Question

Which of the following is correct with regard to development of bitterness in cheese?
A. Poor quality milk
B. Low salt-to-moisture ratio in cheese
C. High solids content in cheese
D. Poor quality starter culture
Choose the correct answer from the options given below

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

Hint:

Bitterness in cheese is caused by the accumulation of hydrophobic peptides. This defect is promoted by high psychrotrophic loads in raw milk (A), low salt levels (B), and starter cultures with unbalanced protease/peptidase activity (D).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Bitterness is a common sensory defect in cheese caused by the accumulation of bitter-tasting hydrophobic peptides.
These bitter peptides are formed by the enzymatic hydrolysis of milk proteins (primarily $\beta$-casein) by proteases and peptidases during cheese ripening.
Under normal conditions, these bitter intermediates are rapidly broken down into non-bitter amino acids by bacterial peptidases.
However, imbalances in the raw milk quality, starter culture characteristics, or manufacturing parameters can disrupt this process, leading to the accumulation of bitter peptides.

Step 2: Detailed Explanation:
Let us analyze the contribution of each factor to the development of bitterness:
1. Poor quality milk (A): Milk with high psychrotrophic bacterial counts contains heat-stable, extracellular proteases.
These proteases survive pasteurization and continuously hydrolyze casein to produce bitter hydrophobic peptides during cheese ripening.
2. Low salt-to-moisture ratio (B): Salt regulates the metabolic activity of starter cultures and non-starter lactic acid bacteria.
A low salt-to-moisture ratio fails to control excessive proteolysis and can inhibit the intracellular peptidases responsible for degrading bitter peptides, leading to their accumulation.
3. High solids content in cheese (C): High solids content (low moisture) generally restricts proteolysis and reduces the rate of bitter peptide formation.
Thus, high solids content is not a cause of bitterness.
4. Poor quality starter culture (D): Some starter cultures possess high cell-wall proteinase activity but low intracellular peptidase activity.
These "bitter" strains rapidly produce bitter peptides from casein but cannot break them down further, causing bitterness in the cheese.
Therefore, factors A, B, and D are directly responsible for the development of bitterness.

Step 3: Final Answer
The factors correct with regard to the development of bitterness in cheese are A, B, and D only.