Question

Which of the following is the most abundant organic acid in milk?

• A. Citric acid
• B. Acetic acid
• C. Butyric acid
• D. Pyruvic acid

Hint:

Citric acid is the primary organic acid in milk. It stabilizes calcium ions and serves as the precursor for diacetyl (butter aroma) during fermentation.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Fresh milk contains small amounts of various organic acids that play roles in salt balance, buffering capacity, and the growth of starter cultures.

Step 2: Detailed Explanation:
The organic acid profile of fresh bovine milk is dominated by Citric acid.
It is present in fresh milk at concentrations of approximately 5 to 0 g/L (0.15% to 0.20%).
Citric acid exists primarily as soluble and colloidal citrates (such as calcium and magnesium citrates).
These citrates are essential in maintaining the salt balance and colloidal stability of casein micelles.
Additionally, citrate serves as a metabolic substrate for aroma-producing lactic acid bacteria (such as Leuconostoc and Lactococcus lactis subsp. diacetylactis), which convert it into diacetyl, a key flavor compound in butter and dahi.
Other organic acids like acetic acid, butyric acid, and pyruvic acid are present only in trace amounts in fresh milk, though their concentrations can increase as a result of bacterial spoilage or fermentation.
Therefore, citric acid is the most abundant organic acid in fresh milk.

Step 3: Final Answer
The correct option is (A).