Question

The principal example of the use of ............ is in the production of ice‐cream and margarine.

• A. Plate freezer
• B. Air blast freezer
• C. Scraped surface freezer
• D. Fluidized bed freezer

Hint:

If the product is thick, sticky, or develops a "skin" when heated or cooled, the answer is almost always a Scraped Surface Heat Exchanger (SSHE).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the type of industrial freezer or heat exchanger specifically designed for products that are viscous, tend to freeze onto surfaces, or require aeration during freezing.

Step 2: Detailed Explanation:

• Ice cream and margarine are complex emulsion systems. Ice cream production requires freezing the mix while simultaneously incorporating air (overrun) and whipping the fat.

• As the mix freezes, ice crystals form on the walls of the heat exchanger. These crystals act as insulation, drastically reducing heat transfer efficiency.

• A Scraped Surface Heat Exchanger (SSHE) or freezer contains a central shaft with blades. These blades continuously scrape the frozen layer off the cold inner walls.

• This constant scraping serves three purposes: it maintains high heat transfer rates, prevents "freeze-on," and ensures that the ice crystals remain small, resulting in a smooth, creamy texture.

• Other freezer types: Plate freezers are for rectangular blocks of meat/fish. Fluidized bed is for small individual items (peas/corn). Air blast is for large carcasses or general cold storage.

• Therefore, the scraped surface freezer is the specialized equipment for viscous/crystallizing liquids like ice cream.

Step 3: Final Answer: The Scraped surface freezer is the principal equipment for ice-cream and margarine production.