Question

Mold button formation in sweetened condensed milk is caused by

• A. Aspergillus repens
• B. Proteus vulgaris
• C. Thermobacterium mathiacelle
• D. Torulopsis globosa

Hint:

"Buttons" in SCM = Mold growth. Aspergillus repens is the classic causative agent because it can handle the high sugar levels.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Sweetened Condensed Milk (SCM) is preserved by high osmotic pressure (sugar concentration) rather than high heat.
"Buttons" are a distinct defect where firm, colored (brownish/reddish) lumps of mold mycelia and coagulated milk form on the surface.

Step 2: Detailed Explanation:
Buttons are caused by the growth of molds that can tolerate high sugar concentrations and low oxygen levels inside the sealed can.
The primary species responsible are molds from the Aspergillus and Penicillium genera.
Specifically, Aspergillus repens (part of the Aspergillus glaucus group) is a xerophilic mold that thrives in low water activity ($a_{w}$) environments like SCM.
As the mold grows, it produces enzymes (proteases) that coagulate the casein locally, creating the characteristic firm "button."
The other options provided (Proteus, Thermobacterium, Torulopsis) do not produce these specific structural lumps on SCM.

Step 3: Final Answer:
Mold button formation is caused by Aspergillus repens.