Question

Which milk product is obtained by dehydration?

• A. Butter
• B. Cheese
• C. Milk powder
• D. Cream

Hint:

Spray drying is the most common dehydration technique used for milk powder because the rapid rate of evaporation prevents thermal damage to milk proteins and maintains solubility.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify which of the given dairy products is manufactured primarily through the process of dehydration (removal of water).
Dehydration is a preservation technique that reduces water activity to a level where microbial growth and enzymatic reactions are inhibited.

Step 2: Key Formula or Approach:
The approach involves analyzing the unit operations used in the manufacturing of various dairy products: Butter, Cheese, Milk powder, and Cream.
Identifying which of these processes uses evaporative or drying technology to remove water systematically leads to the correct answer.

Step 3: Detailed Explanation:
The production methods for each of the options are examined below:

• Milk Powder: The industrial production of milk powder is a two-step dehydration process.
First, raw milk is concentrated in a multi-effect falling-film evaporator to remove about $85\%$ of the water.
Second, this concentrated milk is subjected to spray drying (or drum drying), where it is atomized into a chamber of hot air.
The remaining water evaporates instantaneously, yielding a dry powder with a moisture content of only $3\%$ to $5\%$.
Thus, milk powder is a direct product of extensive dehydration.

• Butter: Butter is produced by mechanical churning of cream, which causes the fat globules to coalesce and form a continuous fat phase, separating the buttermilk.
It is a phase-inversion process rather than dehydration (eliminating Option A).

• Cheese: Cheese is produced by the enzymatic or acidic coagulation of milk proteins (casein), followed by the physical syneresis (expulsion) of liquid whey.
While some moisture is removed as whey, the primary mechanism of cheese making is coagulation and fermentation, not thermal dehydration (eliminating Option B).

• Cream: Cream is a concentrated fat-in-water emulsion separated from raw milk by centrifugal separation based on density differences, not by water removal (eliminating Option D).

Step 4: Final Answer:
Therefore, milk powder is the dairy product obtained by thermal dehydration of milk.