Question

Match List-I with List-II

List-I (Causative organism)	List-II (Defect)
(A) Pseudomonas nigrifaciens	(I) bacterial thickening
(B) Lactococcus lactis spp Lactis biovorin maltigenes	(II) bitterness in evaporated milk
(C) Bacillus panis	(III) black discolouration on butter
(D) Staphylococcus albus	(IV) malty taint

Choose the correct answer from the options given below

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (III), (B) - (IV), (C) - (II), (D) - (I)
• (A) - (I), (B) - (II), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

Associate these key dairy spoilages with their causative organisms:
- P. nigrifaciens \(\rightarrow\) Black surface discoloration on salted butter.
- L. lactis biovar. maltigenes \(\rightarrow\) Malty flavor defect.
- Bacillus panis \(\rightarrow\) Sweet/bacterial thickening of condensed milk.
- Staphylococcus albus \(\rightarrow\) Bitterness in canned evaporated milk.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Microbial spoilage causes specific quality defects in dairy products.
Different species of bacteria produce unique enzymes or volatile compounds that lead to characteristic defects in butter, milk, or condensed milk during storage.

Step 2: Detailed Explanation:
Let us match each organism in List-I with its associated defect in List-II:
- (A) Pseudomonas nigrifaciens matches with (III) black discolouration on butter:
This psychrotrophic, halotolerant bacterium can grow on the surface of salted butter under refrigeration.
It produces a dark, insoluble blue-black pigment, causing black spots or discoloration on the butter surface.
Therefore, (A) matches with (III).
- (B) Lactococcus lactis subsp. lactis biovar. maltigenes matches with (IV) malty taint:
This specific starter culture biovar ferments amino acids (such as leucine) to produce 3-methylbutanol.
This volatile alcohol imparts a distinct, undesirable malty taste and aroma to milk.
Therefore, (B) matches with (IV).
- (C) Bacillus panis matches with (I) bacterial thickening:
This sporeforming bacterium can survive processing and grow in sweetened condensed milk.
It produces extracellular rennet-like enzymes that slowly hydrolyze casein, causing the milk to thicken and gel without gas production.
Therefore, (C) matches with (I).
- (D) Staphylococcus albus matches with (II) bitterness in evaporated milk:
This proteolytic bacterium can grow in canned evaporated milk if there is pasteurization failure or container leakage.
It produces highly active proteases that break down caseins into bitter hydrophobic peptides, causing a distinct bitter taste.
Therefore, (D) matches with (II).
This matching sequence corresponds to Option (D).

Step 3: Final Answer:
The correct matching sequence is (A) - (III), (B) - (IV), (C) - (I), (D) - (II).