Question

Sterilization of food in containers can be done by
(A). Indirect heating by a saturated steam
(B). Forced convection hot air
(C). Exposing to blue light
(D). By direct flame contact

Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A), (B) and (C) only.
• C. (A) and (D) only.
• D. (A), (B), (C) and (D).

Hint:

In-container food processing requires highly effective heat transfer methods. Saturated steam (high latent heat) and direct flame heating provide the necessary rapid thermal energy transmission.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
In-container thermal sterilization processes use heat to destroy spoilage microorganisms and pathogens inside sealed food cans or packages.

Step 3: Detailed Explanation:
Let us evaluate each method for in-container processing:
(A)

Indirect heating by saturated steam: This is the most common commercial retort process, where sealed containers are heated under pressure by condensing steam. Thus, (A) is correct.
(B)

Forced convection hot air: Hot air has a very low convective heat transfer coefficient, making it highly inefficient and rarely used for standard in-container pasteurization or sterilization of food.
(C)

Exposing to blue light: Non-thermal light techniques (such as blue or UV light) only disinfect surfaces and cannot penetrate the container walls to sterilize the food inside.
(D)

Direct flame contact: In specialized commercial flame sterilizers (e.g., the Steriflamme process), metal cans are rotated directly over open gas flames, achieving rapid heat transfer. Thus, (D) is correct.
Therefore, (A) and (D) are the recognized in-container sterilization methods.

Step 4: Final Answer:
The correct option is 3, which corresponds to (A) and (D) only.