Question:
Discoloration of milk can occur due to several factors. Which of the following could cause a Blue colours tint in milk?
Discoloration of milk can occur due to several factors. Which of the following could cause a Blue colours tint in milk?
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Keep these color-defect associations in mind:
- Blue milk = Pseudomonas syncyanea
- Red milk = Serratia marcescens
- Yellow milk = Pseudomonas synxantha
- Blue milk = Pseudomonas syncyanea
- Red milk = Serratia marcescens
- Yellow milk = Pseudomonas synxantha
Updated On: Jul 8, 2026
- Pseudomonas Syncyanea
- Bacillus subtilis
- Lactobacillus acidophilus
- Streptococcus thermophiles
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Microbial discoloration of milk occurs when pigment-producing (chromogenic) bacteria multiply and release water-soluble or fat-soluble pigments into the milk.
Step 2: Detailed Explanation:
- Pseudomonas syncyanea (also known as Pseudomonas coaerulea) produces a water-soluble blue pigment called pyocyanin.
- When this bacterium grows in milk, especially in the presence of acid-forming bacteria (such as Lactococcus lactis), the acid turns the bluish-grey pigment into a distinct blue color tint.
- Bacillus subtilis is associated with sweet curdling, while Lactobacillus acidophilus and Streptococcus thermophilus are standard lactic starter cultures that do not produce pigments.
Step 3: Final Answer
The organism responsible for producing a blue color tint in milk is Pseudomonas syncyanea.
Microbial discoloration of milk occurs when pigment-producing (chromogenic) bacteria multiply and release water-soluble or fat-soluble pigments into the milk.
Step 2: Detailed Explanation:
- Pseudomonas syncyanea (also known as Pseudomonas coaerulea) produces a water-soluble blue pigment called pyocyanin.
- When this bacterium grows in milk, especially in the presence of acid-forming bacteria (such as Lactococcus lactis), the acid turns the bluish-grey pigment into a distinct blue color tint.
- Bacillus subtilis is associated with sweet curdling, while Lactobacillus acidophilus and Streptococcus thermophilus are standard lactic starter cultures that do not produce pigments.
Step 3: Final Answer
The organism responsible for producing a blue color tint in milk is Pseudomonas syncyanea.
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