EXP_052 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Preservation of Food

Subtopic: Preservation of food by cooling and freezing

Question Statement:

A food material containing $80.0\%$ water is frozen. The latent heat of fusion of water is $333.6\text{ kJ/kg}$. The latent heat of freezing of $1.0\text{ kg}$ of this food material in $\text{kJ/kg}$ is ________ (round off to 1 decimal place).

Answer Key:

266.9

Step-by-Step Solution & Explanation

Latent heat of freezing of food $\lambda_f$: $\lambda_f = w \times \lambda_{water} = 0.80 \times 333.6\text{ kJ/kg} = 266.88\text{ kJ/kg} \approx 266.9\text{ kJ/kg}$
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